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Tundra Twin Track
06-15-2019, 12:30 AM
Was side milling some flame cut 1" plate unknown grade but drilled fine with a HSS drill bit.Was running the 7/8" HSS ENDMILL at 400 rpm at 4" per minute removing 1/8" material did not go well,have used this setup dozens of times.
Tryed the 3/4" Carbide at 1500 rpm no good flutes chipped.
Had lots of coolant ,first time trying this carbide both Endmills were sharpened at a accrediated tooling shop.https://i1371.photobucket.com/albums/ag292/tundratwintrack/image_zpsszwaswth.jpg (https://s1371.photobucket.com/user/tundratwintrack/media/image_zpsszwaswth.jpg.html)

RB211
06-15-2019, 01:00 AM
Took out carbide as well? Hmm, something that hardened incredibly from the heat...

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Tundra Twin Track
06-15-2019, 01:09 AM
Took out carbide as well? Hmm, something that hardened incredibly from the heat...

Sent from my SM-G950U1 using Tapatalk

The Endmills were ice cold was using excessive coolant,a regular HSS drill bit would bite right in where I destroyed the Endmills,I even checked that I wasn't in reverse lol!

RB211
06-15-2019, 01:14 AM
The Endmills were ice cold was using excessive coolant,a regular HSS drill bit would bite right in where I destroyed the Endmills,I even checked that I wasn't in reverse lol!Stupid question for you, but is the workpiece solidly clamped down near the cut, or can the workpiece flex? I've destroyed endmills from that.

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Tundra Twin Track
06-15-2019, 01:23 AM
Stupid question for you, but is the workpiece solidly clamped down near the cut, or can the workpiece flex? I've destroyed endmills from that.

Sent from my SM-G950U1 using Tapatalk

No it was solid ,Mill is real sturdy can't figure out how a drill bit can go in so easy yet wrecked Endmills even tryed slower feed rate with no success.

754
06-15-2019, 01:41 AM
I bet the drill was not going thru the flame cut part. Try annealing it.

plunger
06-15-2019, 01:58 AM
I think maybe your milling machine is not rigid enough.:p Is it possible the drill just gets through the surface and into soft steel where as the end mill is dealing in extended lengths of hardened case steel from the flame cut. Maybe pull out the angle grinder and prep or use a tungston carbide rose cutter with choice selected blunt inserts to get rid of the outer skin.

JRouche
06-15-2019, 04:25 AM
Thread: Destroyed some End Mills?

WoW. What is nice is I am not the only one that has cooked a cutter. For me it is all about learning. Otherwise, what is the point I slowed down my rpm quite a bit and I was happy with the shavings and finish.... JR

JoeLee
06-15-2019, 07:08 AM
Flame cut edges end up with like a case hardened surface or glaze. Take a grinder to the edges first and get below the hard layer first and you should be fine.
I uses a 36 grit fabric disc. Drilling is different, you can drill through it all day with the same bit and not hurt it. Once the tip of the drill breaks through you home free.

JL..............

A.K. Boomer
06-15-2019, 07:18 AM
That sucks must have been some high carbon stuff and like everyone is saying got heat treated with the cutting torch,

Iv never seen a threaded endmill before that's very unusual...

JoeLee
06-15-2019, 07:23 AM
I have a few of those threaded shank end mills. I wasn't crazy about buying them, but I got a deal. They can be put in a collet with no issues.
Not my best end mills.

JL...........

A.K. Boomer
06-15-2019, 07:45 AM
what is the purpose of that?

JoeLee
06-15-2019, 07:53 AM
I have no clue. DoAll is the only brand that I've ever seen with shanks like this. They must have had some special machine or holder for them.
What I'd like to know is how do you get them out (un-screwed) from the holder after they tighten themselves up?? Pipe wrench ??

JL..............

wierdscience
06-15-2019, 08:06 AM
Couple possibilites,T-1 steel plate has a tendency to harden on cut edges,also if the plate was actually plasma or laser cut insted of OA cut,then that can also harden the cut edges.
I had a job come it at work a few years ago that involved opening up some holes in some steel connection plates that were laser cut.The cut edge was hard enough to isntantly dull HSS and dull carbide almost as quick.The only solution was to plasma cut the holes bigger.

cameron
06-15-2019, 08:11 AM
That's a Clarkson type cutter, I believe. No experience with them, but they were more common in the past, I think, probably more so in the UK than in NA.

