How Can I Reduce Parting Tool Chatter

[Rannunzi]

I've got an Atlas Craftsman 12x36. Whenever cutting with my carbide insert parting tool it seems to create a lot of chatter if I don't go incredibly slowly. I took care to ensure that the blade is at 90° to within ~0.002", but the workpiece wants to vibrate a fair bit while cutting. Today I was using it to make a groove for a piston seal o-ring but the resultant groove is quite messy. The ID of the groove looks like a series of flat faces rather than a cylindrical surface. What can I do to improve the cutting? Thanks.

 

[Larry$]

I think chatter is usually a case of flex. Lack of rigidity! Two suspects: the work or the tool. Both could contribute with too much stick out. If you are working close to the chuck and your machine bearings are tight then it is likely a tool problem. Is the tool mounted correctly? Minimal stick out? Cutting at center? Tool holder held solidly to tool post? Tool post mounted solidly to compound. Compound not extended & locked? RPM & feed rate suitable for the tooling? Most inserted carbide tools require a depth of cut to keep whatever radius they have on the cutting edge cutting deep enough to keep forming a chip and not slipping out of the cut due to that ease of the cutting edge.

Try HSS in a tool holder designed to hold the tool at a positive cutting angle. (top of tool pointing upwards a few degrees.)

If you use a T shaped tool Make sure it stays vertical. Some people use a shim on the side to make sure the tool is straight up.

Took me a while to write this so there is probably another answer by now.

 

[Mitch Alsup]

Cutoff tool: minimum stick out that reaches the final cutoff point.
Rigid compound and turning directions.
The above makes the lathe as stiff as possible for parting off.

Cutting edge sharp, possibly up to 7º cutting rake for easier cutting.
Lots of cutting fluid, continuously applied.
Slower RPMs than when turning. ~= /2

Once the tool starts cutting, make sure the pressure on the point of cut stays constant.
This generally means driving the blade in harder than you think you should.
If the pressure on the cutting point varies, the cutting point will go down as the blade cuts, and come back up when there is no material to cut. This is what causes chatter.

 

[benmychree]

Also, the tool should not overhang the front side of the compound if possible. HSS tool, plenty of cutting fluid, a bit of back rake and slower speed and moderate feed rate, and/or a more rigid machine. A carbide insert parting tool has no place on a machine such as yours, and carbide insert tools need speed, and you do not have th machine to give it what it likes.

 

[savarin]

Remove to top slide/compound and replace it with a solid plinth to mount the tool post to.
This single change solved all my parting woes in one swoop.
I only replace the top slide now when I need to cut short tapers.
As has been mentioned use very sharp HSS tool bits.
I regularly part mild and stainless with no worries up to 1.5 inches thick.

 

[Nutfarmer]

You are fighting a losing battle to part with carbide on an atlas lathe. I just remove the part and cut off on the horizontal band saw. Saves a lot of frustration. I know some will tell you it will part off just fine. I am only relating what I do. If you want to run production parts and part off as part of the process watch what a heavy screw machine will do. Most of us use what we have. I have seen some beautiful work by some of the members here with an Atlas lathe. Some times it's just easier to work with the limits of what we have.

 

[Dhal22]

I wonder if @chatter chatter cut cut would have an answer?


: )

 

[mickri]

What type of tool post/tool holder are you using? A picture of your setup will help you get better answers to your question. I have a Craftsman 12x36 and parting was not fun to begin with. I solved my parting woes by first lining the compound up with cross feed and locking the compound in place so it can't move. I also tightened the gibs on the cross slide. This helped a little. Next I made a tool holder just for parting based on the design in Winky's Workshop.

This solved my parting woes and now parting is no big deal. Just another operation on the lathe.

 

[chatter chatter cut cut]

with my 7x14 no name chinese i have to lock everything down and still have problems . if i feed too fast the lathe stalls if too slow it stops cutting. iv sharpened the hss tool on diamond hones through 5 steps til it is very sharp! changing the angle is something i will try

 

[WobblyHand]

Tried to part some 1.5" 304 and my 7x16 mini-lathe met its match today. Actually burned one edge due to work hardening. And chipped the other side. Chatter, stalling, you name it. It would cut for a short time then dig in and stall. Just not rigid enough setup. Everything was reefed down. I had parted 1.5" 1045 with minimal problems. Right side was the edge that burned back.

Gave up and pulled the part from the lathe. Put it in my modified power hacksaw and it cut through no problem. Going to make a plinth to get rid of the compound. One less thing to shake, rattle and roll.