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paulx
04-19-2007, 08:20 AM
I tried a new endmill holder yesterday for the first time.I got about .003 tir.Is that normal?Maybe I should be using a collet?

lazlo
04-19-2007, 09:47 AM
Endmill holders will have more runout than a collet, because the set-screw pushes the tool against the side of the holder, where a collet grips the tool concentrically.

But 3 thou is a lot of runout. What's the runout of the spindle mouth?

bob_s
04-19-2007, 10:38 AM
I tried a new endmill holder yesterday for the first time.I got about .003 tir.Is that normal?Maybe I should be using a collet?

What size holder?

Have you mic'd the bore of the holder? Plug gauges?

I'd expect that 3 thou would be nominal runout for an endmill holder, simply because if the fit is much tighter than that you are going to have issues with tool insertion and removal. One thou is pretty much a press fit.

SGW
04-19-2007, 12:37 PM
Hmmm...I'd call 0.001" a loose fit. 0.003" ought to feel as though it's rattling around.

Try indicating the mouth of the hole in the holder, as you turn the spindle (by hand!) and see what runout you get. Any more than half a thou IMO would be too much.

PaulT
04-19-2007, 12:44 PM
"Endmill holders will have more runout than a collet, because the set-screw pushes the tool against the side of the holder, where a collet grips the tool concentrically."

A good quality endmill holder is compensated for this, they grind the hole slightly offset to compensate for the set screw clamping effect. You should see less than 0.0005" runout with a quality endmill holder or a good collet system, assuming your spindle is straight and its taper isn't worn.

Keep working on this until you find the problem, .003" runnout is going to cause problems for you.

Paul T.

lazlo
04-19-2007, 12:57 PM
Endmill holders will have more runout than a collet, because the set-screw pushes the tool against the side of the holder, where a collet grips the tool concentrically.
A good quality endmill holder is compensated for this, they grind the hole slightly offset to compensate for the set screw clamping effect.

Yes, the ETM holders are offset-ground, but I'll bet a six-pack he's using a Chicom endmill holder. The ETM holders are expensive as hell.

PaulT
04-19-2007, 02:46 PM
I just picked up a couple of ETM R8 endmill holders from www.use-enco.com a couple of weeks ago, they were on sale for around $35. each then, not too bad. I don't know if the sale is still on but if anybody needs some give it a shot. They are very nicely made.

Paul T.

Evan
04-19-2007, 04:44 PM
I made an end mill holder for my lathe using a MT2 stub arbor and a MT2 to MT3 sleeve. Even with that it still only has about .001" runout. .003 sucks.

paulx
04-19-2007, 04:52 PM
Holder is no name r-8 3/8 round.I`m getting an old round ram bridgeport running that my brother rescued on its way to the scrapyard for forty bucks.I`ve changed the spindle and motor brgs.Not much tooling yet,a round stock vise,endmill holder(1) and the jacobs chuck that came with the mill.Yesterday I cut metal for the first time,a 1/4 keyway on a motor shaft.The keyway didn`t turn as tight as I would have liked.I`m going to make a mental note to use collet s for keyway cutting.

BadDog
04-19-2007, 05:53 PM
Did you try to use a 1/4" end mill to cut that keyway? I made that mistake on my first, and it will cut oversize as well as rough. Better to use an undersize mill, cut down the middle to open it up, then clean up light cuts on both sides.

lazlo
04-19-2007, 06:07 PM
.Ive changed the spindle and motor brgs.

Did you check the runout after you changed the spindle bearings? Did you use precision (ABEC-5 or ABEC-7) bearings?


I`m going to make a mental note to use collets for keyway cutting.

I use endmill holders for big cuts with a roughing mill, and collets for everything else.

rgsparber
04-19-2007, 06:59 PM
Paul,

What kind of trouble would you expect besides having a larger effective end mill diameter?

Rick

SGW
04-19-2007, 08:57 PM
Dunno what Paul's thoughts might be, but one problem I can think of is that with 0.003" runout the chip loading is going to vary widely from tooth to tooth on the end mill as it turns.

Evan
04-19-2007, 09:18 PM
It's also going to excite the entire system vibrationally. If it happens to be resonant severe chatter can result. Whether it excites resonance will depend on rpm.

J Tiers
04-20-2007, 08:02 AM
I completely agree with the idea that 0.003 ought to feel so loose the EM falls in and out.

I use the Bison Em holders, and generally the EM slides in smoothly with no perceptible shake, AND you have to let the air leak out or the EM pops right back out.

0.003 is beyond bad in that application.

JCHannum
04-20-2007, 08:15 AM
The hole can be on size, but still be bored off center. I believe that is the problem. It will result in a larger slot, and lumpy finish, but probably not much else.

That is too much runout, but it may be coming from sources other than the holder. Measuring the end mill adds all the sources of runout, it is called tolerance stack up. Backtrack, and measure each element to determine where the runout is occurring. A collet may not be the solution.

A $40.00 round ram Bridgeport rescued from the scrapyard with new spindle bearings has some history, and 0.003 TIR may be the best it is capable of.

A.K. Boomer
04-20-2007, 09:27 AM
"Endmill holders will have more runout than a collet, because the set-screw pushes the tool against the side of the holder, where a collet grips the tool concentrically."

A good quality endmill holder is compensated for this, they grind the hole slightly offset to compensate for the set screw clamping effect.
Paul T.


I did not know that they actually grind offset, that makes me think a little different of the set screw type endmill holder but still I do not like the concept --- I know theve been around forever, I know they can handle much load and many believe are the only thing to use on the larger machines but still - My belief has been that we all know to be able to get the tool in and out there must be a certain amount of clearance, so in an exaggerated view your actually pushing a smaller diameter up against a larger bore, this really results in only 2 contact surfaces with one being the set screw, In theory one side has to have a contact patch of less than 180 degree's and the other a very tiny fraction of that, Personally I do not like that, and as far as my little mill its only R8 and i never had a tool "walk" out of its holder, The set screw holder may have a few advantages but Holding a tool at three points with the identical amount of surface area and lots of surface area at every point is superior as compaired to the two uneven contacts ---- Keep in mind that that tool has to rotate, and when it comes around and is cutting on the side opposite to the set screw that means that all the side load is getting put in one area --- the set screw end --- and the small foot print it has on the tool (whether the tool has a flat or not) To me this is crude ------- It also sets up some strange Load resonances and such, another advantage of the collet system is if your tool is 5/10's under or over it makes no difference, in fact if im just drilling and the Drill bit is .005" + or - its a go, nice to have sometimes for acuracy and rigidity and also some times with limited room between the quill and table, As far as For the little shop - R8 rules.

A.K. Boomer
04-20-2007, 09:37 PM
You guys are going to think im beating on the set screw style endmills but I did want to add this ------------- we are all taught to grab as much endmill as posible to reduce flex,chatter,keep them from breaking ect.
So if it makes that much off a difference (and it does) then how come the set screw style holders not only ignore this rule in design, they create something even worse, A variation...

