# parting on an atlas 12" lathe



## bkcorwin (Nov 4, 2013)

What types of blades are people using for parting on their atlas lathes?  The lathe works great for drilling, turning, facing operations, but the second I go to part something the thing chatters and on my aluminum sometimes the blade sticks into the material causing the spindle to stop turning and a belt to slip.  

I am using an 1/8" blade at the moment with the tool on center.  I have locked down the cross slide, and tightened the compound gibs to lock the compound down.

Basically, I am looking for any suggestions on what to do to fix the problem.  The blade getting stuck in the material seems like it should be a clue but i am not sure how to interpret it.  Maybe feeding too slow? However, with the chatter problems its hard to feed it in faster.

Thoughts?

Thanks
Brian


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## Codered741 (Nov 4, 2013)

Are you using a cutting lubricant?  This is ABSOLUTELY essential while parting.  I like plain Mineral Oil for Aluminum.  

Also, with the tool being exactly on center, you need to make sure that it is perfectly square to the work.  And use as little stick-out as possible with the blade, no more than an inch to an inch and a half.  

-Cody


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## pdentrem (Nov 4, 2013)

I would not use an 1/8" wide blade. That is pretty wide for such a flexible lathe. On my 10F Atlas, I used a 1/16" wide blade and lots of lube. On center, sharp like a razor, make sure the blade is square to the work. Check the top of the tool. It should be flat on the top. Maybe a groove on the top to force the chip to reduce in width.
I have parted 2 1/2" diameter Al rod with this narrow of a blade. You have to watch the chip as you feed in. You should see a chip that curls on itself and moves out of the slot. Lube is your friend. Others may have more to add as parting is a complex operation. It is like using a form tool.
Pierre

PS best success was after I changed to a QCTP setup. The lantern tool post was a disaster. Lots a tool jamming and blade breaking.


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## itsme_Bernie (Nov 4, 2013)

pdentrem said:


> I would not use an 1/8" wide blade. That is pretty wide for such a flexible lathe. On my 10F Atlas, I used a 1/16" wide blade and lots of lube. On center, sharp like a razor, make sure the blade is square to the work. Check the top of the tool. It should be flat on the top. Maybe a groove on the top to force the chip to reduce in width.
> I have parted 2 1/2" diameter Al rod with this narrow of a blade. You have to watch the chip as you feed in. You should see a chip that curls on itself and moves out of the slot. Lube is your friend. Others may have more to add as parting is a complex operation. It is like using a form tool.
> Pierre
> 
> PS best success was after I changed to a QCTP setup. The lantern tool post was a disaster. Lots a tool jamming and blade breaking.



+1 on everything here.  Words right out of my mouth.  Almost word for word.

I used to part 2+ inch steel on my 6 inch Atlas.  EVERYTHING needs to be "tight".  Not hard to turn, but get the gibs adjusted nicely, lube your machine well.

Many people say to cut at a slow speed.  I have always done better parting at almost turning speeds.  With the smaller machine, I used to use a hyper dermic needle with cutting fluid, and squirt it right into the cut, just above the parting blade.  

Like Cody said, smaller parting blade.  

Bernie


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## bkcorwin (Nov 4, 2013)

Thanks everyone I ordered some thinner blades.  One more question, the tool holder I have is an aloris knock off that has the 7 degree back rake built in to the tool holder.  Does everyone just leave the blade square?  I could see grinding the top of the tool to take out some of this built in rake?

Thoughts?

Brian


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## itsme_Bernie (Nov 4, 2013)

bkcorwin said:


> Thanks everyone I ordered some thinner blades.  One more question, the tool holder I have is an aloris knock off that has the 7 degree back rake built in to the tool holder.  Does everyone just leave the blade square?  I could see grinding the top of the tool to take out some of this built in rake?
> 
> Thoughts?
> 
> Brian



Ok.  I have not done this.  I have a heavy 10 with a DTM toolpost (American, but no matter) with the same blade holder (#7 if I remember).

