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Big T
03-02-2009, 03:53 PM
I have the HSS cutoff blades with the top cutting edge beveled. My ? is if the highest part of the bevel be set dead on center? I have tried .030 thou above center, slightly above center, on center, and slightly below, and still have grabbing. It feels like the work piece is going to pull the toolholder underneath it at times.

12x36 import lathe parting a 1" mild steel shaft. Tried rpm from 180-550, auto feed from the slowest up to about the fifth slowest. Turned the tool in by hand also. Any ideas? Thanks

Davek0974
03-02-2009, 04:06 PM
I had one of those blades too, about 1" x 1/8", the only way i could get anywhere with it was to grind some rake on the top. It was still grabbing though.

Shortly after a good spank-up with it, it bought a tipped parting blade and have never gone back.

Really is the best tool i've bought yet.

Dave

Doozer
03-02-2009, 04:13 PM
I second the idea of getting a carbide tipped part off blade. The ones with adjustable stick-out are super nice. One thing I found, get the .125 wide blade. I had a .093 wide blade, and it kept snapping out the insert. The .125 wide blade is way more rigid. I bought a Newcomer brand, and was very disappointed with it. Then I tried an Iscar blade, I think I have had the same insert in it well over a year.
--Doozer

Mark Hockett
03-02-2009, 04:13 PM
One problem might be the fact that you are trying to part mild steel. Mild steel is not free machining steel, mild steel is for welding projects. You need to get some free machining steel like 12L14 or 1215, try parting it and let us know how that works for you.

ckelloug
03-02-2009, 04:15 PM
As I recently got flamed for here, make sure you are as close to the chuck as possible aka a couple of parting blade widths away from the chuck if you can get that close. I've also observed that some of the cheaper import parting blades are too soft to part anything of significance. I've had better luck with a brazed carbide parting tool but you still have to be as close to the chuck as possible with the work as well centered as possible (using the 4 jaw) if you want any sort of success.

Carld
03-02-2009, 04:18 PM
Your best bet is with the top of the blade flat and a very sharp edge. Any back rake or chip breaker in the top will cause it to dig in and cause damage. You need the top at center line 0 back rake and as square to the work as posible. You don't have to have much clearance on the front of the blade but you do have to have side clearance. HSS parting blades need a slow speed and lots of oil. If they dull it's crash city coming up. The major issue with the HSS blades is they are the same width from tip the the rear and that has no side clearance and is rubbing most the time. Any side movement can bind the blade.

Parting can be an accident looking for a place to happen. It is best done with a straight line holder because the downward tool deflection can't stand any side movement of the blade.

The first time I used a carbide insert parting blade I never looked back and while I still have the HSS holders I refuse to use them.

Parting is no longer such sweet sorrow, it is now happiness and delight.

Big T
03-02-2009, 04:20 PM
One problem might be the fact that you are trying to part mild steel. Mild steel is not free machining steel, mild steel is for welding projects. You need to get some free machining steel like 12L14 or 1215, try parting it and let us know how that works for you.

I have cut the heads off some 3/4" grade 8 bolts, and had a nice coil of chips coming off. I am not sure what metal grade 8 bolts are made from, but I had no problems parting them.

I have looked at the Iscar blade type, but I don't have a QCTP, just a turret type tool holder.

Carld
03-02-2009, 04:24 PM
Big T, you can use the insert type in a turret type tool post. I did that for a long time untill I got my QCTP.

Go back and read my post above your last post.

bruce.heron
03-02-2009, 04:25 PM
It sounds as though there is insufficient rigidity in your cut-off tool, tool holder, tool post, and/or the work itself. Providing a positive rake reduces the cutting forces, hence the deflection. Try to make the entire set-up as rigid as possible while parting off.

Big T
03-02-2009, 04:30 PM
Big T, you can use the insert type in a turret type tool post. I did that for a long time untill I got my QCTP.

Go back and read my post above your last post.

You are right, I was thinking about the blade style with the insert on either end.

I part tight to the chuck, and use lots of oil. Tried water soluable oil solution as well, spraying right in the groove.
Turning at 550 rpm the finish is smoother, just a little more tense!!

tattoomike68
03-02-2009, 04:35 PM
I used to fight parting till I just took the time to grind a 1/2 HSS square bit and grind most the right side off for .600" long or so and leave an 1/8" of the left edge then I could also add more clearance to the sides so it wont bind.

I will see if I can video what a small parting tool I make looks like.

BRB

tattoomike68
03-02-2009, 04:49 PM
Here is a video of one made from 1/4" HSS, its better then them blades that bind up. Use a bigger peice for bigger work is all.

http://www.youtube.com/v/lSmGH6TF2M4

Lynn Standish
03-02-2009, 06:11 PM
Maybe I missed it, but I didn't see any discussion of speeds. I turn my lathe down to the lowest (60 rpm, regardless of workpiece diameter) and advance the tool with my left hand while keeping the the tip flooded in oil with my right. Don't stop and let the tool rub and harden the work. If you need to pause the operation for some reason, back the tool out a little so it doesn't contact the work.

I use a HSS tool that is 1/8 x 5/8 or so, with a wider top, and little relief under the nose of the tool.

