# Parting off problems... advice needed...



## ttrikalin

Here's my thoughts.. I'd value any feedback... 


I get a lot of chatter when I part off on my Sherline. Gibs are tight. 

1. I often use a 1/8 inch cutoff tool (from taig) that I have mounted on the forward tool post. The bit cuts exactly at the center. I get lot of chatter with larger diameter stock (above 0.500"). cutting closer to the center (lower forces?) is much better. 
2. Today I ground a 1/16 toolbit, again mounted on the center. It does better compared to the 1/8 tool - but I do get a lot of chatter on a 3/4 steel part... 


Questions... 

1. Why do I get so much chatter? Am I pushing the limits of the machine trying to part off 3/4" steel or aluminum?

2. Can I get rid of the chatter by using a thinner tool? Perhaps make one by grinding a piece of a hacksaw blade (.032")? 

3. Does a rear parting tool help?

4. If I clamp down the cross slide on the bed, would that help? Any ideas how to do that (if it's helpful that is...)... 



thanks in advance for your thoughts... 

tom 


PS. I'm posting the same e-mail to the other lists... I'll compose a list of answers as I get them and I'll feed back to this list also...


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## BAH101

I had the same problem with my Taig lathe. I built a rear cut-off tool holder and have no problems now. It could be that there is just not enough mass in these small machines to work as well as it should.
Bryan.


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## Tin Falcon

Tom the answer to your questions is likely yes. except maybe diameter of the part. 
parting can be tricky but remember basics because parting is a little less forgiving than other operations. 

speed general slower than turning . you do not want the part resonating. 
feed you need to take a nice chip but do not get greedy . steady as she goes. 
tool height center line or slightly low never high. (except for reverse parting with the tool behind) 
use plenty of the popper lube/ cutting fluid sulpherized oil for steel w-D -40 kero or A-9 for aluminum
make the compound as rigid as possible tightening the ways can reduce chatter. 
make sure the tool is dead sharp hone the tool. 
use a real parting tool that is much higher than it is wide with clearance. insert tools are nice because they have clearance behind the cutting edge as well as on the sides.
Minimum stick out of the part and of the tool.
Tin


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## BenPeake

Hi Tom

I don't have a taig, but I had the same problem. No matter what I did, parting was such a messy affair that I invariably reached for the hacksaw. Since then I built a rear mount parting tool and now I can part just about anything at any speed with a 1/8" hss parting blade. So I have to agree with Bryan on this one. Rear mount parting tools are the way to go.

Ben


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## GWRdriver

ttrikalin  said:
			
		

> I'd value any feedback . . . I get a lot of chatter when I part off on my Sherline. Gibs are tight.


Hi Tom,
The world's best industrial machine tools are massive things. But why in the world does a 10" lathe need to weight 3500lbs?? The answer is . . . for rigidity which is a requisite for accuracy. The reason the Sherline and many other small lathes chatter is because there s not enough rigidity and mass in the machine to oppose and damp the tendency of the tool tip to run away from the cut, which is what chatter is. Tightening the gibs helps, as does narrowing the cutting face as you have discovered, but there is still going to be flexure in a small and light machine which won't go away and yes you are pushing the limits of the machine. 

The answer to your second question is _maybe_, but in any case I can tell you that a ground hacksaw blade (in a holder) makes for a great cutoff tool. The problem I have, and you may discover, is that a hacksaw blade is flexible (duh!) and if too much blade is left hanging out of the holder without lateral restraint the blade will drift left or right in the cut, depending upon which way the tip grind slants. The result is that I am only able to expose maybe 1/4" of hacksaw blade without having a problem with drift so I limit my cutoffs with those blades to maybe 3/8" stock, 1/2" at most.