I have not had to square it.  First make sure you have enough relief in front of the blade (not rubbing in the front) although with the tip of your tool digging in, I don't think that's your issue.

What spindle speed are you running at?  I run at full speed with steel.  If you are cutting a gummy alloy of aluminum, I picture you having problems at slow speeds.

If you can't get your setup tight, raise the blade a little higher to compensate for the flex.  You DON't want to be below center.

Bernie


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## pdentrem (Nov 5, 2013)

I currently use the supplied tool holder that builds the rake right in. I do not change the back rake of the blade either.

I was discussing this topic at work and a real old timer, he is older than me, suggested something. If the lathe is a babbitt version, there could be a bit of slop and when the tool makes contact the spindle and work might climb up over the tool. Thus causing the parting tool to be slightly under center. If this was the case, then one has to raise the tool a tiny bit from center.

I still think the wide blade is likely the real issue but any ideas are good in my book.
Pierre


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## iron man (Nov 5, 2013)

I use a 1/16 and an 1/8 with no problem it seems interesting to me that no one mentioned or maybe it was just me that was taught this way but when you start feeding in with the parting tool you move the carriage back and forth slightly to provide clearance for the parting tool otherwise yes it will bind.


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## calstar (Nov 5, 2013)

iron man said:


> ... when you start feeding in with the parting tool you *move the carriage back and forth slightly to provide clearance* for the parting tool otherwise yes it will bind.



Nice tip!  Brian


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## wa5cab (Nov 6, 2013)

If the parting tool is ground with a little side relief, it won't bind.  The down side of doing that, of course, is that every time that you sharpen it, the tip gets a little narrower.  I use something called a Thinbit.  This consists of a holder that fits in one of my QC tool holders and takes a replaceable carbide insert.  The inserts come in several lengths (depth of cut) and widths.  The only two widths that I've bought and used are 1/16" and 1/32".  Also good for cutting circlip (snap ring) and O-ring grooves.

Robert D.


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## GK1918 (Nov 6, 2013)

One more note;  have you ever physically grabbed the carriage cross slide & all and tried to lift it.  This just may suprise you.


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## wa5cab (Nov 6, 2013)

Yes, this is something that could be checked maybe once in the lifetime of your having the lathe.  Referring to the Atlas 10F carriage exploded view drawing, you will see two bearing plates, 10F-54 and 10F-55.  And two shim packs whose part numbers depend upon the vintage of the manual copy.  These prevent the carriage from being lifted straight up off of the bed (never mind other things that would prevent that).  AFAIK, Atlas never published specs on what the running clearance between the bearing plates and the bottom of the ways should be.  But presumably sufficient to allow the carriage to be run all the way off the end of the bed without loosening the bearing plate screws.  

Because turning and parting exerts both a vertical and a horizontal force (push) on the tip of the tool, there is a force trying to lift the rear of the carriage off of the ways.  So clearance between the rear bearing plate and way would be the more critical IFF (if and only if) the force exceeds the weight of the carriage being supported by the rear way.  To check the clearance, use a feeler gauge.  Checking it both in the common operating area and at the right end of the bed would give some feel for wear.  But there are four potential wear surfaces and the feeler gauge will not resolve which surfaces have worn.  Other measurements would have to be made.

However, I was just looking at the carriage exploded view drawing of a Clausing 4800 series (V-bed) lathe and although it does show a shim for adjusting clearance of the front bearing plate, there is none for the rear.  From which I surmise that those designers didn't consider it a problem worth worrying about.  I don't have access this morning to the manuals on an equivalent South Bend or Colchester for comparison.

Robert D.


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## bkcorwin (Nov 7, 2013)

well 1/16 blade made a big difference.  I was parting a 2" bar of aluminum, and it chattered a bit on the 1"-.5" radius section, but ran nice and quiet for the smaller radius section.  I drowned the thing in wd40, so while messy, i parted off a nice disk of 2" aluminum.  

I see no noticeable movement of the carriage up and down.  Overall I'd call it a success.

thanks
b


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