I had pure misery before going to low speed.

franco
03-02-2009, 08:25 PM
I found most of my parting problems disappeared on both an old 9 x 18 conehead with a bit of wear, and a 13 x 40 import, when I switched to a sprung tool holder which uses tapered 3/32 (at the top) HSS blades. Works well on mild steel with a small back rake and set right on center height.

franco

Carld
03-02-2009, 09:12 PM
Big T, the double end insert blade is what I am talking about. They mount in a holder that mounts in any turret tool post or QCTP holder. The QCTP kit comes with a parting tool holder for the HSS blades and I have blades for it but don't use it.

tattoomike68
03-02-2009, 10:55 PM
[QUOTE=Carld]Big T, the double end insert blade is what I am talking about. They mount in a holder that mounts in any turret tool post or QCTP holder. QUOTE]


Thats one of the types I like. The term for the insert is a dog bone they work well for parting through welds on stuff like drivelines. If it will stand up to welds, HSS is a joke with welds.

In repair type job shops where I worked we did not part with HSS very much unless you are doing plastic. When I worked repairing screw machines they parted at full blast RPM but also had 2 big manifolds with high pressure and low pressure oil and a gang of outputs for all the hoses you want. A 100 PSI oil pipe was common on the parting tool. HSS was used alot but not always.

John Stevenson
03-03-2009, 04:52 AM
Contrary to what all the books say it helps if you can use the tail centre for support, even on study lathes, light lathes gain far more.

Everyone tells you that it's a no no as it jams up as it cuts thru but if you try it you will find out that's rubbish unless you are parting off 12" diameter chunks that weigh #300

What happens is as you cut thru it stops rotating and tilts away from the tool very slightly.

I do one job, some gear blanks that have to be cut off at 10mm wide out of 1-1/2" steel with a 5/8" hole.
I start off with about 12" sticking out the chuck, support with a centre and part the first off, follow up with the centre and do the next.

Two reasons for being this far out, I can get about 10 cut before having to move the work and using oil for cutting it's stop the chuck flinging it.

So 12 " out and using a centre ? two no no's but it works.

.

airsmith282
03-03-2009, 06:38 AM
perosnaly ihavent had any parting problems i use 115 rpm for mild steel and stainless steel and for aluin 210 and brass and bronze i like to take it up to 550 gets a bit wild on the flakes but works rather well for me ,,
i have 3/32" x 1/2" x 4 parting tool and i set it about 3 thou below center, seems to work for me thati just have a knack for parting,, when i got my first lathe my parting tool also did all my parting and turnning operations for the first month for sure was different ill tell you but tought me alot at the same time now i got all kinds of tooling and still want more and i got alot bigger lathe to then when i first started out anyhow
use lots of cutting fluid as well and take it slow on the feed to and should be fine

Your Old Dog
03-03-2009, 07:44 AM
I use old style HS cutter but grind a flat spot on top. then I stab the cutter into the face of my grinding wheel till I have a slight concave face, I tilt the blade up ever so slightly while doing this. When its done right, the bits cutting edge feels sticky or grabs on my thumb nail.

Then I chuck the work up close and often times use the tailstock till it's almost cut through.

I don't worry much about speed but do make sure the parting bit ain't lolly gagging around in the cut. It's either cutting or pulled back quickly to keep it from rubbing. I have equal luck feeding by machine or hand. I have a hard time with gummy steel even if all sources of vibration are addressed.

.RC.
03-03-2009, 07:50 AM
I donlt think anyone has mentioned the most important thing when parting off with HSS tools...Lubricant...You must use some sort of cutting oil when parting off with HSS blades.

quadrod
03-03-2009, 07:56 AM
when parting sometimes i will get chatter at first and just have to bone up and plunge the tool in and make it cut, then it goes pretty as you please.

Evan
03-03-2009, 08:56 AM
Contrary to what all the books say it helps if you can use the tail centre for support, even on study lathes, light lathes gain far more.


Absolutely true.

The secret to parting easily is to sneak out in the middle of the night.

uh, never mind.


Use the thinnest tool possible, a steak knife...

Hmm, this isn't going well.


Really though, I use a variety of parting tools, all shop made. The easiest is to grind a tool from HSS bit stock. Thin is the key. For depths up to about 1/2 inch the blade need be no thicker than about .050", best ground from a 5/16 or 3/8 stick of HSS. Flat on top, relieved under the nose at about 15 degrees and ever so slightly relieved on each side under the top flat, maybe a degree or two.

For carbide insert tooling I make them like this:

http://metalshopborealis.ca/pics/yact1.jpg

http://metalshopborealis.ca/pics/yact2.jpg

http://metalshopborealis.ca/pics/yact3.jpg

DICKEYBIRD
03-03-2009, 09:42 AM
Evan, where did you get your Handy-Flux and your silver-brazing sheet material? I NEED some of that stuff.

I did a search on Handy-Flux and found the Lucas Milhaupt website....man, what a resource! https://www.lucasmilhaupt.com/htmdocs/brazing_support/everything_about_brazing/what_brazing_about.html

Evan
03-03-2009, 10:40 AM
My wife sells it. At least as long as she is employed she does. Seven more mills closing in BC as of this am news.

see here: http://lsind.bc.ca

airbrush1
03-03-2009, 11:19 AM
I haven't seen any one mention it but I usually try and remember to lock my carriage down.