At least, they are not likely to pull themselves out of the holder and into the work, as happens too often to me.

JoeLee
06-15-2019, 08:29 AM
You're right Clarkson, made in England. I think the bunch that I bought came from Canada.
So, where is the tool holder for these screw-in end mills and how do you remove them once they've tightened up? There are no flats to grab with an open-end wrench or anyting.

JL....

J Tiers
06-15-2019, 08:34 AM
Specifically, the flame heats only a small area, as you can see from the oxide colors on the surface if the material. So the edge is heated well above hardening temp, but the cold remainder of the piece nearly instantly cools the hot part. Just like any flame hardening process, only the kerf material was actually melted/burned away.

Often does not happen with thin stuff, but thicker material has the mass to quench the hot edge.

That chipping and mangling of the edge is what I have gotten when I hit hard material.

Black Forest
06-15-2019, 09:22 AM
You're right Clarkson, made in England. I think the bunch that I bought came from Canada.
So, where is the tool holder for these screw-in end mills and how do you remove them once they've tightened up? There are no flats to grab with an open-end wrench or anyting.

JL....

I have a Clarkson endmill holder. The bottom of the collet is threaded. The tightening of the collet and subsequent clamping stops the endmill from turning and tightening excessively. Mine is a MT5 holder. It came with my horizontal mill when I bought it.

Fasttrack
06-15-2019, 09:36 AM
I have no clue. DoAll is the only brand that I've ever seen with shanks like this. They must have had some special machine or holder for them.
What I'd like to know is how do you get them out (un-screwed) from the holder after they tighten themselves up?? Pipe wrench ??

JL..............

They're made for Clarkson Autolock Chucks. It's still a collect like arrangement, i.e. the pressure of the collet keeps the end mill from turning but the threads ensure that the endmill can't slide up or be pulled out of the collet like they can with an ordinary setup.

Example: https://www.ebay.com/i/221833335288?chn=ps

Edit: BF beat me to it!

Toolguy
06-15-2019, 09:54 AM
The best way to deal with flame cut edges is to grind past the hard part on one end, then start the end mill in the soft metal with a conventional cut. This way the cutting edge is coming in behind the flame cut part from the soft side, rather than trying to chop through the rough, hardened part.

plunger
06-15-2019, 10:06 AM
That sucks must have been some high carbon stuff and like everyone is saying got heat treated with the cutting torch,

Iv never seen a threaded endmill before that's very unusual...

Most of my end mills look like this . If they dont I cant use them.

A.K. Boomer
06-15-2019, 11:39 AM
So you obviously have some kind of strange way of holding them, if you have a pic then show us?

Tundra Twin Track
06-15-2019, 12:23 PM
Thanks for the replys guys , was really shocked when test drilling directly on cut surface that Endmills got damaged,it was OA cut.Always something to learn lol!

garyhlucas
06-15-2019, 12:40 PM
This is where waterjet shines. I used to get some parts made that looked like a tuning fork and the only way to cut them without bad warping was using a waterjet. No hardening so post machining was a piece of cake.

JoeLee
06-15-2019, 01:12 PM
So you obviously have some kind of strange way of holding them, if you have a pic then show us?

I've never seen the collet but I'm guessing it's a split collet that's threaded up inside. So when it slips during machining it can only turn and slide so far. When you loosen your collet the internal threaded part expands just enough to unscrew the end mill.

JL.....

plunger
06-15-2019, 02:18 PM
I've never seen the collet but I'm guessing it's a split collet that's threaded up inside. So when it slips during machining it can only turn and slide so far. When you loosen your collet the internal threaded part expands just enough to unscrew the end mill.

JL.....

It has a loose collet that screws on the end mill . This then goes through the nut .The collet has two ears at the end of it and there is a sharp point in the collet body that fits into the center point of the back of the end mill. They work real well..I have two sets of autolock clarckson holders. The smaller has four collets and goes from about 4mm to 20mm My bigger one has two collets and the shank is 25mm . Theres no slipping or pulling out with this system.
The end mills cost more though.