The reason that I think they are of poor design is this - whether you choke up on an endmill or not your set screw is a good 1/2 to 1 inch above the bottom of the holder, because you are forcing the tool to one side this means that the tool is contacting the bottom of the holder on one side and is pushed away from the holder on the other --- this means that your set screw is effectivly the holding hight for the tool in the holder -- so you have a tool thats being held properly on one side and then is held much higher on the other, I dont like that, I have no problem with something like that on my cement mixer or my roto-tiller drive but this is the end drive/cutting system of a milling machine (where the bits are built to get side loaded) this is were everything should be as uniform as possible --- we dont have spindles ground to 1/10ths runout and then throw crap like that on as the iceing on the cake.....

I got a burr up my ass about set screw holders, I dont like them, if you ask me its something that i would expect to see in my granpa's garage..


Keep in mind im just a mechanic not a machinist:D

lazlo
04-20-2007, 09:51 PM
I got a burr up my ass about set screw holders, I dont like them, if you ask me its something that i would expect to see in my granpa's garage.

I agree A.K. -- I'm not a big fan of endmill holders either.

You know why they're called Weldon" shanks, right? Because when you take too big of a cut with an endmill holder and the cutter spins, it welds on to the set-screw, and you need a jackhammer to get it out :D

JCHannum
04-21-2007, 06:52 AM
The Weldon shank has one or two flats to prevent the endmill from spinning. If you are spinning Weldon shank end mills in an endmill holder, you are doing something very wrong.

A.K. Boomer
04-21-2007, 09:00 AM
They still are subject to all the poor design flaws previously mentioned, and now one more, Because the tool is always clamped in the same way and loaded in that direction its previous mentioned deviations never get changed,
This will result in a variation in the wear of the cutters sharpness and also set up an even worse repetitive flex pattern for the cutter breaking down the road.


I dont like them damn things and im going to raise a little stink about it.

J Tiers
04-21-2007, 09:49 AM
Well, I think that the theoretical problems that you are bringing up are washed out by reality in most cases.....

EM holder:

Holds by screw and opposite side, but does have very small clearance, so limited runout from that source.

Is solid, so any runout is consistent, and simply causes an oversize cut.

Holds by 4 or 5 diameters worth of LENGTH, and so develops the full bending strength of the EM itself.

My have inherent runout, but if you expect ANY EM to cut a precise diameter, you will be sadly disappointed.

Will NOT let the cutter "walk out" of the holder


Collet:

Holds by more circumference, picking up 3 spots instead of two

Holds by very little LENGTH, possibly 1 diameter to maybe 1.5 diameters worth of length, and is springy to boot. Hence it can let the tool tilt, creating a movement away from the cutting edge that is possibly as bad as any runout, and a good deal less predictable.

Holds by 3 spots, instead of two, but has no guarantee that they are concentric, since it depends to some extent on the way the collet springs.

Has a theoretical problem in that the collet can only hold with surfaces parallel to the shank for one diameter, and THAT depends on it never having been tightened up on an off-sized shank.

May let the cutter "walk out" and change the cutting depth. I have seen this.

toolsrul
04-21-2007, 10:16 AM
.003" runout is either a bad manufactured holder (cheap) or a damaged holder from people using excessive force to tighten set screw. If your holder bore is .0005" bigger then your tool shank you'll have a .001" runout, that's assuming your holder mounting surface (R8, CAT 40, etc.) is in good shape, clean, good bearings, etc. If you're running out .001" at the shank (near holder) check at the flutes, if more runout there you have more problems. A good quality collet system should be way less then a .001", maybe .0002" to .0005" max. Imagine what is happening to an end mill, that flute that has the highest runout condition is taking all the pounding while cutting, don't blame that on the tool mfg. Not worth going cheap. Good luck.

lazlo
04-21-2007, 10:51 AM
Based on Paul's description, I have a hunch that he used common, ungraded bearings in the spindle, hence the bad runout.

If this is the case, he'll have similarly bad runout with a collet.

lazlo
04-21-2007, 11:00 AM
Holds by screw and opposite side, but does have very small clearance, so limited runout from that source.

The problem is there's two clearances -- the clearance that the hole was ground in the holder, and the tolerance of the endmill shank A good endmill holder like an ETM or a Weldon has about 5 tenths tolerance, but they are very expensive. The majority of the Chicom endmill holders I've mic'ed have pretty lousy runout (as do the many of the Chicom collets).


Will NOT let the cutter "walk out" of the holder

But will spin and seize. That "Weldon" joke is an old, old machinist's joke.


Has a theoretical problem in that the collet can only hold with surfaces parallel to the shank for one diameter, and THAT depends on it never having been tightened up on an off-sized shank.

I'm not sure that's a con for the collet -- that's just saying don't stick the wrong sized toolbit in the collet.


May let the cutter "walk out" and change the cutting depth. I have seen this.

I've only seen that happen when folks didn't tighten the drawbar enough.

J Tiers
04-21-2007, 11:51 AM
The problem is there's two clearances -- the clearance that the hole was ground in the holder, and the tolerance of the endmill shank A good endmill holder like an ETM or a Weldon has about 5 tenths tolerance, but they are very expensive. The majority of the Chicom endmill holders I've mic'ed have pretty lousy runout (as do the many of the Chicom collets).



But will spin and seize. That "Weldon" joke is an old, old machinist's joke.

I'm not sure that's a con for the collet -- that's just saying don't stick the wrong sized toolbit in the collet.

I've only seen that happen when folks didn't tighten the drawbar enough.

If you sieze and spin one, you must have really been doing something..... Hard to do with a good EM, I'd think, never came close, even holding a saw arbor in an Em holder

Chicom /India low-budget ones? Sure. Cheap is cheap.

Bendix EMs and a Bison holder? Nary a problem.

Dual clearances? chicom holders etc? Sure.... cheap is cheap.... Buy good ones.

paulx
04-21-2007, 12:09 PM
I bought a couple lyndex r-8 collets this morning and indications are good!

I paid over $200.00 for the spindle brgs so I hope they are the right ones.

Now I need a dro...

A.K. Boomer
04-21-2007, 12:11 PM
EM holder:
Holds by screw and opposite side, but does have very small clearance, so limited runout from that source.

Is solid, so any runout is consistent, and simply causes an oversize cut.

.



Depending on the length of the cutter this is an area where 5/10th worth of clearence can translate to .003" worth of deviation at the end of the cutter, not to mention the "stepped" way of holding the tool, You wouldnt saw a collet end off on a thirty degree angle and then stick a tool in it would you, welp --- not far off from whats going on with the set screw type holder, just because the bottom of the holders screw side is getting invloved in a heavier cut doesnt mean anything but the fact that its occillating around in the holder ----------- Nice, yeah sounds really rigid...

lazlo
04-21-2007, 12:17 PM
I paid over $200.00 for the spindle brgs so I hope they are the right ones.

Oh, then my apologies Paul -- those are definitely precision bearings.

So it probably is the endmill holder.