The rear parting toolpost can be an improvement, so I hear from our British cousins where those are popular, due to the dynamics of the lathe and the cutting forces. This may be in part because so many folks in England have Myford lathes and apparently a rear toolpost works better in that particular machine. I've read the technical explanations (or claims) but I haven't tried one. However the newest thing for the UK has for some time been a carbide insert cutoff tool sold by Greenwood Tools (IIRC) which practically eliminates chatter and zips through almost everything, but it's for larger machines 7" swing (3.5" in the UK) and above.


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## ttrikalin

Thanks to all for your feedback... 

On the side, what is the correct height for a part-off tool (forward mounted)?

1. I always thought that right on center is best. This is also what an experienced machinist told me (I buy stuff from him at the MIT swapfest during the summer)... 

2. The Sherline book says a bit lower than center for larger stock (a bit), on center for small diameters.

3. I have received advice to have the tool up to 10 thou per inch HIGHER than the center.

Any firm answer? 
tom


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## Tin Falcon

always set up tool to defect away from part not dig in . 
For normal parting if you set the part on center or slightly below the tool will cut a bit less. If the tool is high there is a risk of rubbing and not cutting or if the tool deflects down in it will take a deeper cut.
again I say set up the tool to defect away from the part not into it.
Tin


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## peatoluser

I use a tiag lathe and i found that the 2 big improvements to parting off where a rear toolpost and plenty of cutting oil. I keep a small bottle filled with cuuting oil and use a small paint brush to apply it. I soak the brush and just rest it on the job. Tin's dead right about taking a nice chip and steady feed. if you're too tentative the tool will start rubbing go blunt and chatter will ensue. 
Something not mentioned is choice of material for parting off. If you're not going to harden, solder or braze the part afterwards then it's worth investing in the freecutting materials available. they really do make a difference. I have no problem parting 1 inch dia. bar in the tiag with freecutting MS.
I've also parted the heads off some 16mm by 150mm (that's about 5/8 by 6 inches in the understanable scale ) allen bolts in, I believe, high tensile steel. what are they made off? all i know is they blunt my hacksaw blades ruddy quick. 
if I've posted the link right this should be a photo of it.






blade is off hand ground 3/32 thick about 1 degree rake . I reckon it was the cutting oil that made it possible.


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## ttrikalin

Thank you peatoluser!

I think I'll go for rear mounted tools and revisit setup and cutting oil, as suggested here. 

BTW, any clues on why rear cutting seems to work better than forward cutting? The only difference see is the direction of the forces on the knife. 

downward and proximal (forward cutting) 
upward and distally (backward cutting)

but other things being equal, why would that make a difference? 

tom in MA


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## BenPeake

ttrikalin  said:
			
		

> BTW, any clues on why rear cutting seems to work better than forward cutting? The only difference see is the direction of the forces on the knife.
> 
> downward and proximal (forward cutting)
> upward and distally (backward cutting)
> 
> but other things being equal, why would that make a difference?
> 
> tom in MA



Hi Tom

I think the main reason it works so much better is because you are mounting the tool directly into the toolpost which is mounted directly on the cross slide. This severely limits any flex in the setup:






If you mount it conventionally, the tool is in a toolholder, which is held in the toolpost, which sits on the compound slide, which sits on the cross slide leaving plenty of opportunity for a little flex. 

I have a Myford brochure which advertises a parting tool/slide which mounts directly to the bed of the lathe, which I suspect would perform best of all.

I'm no authority on this I just know it works and this is my guess as to the reason. Hope it helps,
Ben