LKeithR
06-15-2019, 02:22 PM
Even when milling mild steel breaking through the HAZ (Heat Affected Zone) of a flame cut part can be a
real problem; with higher carbon steels it becomes even more of an issue. If you plan to machine a flame
cut part it's always a good idea to leave yourself some extra material so you can get under the HAZ with
a milling cutter or lathe tool.

I'm pretty sure that in the case of both end mills the RPM was way too high. When faced with situations
like that the best approach is often to slow the machine way down, take a deeper cut and plow your way
through. If I were faced with that situation I'd slow the RPM down to maybe only 100-150 and use a good
roughing end mill to take a cut at least 3/16" to 1/4" deep. And this is definitely one time where you want
to use conventional millling--you want the cutter to be breaking through the HAZ from the backside, not
trying to cut into it. With a rouging mill--even in tough situations like this--you can use a pretty good DOC
and feed rate; just keep the RPM down low.

In this case machine rigidity won't me an issue; Dales Varnamo is probably one of the heaviest mills that
anyone on this forum owns...

Tundra Twin Track
06-15-2019, 08:16 PM
Even when milling mild steel breaking through the HAZ (Heat Affected Zone) of a flame cut part can be a
real problem; with higher carbon steels it becomes even more of an issue. If you plan to machine a flame
cut part it's always a good idea to leave yourself some extra material so you can get under the HAZ with
a milling cutter or lathe tool.

I'm pretty sure that in the case of both end mills the RPM was way too high. When faced with situations
like that the best approach is often to slow the machine way down, take a deeper cut and plow your way
through. If I were faced with that situation I'd slow the RPM down to maybe only 100-150 and use a good
roughing end mill to take a cut at least 3/16" to 1/4" deep. And this is definitely one time where you want
to use conventional millling--you want the cutter to be breaking through the HAZ from the backside, not
trying to cut into it. With a rouging mill--even in tough situations like this--you can use a pretty good DOC
and feed rate; just keep the RPM down low.

In this case machine rigidity won't me an issue; Dales Varnamo is probably one of the heaviest mills that
anyone on this forum owns...

Thanks Keith donít have any roughing endmills but might try a new piece of metal,this last one cost me some money!

wyop
06-15-2019, 10:22 PM
I see this happen with students in a school machine shop all the time.

Machine shop/welding shop businesses donate materials to the school shop, and the alloy spec, heat treating spec, etc. is lost in the donation process. Student(s) put the material into a lathe or mill, make an optimistic assumption, and ruin inserts or HSS tooling trying to machine the mystery metal.

Something I really emphasize to students is this: when you don't know, for certain, what alloy the steel is, make the worst possible assumption(s) as to hardness and possible cutting speeds. You can always increase the speeds and feeds after you see how easily it is cutting - but reducing speeds and feeds after you've realized that the material is seriously hard or has a low cutting speed requirement will usually require a fresh edge be put on the tool. Cutting tools are ruined most quickly by high RPM's, especially when one is putting significant chip loads on an end mill. End mills can be ruined by putting too much feed on them (ie, asking for too high a chip load per tooth), but this tends to happen more slowly than RPM-based damage.

Lower-carbon "plain carbon steel" are those such as 1018, 1020, etc. Lots of "cold rolled steel," especially plate steel, might be 1018. 1018 and other low-carbon steels cannot harden appreciably in the typical heat-to-red-hot/quench cycle You can flame cut them and then machine the flame-cut edge just fine at 65 to 120 SFM (surface feet per minute) cutting speed with HSS.

We can do a quick mill RPM range estimate for the range of SFM using the (SFM * 4) / diameter (in inches) formula:

65 * 4 / 0.875 = 297 RPM at the low end,

120 * 4 / 0.875 = 548 RPM on the high end.

So 400 RPM wasn't a wildly high RPM - if we know, with certainty, that the steel workpiece is low-carbon, plain carbon steel.