I bought a couple lyndex r-8 collets this morning and indications are good!

Fantastic! Problem solved :)

J. R. Williams
04-21-2007, 12:28 PM
Time to move up to the "heat shrink" tool holders.
JRW

J Tiers
04-22-2007, 02:28 AM
Depending on the length of the cutter this is an area where 5/10th worth of clearence can translate to .003" worth of deviation at the end of the cutter, not to mention the "stepped" way of holding the tool, You wouldnt saw a collet end off on a thirty degree angle and then stick a tool in it would you, welp --- not far off from whats going on with the set screw type holder, just because the bottom of the holders screw side is getting invloved in a heavier cut doesnt mean anything but the fact that its occillating around in the holder ----------- Nice, yeah sounds really rigid...

"Oscillating around in the holder"??????????

Really? May I suggest you invest in some better allen wrenches....... you are obviously not getting the job done with yours.

If it were "oscillating around in the holder", it would be coming out next.

May I suggest gently that your statement is, well, "BS" unless you can come up with some proof.... I have for instance, never seen any gall marks on tool nor holder from this "oscillation"........

I have no clue what you mean by your 30 deg angle, and teh rest of it, but whatever floats your boat...... You go ahead and use those collets, and I'll stick with the EM holders that have proven to my satisfaction to be superior in every way.

texas_po_boy
04-22-2007, 07:38 AM
They still are subject to all the poor design flaws previously mentioned, and now one more, Because the tool is always clamped in the same way and loaded in that direction its previous mentioned deviations never get changed,
This will result in a variation in the wear of the cutters sharpness and also set up an even worse repetitive flex pattern for the cutter breaking down the road.


I dont like them damn things and im going to raise a little stink about it.


Hey Boomer, quit beating around the bush and just tell us what you think of them end mill holders.

John Stevenson
04-22-2007, 08:20 AM
Use ER series collets.
Will grip parallel no matter what size.
Will grip concentric.
Has a full 1mm or 40 thou clamping range.
Can be used as work holding as well as tool holding and yes you can get open ended holders to hold long pieces of bar.
Self extracting.

Grandpa would wet himself if he'd have had these in his shop.

.

A.K. Boomer
04-22-2007, 09:33 AM
"Oscillating around in the holder"??????????

Really? May I suggest you invest in some better allen wrenches....... you are obviously not getting the job done with yours.

If it were "oscillating around in the holder", it would be coming out next.

May I suggest gently that your statement is, well, "BS" unless you can come up with some proof.... I have for instance, never seen any gall marks on tool nor holder from this "oscillation"........

I have no clue what you mean by your 30 deg angle, and teh rest of it, but whatever floats your boat...... You go ahead and use those collets, and I'll stick with the EM holders that have proven to my satisfaction to be superior in every way.



Uhhhm, re-read what i wrote, and actually oscillation was a great word to use and has nothing to do with spinning, in fact my dictionary states ---oscillation; --- fluctuation; instability; variation, to swing or move regularly back and forth... It has nothing to do with the tool coming loose or spinning in the holder but has everything to do with it rocking back and forth at the end of the holder, if the set screw is tight enough this will not loosen the tool as the tool has flex and then gets involved with the lower part of the holder but this still means its going through all kinds of deviations to do so.

The fact is is you can have your set screw as tight as posible and it wont take up the clearance at the bottom of the tool holder, in fact the tighter you get the screw the more clearence you create, This is the high/low offset im talking about, one part of your tool is actually being held down low and the other thats the set screw side is a half inch or more above (at the screw itself) without the tool even being pressured on the bottom side of the holder, that makes for an uneven pressure "step" way of holding the tool, to some degree it is the equivelent of using a collet that has been cut off on an angle at the end, The system is archaic in design and I really cant believe exists on the final drive cutting system of a precision milling machine, This is the most critical part of the cutting process and it is not the place to "drop the ball". Its a good way of attaching your pulley drive to your mill motor shaft but should be left on that end of the mills drive system, if its on your cement mixer final drive or roto tiller please disregaurd, its an easy way of getting things done and the deviations can actually help in both the mixing process and tilling...

Its not BS bro, all it is is common sense.

lazlo
04-22-2007, 09:50 AM
Use ER series collets.
Will grip parallel no matter what size.
Will grip concentric.
Has a full 1mm or 40 thou clamping range.
Can be used as work holding as well as tool holding and yes you can get open ended holders to hold long pieces of bar.
Self extracting.

Yeah, no kidding John -- I love the ER collets, and the Americanized version: TG collets. I just wish you could buy a milling machine with an integral ER spindle, so there's not that big overhang on the conversion chucks.

A.K. Boomer
04-22-2007, 09:53 AM
Grandpa would wet himself if he'd have had these in his shop.

.


Indeed, almost perfect pressure concentration around the entire tool and all at the same hight, To me Tool holding is just as important as spindle bearings and spindle deviation as they are all connected and can mimick the same symptoms.

lazlo
04-22-2007, 09:53 AM
By the way, arguing collets versus endmills is about as fruitful as arguing politics, religion, or gun control. You're never going to change anyone's mind :)

A.K. Boomer
04-22-2007, 10:30 AM
Yeah but you could possibly keep a newbie from purchasing something he's not going to be happy with down the road, -- or not, one thing for sure, it dosent hurt to think about it... To me the only arguement against the collets side is bit walking and Iv yet to experience this, and iv also heard that on the bigger machines when crude removal of lots of material is required the set screw style holders do a good Job --- im not here to argue that as I really cant answer that with experience... but this is a "home shop machinist site" and I dont think most of us are concerned about how much material we can remove in the shortest amount of time as much as we are concerned with accuracy and finish, but now im starting to speak for myself.

BobWarfield
04-22-2007, 10:33 AM
I'm surprised nobody mentioned what I like best about end mill holders--faster toolchange.

Once having invested in a power drawbar, end mill holders are the only thing that makes sense to me. I don't want to fool around with R8 (at least they benefit from the power drawbar) or ER collets (gotta get a wrench and forget the powered drawbar!) when I've got a rack of end mill holders already tee'd up with all the tooling I might need. Grab one, pop it in, hit the drawbar button, and go. Using a collet chuck in that mill would feel like taking the QCTP back off my lathe and going to the old turret that came with it. I just couldn't do it, even if I thought performance in other respects was a little less, and I don't.

I use my ER collets for the oddball sizes that aren't tee'd up, so it's kind of a floating holder. I have an R8 collet set I've never bothered to clean the cosmolene off of. Maybe I'll think of a use someday for them, but between preferring end mill holders and having the the ER, it hasn't seemed urgent.

If they're working right, they're going to have very little runout and are very rigid. Probably my one objection to them at the moment is they're so short. Many would consider that an advantage, and I guess my real problem is that my Albrecht drill chucks are so long, and my mill head is so heavy, I hate cranking it up and down! Just need a power feed on Z I guess.

In any event, these mill holders are here to stay. Except in the very higher end (heat shrinks were mentioned!), most folks don't buy a whole cart full of ER CAT40's, they'll buy the end mill holder CAT40's. Works for them, works for me.

