parting on an atlas 12" lathe

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bkcorwin

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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
 
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
 
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.
 
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.
Click to expand...

+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
 
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
 
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
Click to expand...

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
 
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
 
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.
 
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.
Click to expand...

Nice tip! Brian
 
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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