But now let's add a bit more carbon. Let's say the steel is 0.45% carbon, or we have 1045 carbon steel. Or let's say that it is a alloy carbon steel, like 4140 or something similar. Now when we flame cut it, the thermal mass of the rest of the plate can quench the red-hot flame cut edge, and we could end up with significant hardness at the flame-cut edge, or possibly just behind the edge. Or let's say that we're just talking of hardened steel, with a Rockwell C hardness in the 40's. Then the cutting speed could be reduced as low as 25 SFM for cutting hardened medium-carbon steel with a HSS cutter, and maybe as high as 50 to 60 SPM if the steel has additives to added machinability. This yields RPM ranges like so:

25 * 4 / 0.875 = 114 RPM.
50 * 4 / 0.875 = 228 RPM.

Now we can see that 400 is significantly high RPM for the material at hand.

A common rule of thumb for using carbide tooling is to triple or quadruple the SFM. OK, so let's say that for the steel with hardness at the edge, we quadruple the 25 SPM to 100 SFM. What's the RPM range?

100 * 4 / 0.875 = 457 RPM
200 * 4 / 0.875 = 914 RPM.

1500 RPM is significantly over the desired RPM targets here.

One of the things I keep in my shop for trying to spot these situations is a beat-up hand file. I strike the flame-cut edge with a "bastard" 10" file, and I see what happens. If the file "skates" over the edge, then I know the steel on the edge is hardened. If the file bites and will cut steel off the edge, OK then, it is probably soft enough that I don't have to start with a very low SFM - I could start with a SFM of 50 to 60 SFM and see how things go. If the file skates off the steel sample, then I'll start with assumptions like a SFM of 25 for HSS.

ncjeeper
06-15-2019, 10:37 PM
Been there done that. I usually opt for the shaper to do its thing and then take it over to the mill for final dimensions.

754
06-15-2019, 11:30 PM
Clarkson, select the proper collet, small holder is 1/4 3/8, 1/2 , and i think 5/8.
Large Autolock holder has 1 inch and 1 1/4 inch collets.
Install collet into chuck, and thread nose piece mostly on. With fingers thread in the endmill. With fingers turn in nose till it bottoms, then back off about a 1/16 turn. Run in endmill with fingers till it bottoms , the tighten nose with special wrench till it bottoms.
This tensions the collet gripping cutter tightly, you are ready to go.

A.K. Boomer
06-16-2019, 12:19 AM
It has a loose collet that screws on the end mill . This then goes through the nut .The collet has two ears at the end of it and there is a sharp point in the collet body that fits into the center point of the back of the end mill. They work real well..I have two sets of autolock clarckson holders. The smaller has four collets and goes from about 4mm to 20mm My bigger one has two collets and the shank is 25mm . Theres no slipping or pulling out with this system.
The end mills cost more though.

My endmills work real well also, I have never had one slip save one time when i spaced out tightening it --- R-8 taper system

I cannot imagine the extra expense like this for something not really needed, and putting threads on a carbide one? that's as hard as making the cutter side, all for an "expendable" No Thanks... but thanks for explaining it all and all the other pieces it takes to make the dang thing work...

Peter S
06-16-2019, 01:03 AM
My endmills work real well also, I have never had one slip save one time when i spaced out tightening it --- R-8 taper system

I cannot imagine the extra expense like this for something not really needed, and putting threads on a carbide one? that's as hard as making the cutter side, all for an "expendable" No Thanks... but thanks for explaining it all and all the other pieces it takes to make the dang thing work...

The Autolock system is great, don't knock it. The cutters cannot move. If you ask for an HSS milling cutter in NZ, it will be threaded, even though Clarkson isn't around any more and I suppose most people use ER or R8 collets.

R8 does not hold cutters that well, in heavy milling the cutter can pull out (maybe only 1mm, but that might be critical). You haven't been trying hard enough :). From memory it only happens with large cutters, say 3/4".

Other (British) chuck makers using the same system/threads were Larcher and Qualcut. I have a Qualcut on my BP, I like it. Qualcut, like Clarkson, made cutters. Larcher was a very good quality chuck also. I am guessing anyone making these chucks now is from Asia.