What works for you is good too, that's the pleasure of a hobby pursued in the comfort of your own shop where you are the boss, and one reason why they make both vanilla and chocolate.

Cheers,

BW

lazlo
04-22-2007, 10:54 AM
I'm surprised nobody mentioned what I like best about end mill holders--faster toolchange.

True, but that requires that you buy a separate endmill holder for each tool. We started off this thread by noting that the Chicom endmill holders have a lot of runout, so buying ETM or Weldon-brand endmill holders for each of your tools is going to get very expensive.


I use my ER collets for the oddball sizes that aren't tee'd up,
If they're working right, they're going to have very little runout and are very rigid.

The problem with any of the quick-change chucks, including the ER collet chucks, is that they stick out 2-3" beyond the end of the spindle, which really decreases the rigidity of the spindle.

Forrest has often warned newbies against getting conversion chucks for precisely this reason.

But I agree, a complete set of 30 taper collet endmill holders in a 30 taper spindle is a sweet setup.

J Tiers
04-22-2007, 12:44 PM
AK, your own fault..... explain bettter and no misunderstandings.

It seems however, that you are talking about the rigidity, or lack thereof, of the actual end mill.

Since the solid shank has a lot more material than the fluted end, and so the fluted end will bend lots more than the solid part, you will just have to forgive me for not getting awfully concerned about how the solid part bends away from teh "single support point".

Then also, the collet, holding "probably" with a parallel grip, over a relatively short length of the end mill, AND being made to spring, with a lot less solid material around the EM, is unlikely to be a lot more rigid. The short steep taper of the R8 is not well adapted for converting linear motion into a grip, nor for making it rigid.

If you want to discuss a morse taper collet, we'll be in a lot better shape on rigidity and grip.

I think for the stuff you are discussing, the shrink holder is your obvious solution. Better than any of the above.

However, your collets never let the EM walk, and my EM holders dont let the EM flail around loosely like yours do, so we can just keep happy using the stuff as we do.

I do, however, think you should be careful, and not give new folks the idea that EM holders are "a pathetic kludge that can't and does not work". And that collets are far superior in holding ability.

That is patently not the case, which should be intuitively obvious to the most casual observer.

Each has their points, and neither is nearly as good as a shrink holder

A.K. Boomer
04-22-2007, 05:09 PM
AK, your own fault..... explain bettter and no misunderstandings.

Im sorry, its a tough one to explain without pictures but since we all know what the difference is i thought it easily visualized and for the most part is seems no one else had trouble with it...


It seems however, that you are talking about the rigidity, or lack thereof, of the actual end mill.

Since the solid shank has a lot more material than the fluted end, and so the fluted end will bend lots more than the solid part, you will just have to forgive me for not getting awfully concerned about how the solid part bends away from teh "single support point".


It doesnt matter that the shank is solid, the more end mill that hangs out the more leverage that is against it the less rigidity, thats why we are all taught to "choke up" to the maximum depth of the endmill shank unless we need the extra length for a reason then rigidity gets sacrificed for getting the job done with lighter cuts... the trouble with the set screw style is you can choke up to maximum and its still effectively being held high on one end



Then also, the collet, holding "probably" with a parallel grip, over a relatively short length of the end mill, AND being made to spring, with a lot less solid material around the EM, is unlikely to be a lot more rigid. The short steep taper of the R8 is not well adapted for converting linear motion into a grip, nor for making it rigid.

Not well adapted, What? didnt somebody mention on hear awhile ago that the leverage ratio is close to 100 to 1,,, even at 10 to 1 look at the size of my drawbar threads VS a wimpy little set screw




However, your collets never let the EM walk, and my EM holders dont let the EM flail around loosely like yours do, so we can just keep happy using the stuff as we do.
My collets have no chance of flailing around loosely, the entire tool bit is surrounded by identical force on all sides, It is your tool holder that developes an "ovalized" deviation pattern under loads, not mine. but i agree its important to be happy with what you have


I do, however, think you should be careful, and not give new folks the idea that EM holders are "a pathetic kludge that can't and does not work". And that collets are far superior in holding ability.



I was a little rough on them but it is my way of getting the best out of people, they really do bother me when i think about them so i will try not to think about them so much because then i start getting upset all over again. [quote]

Fasttrack
04-22-2007, 05:20 PM
I made my own endmill holder and cut my own taper too. Made it as a sort of "end-mill extension" when i first got my machine. Since the purchase of 2-4-6 blocks i haven't used it since it had about .003" runout. I found that was way to much for most stuff...

J Tiers
04-22-2007, 10:16 PM
Not well adapted, What? didnt somebody mention on hear awhile ago that the leverage ratio is close to 100 to 1,,, even at 10 to 1 look at the size of my drawbar threads VS a wimpy little set screw

I don't know where those numbers could possibly come from..... They have to be crazy wrong.

Just look at the angles, and recall that there is such a thing as friction.

"wimpy little set screw" ????

On mine the recess for the allen wrench is over 1/4" on all, the set screw is obviously larger than that in diameter, and it is a flat-ended set screw with a wide grip on the end.

The thread size on the set screw and the drawbar threads are comparable for the 3/8", and on the 1/2" holder, the threads are 7/16" diameter..... larger than the drawbar.

So that "wimpy little" deal seems like a doubtful description.... of course your chicom EM holder might be anything, with screws made of that chinese peanut butter steel.

And, leverage or no, a 1/2" shank, even with a small flat in it, is gonna bend less than the part of the same shank with 2 or 4 big flutes cut into it removing huge proportions of the cross-section, mostly at the outside.

The EMs deflect in a cut. Why else would everyone universally suggest that cutting a keyway with an exact size EM is a bad idea? Because it will deflect, and the keyway may be not straight, may be slightly oversize, or may be in the wrong place by the deflection amount, with slightly angled sides.

A.K. Boomer
04-23-2007, 01:17 AM
I don't know where those numbers could possibly come from..... They have to be crazy wrong.

Just look at the angles, and recall that there is such a thing as friction.

.

XACT Rapid 5C Index Fixture - Hardinge Type - Horizontal/Vertical
Click Here for more information or to order Spindle has a taper seat in the body frame.
Rapid opening and closing of the collet on a production basis is done with the lever collet closer having a leverage ratio of 100 to 1.
A ratchet device on the front of the spindle permits rapid rotation of the spindle nose.
Index plate has a screw in each of the 24 index holes so that holes not required for a particular job can be masked.
Threaded spindle is hardened and ground 2-1/4-8TPI.

Dimensions
Horizontal base: 4" x 6"
Vertical base: 4" x 8"
Height vertically: 8"
Swing: 8" Center height: 4"
Weight: 27.5 lbs.