Jpfalt
03-03-2009, 11:31 AM
Most of the time the problem is with backlash in the cross slide.

We have a 14 x 40 import lathe and when new it would part off like a dream.

As time went by, the tool started grabbing and it got progressively worse. It just so happened that as the backlash in the cross slide screw got worse, the grabbing got worse. Changing the tool grind had little effect and I got to the point that to part off I would sidestep the tool about .030 in a series of cuts so that the cut was always wider than the chip coming off.

About a month ago I went through and adjusted backlash and gib tension and the smooth one-shot parting is back.

Carld
03-03-2009, 11:39 AM
Yes, locking the carriage does help.

I used the tailstock with a bullnose center once. When the parting tool broke through the part wedged and broke the parting tool and damaged the part and the remaining stock.

I started with some new stock and didn't use the tailstock center and parted it off just fine. If I had something out to far I would use a steady or follower rest rather than a center.

Evan
03-03-2009, 11:43 AM
If the part is big enough that it will wedge when free use the center until you begin to hear the change in pitch that means the tool is nearly through. Then back off the center to give it some room. If you don't know what I mean by "change in pitch" then listen closely the next time you part something.

Liger Zero
03-03-2009, 12:35 PM
Ok the jist of this thread is "I am not an idiot, other people have trouble with parting off too."

I'm trying to part off 3/8" aluminum, machine does NOT like parting anything other than plastic.

keelan
03-03-2009, 01:10 PM
I've read about using the parting tool upside down, with the lathe in reverse, or using one on the opposite side of the work with the lathe running normally. Are there any HSMs that do it this way? It seems to be quite common in turret lathe work, and most turret lathes seem to have tool posts on both sides of the work to accommodate it.

Norman Atkinson
03-03-2009, 01:39 PM
Parting Off Problems? Not I.
Other people maybe , but there we go, 'Laughing And Scratching'

Norm

tattoomike68
03-03-2009, 08:01 PM
I've read about using the parting tool upside down, with the lathe in reverse, or using one on the opposite side of the work with the lathe running normally. Are there any HSMs that do it this way? It seems to be quite common in turret lathe work, and most turret lathes seem to have tool posts on both sides of the work to accommodate it.

That does work best, 6 spindle screw machines have on up and one down if doing 1 part per 3 indexes. the one up will screw up first 90% of the time.

I like to part with a backside toolpost.

franco
03-03-2009, 08:44 PM
keelan,

You asked: "Are there any HSMs that do it this way?"

Yes, I made a cross slide mounted rear toolpost to allow the parting tool to be used upside down on an old, fairly light lathe and it certainly was an improvement on mounting the parting tool holder on the compound; there were still occasional problems though. I don't think I have had to use it since I got a sprung tool holder, which I just mount normally on the compound.

franco

motomoron
03-04-2009, 12:21 AM
I made a big honkin' base to take the place of the compound on my Smithy Granite 13x24 to do some heavy-ish work. It greatly improved finish quality, which got me to thinking...

Recently I was ordering some AXA tool holders from CDCO Tools ($8ea!) and noticed that a whole tool post w/ 5 holders was like $80. Easy choice.

I leave the compound on the front w/ my Phase II post, and the big block thing on the back w/ the new copy of a copy of an Aloris post on the back w/ a cutoff blade upside down.

It saves so much time, and it chews through anything leaving a nice finish. I recommend it highly.

http://img.photobucket.com/albums/v341/motomoron/DSC05748.jpg

http://img.photobucket.com/albums/v341/motomoron/DSC05750.jpg

http://img.photobucket.com/albums/v341/motomoron/DSC05751.jpg

Big T
03-04-2009, 08:57 PM
OK Here is what I did.

Set blade height just above center, so under load and some deflection should run on center.

Tuned up the lathe as in tightening gibs a bit for the wear.
Ground the blade with a concave face, got her good and sharp.
Slowed down to 180RPM, and kept steady pressure on the feed screw.
Used lot's of cutting fluid.
Cut quite well, just about fun!!!
Eventually I will up buy a dog bone style.

Thanks for all the help

garyphansen
03-04-2009, 10:07 PM
Motomoron: I was thinking about doing that a couple of years ago. Everyone here said it was a bad idea because the forces would make the tool holder fly up if it was not locked down tight. They were wrong, but they talked me out of it. I recently did some turning with the lathe running in reverse and the tool mounted upside down in front of the work piece, and it worked fine. (it was the only way to do what I needed to do) By the way a threaded chuck can not unscrew if you are using a live center. May be I will mount a Phase II tool post on the back side just as you did. Gary P. Hansen

GKman
03-06-2009, 06:21 PM
Despite doing about 14 of the above mentioned right I was still having trouble. I could see that the quick change toolpost flex down so I wedged a jack directly under the cutoff tool holder. GREAT improvement and S-O-O-O simple.

http://img.photobucket.com/albums/v494/gkman/P3060077.jpg

Evan
03-06-2009, 07:52 PM
That tool holder is just dangling around in space without that jack. Can't you move it back onto solid ground more than that?

JCHannum
03-06-2009, 08:29 PM
That is a standard BXA series QC toolpost, and standard setup. I use it all the time without the jack when I don't use a thinner cutter in an auxilarry holder that has even more overhang. I rarely have a problem.

