One of the guys I share my shed with has the lathe bug now (nothing to do with me, probably!
), so he's bought himself a shiny new Warco WM280V lathe.
One of the issues he's having with it is trying to part off something - the chatter is indescribable! Now... when I'm parting off, I generally have the lathe at 680rpm (i.e. flat out) and use a 3mm wide parting tool (Mircona with carbide inserts). So long as my carbide is good, and so long as the part is held firmly enough, and so long as I stick oil into the cut, this generally proceeds without any real issues. If I'm cutting quite a lot of metal off, I'll usually stop it before it's cut all the way through & finish with a hacksaw, that's only to stop the cut-off material from sagging inwards & jamming the tool (guess how I know THAT happens!)...
Trying the same thing on my mate's lathe, and it starts vibrating so hard I'm worried it'll bring the building down!
Is this just a rigidity thing, or is there something else at work here?
At the moment he's using the standard tool post (QCTP to come), and HSS parting off blades.
Which actually leads me to another question: His parting off blades (as supplied) have a slightly triangular top face, so the top of the cutting edge isn't flat. Apparently this reduces tool load & chatter, but to my mind it means there's no top rake, and it's harder to get a truly sharp edge (now you need two razor sharp edges)... anyone got any experience of this? FWIW, the amount of chatter & vibration seemed to be about the same no matter what the tool form was. The only way we could get close to making it work was to slow the lathe right down, at which point it became very easy to stall.