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## peatoluser

I'll try and answer that as best as I can. But I can only go on what I've been told and observed personally. Whether to use front or rear for parting off can often degenerate into one of those never ending debates like we have on this side of the pond about the virtues of metric v imperial.
For large machinery with taper headstock bearings, ball leadscrews etc, I honestly think it doesn't make any difference, except in one respect, which I'll mention at the end. (well, so I've been told), but, from what I've observed at our size of lathe it can.
The main problem a rear mounted tool solved for me was dig-in. Given that nothing is truly rigid and that all moving parts have some clearance, as we plough in from the front the work is always trying to climb onto the tool. this is not such a problem until the diameter reduces and, as we are hand feeding, the pressure we apply varies so the tool can stop cutting momentarily . the work piece will deflect minutely and try to climb onto tool. Because we are feeding from the front, the cross slide nut is pushed back onto the cross slide screw and there is clearance in front of it (the backlash we have to deal with when we mill on the lathe) All these clearances, deflections forces etc. can, when the tool tries to start cutting again, cause it to take too big a cut and be pulled into the work, stalling the machine
(I'm sure we've all seen something similar to this when we've inadvertently set the parting tool too low and just when we expect the job to drop off it rides over the tip pulling it forward, or is that just my sloppy workmanship ;D)
now ,from what i understand, when the tool is inverted at the back of the lathe, the forces are trying to push the tool up and away from the cut and the saddle back against the cross slide nut, so when it starts cutting again there's less chance of it being pulled into the job.
Now, the problem with all this theory, is that when I've mentioned to some machinists as to why the work doesn't try to climb under the job and pull the tool forward i never get a clear answer.
like i said , it can be a can of worms starting this debate, I just know i have less problems parting from the rear than the front.
but i did mention one difference at the beginning and that is chip clearance. with a rear mounted tool the swarf just drops onto the bed rather than sit on the tool, and given the slap dash method i use for putting on the cutting oil, it may be that rear mounted the tip is lubricated better than forward facing so cuts better.
incidentally there is also one more reason for using a rear tool post in our size, and that is, if you're using the standard tool blocks like me, you don't have to keep changing them to part off, thereby loosing any datums you are working too. Although It can get crowed on that small cross slide!.


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## Lakc

Some of the wisest and most helpful words on parting off by teenut
http://yarchive.net/metal/parting_off.html

That really helped my parting off. Rereading it every so often helps quite a bit as well.


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## Tin Falcon

The other option is turn the tool upside down in the front tool post and reverse the spindle direction. But will not work on a threaded spindle nose like a Sherline or south bend. It will work well on a mini lathe as the chuck is bolted on.
Tin


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## compressor man

I too have come to dread whenever I have to part steel. I am intrigued by many here saying that a rear mounted cutter works much better on small lathes (I have a mini lathe). Would someone mind elaborating a little on this, I have never before heard of this term.

Chris


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## Tin Falcon

CM some lathes have a place or the capability or room to place a second tool holder behind the work . Typical these hold a tool that would be upside down in reference to a tool held in a front tool holder. 
If you have a mini lathe try the above mentioned method. 
Tin


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## vedoula

thanks all for the advice. 

Still I do not understand the front vs rear debate. 

The setup/arrangement is symmetric and should not matter IF THINGS ARE RIGID... I am sure I'm missing something... 

If the setup is not rigid, then the tendency of the rear mounted tool to deflect upwards ("extension") vs that of the front mounted tool to deflect downwards ("compression") is the only difference I can see... And this would only matter if they are not symmetric... 

And this is where I lose the ball... 

tom in MA.


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## Lakc

vedoula  said:
			
		

> The setup/arrangement is symmetric and should not matter IF THINGS ARE RIGID... I am sure I'm missing something...



With all things equal, rigidity, tool height, etc. the rear mounted toolpost gets a 9.8m/second head start evacuating the chips thanks to gravity. Sometimes that is a big help.


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## BAH101

Not really sure why it works so well, but it does. Before I made my rear holder, I dreaded using the cut-off tool, like Ben, I would use a hack-saw. Now, I can cut pretty much anything, and if you get the feed right, it is like going through butter with a hot knife. I usually just drip cutting fluid onto the cut-off bit and let it run down into the cut. 
Bryan.


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## Ken I

As Tin mentioned your blade needs to be below centre (not by much) so that the tool always gives away from the work rather than into it.

