# Parting Question: Seems Feed Is Really Fast.....



## great white (Feb 9, 2016)

My setup is an atlas TH42 with an AXA QCTP. Using a parting blade, edge polished on a wet stone to make the cutting point as clean and sharp as possible. I've tried a curved, flat and no back rake angle on the tool. Seems to make no difference other than curling or throwing the chip.

It seems I have to feed into the stock really fast in order to minimize chatter. Spindle speed doesn't seem to make a big difference either, fast or slow. Slow just gets big chatter marks and noise, fast makes finer chatter marks but an intolerable "screech" sound to go with it. 

I mostly just work in 6061, but it seems I REALLY have to hog in the parting tool to keep chatter away.

Minimizing tool and work stick out doesn't seem to make a lot of difference. Still chatters unless I feed uncomfortable fast into the material.

I've locked down all my carriages and even gone so far as to lock down the gibs on the compound.

The feed is so heavy that I worry about it digging in. Sometimes it does if the chuck doesn't have a death grip on the piece.

Am I doing something wrong?

I've watched parting videos and they seem to not have to feed as fast I I do to keep away chatter.

I know the atlas isn't the most rigid structure out there, but I've watched videos where guys cut off just fine on a 10/12" atlas and not have any significant chatter. At least not the way mine does.

I'm kind of perplexed. I've gone through most I've what I've found online and I still get chatter....


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## Randall Marx (Feb 9, 2016)

How fast are we talking about for spindle speed? Remember that speed needs to be about half of turning speed for parting. Also, are your spindle bearings adjusted well? That could cause chatter here.


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## TomS (Feb 9, 2016)

I agree with what Randall says above with the caveat that your parting blade needs to be perpendicular to the lathe centerline, the tip needs to be on center, and use a liberal amount of cutting fluid.  Loading the parting blade with a heavy in feed can reduce chatter, and sometimes eliminate it, if your machine is up to it.  How wide is your parting tool?  Going to a narrower blade might help.  I use a 3/32" wide blade on my 12 x 36 and have no problems.  

Hope this helps.

Tom S.


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## Bill C. (Feb 9, 2016)

Make sure your blade doesn't extend to far beyond the diameter of the stock plus maybe a 1/4" of an inch. If the chip curls up on top of itself them the setup is a good one.  

Parting can be a challenge no matter what your skill level is.


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## f350ca (Feb 9, 2016)

There seams to be a geometry thing, and maybe a combination of slop in the gibs of some lathes that they just don't like parting. My first lathe was a 14x40 Taiwanese, I could never get it to part well, same thing chatter grab etc. I bought a heavy 16 x 80 Summit, it parts effortlessly, still couldn't get the 14 x 40 to part. Sold the 14 x 40 and bought a wore out Colchester Student, it had no trouble parting. Sold it and bought a Hardinge HLV, again no problems parting, except it will run out of power. From my experience it might just be the lathe.

Greg


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## pineyfolks (Feb 9, 2016)

These old-school tool holders will surprise you with their results. Instead of digging in the tool springs away and reduces chatter.


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## mikey (Feb 9, 2016)

It sounds like you're doing everything right. The only thing I can think of is that you may not be quite on center. If your tool is a tad high it can require higher feed pressure to cut. Try taking a very light facing cut with the corner of your tool at the current height and see if there is a tit on the work. 

If you're using that horrid tool holder that holds the tool at an upward angle you may want to increase the front relief angle a bit more; this can make a difference.


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## stupoty (Feb 9, 2016)

My lathe can just about handle power parting in aluminium on the slowest feed, on steel it's plunging too quick I find.

The blade being just a little to high definetly stops me from parting,  i had to set it quite low the otherday (maybe 50-75 th) to get a good cutting action on mild steel, this does leave a big ish nib but it was small enough i could snap the last bit off the stock in the chuck.

Parting holow stuff is much easier i find , especialy if the cutter is set a bit low as it tends to get dragged in a bit which can be unplesent towards the centre of the part.

I like to peck part, i dive in quite fast then withdraw at the first sound or feal of unhappyness and use a brush to clear all the chips and add more cutting fluid.

I like parting off brass the most it's amzing 

Stuart


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## great white (Feb 9, 2016)

I've fooled around with my on center a fair bit. Doesn't seem to make a difference where I have it.Horrible screeching chatter.

Spindle bearings are adjusted IAW the Atlas manual instructions.

I don't' run out of power, I'm running a Baldor CDP 3440. 3/4 horse. Runs super smooth.