Use RPM and infeed at about 1/2 what you would use for turning. Use power infeed, this removes effects of backlash. Do tune your lathe up and keep things snug.

I think a lot of the problems with cutting off are that being aggressive is better than nibbling at it. Get a cut on and keep a nice curl coming off and things will progress nicely. It is non-intuitive, but when you hear chatter, increase your infeed. I drip high sulfur cutting oil on steel and WD-40 on aluminum.

I use a center on longer pieces, but back off slightly when near the end. You can even stop the lathe and saw the last 1/4" of diameter with a hacksaw.

BadDog
03-06-2009, 08:51 PM
My experience is exactly as Jim describes. At first I was far too timid, but a friend of mine prevailed upon me to push harder, and things got much better. I now routinely part with power feed and it's been ages since I had a chatter or other problem (well, not one related specifically to parting anyway).

Likewise I've never had a problem using my Aloris clones as designed. And I've used them with HSS bits ground for parting (only small), commercial HSS blades, and carbide insert blades. They all respond the same, but to varying degrees.

I will say that you need to go considerably slower than you might think. I also lock the compound and the saddle as well as generally keeping my cross slide relatively snug. And also, make sure the blade is perfectly square (normal) to axis of rotation.

Evan
03-06-2009, 08:53 PM
That is a standard BXA series QC toolpost, and standard setup.

Apparently it's a setup with shortcomings.

clint
03-06-2009, 10:17 PM
I had the same problem with HSS parting tools, as posted before it can/is a accident waiting to happen. I was pulling my hair out, I purchased a Manchester tool holder off Ebay that came with 9 inserts (this was used, inserts new) for around $30, it was 5/8" so I had it milled down to just under .5" to fit my Aloris AXA tool holder, I would never go back to HSS, I use carbide for pretty much everything now.

I would scrounge ebay looking for a parting tool holder, you can always modify it to fit your tool holder, before you purchase look at cost/availability of inserts, I have never used them, but have been interested in the dogbone type inserts as they are plentiful, and cheap on ebay.

Clint

JCHannum
03-06-2009, 10:48 PM
The Aloris QC toolpost is almost an industry standard. I believe Aloris first made them in the 50's and are still in production today. They are in wide use, in thousands of shops. They have been widely copied by Dorian, Armstrong and more recently the imports. Dorian also sold many under house brands.

Such widespread acceptance and long life in a market that is as demanding as machine tools is evidence of an excellent product and design. Aloris is another term that approaches being generic and is commonly used to describe all tools of this type, much as servo is used to describe that type of power feed.

I have played around with a few of the various carbide inserted systems, but find that HSS works just as well, and better in most cases. I rarely venture into exotic alloys, just steel, aluminum and the various brass/bronze alloys.

GKman
03-07-2009, 12:15 AM
That tool holder is just dangling around in space without that jack. Can't you move it back onto solid ground more than that?

No Evan. Can you see the compound cranked all of the way back?

As for the rest, I'm delighted that so may of you can part off unobtainium nitride at 4,000 ft per minute, winding the feed like a air-raid siren, blindfolded but I seem to have been born with a black cloud over my head that the little jack pictured does a pretty good job counteracting.

tattoomike68
03-07-2009, 12:35 AM
Despite doing about 14 of the above mentioned right I was still having trouble. I could see that the quick change toolpost flex down so I wedged a jack directly under the cutoff tool holder. GREAT improvement and S-O-O-O simple.

http://img.photobucket.com/albums/v494/gkman/P3060077.jpg

You could reel that in a half mile. Evan is right, get that topslide over the meat of the machine.

J Tiers
03-07-2009, 01:02 AM
The center deal works fine as long as the part is not heavy enough to fall down and jam the parting tool into the end of the rotating stock.....

If the part has a hole in the end, I prefer to use a piece of rod in the hole, but that doesn't offer support, just "flop prevention"....

The deal about "if you hear chatter, feed harder" works, so long as you don't get too free about it.... "harder" has it's limits, and it will work fine until you get too aggressive and have a dandy crash.

The big deals for me are to have the shortest possible parting blade (the width to "stickout" ratio is important), to have the blade as close to the headstock as possible, and to have the blade dead parallel to the crossfeed.

I am another one who likes parting blades ground from HSS blanks.... they are stiffer.


You could reel that in a half mile. Evan is right, get that topslide over the meat of the machine.

I think that is overblown..... if you look at it, the center of the two supports, the jack and the toolpost, is pretty much right over the topslide pivot...... hard to do better than that.

it would be possible to get it closer to the end of the topslide, moving the jack, but it doesn't look THAT bad as-is. And moving it "in" like that would actually put the pressure more eccentric vs the topslide pivot.

I might argue for getting the cutter more in-line with the topslide, but the jack has to rest on something. Maybe I'd move the jack closer to the cutting end of the toolholder.

BadDog
03-07-2009, 01:21 AM
The Aloris QC toolpost is almost an industry standard. I believe Aloris first made them in the 50's and are still in production today. They are in wide use, in thousands of shops. They have been widely copied by Dorian, Armstrong and more recently the imports. Dorian also sold many under house brands.