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=5499&d=1560660761

Felsted_Skiver
06-16-2019, 04:24 AM
The Autolock system is great, don't knock it. The cutters cannot move. If you ask for an HSS milling cutter in NZ, it will be threaded, even though Clarkson isn't around any more and I suppose most people use ER or R8 collets.

R8 does not hold cutters that well, in heavy milling the cutter can pull out (maybe only 1mm, but that might be critical). You haven't been trying hard enough :). From memory it only happens with large cutters, say 3/4".

Other (British) chuck makers using the same system/threads were Larcher and Qualcut. I have a Qualcut on my BP, I like it. Qualcut, like Clarkson, made cutters. Larcher was a very good quality chuck also. I am guessing anyone making these chucks now is from Asia.

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=5499&d=1560660761

I agree with Peter. Clarkson invented the Autolock system in the mid twentieth century to overcome the problem of cutters pulling out of collets. Inexperienced operators and looser tolerances on shanks and collets were common. The 20tpi thread is a few thou under shank diameter so threaded cutters can be used in plain collets but not vice verse - plain shanked cutters donít work in Autolock chucks.

Clarkson licensed the system to other manufacturers so there are other makes on the market and they can still be bought new. This does make them more common in the UK than US where the Weldon flat predominates.

The Autolock system works really well when used correctly and the extra cost of threading a HSS shank is marginal compared with tightening tolerances on shank diameters. Itís a different story with solid carbide of course, but these days we take for granted the much tighter tolerances that can be achieved on shank diameters in good CNC grinders compared with the machines of 70 years ago.

Mal

JoeLee
06-16-2019, 08:36 AM
I agree with Peter. Clarkson invented the Autolock system in the mid twentieth century to overcome the problem of cutters pulling out of collets. Inexperienced operators and looser tolerances on shanks and collets were common. The 20tpi thread is a few thou under shank diameter so threaded cutters can be used in plain collets but not vice verse - plain shanked cutters don’t work in Autolock chucks.

Clarkson licensed the system to other manufacturers so there are other makes on the market and they can still be bought new. This does make them more common in the UK than US where the Weldon flat predominates.

The Autolock system works really well when used correctly and the extra cost of threading a HSS shank is marginal compared with tightening tolerances on shank diameters. It’s a different story with solid carbide of course, but these days we take for granted the much tighter tolerances that can be achieved on shank diameters in good CNC grinders compared with the machines of 70 years ago.

MalSeeing the diagram verifies how I imagined the collet had to be designed once I started thinking about it. Interesting system, however I'm guessing that the choice of cutters is very limited.

With the Weldon shank design it's easy to grind a small flat on any end mill if so needed, but threading the end ??? not so.

JL................

Mcgyver
06-16-2019, 08:56 AM
Thanks for the replys guys , was really shocked when test drilling directly on cut surface that Endmills got damaged,it was OA cut.

flame cut and plasma can leave a mess of a tough irregular surface, but I'm wondering if its the endmills. Whats the pedigree? It looks like they have been reground (edit, I see you said that they are) and if so, and if whoever did it didn't put enough clearance on them, it might explain it.

old mart
06-16-2019, 09:18 AM
I had a bad experience trying to drill some unknown plate, it work hardened, maybe it was an armour plate or had manganese in the alloy.
I use those threaded hss and cobalt end mills and slot drills in a NOS Osborn Titanic, works just the same as Autolock, but runs true, unlike the well worn Clarkson I used to use.
The small size collets are 1/4", 3/8", 1/2" and 5/8" for imperial cutters and 6mm, 10mm, 12mm and 16mm for metric cutters. There is a larger version for 1" and 1 1/4" collets.

wyop
06-16-2019, 11:30 AM
With the Weldon shank design it's easy to grind a small flat on any end mill if so needed, but threading the end ??? not so.