There should be no difference between front and rear - BUT THERE IS - the rear post is generally mounted directly on the cross slide so you are eliminating the give / clearance etc. in your compound slide / swiveling toolpost etc.
And yes gravity helps in clearing the chips.
The upward forces tend to pull the dovetail slide tighter - downward there is always going to be some clearance or "wiggle room".

I have run a fairly large NC / Auto lathe shop and part to centre is normal.

One thing I have noticed is that chatter is less prevalent in a collet chuck than in a three or four jaw (less so with contoured "soft" jaws) - I have come to the conclusion that internal flexing within the material is also a factor - you have probably broken a part off blade and you will notice the turned diameter has three lobes when turned in a three jaw chuck.
This might just be unjustified superstitious speculation on my part however but I think it significant.

See my post on the laws of physics being out to get you with chatter.

Ken


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## Ned Ludd

Hi Guys,
A couple of years ago Cherry Hill's hubby, sorry I can't remember his name, was showing some sprung tooling for parting tools at Harrogate(?). Although not a new idea they are, I am told, very good at preventing chatter.
Ned


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## Russel

I find with my Sherline lathe that everything must be perfectly straight. For example, I use a machinist square to align the tool post. The work must be mounted solidly. Use plenty of lubricant. But, I also noticed that speed and feed are kind of finicky. At first I had a hard time cutting off anything larger than .75", but as I aquired a better feel for it, I find that 1.25" aluminum isn't too hard if you are carefull. I keep the speed down to about 200 rpm and the feed rate by "feel" I begin the cut and adjust the feed to where it is smoothest. I know that doesn't tell you much, after a while it becomes obvious as you cut. I know that if I feed into the work too slowly, it will chatter, and if I feed to quickly, it will "bite" forcing the part out of alignment in the chuck and lock up the machine. Like most things I have tried, it takes practice.







Edit to add another photo:


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## ttrikalin

Russell, 

is this the Sherline parting tool you show there? 

tom


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## Russel

Yes, it is a standard Sherline parting tool in the photograph. It has served me well so far.


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## oops again

Has anyone used the double cut method. That is what I call it anyway. Start the cut and keep going untill it starts to chatter or has a mild digin, then start another cut to widen the grove, usually the full width of the tool as it will drift in towards the existing grove. Take this cut down till it starts to give a bit of bother and go back and work on the first cut. Work like this untill it is done. I have parted 75mm like this admitadly on a bigger machine. 
I think that when you can part off without any problems and cut a thread with a singlepoint tool that you have ground yourself you can call yourself a competant machinest. I have a good suply of broken parting blades that I have not added to for years. Partly because of experiance and partly becouse I have a bandsaw 

Dave


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## Ken I

Yeah - I use the "double cut" fairly regularly.

In most cases once the chatter has put a pattern on the cut its difficult to resume without chatter - by offsetting the tool by about half its width you only encounter half of the chatter when you next reach it.

It also helps with the chip clearance.

Sometimes it works sometimes it doesn't.

Wasted effort and material - goes without saying.

The problem of chatter with all tools stems from a fundamental rule of physics :-

The rules of physics are out to get you !

Cutting metals requires an almost constant unit of power for the amount removed - a good rule of thumb for mild steel is 3H.P. per cubic inch per minute. (The "K" factor)

If the cutting speed is increaced, the force required to perform the cut diminishes - force x velocity = power - more velocity = less force and of course vice versa. This seems counter intuative but I assure you it is true - in fact if the force increaced with velocity, chatter would not occur at all.

So if a tool (or any other part of the machine for that matter) deflects then the force increaces (in reponse to the diminished cutting speed caused by the deflection) - and the deflection worsens - until the cutter gains the upper hand and the process reverses.

If the natural resonant frequency of any part of your set up falls into line with this the problem goes from bad to worse.

What to do - obviously the more rigid the tool and support structure, the less the problem is going to be and of course changing speeds and feeds might move you out of resonance.