And if anyone has a issues with the lowly Aloris (joking), take a look at the much vaunted KDK! That thing has a big long bar of a holder with the parting tool hanging some 2" off the side in the middling (200?) series. WAY worse than the Aloris style. Support and more rigid is always a good thing, but there is nothing I've seen to complain about in the AXA or CXA series that I've used (or for that matter the KDK that I used on a Mori).

The Fixer
03-07-2009, 10:50 AM
Rigidity of tooling is the #1 requirement for either carbide or HSS. that lst pic just shows the classic mistake of people having problems parting. Feeds and speeds are also crucial to successful parting, in that order.
Knurling is also another task that has the same requirement for rigidity
jmho
al

JCHannum
03-07-2009, 10:57 AM
No Evan. Can you see the compound cranked all of the way back?

As for the rest, I'm delighted that so may of you can part off unobtainium nitride at 4,000 ft per minute, winding the feed like a air-raid siren, blindfolded but I seem to have been born with a black cloud over my head that the little jack pictured does a pretty good job counteracting.

I have no problems with your set up. The jack is a good idea, and will help to stiffen things. Different machines will perform differently, and different methods are sometimes needed. In general, it it best to have the topslide pretty much forward. Backing off to provide room for the jack is not a problem as the force is then moved to the jack.

My response was toward Evan's comments on the Aloris toolpost. It is a good system, probably one of the more rigid available and quite capable of handling the task.

I qualified my advice to the materials mentioned, and spoke in general terms. The subjects of parting and threading come up frequently and often have complex solutions suggested, "stand on left foot and tug right ear lobe" or to make or buy some complex or expensive doo-dad. These might work for some, but I feel they do more of a disservice to the inexperienced than help. The real solution is to go back to the basics that have proved successful for the last century or so and apply them and practice to improve your skills.

The basics of parting are a solid set up, the tool properly ground and presented to the work piece and the proper feeds & speeds.

Evan
03-07-2009, 11:40 AM
My response was toward Evan's comments on the Aloris toolpost.

Strange, I made no comment on the Aloris tool post, only the setup. And you try to complain that I am putting words in your mouth.

Evan
03-07-2009, 12:24 PM
I think that is overblown..... if you look at it, the center of the two supports, the jack and the toolpost, is pretty much right over the topslide pivot...... hard to do better than that.


Put your glasses on Jerry. While the jack is better than nothing a chunk of solid metal is much better than the jack. Also, it is very important that the tool holder be actually resting on the surface that supports it, not a piece of swarf that causes even the slightest gap.

In these two picture are two rings that were parted from used aluminum hub grinding wheels. They are at the maximum capacity of my South Bend to handle. I used a parting tool the same as shown earlier but with a slight negative rake as it gives better control on large diameters since it won't dig in. The negative rake makes the tool move away from the work if it is overloaded but does take more power and a shallower depth of cut.

The top ring was trepanned to remove the remaining abrasive from the aluminum hub and the bottom ring was parted about 3/8" inch deep to do the same. No chatter or other problems presented themselves. The tool is shop made as is the tool holder and there was no magic involved, only a solid setup and a correctly sharpened and applied cutter.

http://ixian.ca/pics6/parting1.jpg

http://ixian.ca/pics6/parting2.jpg

Ian B
03-07-2009, 12:27 PM
Here's how I solved all my parting off problems:

http://smg.photobucket.com/albums/1003/IanBartlett/?action=view&current=Assembled.jpg

http://smg.photobucket.com/albums/1003/IanBartlett/?action=view&current=FrontView.jpg

http://smg.photobucket.com/albums/1003/IanBartlett/?action=view&current=Dismantled.jpg

The block fits inside the tool slot on a standard Dickson T3 toolholder. The front 2 screws clamp down on the blade, the back two hold the block in place.

Power feed at the depth/rev recommended by the manufacturers (5 thou/rev I think), lots of flood coolant.

Works for me...

Ian

JCHannum
03-07-2009, 01:05 PM
Strange, I made no comment on the Aloris tool post, only the setup. And you try to complain that I am putting words in your mouth.

Well, in post 38, you said; "That tool holder is just dangling around in space without that jack. Can't you move it back onto solid ground more than that?", and in post 41, you said; "Apparently it's a setup with shortcomings."

Both comments I took to be somewhat disparaging of the Aloris toolpost, particularly the first. The set up is proper and solid and well thought out. I see no swarf or anything else that would lead me to believe that it is less than the good solid set up that is used in tens of thousands of shops.

JCHannum
03-07-2009, 01:49 PM
Here are a couple of photos of a parting operation. Unknown steel out of the scrap bin, Aloris BXA wedge toolpost and chicom cutoff toolholder. The 1/8" HSS blade is of unknown provenance but I have been using it for several years now.

The first photo is kind of hard to get, but it gives a fairly good picture of the curl you should be looking for. This is the "sweet spot" of parting;

http://i320.photobucket.com/albums/nn351/jchannum/P1060571.jpg

The second is a long shot of the set up, with the toolholder "dangling around in space";

http://i320.photobucket.com/albums/nn351/jchannum/P1060569.jpg

Evan
03-07-2009, 01:49 PM
Both comments I took to be somewhat disparaging of the Aloris toolpost, particularly the first

Strange interpretation. I suspect you are alone in that.