I use the simple formula 4XSFPM/diameter = spindle rpm to set my rpm for cutting. Doesn't seem to matter if I do half it or double it, I still get chatter.

I do think I am using the references "horrible angled holder". Looks like this:




Can't remember off hand what the tool width is.

So, how should I try and adjust the rake if using this tool? more angle or less on the cutting surface? I'm not really understanding how less angle could be helpful. Doesn't that mean the chip edge would be broader/blunter?


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## David S (Feb 9, 2016)

GW your lathe is larger than mine.  I part all the time on my Atlas 618 with brass and aluminum.  My parting tool is 0.040" wide, so may be too narrow for your application.  Also the there is no top rake.  Rather than the tilt that you show, mine is not tilted.

David


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## mikey (Feb 9, 2016)

You're using a P3S blade, which is 1/8" wide. It will take more pressure to cut than a thinner blade will. 

If you look at the front relief angle with the tool holder on a level surface you have maybe 5 degrees of relief? With high feed pressure you may have some contact with the work. I would try increasing that to 10 degrees and see if that makes a difference.


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## higgite (Feb 9, 2016)

David and Mikey beat me to my other suggestions while I was typing with my usual hunt and peck aplomb, but I'll throw this out there to chew on.

I can’t speak to your angled tool holder because all I have used is a horizontal one. I part on my 8.5x20 with a 3/32” blade with no chatter or squeal with steady drip of fluid and faster-than-you-think-it-oughta-be manual feed, especially with aluminum.

The squeal could be the blade rubbing, either on the front of the blade from not enough relief due to the angled holder or on the side from not being perfectly perpendicular to the spindle axis. Or both.

I don’t know that it would make any difference, but just for grins, you could turn the blade end for end in the tool holder and grind a small flat on top so the cutting edge is horizontal. And of course, grind some front relief. If that doesn’t help your problem, you wouldn’t have altered the “good” end of the blade and can just flip it back around.

Tom


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## great white (Feb 9, 2016)

mikey said:


> You're using a P3S blade, which is 1/8" wide. It will take more pressure to cut than a thinner blade will.
> 
> If you look at the front relief angle with the tool holder on a level surface you have maybe 5 degrees of relief? With high feed pressure you may have some contact with the work. I would try increasing that to 10 degrees and see if that makes a difference.


that's just a pic I grabbed off the 'net as an example. It's not actually mine.

Comments noted though once I have a look at my actual tooling....


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## Paul in OKC (Feb 9, 2016)

Agree with the more front relief. I wouldn't touch the top of the tool. Might angle the cutting edge about 5 degrees, instead of square with the od of the part, if that makes since.


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## Dranreb (Feb 9, 2016)

Have you checked for tiny chips or maybe a small ding with a raised edge in between your tool post and compound? Check the mating surfaces of your toolholder dovetails as well.

There was a number stamped under my milling attachment and the tiny raised area around it caused me no end of headaches trying to mill without chatter, until I found it.  Once I'd cured that it was a different machine, smooth and all chatter gone.

Bernard


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## Grumpy Gator (Feb 9, 2016)

_GW,_
_You say you are parting 6061 but neglected to give us the OD._
_Your parting tool might be getting hot and expanding there by touching the sides of the cut._
_ I was taught to feed into the piece and when chattering occurred to back out and move the tool to increase the diameter of the cutting slot on the waste side._
_******Just Saying********G*********** _


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## great white (Feb 9, 2016)

Dranreb said:


> Have you checked for tiny chips or maybe a small ding with a raised edge in between your tool post and compound? Check the mating surfaces of your toolholder dovetails as well.
> 
> There was a number stamped under my milling attachment and the tiny raised area around it caused me no end of headaches trying to mill without chatter, until I found it.  Once I'd cured that it was a different machine, smooth and all chatter gone.
> 
> Bernard


Worth a look. I'll check next chance I get.


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## great white (Feb 9, 2016)

grumpygator said:


> _GW,_
> _You say you are parting 6061 but neglected to give us the OD._
> _Your parting tool might be getting hot and expanding there by touching the sides of the cut._
> _ I was taught to feed into the piece and when chattering occurred to back out and move the tool to increase the diameter of the cutting slot on the waste side._
> _******Just Saying********G*********** _


Recently,  38 mm.

Steel doesn't seem to matter. Any diameter, intolerable screech and chatter.