I tried to copy the pic also but it wouldnt take, and this is of course 5C, it is of typical design though and is getting the extra leverage from the arm pivot and collet ratio combined.

there is a big difference tightening with just a screw and a small 3" allen as compaired to tightening a massive bolt thats tightening a leverage device (like a collet) and useing a foot long spanner to do so, it gets "crazy"

The mistake your making is your not taking into account the inclined plane of the bolt threads that tighten the collet itself, this coupled with the collet taper is EXTREME,,, uhhh - but dont look for that on the set screw style holders, remember, all they have is a screw, and one that tightens the tool unevenly I might add...

J Tiers
04-23-2007, 01:35 AM
I do NOT think the leverage AT THE COLLET GRIP is 100 to 1.

The leverage referred to is almost certainly a mechanical leverage in the closer system.

If you look at the collet angles, and resolve the forces, I see no possible way in which the axial pull can be converted to a grip on the collet of 100 times greater, or anything remotely close to that.

it ends up as the axial pull essentially sliding the collet jaw up an inclined plane corresponding to the collet angle. Even with a totally frictionless system you can't get near that ratio with the sort of angles involved.

When you consider friction, it appears to become even less credible. As the grip force increases, the frictional resistance to being pulled in tighter increases also.

3" allen wrench? I use a 6" to tighten mine, and you may be sure it gets quite tight......

Angular displacement is minimal since there is a long "engagement" length which is at a fit so close that it will 'air cushion" and requires to have the EM held in for several seconds to leak down. Not exactly a loose fit that can "oscillate" all over the place.......

You are left with bending at the point the screw is.... Which is reasonably close to the end of the holder. Any shank bending is going to be far less than the spring of the weakened area where the cutting edges and flutes are.

I think your argument is not really proceeding.... the points are not clearly indicating any superiority of a collet. The holder is really quite secure, restraining the EM as well as a collet, or better.

A.K. Boomer
04-23-2007, 08:58 AM
I do NOT think the leverage AT THE COLLET GRIP is 100 to 1.

The leverage referred to is almost certainly a mechanical leverage in the closer system.

If you look at the collet angles, and resolve the forces, I see no possible way in which the axial pull can be converted to a grip on the collet of 100 times greater, or anything remotely close to that.

.


JT, you need to read what i just wrote; "The mistake your making is your not taking into account the inclined plane of the bolt threads that tighten the collet itself, this coupled with the collet taper is EXTREME"
You wrote --
the "leverage referred to is almost certainly a mechanical leverage in the closer system"


Part of it is and part of its compounded with the added leverage of the collet so then you have to include that along with the added leverage from the collet, be it an indexer or a milling spindle and along with a wrench well over twice the length of yours

You can calculate the thread pitch and the collet angle if you wish, All I know is it has allot of advantage over a system that doesnt use a multiple leverage system (like your set screw)

Xact has already done it for us in thier sales advertizment and it apears that the handle along with the collet taper is 100 to 1

I actually have three increases in leverage, the collet taper being pulled by an inclined plain thats being torqued by an extra long wrench --- dont try to put a cheater bar on your little set screw cuz youll pull threads, not the case with the massive threads on my draw bar.
as far as friction --- I dont know what kind of collets and spindle bore you have but my collets are nice and smooth and so is my spindle and they both seem to always have a film of oil on them from machining, They not only torque up much greater than what you can achieve, once they do they will do nothing but get tighter --- the length of the draw bar under extreme tension assures this --- its like a heavy duty stretch spring that sinks the collet in tighter and tighter should a bit go through lots of chatter or the like,
after the point of tightening the "friction" between the collet and the spindle is a welcomed event, it makes the tool one with the spindle unless a major upset is involved. what a beautiful system, somebody was using thier noggin.... Its light years ahead of a set screw pressing into the side of a tool bit.

JCHannum
04-23-2007, 09:53 AM
R-8 collets were designed by Bridgeport for the first Bridgeport milling machines. These machines hadd 1/2HP motors. The collet' maximum diameter is 3/4". Since then horsepower has been increased as has the diameter of end mill shanks. There are collets available with larger than 3/4" bore, but the holding area is necessarily reduced.

The solid endmill holder is designed to use the Weldon shank endmill, which has one or two flats depending on the shank diameter for the setscrews to bear against. The endmill is positively and securely held in the holder, and cannot and will not move. If plain shank endmills are used, a flat should be ground for the setscrew to bear against.

For positive rentention in a machine with a R-8 spindle, any endmill shank over 3/4" diameter must use an endmill holder, an ER collet chuck or heat shrunk tooling.

A.K. Boomer
04-23-2007, 10:11 AM
R-8 collets were designed by Bridgeport for the first Bridgeport milling machines. These machines hadd 1/2HP motors. The collet' maximum diameter is 3/4". Since then horsepower has been increased as has the diameter of end mill shanks. There are collets available with larger than 3/4" bore, but the holding area is necessarily reduced.

.



My friends cnc sharp mill is R8 and has 3 horsepower he uses it almost daily to remove lots of material with fair size bits in a professional shop, How often has he had a bit "slip" --- never, I will add once again that this is after all "the home shop machinist" and not many of us have an 8 ton chigago sitting in our basement and are worried about how much material we can remove in the shortest amount of time with a tool bit thats running eccentric to the spindle bore, we -- or at least I am concerned with accuracy and finish --- My R8 taper is massive overkill for my 1 1/2 hp motor, and i like it that way.

lazlo
04-23-2007, 11:12 AM
R-8 collets were designed by Bridgeport for the first Bridgeport milling machines. These machines hadd 1/2HP motors.

JC,

The R8 collet was designed for the J-Head, which shipped with a 1 HP motor.

The 1/2HP M-Heads do not come with an R8 spindle. They were available in No. 2 Morse, B & S No. 7 or a B-3 taper,
all with a 1/2" maximum collet size.

Robert

JCHannum
04-23-2007, 12:35 PM
OK, 1HP. But the R-8 collet, while being common, is used only in smaller, low powered machines of the Bridgeport class. It never had the gripping power to be adopted by larger machines.

It is good up to about the 1/2" shank, but my comments about the Weldon shank holders are still valid. It is not to be considered as some second rate method of tool holding.

lazlo
04-23-2007, 12:39 PM
OK, 1HP. But the R-8 collet, while being common, is used only in smaller, low powered machines of the Bridgeport class.

It is good up to about the 1/2" shank, but my comments about the Weldon shank holders are still valid. It is not to be considered as some second rate method of tool holding.

Sure, agree completely JC -- although I think you meant to say that R8 collets are good up to 3/4", right? I have a 7/8" R8 collet (and it's Western),
but I've never bought a 7/8" shank tool :) For 1" roughers, I use an ETM endmill holder.

This is when I meant earlier when I said that I use collets mostly, but I use endmill holder for taking big roughing cuts. I think "must" is a little strong -- there's a lot of personal preference/judgment involved, but I agree with the overall sentiment:

From JC:
"For positive rentention in a machine with a R-8 spindle, any endmill shank over 3/4" diameter must use an endmill holder, an ER collet chuck or heat shrunk tooling."

J Tiers
04-23-2007, 01:34 PM
AK, I read it, but I don't agree with it being important in the comparison.......