Also, if you look closely it looks like the main block has been jacked up off the compound slightly just behind the shadow of the tool holder.

I also seem to recall John S. showing a setup where he eliminated the compound entirely in favor of a much more rigid block fastened directly to the cross slide. I also use that setup from time to time. Anything that can be done to remove flex will improve the operation.

JCHannum
03-07-2009, 01:54 PM
Strange interpretation. I suspect you are alone in that.

Also, if you look closely it looks like the main block has been jacked up off the compound slightly just behind the shadow of the tool holder.

Whatever. I do believe the gap you are seeing is between the T-nut and the base of the toolpost though. At least, that is the only gap I can see.

Evan
03-07-2009, 02:08 PM
Since you bring up the Aloris tool holder I will point out the shortcoming that it imposes on the setup. It is characteristic of all tool holders of that style. There is a basic concept in machine design that is predictive of the rigidity of a machine. It is the size of the loop that connects the support of the work to the support of the tool. The smaller this loop is the more rigid the machine will be given other factors are the same.

In your image I have depicted the loop in yellow. The red portions illustrate the reduction in the size of the loop that could be obtained by using a turret toolpost such as mine instead of a quick change. It amounts to nearly a third reduction in the total loop width which is a very significant difference since that represents the relevant lever arm over which the cutting forces act

http://ixian.ca/pics6/partingloop.jpg.

Peter.
03-07-2009, 02:34 PM
Since the parting tool is set at spindle centre-height why not mill a parting-tool holder on the back of the aloris post. It's not like it's used for anything.

JCHannum
03-07-2009, 03:27 PM
Since you bring up the Aloris tool holder I will point out the shortcoming that it imposes on the setup. It is characteristic of all tool holders of that style. There is a basic concept in machine design that is predictive of the rigidity of a machine. It is the size of the loop that connects the support of the work to the support of the tool. The smaller this loop is the more rigid the machine will be given other factors are the same.

In your image I have depicted the loop in yellow. The red portions illustrate the reduction in the size of the loop that could be obtained by using a turret toolpost such as mine instead of a quick change. It amounts to nearly a third reduction in the total loop width which is a very significant difference since that represents the relevant lever arm over which the cutting forces act

http://ixian.ca/pics6/partingloop.jpg.

Interesting, but relatively meaningless as the photo is at an angle to the axis of the lathe. The "loop" is actually somewhat smaller than depicted as a result. It would also appear the major portion of the "loop" is comprised of the headstock and spindle, leading me to think the toolpost is not the weak sister in that set up.

There are more rigid setups possible, of course. One must strike a balance between what might be the best and what is the most workable in a shop environment. If one needs to spend an inordinate time between operations setting and resetting the machine for the optimum, he will not get much accomplished.

The Aloris tool system might not be the most rigid set up for any given operation. But it is as good as any for most. Mine sits pretty much in the pictured location day after day and I swap preset tools in and out as needed. Any inconvenience caused by a real or imagined lack of rigidity is more than offset by the convenience, accuracy and speed it affords.

J Tiers
03-07-2009, 05:09 PM
Put your glasses on Jerry. While the jack is better than nothing a chunk of solid metal is much better than the jack. Also, it is very important that the tool holder be actually resting on the surface that supports it, not a piece of swarf that causes even the slightest gap.


Whatever............

The jack is right under the tool, and directly carryig forces into the compound support. It's just as you demand, and you don't see it.

Pfooey.

He could mive the jack over a bit towards the end of the tool, that's about it.

Evan
03-07-2009, 05:21 PM
The "loop" is actually somewhat smaller than depicted as a result. It would also appear the major portion of the "loop" is comprised of the headstock and spindle, leading me to think the toolpost is not the weak sister in that set up.


The rule of small angles means that my depiction isn't far off. The parallax isn't that great. This principle is directly from Alexander Slocum's MIT course on Precision Machine Design. The headstock/spindle is generally the strongest part of the machine because it is both more massive and very short coupled. It doesn't matter a bit anyway which is stronger or weaker, the benefit is realized by shortening the loop regardless. It's like a tuning fork and by shortening the loop the resonant frequency is raised. That raises the rpm and tool fps that it takes to produce resonant chatter.

John Stevenson
03-07-2009, 05:28 PM
Rigidity of tooling is the #1 requirement for either carbide or HSS. that lst pic just shows the classic mistake of people having problems parting. Feeds and speeds are also crucial to successful parting, in that order.
Knurling is also another task that has the same requirement for rigidity
jmho
al

Knurling ????????????

Did someone call me ??????????????

.

JCHannum
03-07-2009, 06:46 PM
Regardless, I have little doubt that Aloris did a bit of design engineering themselves and added enough mass where needed to compensate as their tooling, when properly applied, is more than adequate to handle any normal machining operations.

Glenn Wegman
03-07-2009, 06:46 PM
I am curious as to what the attracton is to putting the largest possible QCTP on a small lathe! (Read oversized) I've seen statements on Forums claiming the use of CXA tool posts on their 12" lathes. I would seriously doubt that the weak link in rigidity on the average small lathe 12" and under would be the 1/2" tool shank. Other than working with stock that's diameter exceeds the swing over the cross slide, the closer the tool is to the center of the cross slide the happier everything will be rigidity wise. An oversized QCTP does nothing but move the tool to the extreme left boundary, cancelling out any percieved rigidity gain from using larger shank tool bits in the first place! A small difference in tool placement in X or Z as far as overhang can sometimes mean the difference between life and death as far as chatter.