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## Bill C. (Feb 9, 2016)

mikey said:


> It sounds like you're doing everything right. The only thing I can think of is that you may not be quite on center. If your tool is a tad high it can require higher feed pressure to cut. Try taking a very light facing cut with the corner of your tool at the current height and see if there is a tit on the work.
> 
> If you're using that horrid tool holder that holds the tool at an upward angle you may want to increase the front relief angle a bit more; this can make a difference.


-----------------
If you ever see your parting tool and holder take a dive when you start your cut you will know your are just below dead center or the parting tool is not sturdy enough for what you cutting.  

I used to double check my parting setup by moving the carriage to the face of the part. Then move the blade until the parting tool cutting edge is in contact with part. Doing so makes the tool parallel with the face of the part. Carefully tighten the QCTP so your settings didn't move. If I wanted to double check my setup while the blade is against the face of the part I would lock everything down and take a very light cut if the was a hair thin shaving I was ready.  You should be ready to move the carriage back to where you want to cut off the part.


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## TomS (Feb 9, 2016)

great white said:


> I've fooled around with my on center a fair bit. Doesn't seem to make a difference where I have it.Horrible screeching chatter.
> 
> Spindle bearings are adjusted IAW the Atlas manual instructions.
> 
> ...



I have the same holder and parting blade.  The problem is the holder is not made for that type of parting blade.  The holder has no relief for the top portion of the blade that is wider than the body portion.  What happens when you install the blade flush with the holder the blade is not held vertical and it is somewhat tilted to the side.  What you need to do is mill a relief slot in the holder so the body portion of the blade can be mounted flush to the holder.  Hope I'm making myself clear.  I can take a picture of my holder in the morning and post it if that will help.

Tom  S.


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## great white (Feb 10, 2016)

TomS said:


> I have the same holder and parting blade.  The problem is the holder is not made for that type of parting blade.  The holder has no relief for the top portion of the blade that is wider than the body portion.  What happens when you install the blade flush with the holder the blade is not held vertical and it is somewhat tilted to the side.  What you need to do is mill a relief slot in the holder so the body portion of the blade can be mounted flush to the holder.  Hope I'm making myself clear.  I can take a picture of my holder in the morning and post it if that will help.
> 
> Tom  S.



Yep, I understand. I have looked at that before. I haven't milled the slot yet, but maybe it's time to do so...


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## Dranreb (Feb 10, 2016)

Something my retired machinist friend told me was to support the workpiece by putting a spacer (flat one side centered the other) against the trued end, with a live center in the tailstock.

Works for turning as well but when parting just go 3/4 through and then remove the support.

He supports most work, reckons it doesn't hurt to do this even without too much stickout from the chuck on a small lathe as they need all the help they can get, yes it goes against usual parting wisdom but I've tried it a couple of times on larger diameters with good results.

When altering things to try and get better results, only change one thing at at time and test again before trying the next change, so you'll know what the problem was.

Bernard


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## Finster (Feb 10, 2016)

TomS said:


> I have the same holder and parting blade.  The problem is the holder is not made for that type of parting blade.  The holder has no relief for the top portion of the blade that is wider than the body portion.  What happens when you install the blade flush with the holder the blade is not held vertical and it is somewhat tilted to the side.  What you need to do is mill a relief slot in the holder so the body portion of the blade can be mounted flush to the holder.  Hope I'm making myself clear.  I can take a picture of my holder in the morning and post it if that will help.
> 
> Tom  S.


Tom, can you post that pic? I would like to see it. Thanks.


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## great white (Feb 10, 2016)

Theres a couple threads on the board about it. 

Heres one: http://www.hobby-machinist.com/threads/setting-up-parting-blade.33260/


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## DSaul (Feb 10, 2016)

I've found that holding a chip brush full of lube in the slot with one hand and feeding the cutter with the other hand helps immensely with chatter and squealing issues.  It needs to be continuously lubed while you're cutting.


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## Paul in OKC (Feb 10, 2016)

One random thought.......there is an anomaly that runs around shops randomly stirring up trouble. I always tell my guys this when they struggle with something that has been done before. Nine out of ten times you can do things the same way, then there is the day when nothing works like it is "supposed" to! Usually figure it out, but............


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## Tozguy (Feb 10, 2016)

Great white,
Just another thought but how is the compound set when you get chatter? You mentioned locking the gibs on the compound but it is also a good idea to crank the compound back as far as practical to get minimal overhang of the compound.
I use the 207 parting holder with a tapered blade and get good results on steel and brass when the sharp blade is vertical, square to the work and on centre.
It does seem to like a hungry feed.
Mike


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## Bill C. (Feb 10, 2016)

I remember the first shop I was a operator in. There was a senior machinist who for some reason make a series of small parts with cutting groves. I can't recall why he couldn't part off these pieces but came over to the horizontal bandsaw area they used to cut material. You can guess what happened when the shaft slipped during the first cutoff. He lost a little tip of his thumb but bled like he lost his finger.  