Ken


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## mc_n_g

On my South Bend 10K and cheap Chinese 7X lathe I always put a small flat on the top of the 'T' shaped blade. My holders hold my HSS 1/2" blades at an incline. I always grind a little flat on the top of the blade approximately 1/8 to 3/16 in length. Never had any problems. I use 0.040, 0.062, 0.093 and 0.125 parting blades. I find the rake of the tool in the holder to be too much.


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## bambuko

Pat J  said:
			
		

> ...When you part on the back side of the carriage, you are creating a moment about point "B", and any flex in the tool post or carriage moves the tool bit away from the work, and places the tool post and carriage in tension.
> The difference is that the power from the turning part reduces the cutting when the tool post springs out, and thus automatically reduces the energy that is being transmitted from the rotating work piece to the tool post.
> Since the bit moves away from the work in the process, it will not dig in and keep trying to transmit energy into the tool post and carriage.
> 
> Pat J



Excellent explanation, and as always made easier to understand by the picture (worth thousand words).
The only comment I would add - it's nothing do do with rear or front tool post ;D
I can do exactly the same using front post, as easily shown on (your) modified picture:



It will be (I hope) clear from this picture, that it is all to do with work rotating away from lathe bed and away from tool - this stops digging in, which is such a common problem when using "normal" turning/parting configuration, which actually encourages tool digging in.
The only (historical) reason for using rear toolpost to solve this problem, is that the chucks tended to be screwed on the spindle and using spindle in reverse you ran the risk of chuck unscrewing - so the only way to achieve this tool/work with spindle rotating as normal was by using rear toolpost.
With modern lathe and chuck secured positively on short taper spindle I can run it rotating back or forward without any concern and I can use upside down tool easily by simply changing rotation of the spindle  

Chris
ps this I hope will also answer question being asked by *tom in MA*


			
				vedoula  said:
			
		

> ... Still I do not understand the front vs rear debate...


The answer  - it's nothing to do with front ve rear


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## compspecial

Yes Pat its amazing how many lathes have threaded spindle noses these days.
 Could do some mischief to the bed as well if it landed there, then there are the stubborn ones that won't unscrew for love nor money when you want them to! :


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## bambuko

Yes Pat, you only make this mistake once  and I bet you have learned your lesson 
So for the sake of those who are reading fast and not very carefully, let me repeat again:
To avoid parting tool digging into work it's best to have it rotating away from the lathe bed.
The only SAFE way to do it on a lathe with chuck screwed on is by using rear toolpost.
On a modern lathe, with any of the *positive, secure fittings* you can use front toolpost and simply rotate spindle backwards.

Chris


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## peatoluser

In reply 4, GWRdriver mentioned parting off with a hacksaw blade. I filed this at the back of my mind with a view to perhaps trying it sometime in the future. Well, having a lot of small components to make, I thought I would have ago at making one for my peatol. just for a quick trial, I used a piece of 1" sq mild steel for the body and just welded a piece of 1/8" by 1 1/4" high MS plate on the front (gives the correct hight for rear parting on a tiag), ground the teeth of a piece of an old blade clamped it to the body and welded a top piece on, then drilled and hacksawed the clamping slit. I just ground about 2 degrees front clearance, no top rake or side clearance. As you can see from the photo, i've brought a new low to the meaning 'utility engineering' :-[. but all I can say is it works like a dream. so good it's unlikely i'll bother making a 'posh' version. for 3/8" Dia and below ,I use it exclusively. For 1/4 Dia, I turn and part off at the highest speed with just a dab of cutting oil. Next to it is one of the small comercial blades you can buy with it's dedicated holder and correctly ground angles. almost impossible to clamp up properly in on of the tiags tool blocks, and the blade would often slide backwards in the holder. it is going in the bin.


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## Ken I

See my earlier post

http://www.homemodelenginemachinist.com/index.php?topic=11974.msg134698#msg134698

Using old Stanley knife blades.







Ideal for small parts - may look like a dumb idea but it works fine on the right application.