You are not considering the whole mechanical system. Much of that leverage gets "used up" later.

The leverage number is really "sort of unimportant" until you get right to the point where you convert axial to radial motion and force. obviously more pull should mean more grip, but the conversion is not direct.

The important issue is the direct radial grip of teh collet that establishes the friction holding the tool. Everything else is just helping to get that.

Some differences that are important.........

Holder:

1) The (large) set screw DIRECTLY holds the shank, there is not any sliding of another part on an angle needed.

2) the set screw "clamping" is not necessary to hold the tool against rotation, NOR is it directly necessary to hold it against movement. What it does is to provide an "adjustable interference fit" that can be taken away or replaced.
Tighter may be better, but even if it is just "pretty tight", the shank is still held. The most extreme torque on the setscrew is not a lot better than a reasonable torque, the reasonable torque is already holding solidly. Once the setscrew is "in the way", the tool can't turn, cock, or move significantly.

3) Friction is not a factor in the retention of the tool. The locating factor for rotation and axial movement is the set screw against a recessed flat. "friction" is not directly involved except partly for the axial movement. The shank is positively located in a way not dependent on friction.

4) the total length of the tool restrained in the holder is several diameters. That severely limits the leverage that can be applied to "pry open" the holder and allow movement.

Collet:

A) The collet holds 100% by friction ONLY against rotation and axial movement.

B) the drawbar INDIRECTLY clamps. In order to clamp, the axial drawbar force is converted to a radial force by sliding on the angled collet slope. Friction on that slope increases directly with radial pressure, and forms a limiting factor on teh maximum pressure, and thus on the effectiveness of holding. The axial pull is not efficiently converted to a frictional grip, and you need a LOT of pull to ensure a usable frictional grip.

C) The length of collet holding the tool is typically only slightly over one diameter for the larger tools (where it matters more). There is considerably more leverage available to "pry open" the collet and allow movement.

D) For an MT collet, the above is less true than for an R8 type. The MT overcomes several of the issues more effectively, although the grip is still friction ONLY and still is 'converted" by a friction-limited process from axial to radial.

E) Then also, the long drawbar has elasticity, and itself limits the ultimate amount of axial pull that can be applied. This may not always be a "real" limit but it is always true.


Ultimately, what comes out is that the the holding ability of a holder is not affected by the torquing of the setscrew in the same direct way that the drawbar torque affects the collet grip.

So the wrench length is far less important for the setscrew on the holder vs the drawbar.

Overall, it is a question of a frictional grip that can slip versus a positive interference, where metal would have to be moved and distorted to turn or significantly pull or push the tool.

BadDog
04-23-2007, 01:55 PM
Considering how common/popular EM holders are, and how vigorously they are defended and recommended by experienced machinist, I figure they must be working pretty well. Likewise, collets also work well (within limits) as proven by years of use.

For my needs, I basically run nothing over 1/2 rougher except in Aluminum (I simply haven't seen the need to pay for a big EM yet) where I run 2 flute 1" EMs for roughing. So I use collets rather than spend what it would cost for good EM holders. Like 5C collets, I've heard too much bad about ChiCom EM holders with respect to fit and run out; some things just aren't worth the "risk" to me.

However, my reluctance to go to EM holders (in spite of dire warnings of slipping EMs if I run them in collets) is not only based on cost/benefit, but rather in my perception of there effect on rigidity unrelated to the EM mounting itself. Those same folks who warn me of slipping collets are also quick to warn about minimizing spindle extension, particularly when hogging. So I should retract the spindle and set the lock, raise the knee as needed for the cut, AND hang the EM another 1.5-2" below where it would be with a collet???

Extra cost, yet more tooling to store/clean, AND rigidity combined with my relatively modest needs seem to make R8 collets right for me. Plus, I can go from my 1/2" rougher, to 1/2" finisher, to 1/2 shank drill chuck, all by only loosening (and whacking) the draw bar. Of course, to get that drill chuck in there, it takes about 5 minutes of cursing and cranking the knee down...

JCHannum
04-23-2007, 02:16 PM
From JC:
"For positive rentention in a machine with a R-8 spindle, any endmill shank over 3/4" diameter must use an endmill holder, an ER collet chuck or heat shrunk tooling."

Take a look at the bore of that 7/8" collet. It does not permit full insertion of a long shank, which can leave a large extension.

The gripping area of an R-8 is only in the area of the taper, and, with most manufacturers, the bore is relieved above this area to permit the collet to spring. What is an adequate grip length for a 3/8" end mill is inadequate for a 7/8" end mill.

A.K. Boomer
04-23-2007, 08:54 PM
Indeed --- I have a 7/8" r8 and the wall just above the taper is scary thin, I really wouldnt trust it as much, I dont even own a 7/8" cutter anyhow, I do however use it for workholding ocasionally when i turn my mill into a lathe...

J Tiers
04-23-2007, 10:35 PM
I've heard too much bad about ChiCom EM holders with respect to fit and run out; some things just aren't worth the "risk" to me.

That's why Bison is better. I recently got the Bison part that Victor shipped me free to replace the horrible (and wrong) chicom EM holder that they originally shipped.

Same deal as with the others. Push in EM and hold to let air out..... NO perceptible shake, close fit that even traps air, concentric, what's not to like?

OK the price...... Bison at $25 to $35, or Chicom at $8 (and worth every bit of it... but no more).

Life's too short to buy that type of crap.

lazlo
04-23-2007, 10:41 PM
That's why Bison is better. Bison at $25 to $35.

JT, is that price for the Bison endmill holder at Victor Machine Exchange?
I'm searching through their web page right now, and they only seem to
have the Chicom holders?

J Tiers
04-23-2007, 11:01 PM
Well, I got a wrong type from them, that was also chicom.

I emailed them about the bad one (it had the wrong drawbar thread, subject of a previous posting here) , and mentioned that the Bison they USED to carry had been much better.

They admitted that, mentioned that Bison was upping the price, but I don't know if they will go back to Bison. If not, I will go elsewhere, I ain't paying $30 and getting a badly made chicom part. I'd rather pay $45 if that's what it takes to get a decent Bison part.

I got the Bison as fulfillment on what they were supposed to have shipped me.

cybor462
04-25-2007, 11:43 PM
I got the Enco EM holder set, comes in a blow mold red plastic case. Quality is extremely good. Sized from 1/4 - 1 1/4

I find I use them all the time now. Never use collets anymore. Say what you will but my cuts are always right on the money now. Collets must have been slipping. Yeah I know they were imports too.

cybor462
04-27-2007, 11:48 PM
Forgot to mention the set was a MHC set. Anyone have used the MHC brand. What do you think about them?

