Parting off

[roofman]

Tipped parting tool, having a bit of trouble with it not performing. Is it best to put it centre height or just below?. have the cross slide locked on the bed and everything nice and ridged but still getting chatter even going in heavy.

 

[Agroshield]

What machine? What material?

The inserts are 4mm wide, so if you were to answer 'Chinese mini lathe' and 'Inconel' to those questions, well there's your problem missus.

 

[MattF]

On centre height.

 

[roofman]

What machine? What material?

The inserts are 4mm wide, so if you were to answer 'Chinese mini lathe' and 'Inconel' to those questions, well there's your problem missus.

Harrison 11" with no recognizable wear

 

[addjunkie]

Di you get same issue with an hss tool steel blade, how hard are you driving it, coolant, oil or not

 

[Pete.]

4mm parting inserts are a bit on the fat side for a lathe that size TBH.

 

[roofman]

Di you get same issue with an hss tool steel blade, how hard are you driving it, coolant, oil or not

HSS fine and i drive it in pretty heavy with a soluble coolant feed on it.

 

[Other Daniel]

I like to set the parting tool just under half the diameter of a gnat's pubic hair below centre height.
I find this works well.
Perhaps less so for the gnat.

 

[roofman]

4mm parting inserts are a bit on the fat side for a lathe that size TBH.

leaning towards this myself tbh...hss and my thinner tipped seem to be fine.

 

[addjunkie]

leaning towards this myself tbh...hss and my thinner tipped seem to be fine.

Youve answered your own question, some steels part no issues at all others are pants too….always a mystery to me, never like parting off.

I set too a ball hair above centre, so when cutting its on centre.

 

[Seadog]

I generally use a 2mm for my Boxford, but have used a 3mm tool with some horrible overhang, because I've yet to sort out the holder. If I'm careful I get no problems.

 

[500e]

Always had problems, then it was suggested auto feed on slowest speed have a lot less trouble same make holder for the wider 4mm works for me

 

[roofman]

So i guess 4mm is a bit too thick for what i have...lesson learned as i have just bought the tips and gladly for only a fiver for 4 of em. Thanks all for your input

 

[brightspark]

hacksaw when its running or make your own from cutting a piece out of a carbide tipped circular saw blade and touch it up on a green stone

 

[roofman]

hacksaw when its running

many times and still do when its really thin stuff like a small brass rod etc

 

[RobCox]

On centre or (very!) slightly above. Never below, otherwise the tool may get sucked under the work, with the ever so familiar sphincter loosening BANG!

I use a GTN2 insert on an M300 BTW, at quite high spindle revs (800rpm for 1" dia). I have 3mm wide inserts and tool but the 2mm works well. I dont think I'd venture as far as 4mm. Too much wasted stock!

 

[Hood]

On centre although if you have a bit of play fractionally above can sometimes help.
4mm is too much I use 3mm even on the CNC.

 

[8ob]

Is 4mm for parting or is it for a groove?

Bob

 

[Agroshield]

A couple of other things to try before giving up:

Try to part something up close to the chuck jaws (like 1mm between forward edge of blade and jaw). The amount of overhang can make a lot of difference.

Double(boost) check the blade is parallel to the face of the chuck.

If you are forced to part something off with a long stickout, move the blade to the tailstock side of the Dixon toolpost. Then the force is going more directly downwards, closer to the compound slide pivot. At the moment, with a Dixon toolpost and a parting holder in that toolpost, the force is quite a way forward of the dovetails under both compound and cross-slides.

 

[Pete.]

Is 4mm for parting or is it for a groove?

Bob

If you go right through it's parting, if not - groove