I had a blade that was straight not tapered that may be your problem. If the holder was built for a tapered bottom slot I agree with Tom.  

Be careful and I hope you get this problem fixed soon


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## TomS (Feb 10, 2016)

great white said:


> Theres a couple threads on the board about it.
> 
> Heres one: http://www.hobby-machinist.com/threads/setting-up-parting-blade.33260/



Yes, this is the modification I was describing in my post above.

Tom S.


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## epanzella (Feb 11, 2016)

I think your setup is just not rigid enough for good parting.  I had an old Logan that wouldn't part. I replaced the compound with a solid block of junkyard steel with a slot milled in it to hold the parting blade. Cut fine after that in all metals.  I did the same thing with my 12 x 36 Grizzly. It already cut  well but really cuts like a champ after eliminating the compound.




	

		
			
		

		
	
 .


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## BGHansen (Feb 11, 2016)

I agree with epanzella, you can't have too rigid of a set up for parting.  I had problems on an Atlas 12 x 36 and a Rockwell 10 x 36 using latern style tool holders.  I made a tool holder block for a piece of 5/8" x 1/8" HSS cut off blade.  Mounted the steel block to the compound with a bolt/T-nut.  Marked the center line of the lathe on the block with a chucked up scribe.  Milled the slot for the blade, drilled/tapped a couple of holes to lock the blade.  Went from pecking away to getting through 1 1/2" rounds of steel with no issues.  Tom's Techniques has some good info at his web site.  He always sharpens the HSS blade before cutting.

Bruce


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## great white (Feb 11, 2016)

So I'm going to cautiously say I've got it figured out.

Operator error would be the world.

I went out yesterday and bought a machinist square, good to .0025

I chucked up a piece of 6061, set it up my usual way and chatter chatter chatter.

I backed off the tool and dropped the square against the work piece, rolled up the tooling to the square and there it was: not square to the piece as indicated by the square.

A quick little adjustment to the compound and try again.

Touch of chatter as I entered, then nothing but a nice smooth curl as I plunged into the work. Still need some pressure, but nothing like before.

So, it seems somehow that all this time I have been messing up getting the tooling square to the work.

Hopefully, that was the problem but I will be looking at the other items mentioned in this thread. To optimize the setup if nothing else....


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## David S (Feb 11, 2016)

We don't call it "operator error", or "human error" any more.  We call it human factors. .

Sure hope you found the problem.  Keep us posted.

David


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## TomS (Feb 11, 2016)

great white said:


> So I'm going to cautiously say I've got it figured out.
> 
> Operator error would be the world.
> 
> ...



Good to hear you got it figured out.  I line up my parting tool to the face of the chuck.  With it not turning of course.

Tom S.


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## great white (Feb 11, 2016)

Well, worked for a while.

Chatter is back, although not as bad as it was.

I think maybe it's lack of ridity in the compound assembly. I can make chatter appear and disappear be leaning on the end of the compound.

I guess I'm going to have to play with the gibs and see what I get....


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## Tozguy (Feb 12, 2016)

Glad you are making progress. Any chance of us seeing a picture of your set up?


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## great white (Mar 1, 2016)

Quick update.

I changed out all the gibs screws for slighly longer Allen heads and that allowed me to get the slides a bit tighter and a bit more precise. Basically, took out some slop. It's stiff to turn the hand wheels, but acceptable for parting operations and then easily backed off a bit for turning operations.

I also made sure the front of the compound did not extend past the carriage support.

I cut off some 1" steel rod and was able to do it with minimal/no chatter. I did have to feed (what seemed like) heavily. If I backed off the feed it would start to chatter/squeal, but a heavier plunge back into the material would get under the chattered surface and start cutting well again.

I was also able to play with speeds as i was cutting, which also seemed to help. There was a pretty fine line between chatter and none for speeds. The variable speed DC motor conversion was worth its weight in gold there. Even at low rpm, it just leaned into it and got it done. Lots of torque and the cycletrol kept the speed constant, unless i was compensating as the tool plunged in to the center.

Still seems like heavy feed is needed, but now I'm guessing I'm just getting used to parting operations on this particular lathe.

The aluminum chatter might be the spring in the material as much as the machine. I'll have to try a really heavy feed next time i cut Al and see how it goes.


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