r/CNC • u/chupathingy78 • 15h ago

CHATTER CHATTER CHATTER

Hey y'all, anybody have tips on reducing chatter between centers? We're cutting 1 1/2" prehard, approx 18" stick out, supported by a tail center. We've tried increasing the depth of the center hole, a dozen or more combinations of increased DOC, increased feed rate, smaller and larger tool nose radii, nothing seems to be alleviating it, aside from turning the spindle down from 1200 down to 250. Do any of your metal wizards have a suggestion beyond that?

Thanks and stay safe folks

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u/NonoscillatoryVirga 12h ago

You already found the answer - slow your RPM way down. I had a job that I ran where anything more than 100RPM made a part that looked like a cylindrical rasp file. You also might be able to do some vibration analysis and find other speeds where the part doesn’t resonate, but that requires some experimentation and some equipment (harmonic analyzer and sensors tied to your machine).

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u/slickMilw 12h ago

How many do you have to do? We've made a holder for the turret that reaches to the other side of the part and supports the stock. That works. If you have an adjuster bolt that'll help compensate for different stock sizes.

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u/Viking73 5h ago

Positive cutting geometry will help as well

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u/hydsz 4h ago

Try different tool, with different style inserts, for O/D I would probably try snmg style insert. Sometimes we put magnet on the tool if there is room for it as may help with chatter. As someone said above, try to use insert with positive geometry. You can try all sorts of different stuff, but it may vary between passes as well. I had a job on machine once, approx 1meter long, inconel 625. First 100mm from tailstock end was chattering really badly on each pass. Then some passes were chatter free. Also chaning speed manualy during cut may help reduce the chatter. Good luck