JCHannum
04-28-2007, 07:00 AM
MHC = Most Happy Chinaman?

cybor462
04-29-2007, 10:35 AM
I thought it meant...Magnificant Hovercraft Corporation.. I guess I was way off;)

rusty steel
05-04-2007, 07:27 AM
I have noticed that nobody has mentioned the Clarkson Autolock Collet system for holding Endmills/Slotdrills etc. Perhaps this English system is not very common in U.S. I used this system at work and also have this system in my own workshop .
Perhaps the most useful setup is the chuck which accepts four Imperial collets which will handle EMs up to 3/4" and four Metric collets which will handle EMs up to 20mm. The EMs/SDs. are threaded and screw into the collet and they also have a center hole in the threaded end which locates with a centre in the chuck. I am no expert but I think this system would satisfy most folk. Clarkson also make a smaller and a larger system as well. Check it out.
Rusty

JCHannum
05-04-2007, 07:44 AM
The Clarkson system does hold the endmill positively. It is not too popular over here.

I have had a couple, but never explored the cost or availability of the replacement endmills with threaded shanks.

BobWarfield
05-04-2007, 01:26 PM
So far nothing here but a lot of religious sturm und drang about what people prefer and what MIGHT be a problem with runout or potentially the efficacy of the grip the toolholder has on the tool.

Who has actually measured their runout? Saw one quote of 0.003". I measured my cheezy Chicom EM holders and saw values ranging from 0.0005" to 0.001" as measured by my Intrarapid tenths DTI. I have one used Bridgeport holder and it has 0.0075" runout.

How many have measured their spindle runout to see what that contributes? Where are the measurements on these ER collet systems, and by the way, what does the expensive non-Chicom ER collet system cost to purchase and how does that compare to say Bison EM holders?

How many are actually seeing these weird chatter effects the EM holders supposedly have or have conversely spun an endmill in a collet? I have, though it was a twist drill in all fairness, and I have read several accounts on the PM boards of people spinning cutters in collets. How may have a mill stout enough that there aren't other deflection and slop factors overwhelming this little tempest in a teapot? And who has "welded on" a Weldon shank? Come on, really?

I stick to my guns on this--the big deal is how fast I can change a tool and EM holders have it all over the collet chucks for that given my powered drawbar. My runout is fine with EM holders bought from Shars, CDCO, or 800Watt--I don't remember which one sold me mine, but those are the Chicom dealers I buy from. If I want less runout, I'll drag out my ER collet chuck or be looking into a couple of Bison or used "insert good brand here" holders on eBay. I'm cutting to 0.001" all day long with this rig, and if I need to get closer very often I'm going to have to look at revamping a lot more than just my EM holders.

I say again, the pros are not regularly buying carts full of collet chucks for their CAT40 tooling. They're buying EM holders because they're cheaper and work well enough for a lot of applications. Or maybe they like the extra runout, I dunno.

If you want to use collets, that's great. I might too if I had no powered drawbar. But I think you're kidding yourself that EM holders are so inferior to your collets. Strike that, I KNOW you are in so far as my mill and the runouts I'm getting would indicate.

And now we return you to your regularly scheduled Jihad slugfest on EM holders versus collets. Go to your respective corners, come out swinging, and keep it a clean fight!

Cheers,

BW

lazlo
05-04-2007, 07:05 PM
Who has actually measured their runout? Saw one quote of 0.003".

If you read through the thread, several folks, including myself. The original poster switched from an endmill holder to collets and got a big improvement in runout, which many of us have experienced first-hand with Chicom endmill holders:


I tried a new endmill holder yesterday for the first time.I got about .003 tir.

...and JTiers:


That's why Bison is better. I recently got the Bison part that Victor shipped me free to replace the horrible (and wrong) chicom EM holder that they originally shipped.

...and me. I just measured a brand-new 3/4" endmill holder I purchased from Enco, and it's got a runout of ~ 4 thou.

The Enco Chicom collets I have are much better (although some have gotten really bad ones). My 3/4" ETM endmill holder is around 4 tenths, and the brand-new Hardinge R8 collets I scored on Ebay are around 4 tenths.

In the same fashion, there were threads here and on PM on how bad the runout was on the Chicom ER chucks sold by J&L, 800Watt, etc:

ER Collet Chuck Sale (http://www.practicalmachinist.com/ubb/ultimatebb.php/topic/30/1764.html)
As far as the awesome deal I got from J&L goes. It says, "made in China", which I don't like. Earlier this afternoon, I popped the chuck into the mill and indicated the ER taper. Then I mounted a 1/4" endmill and indicated it. In both cases I measured over .001" TIR. This is disappointing and the set is going to be returned. Which ever set I end up with will probably last me for 20 years and I want to love it (not doubt it) every time I use it. Why is it I must relearn "you get what you pay for" over and over again?

Not surprisingly, you get what you pay for, whether it's a collet or an endmill holder.

Carld
05-04-2007, 09:26 PM
I was a job shop machinist for the last 10+ years of my work. When we used large endmills and didn't want the endmill to suck out of the holder we used set screw holders. If the endmill is not a snug fit in the holder it is defective or the endmill shank is undersize. We had a collet holder that had a pin that went into the notch in the endmill to hold it in. They didn't spin or suck out in that collet holder.

I have seen an endmill suck out of an R-8 collet even when the drawbar was very tight. It just depends on the speed, feed and depth of cut as to how the endmill will react. Under the right conditions and endmill can and will suck out of an R-8 collet.

An endmill holder has contact on the shank for the full length of the shank that is in the holder. An R-8 collet only has contact for a short length of the shank and is free to woble in the collet if to much load is applied to the cut. That is what causes the endmill to suck out of the collet in my opinion. I believe the feed against the endmill causes it to tilt back out of the cut and the cutting action of the endmill causes it to suck down into the slot or keyway being cut. I have only had endmills suck out when using high feed. If the collet was tight and not worn and the feed was ok I rarely had trouble. Worn collets will have a reverse barrel to them in the bore. That is, they are big at the opening right in the center and big at the top. That usually comes from misuse or abuse.

In my shop at home I use R-8 collets and they are near new and not abused and hold close tolerance. I have two or three set screw endmill holders and have used them a few times. I do what works for me for the job I have to do and I suggest you do the same.

BobWarfield
05-04-2007, 10:55 PM
Lazlo, I don't see those runout numbers being quoted. I can't find but three posts that bothered to actually measure and quote runout. The original poster says 0.003", and he is understandably unhappy. Evan says he made a holder and got 0.001", and I said I measured my cheap holders and got 0.0005 to 0.001". I did not see your quote stating what the runout was for your end mill holders versus your collet chuck. Everyone else is giving subjective opinion as far as I can see. They are either happy with their mill holders, happy with their collets, or giving "logical" arguments why one must be better than the others.

BTW, despite all the talk of offset grinding, I would be amazed if a properly made EM holder required offset grinding to achieve 0.001". As several have said, the ones that are made right have almost a "vacuum lock" on the endmill shank. There is not going to be that much deflection from the set screw. Certainly not 0.001". If there was that much play in the bore, you wouldn't get that vacuum lock effect when you try to insert the endmill.

As you have pointed out from your PM thread example, ER collet runout can stink too, and you've spent a heck of a lot more money on it when that happens. It's got to cost more to build an ER chuck to a level of runout than it does a set screw holder. So unless you're spending the big bucks, the EM holder is likely more accurate for that reason alone.