Well, it's probably easier than the shrink-fit way of holding end mills in a holder, and shrink-fit is probably what you'll see more and more of in the future as more CNC production goes to HSM.

https://www.maritool.com/faq/shrink-fit

https://www.techniksusa.com/metal/pthsf.htm

Rich Carlstedt
06-16-2019, 11:47 AM
Pulling endmills when you use a collet is pretty common if you have a heavy cut or are working with stainless.
Carbide endmills seem the be even worse because they are so hard.
TIP:
If you are on a important part (z Depth critical) do this:

After mounting the endmill, put a dab of Red or White nail polish at the juncture of the collet and the cutter.
Nail Polish is extremely hard and dries very fast.
Now if the endmill pulls, it will break the painted dab and you will immediately see a clear shiny line at the juncture, even if it is a few thousandths and with spindle running ! - This will save you from a screw up
Rich

754
06-16-2019, 12:01 PM
They never pull out with a Clarkson, i have had endmills slip held by other means.
I suspect Clarkson Autoloc runs truer than some Weldon shanks.
I have 1.5 and 2 inch endmills with threaded shanks and many woodruff cutters.

A.K. Boomer
06-16-2019, 12:03 PM
They never pull out with a Clarkson, i have had endmills slip held by other means.
I suspect Clarkson Autoloc runs truer than some Weldon shanks.
I have 1.5 and 2 inch endmills with threaded shanks and many woodruff cutters.

Well there's the diff, biggest I mill with is a 3/4" and iv only got one and a half ponies lol R-8 is just fine with me.

The Metal Butcher
06-16-2019, 12:07 PM
Makes ya wish shapers and planers will still around, eh?

LKeithR
06-16-2019, 12:21 PM
...Thanks Keith donít have any roughing endmills...

Then you need to get yourself some! You will be pleasantly surprised. A 1" diam. roughing mill taking a
full width cut 1" deep and chugging along at 300-400 RPM is a very satisfying sight. On your machine you
would likely be able to run even larger endmills but it won't hurt you to start small. ;) Set the cutter up
for a full width cut about an inch deep and then crank the feed up till the machine tells you it's in the "zone".
Experiment from there till you've reached the limit. I'd be willing to bet that your mill would push a 1-1/2"
endmill through a 1-1/4" deep cut pretty easily...

754
06-16-2019, 12:39 PM
My mill is only 2 hp. My Autolock is only to 5/8 shank. Then I use r8 to weldon holders or 3/4 to R8 collet.
I do a lot of aluminum, but did enough steel with a 1.5 inch roughing endmill, that I had sent it out for sharpening.
Depends on the job, if I was doing say wheel adaptors then the bigger mills come into use for counter boring and stuff like that.
Have lots of tooling by the mill use what fits the job.. sometimes it may be 1.25 dia endmill with 4 inches of flutes just to get down inside stuff.......whatever works.

JRouche
06-16-2019, 10:21 PM
My mill is only 2 hp. My Autolock is only to 5/8 shank. Then I use r8 to weldon holders or 3/4 to R8 collet.

Im solly. Really, only 2hp. Well heck, if is a problem for you fix that.

In my opinion that 2hp rig will cut with a 2" rougher. Been there done it. I also am retired and dont expect much from my machines.

My 2hp BP uses a 2" rougher like its "B". Haa. I just go with my own feeds and speeds. And yes, all dry :) JR

754
06-17-2019, 12:19 AM
I was sorta replying to the guy that said his biggest end mill was 3/4, but he only had 1.5 hp.

Tundra Twin Track
06-17-2019, 01:09 AM
My Mill 5 HP was original 7-1/2 HP,I tryed a 1-1/2" Endmill at 100 rpm with some limited success but mystery metal seems brutally hard so abandoned it and used known peice to machine the part I needed.
I will try some of those roughing end mills at some point,thanks for all the schooling guys!

A.K. Boomer
06-17-2019, 09:28 AM
I was sorta replying to the guy that said his biggest end mill was 3/4, but he only had 1.5 hp.

That was me, but like he stated I don't really push my mill either,,, I whoop up on other machinery like my car and mt. bike but whoopin up on the mill just ain't fun...

I will tell you something im acutely aware of - I tighten my drawbar accordingly --- a little 1/8" endmill barely even gets a cinch up... it's got the same leverage ratio's of the threads and the taper working together to squeeze down on such a small surface area with a tiny radius of torque transfer, barely takes anything,,, I save my drawbar threads for when I need them and larger endmills get increasing cinch up... that's just common mechanical engineering sense...

never had one slip or "walk"