Not aimed at anyone in particular in this thread, just stating my general opinion on the subject.

Glenn

JCHannum
03-07-2009, 06:48 PM
Knurling ????????????

Did someone call me ??????????????

.

Where were you the other day when we were discussing cut knurling and the Quick & Dorian style knurling tools?

Evan
03-07-2009, 06:59 PM
Regardless, I have little doubt that Aloris did a bit of design engineering themselves and added enough mass where needed to compensate as their tooling, when properly applied, is more than adequate to handle any normal machining operations.


The mass of the tool post makes no difference to the leverage it exerts on the rest of the system. That overhang is a lever between the point of contact of the tool and the work to where the load is passed through to the bed and magnifies the tool forces accordingly.

"More than adequate" is not definable. I want and I think most people want their machine to work as well as is possible. Exceeding a mediocre standard of performance isn't a very high point of aim.

JCHannum
03-07-2009, 07:31 PM
Aloris introduced the first quick change toolpost over fifty years ago. The basic toolpost has remained virtually unchanged for that time and has become the industry standard. They are made in the USA, and are among the few machining related manufacturers that have held their own and not been destroyed by imports.

They have not accomplished that by producing a mediocre product.

J Tiers
03-07-2009, 08:29 PM
Aloris introduced the first quick change toolpost over fifty years ago. The basic toolpost has remained virtually unchanged for that time and has become the industry standard. They are made in the USA, and are among the few machining related manufacturers that have held their own and not been destroyed by imports.

They have not accomplished that by producing a mediocre product.

To be fair, the original assertion seems not to be that the tool post is poor, but that it may be poorly applied.

The best tool is no better than the application of it. I don't think it is as bad as claimed, but I didn't perceive the original complaint as being against the toolpost.

A worn toolpost can let the holder move and cause chatter........... that isn't the fault of the design either.

Evan
03-07-2009, 09:00 PM
To be fair, the original assertion seems not to be that the tool post is poor, but that it may be poorly applied.


I did point that out but Jim isn't "listening". I have nothing against Aloris or quick change tool posts in general. Parting however is a job that will show up any weakness in the setup, however small. You need to take advantage of every possible way to increase the rigidity of the machine in most cases, especially on light weight hobby machines.

Also, my comment about mediocre does not refer to the quality of the product but to the application and expected result for the job at hand.

JCHannum
03-07-2009, 10:53 PM
Actually, I am listening pretty well. I did point out that what Evan thought was a gap is just the T-nut under the toolpost, and that GKman's set up is about as solid as can be had. If one feels the Aloris system is lacking, that is a pretty good fix.

You might want to re-read post 59 where I pointed out that while nothing is perfect, Aloris has managed to quite successfully produce what is probably the best combination of positive attributes in QC toolpost.

As to parting in general, I showed a photo of a proper set up as well as the chip curl to look for that will tell you when you are in the sweet spot when parting and stressed the importance of the basic setup and rigidity in another post.

Without moving the toolpost or compound, it is possible to turn and thread OD & ID, drill, groove, face, knurl and part multiple pieces with repeatable accuracy. There are two or three other basic QC systems that can do pretty much the same thing, but none have the wide variety of holders and associated tooling that Aloris provides.

Evan
03-08-2009, 04:27 AM
Regardless of how well made the Aloris system is it is still possible to improve on it. As I pointed out in the diagram a significant gain in rigidity can be had by placing the point of load in a direct line to the bed via supporting structures. No matter how rigid or massive the Aloris is it still imparts a torque to the cross slide and carriage when cutting. Everything has flex, nothing is rigid, so that torque is another source of movement of the tool that can easily be eliminated by using a different type of holder for parting, at least.

BadDog
03-08-2009, 05:04 AM
Rigid is surely better, but every quick change I've seen has the same basic design/issue (and we won't even talk about the old rocker style, yikes!). Aloris (and clones) being the bottom of the line price wise, but also including KDK, Multi-Fix, and others. In fact, as I mentioned, KDK is, so far as I've seen, by far the worst about hanging tools WAY out from the block. But most anything with a conveniently replaceable and adjustable height block is going to have that same issue. As stated, these are used day in and out by both pros and HSMs with no complaints. Most anything can be improved in some area or other, but that often requires unacceptable compromises and/or going beyond the point of diminishing returns (really, just another compromise anyway).

However, it might be nice to have blocks set up with integral jack for those "special occasions" where you need (or just want?) the extra support. Somewhat like KDK with the hidden adjustment, but driving a support jack instead of simple limit on the post. But for those who want the ultimate rigidity at all costs, you really can't beat (so it seems) purpose built monolithic tool posts that replace the compound and work somewhat like a typical turret. I've actually gathered some materials for such a project, but mostly focused on use for boring. Basically, it just needs the time/work to complete the mounting base. However, I've not encountered enough related issues for that project to achieve much importance, so it languishes at the bottom of the list.