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## George_Race

I have had many of the same kind of problems as described in these posts with my HF 7X10 as well. I recently purchased both 1/8 and 1/16 cutoff blades from an ebay source, as I remember in Ohio, that really make my cutoff task much better. Less chatter, easy to set parallel, and no side cutting necessary of the tool.

The difference is that the blades have a "T" shaped top edge which gives a nice side clearance to the tool. Looking at the top of the blade, at the cutting edge, it has a "U" shape which seems to cut on an angle from both sides when you crank it into the work.

The only problem that I ran into was that I could not clamp them into my AXA tool holder. The "T" top on the blade made the blade sit at a slight angle. I carefully milled across the tool holder at just slightly wider than the height of the "T" part of the blade. I then had problems tightening the screws that hold the blade, and keeping the blade flat in the holder. The answer to the problem was two fold, first the milling of the tool holder and then clamping a second blade, upside down in the tool holder against the first. Hope that makes sense.
I can post a pictures of the assembled AXA holder with blades if that would make more sense.
George


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## mzetati

T-blades work like charm; they can be purchased from LittleMachineShop, too.
I made a special toolholder for them, with a kind of T slot, narrower on the bottom part.
Marcello


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## peatoluser

Nothing dumb about that idea Ken, I quite like it.
 may even have a go at making one as well, although i,m thinking now along the lines of perhaps fiting a washer with an off-set hole under the front edge to help set the centre hight (no adjustable quick change posts). that way I can grind some top rake on it. as you say, for the right application they're great.


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## Ken I

Peatlouser, good idea - obviously mine's a complete lash up - I must get round to doing a better job of it - but what the hell - it works.

Thanks,
      Ken


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## Tin Falcon

The t shaped ones are great the tared are not bad either but beware . I purchased a set of HSS cutters from harbor freight a while back . It supposedly had a parting tool in the set. Not really I guess one could grind it into submition but the whole point of buying one is not have to grind the whole tool just the tip once in a while . I think it will make a fine scraper blade just need to make a holder for it. 
Tin


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## purpleknif

Having been a full time machinist for about 30 years now I got two words that will make a world of difference in your success with parting and grooving tools. TOOL CLEARANCE ! Straight tools won't get it. Try grinding a back taper on your blade and you'll be amazed at what you can do. I just made an aluminum heat sink on my 7 x 10 with grooves .850" deep x .125" wide. Roughed them with an .060"wide high speed tool in one pass. Positive rake and .010" back clearance on each side. 
 Just sayin'...


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## wongster

Just sharing. I found that parting 12L14 steel is much easier than aluminium. Just part off the 3/4" flywheel to make my first engine - The Millie (the simplest I can find with the least parts). I always had phobia with parting off aluminium rods. Gave me quite some problems till I found that I've to be firm in pushing in the blade.

The 12L14 steel is much easier. I can go rather deep before pulling the blade out to clear the chips. In fact, the chips just fell off while cutting.

Regards,
Wong

www.wongstersproduction.blogspot.com


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## bezalel2000

Hi Tom 

12 months on from your original question, I guess you've got it sorted by now.

But for the benefit of others 

Here is a means of dealing with 'dig-in' - during parting off

The top bar is acting under gravity on top of the job, whenever it tries to climb onto the cutter of parting off tool the top bar stops it.







Bez


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## bigrigbri

If I may add my 2 cents worth, have you considered your jaws may be bell-mouthed at the ends causing the work to be held on a small portion of the jaw facet.
To try and see chuck a largeish piece of stock ,centre drill and support in the live centre and now cut as normal.
Is it any better or worse?

 Brian.


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## jpeter

Parting tools mounted in front tends to lift the work out of the bearings. Any play in the bearings, which all lathes to some degree have, provide the opportunity for chatter. Tools mounted behind the work push the work, chuck, spindle, down into the spindle bearings like the weight of all the parts do. This setup provides less opportunity for the work to move away from the cutter.