My other point to add to that is Asian mill spindle runout may also stink, so it may not even matter that much how accurate your tool holder is until you start getting to 0.003" runout with your tool holding system. In practice the actual cost to keep an interesting variety of cutters ready to go in end mill holders is not very high, and the convenience factor is large. For example, I have 2 0.500" holders (my most common size), one with a rouger, one with a finisher, a 3/8", a 3/4" indexable end mill, a 1/4", and a 1" that I have a Yuasa boring head in. It's really handy to have all those cutters tee'd up and ready to go on a moment's notice with the powered drawbar. I also have 2 Albrecht chucks and a Jacobs. Someday soon I will have a tapping head. I can make 95% of what I make without ever having to mess with a collet chuck or change the cutter out of the R8 shank holder its in. It takes me about 10-15 seconds to change tools in the mill. That's really nice!

Maybe I just got lucky on my runout, but I remain unrepentant about the idea that the EM holders are a better deal than the collets, and particularly so if you have some means of rapidly changing tools. I will submit that even if you want to buy say Bison quality holders, you still come out ahead with EM holders rather than ER collets simply because you can keep the cutters ready to go.

If you like one versus the other, that's great, go with it, but I can't see running down the other guy's approach if you haven't got any numbers to back up your claims.

Best,

BW

J Tiers
05-05-2007, 01:14 AM
1) I just checked the new Bison 1/2" shank EM holder I got.

The runout is in the tenths on the shank of the endmill sticking out of the holder. I have NOT checked to see how much of that is in the mill spindle.......But I'll bet that the low reading is NOT the result of two bad runouts that just happen to cancel..

2) I HAVE had the EM shift in a collet, sucking out and giving a lot deeper cut than I wanted. Spoiled the part, and I was NOT happy.

I also am completely unrepentant about preferring the EM holders. CarlD and BobWarfield have confirmed much of what I said elsewhere.

I don't think it is a "religious issue" but a matter of demonstrable facts.

The supposed errors and "wimpy setscrews" etc may exist with the chicom stuff, made to sell cheap to hobby type folks who may never notice or care.

But it is not true of the Bison or other industrial type products that are made to work.

lazlo
05-05-2007, 10:42 AM
The supposed errors and "wimpy setscrews" etc may exist with the chicom stuff, made to sell cheap to hobby type folks who may never notice or care.

But it is not true of the Bison or other industrial type products that are made to work.

That is exactly my point JT -- a quality (Bison, ETM, Weldon-brand) Endmill Holder can be just as accurate as a collet, and holds better. But at the same price range/quality level, an Endmill Holder is more expensive than a collet, especially at the larger diameter sizes.

With the cheap Chicom's, my experience has been (and Paulx's response as well) that you have a lot better chance getting an accurate Chicom collet than a Chicom Endmill Holder, because for good accuracy in an EM holder, you need to grind the hole eccentric to account for the tool offset from the shank clearance when the setscrew pushes the tool to the side of the hole.

That's why I use collets on my Burke up to 3/4", and use 3/4" and 1" ETM endmill holders for roughing.

By the way, you say "supposed errors" -- but didn't you say that you bought a Chicom Endmill Holder and had Victor Machinery replace it with a Bison because the Chicom endmill holder was so bad? :D

A.K. Boomer
05-05-2007, 11:17 AM
I really believe that thier are inconsistencies with the set screw type --- I dont care if you have to wait for the "air to escape" when inserting a tool, the fact is is there is clearance there, there has to be, its aprox. 5/10ths to be able to insert the tool and remove it, then you go and tighten a screw on one side, THERE IS NO CONTACT ON THE SET SCREW SIDE except for the set screw, Yes the tool still gets supported down low on the holder (under deflection) while in a cut BUT ITS NOT SUPPORTED UNDER PRESSURE, This is unacceptible, it is for me anyways, I dont like the concept for the end drive of a milling machine, I would not own a mill if thats all they came with but im kinda picky that way... in its defence I feel it important to add that its a wonderfull way of transmitting power to my cement mixer and roto-tiller so i believe has a place in the machinery world and dont think it a problem on the step pulley side of my mill, just keep it away from my side loaded tool bits...

J Tiers
05-05-2007, 11:25 AM
By the way, you say "supposed errors" -- but didn't you say that you bought a Chicom Endmill Holder and had Victor Machinery replace it with a Bison because the Chicom endmill holder was so bad? :D

Nope......

I bought an endmill holder that had no statement of origin, at the same general price that the previous Bison holders had been from same vendor. I expected to get the same maker, Bison, as I had before. Same vendor, same price, same part....NOT.

What I got was one that apparently was chicom, and which had a completely wrong drawbar thread, not 3/8-16. The thread also looked like heck.

I have no idea whether it is good or bad for runout. I suppose I could, for argument's sake, check it. But I can't pull it in solidly, it has some huge non-standard metric thread, so I might not get a good reading.

I could also check the runout on the Bison holder as far as the actual hole.... I'll bet there is either NO off-center grind, OR it is so small as to be lost in the noise.

The hole is so close to size that if there is oil on the shank, it holds up as it slides in. Not much room for movement or off-setting.

But I amwith ya.... I am an EM holder bigot, and I don't care what the others think.


BTW:

The setscrew on teh chicom holder is at least as big as the one on the Bison..... I have NO idea if AK has ever even SEEN an EM holder, because all the ones I ever saw have large setscrews.

J Tiers
05-05-2007, 11:36 AM
Well, I went and measured....

Lazlo may have a point, and it ain't on top of his head.

The Bison holder is ground such that the high spot is directly opposite the setscrew.

The off-center is about a half tenth, or not quite one thou TIR. Not a lot, but obviously enough, since it works.

In any case, I still like EM holders. And I like Bison better than any of the cheapo asian stuff "made to sell to hobby types".

I been spoiled by good tools..... :D

Carld
05-05-2007, 01:28 PM
Boomer, it's obvious you have never owned or operated a Cinncinnata horizonal mill. They come with endmill holders for each size endmill shank. There are collet holders for them but it is not the common accessory and they are heavy duty. I guess they have used endmill holders since the eighteen hundreds and they have worked fine making parts and machines since then and are still being used. Many of the machines we consider great were machined with the endmill holders in production. As a mater of fact most professional machinists prefer the holders because of the durability and rigid retension of the endmill. I would bet that all production work before the use of CNC would use the endmill holders and not collets and even the CNC machines use heavy duty collets. The reason is that the endmill never moves in an endmill holder untill it is worn out and manually removed. I have used them for years and do not aggree with your reasoning at all. Now, if you buy cheap endmill holders that are bored oversize or have runout then that is another matter.

I understand that it's your personal opinion that the collets are better but in fact they are not if you are taking heavy cuts. It takes a special production grade collet system to hold up under hard use. On the other hand, when we are working at home we are not pushing our machines like we would in production or if we were concerned with the time to do the job.