I've also, with the recent lathe upgrade, had a chance to really explore the limits. My Phase II CXA with standard blocks can easily drop diameter by over 0.500 with a feed of 0.023+ in 4k series steel at 4" diameter. It'll also wind up heavy/tight 1" diameter clock springs at fast feed on parting, also with no sign of chatter. If there is a problem with rigidity on the standard Aloris style blocks, I didn't see it while searching for the limits of this machine (I eventually chickened out and accepted they were far beyond anything I care to use).

jackary
03-08-2009, 08:21 AM
Here is my version of a rear toolpost. I tried to minimise overhang etc and make it as rigid as possible. The base is sloped to adjust the centre height otherwise it is made from one piece of steel. It works well
Alan

http://s107.photobucket.com/albums/m287/jackary2003/?action=view&current=Reartoolpost1.jpg
http://s107.photobucket.com/albums/m287/jackary2003/?action=view&current=Reartoolpost2.jpg

GKman
03-08-2009, 09:46 AM
Jackary,
Excellent! Keep those posts coming.

Norman Atkinson
03-08-2009, 10:01 AM
Alan( Jackary) is getting near.
I would have raked it at 7 degrees- so no top( which is underneath) hook to grind.
I would have swivelled it like HemingwayKits version( George Thomas) so that it didn't jab fingers and hands.
I would have ground a 140 degree on the underneath 'top' so that the ribbon of swarf coming off was narrow- and didn't jam.
I would have ground a vee( male this time) on front edge.

Otherwise, I would agree. Which describes mine!

Parting off is a 'doddle'

What is ALL the WHOO HAR all about?

N

JCHannum
03-08-2009, 10:24 AM
Regardless of how well made the Aloris system is it is still possible to improve on it. As I pointed out in the diagram a significant gain in rigidity can be had by placing the point of load in a direct line to the bed via supporting structures. No matter how rigid or massive the Aloris is it still imparts a torque to the cross slide and carriage when cutting. Everything has flex, nothing is rigid, so that torque is another source of movement of the tool that can easily be eliminated by using a different type of holder for parting, at least.

I never said anything different. The Aloris might not be the best for everything, but the benefits far outweigh the drawbacks. As Russ points out, in most cases the limitations are beyond the capabilities of the lathe.

clint
03-08-2009, 11:51 AM
One thing I didn't mention in my post about going to carbide, and never looking back to HSS especially the part off tool is I work with a lot of Titanium. It turns great, I do use carbide, it's no big deal to turn, I also use ceramic inserts to get a nice finish, however I had hair pulling problem trying to part Titanium off using HSS, my next big learning curve was tapping Titanium...

John Stevenson
03-08-2009, 07:08 PM
Where were you the other day when we were discussing cut knurling and the Quick & Dorian style knurling tools?

Busy trying to perfect doing long knurls in soft alloy.

Got a job to do 12" long lengths of straight knurl but they have to be perfectly straight. It's not easy in a soft material, I can steer the cut knurl but it's very dependant on the depth, just a slight difference in depth will allow it to spiral and by that time it's too late.

No second chance as they have to be 27mm diameter. Using a travelling steady helps but it's still very haphazard.

Decided to attack it a different way and now getting good results all the time.

http://www.stevenson-engineers.co.uk/files/knurllong.jpg

This is what I'm getting now using off the shelf T6 alloy.

.

JCHannum
03-08-2009, 08:07 PM
I can see the problem with keeping them straight. What was your solution?

John Stevenson
03-08-2009, 08:20 PM
I'll post later with some pics but I will say I can guarantee the final diameter and the pitch before I start the job which is something I have never been able to do before and absolutely no chance of a double pitch.

.

dockrat
03-08-2009, 08:36 PM
I can see the problem with keeping them straight. What was your solution?

Hmmmmm this is way off the wall but by looking at the swarf on the cross slide, did he turn a single point tool on it's side, use the chuck as an indexer, and feed the cross slide along it??:confused:

JCHannum
03-08-2009, 09:11 PM
I doubt that, the photo looks rolled, not cut, and apparently John has a number to do, and that would not be a particularly cost effective for most applications.

John Stevenson
03-08-2009, 09:14 PM
No that's steel turnings.

OK pics will have to wait, it came to me when I was working out what was needed, these rods have about 50 teeth on them, not critical but that's what the original pattern were but these were only 3" long.

So some maths, 27mm OD equals to 84.82mm circumference, say 85 and sod the microns.

85 divided by 50 is 1.7mm or 0.0669" pitch, seeing as nothing is that critical 1.7 could be 1.75mm or it could be 0.0625" or 1/16" pitch.

So if we take a 12mm x 1.75 tap or any 16 tpi tap and stick it in the gear hobber set to 50 teeth and adjust depth to get the correct form we get exact OD which is the start OD as gear cutting doesn't 'grow' the diameter like knurling, we get exactly 50 teeth and no chance of a double knurl. tap set over to the taps helix angle will ensure that we get a parallel 'knurl'

I used a 1" x 16 tap as it was big enough to fit the hobber without having to make a holder, 12mmx 1.75 would have been a bit small.

Using a tap also has another bonus, use UNF / UNC and you get flat tops and roots, BSF / BSW gives you rounded crests and metric gives sharp tops and roots.

.