Chatter?

[vectorsc]

I don't know exactly where to put this - I am chucking a 16" long 1" piece of high carbon steel, about 30RH. Am using a live center in the tailstock.

When trying to run a profile, I'm getting a good deal of chatter closer to the live center that tails off when you get closer to the chuck and the center itself. I get a hell of a snakeskin pattern on the workpiece.

Cutting tool is a CNMG 432 MM Sandvik insert, 730SFM, .01" feed .02" DOC.

Anyone have any advice?

[EliseoMonteverd]

Hi,
Try to change for a DNMG, VNMG (both are negative) or VBMT (this is positive) insert with little radii.

Good luck.

[03clipse]

Stone the cutting edge just i lil bit. I have found that to work sometimes. also very the RPM up and down during the chatter. I think the new HAAS controls have a g code that will vary the rpm up and down a certain percent of what is programmed to help with chatter.

[scotta99fan]

Can you use a follow rest?

[fizzissist]

Assuming you've checked that your center is making good contact and providing good pressure against the part...and the center is locked down real well...it don't hurt to check

I'd also go down to a 431 nose radius to reduce the relative contact area, but slow it down. Feeds look fine, but maybe dropping the SFM to 650, maybe 500? I hate reducing the IPR and DOC because you need the pressure, so I go with lower speed first which lowers the frequency.

A positive rake insert would be a good suggestion too, but I'd be likely to try and fix what's in the machine first. For me, I've found that I get better life with the Sandvik inserts in steel running at 20% less than the factory recommended SFM. (that's just me, though)

[EliseoMonteverd]

Maybe an uncoated insert could help.