Back is better but my lathe doesn't provide for that. If you're using a springy setup like an Armstrong tool holder use a piece of scrap as a prop under the parting tool close to the work to stiffen it up to prevent chatter. You'll be shocked at how it improves your parting jobs. Keep your tool as short as you can.

Regarding tool height, sketch out a profile view of tool and work and you'll see there's no possible way to part with the parting tool above center. Any amount above center and the tool face just rubs on the work surface. Getting exactly on center is tedious so slightly low seems like a good compromise. Parting off low gives you the small tit in the center. The closer to center you are the smaller the tit will be.


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## rake60

When I was training people how to part off on a lathe I'd recommend they
put in ear plugs.

Parting is usually noisy. If you can't hear the popping,snapping and grinding 
it's easier to do. Seriously!

Nobody looks forward to parting off. It's one of the most difficult operations 
to do on a lathe. I don't know of anyone who claims to be a master of it.

I remember having a 9 foot rock crusher adjusting nut on a vertical boring mill
at work. It had a 1/4" thick dust guard on it that needed to cut off so weld
repairs could be made to it. I parted it off. When the steel started to make that
aluminum foil in the wind sound I slapped the E-Stop and RAN! LOL

No big deal. The 200 pound dust guard slid gracefully off the front of the machine.
I picked it up with the overhead crane and hauled it to the scrap hopper.

SO... Parting on a lathe really isn't that tough.

Rick


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## kcmillin

I recently started work at a prototype shop. I was given the task of parting off a part from the CNC Lathe, a 4 inch diameter steel motor coupler with an interrupted cut caused by 8 bolt holes going through it. 

I can't say exactly what type of insert tool was in the holder, but I was able to part it off using the powerfeed at about 400 RPM, and all this on a "Cheap" 14 inch Chinese lathe. 

I never would have though I could so this just a month ago. It goes to show what actually is possible with these tools.

Kel


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## Blogwitch

This is a perennial problem that crops up every few months and always seems to bring the same old answers with it. Maybe we should have a special parting heading where people can be directed to, and when someone has a new idea about tooling or technique, they could add to it.

All these people showing different types of tooling must show you that there is not one perfect tool that will work with every parting situation.

Once people realise that there isn't such a thing as a perfect parting tool, then they will start to make progress.

I must have at least a dozen different tools to carry out parting with, and each one has a particular job to do.

Of course, I do have my favourites that I use most of the time, but I also realise that they won't do every job that comes along.

For any job over about 1", I try to part off under power, it is when you hesitate half way through a cut when problems start to occur. Also, don't forget, you might have to stop half way through the cut to increase the spindle speed. If I am cutting all the way through in one go, I try to start off running too fast from what is normal, so that the further in the tool penetrates the better it should cut as it reaches it's perfect cutting speed. 

Going too slow when parting is a job and tool killer.


[ame]http://www.youtube.com/watch?v=BG4qEw3eMcQ[/ame]

BTW, the above video was done a while ago before fitting my home made spraymist system, and shows me cutting brass, I can do exactly the same with stainless steel now, if I use a little cutting oil or spraymist to keep things cool and lubed.


John


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## AndyB

Hi guys,

When I started out I read all that was said one way or the other.

I use lathes that are getting on for their centenary so the argument about the direction of load on the headstock bearings makes a lot of sense.

I tried both ways. 
My problem with front parting was twofold: setting the parting tool exactly square and chips filling the cut, jamming the tool.

I got a cheap rear parting toolpost. One of the main inclusions is a bar on the base that lines up with the T slots so that it will always be mounted square.
This, to me, is the biggest assistance as I can mount it when I want and not worry about anything except the cutting.

As Bogs says, intermittent cuts and too slow a feed does make life difficult!
I just get on with it, wind the saddle across, and it turns out really well. 
One thing I read, either part off dry or wet but be consistent; my parting off does not like a little of each, that is, a quick squirt at the start and then no more.

Also, support the end being cut off, but not heavily!

Hope that helps

Andy


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