It is not unusual for a new tool to be more prone to some form of chatter than one with a bit of use. I think it is a case that the new sharp edge can easily dig in so when a bit of chatter starts it does dig and then spring back and things build up from there. With a slightly worn tool there is a bit of rubbing and back pressure so the tool is stabilised.
One approach I have taken on manual machines is the hone the edge of the tool to take off the really sharp corner. You must not overdo it otherwise the tool life is drastically shortened, but sometimes a little bit of honing can extend the tool life because it prevents micro-chipping of the sharp edge from the chatter.
Another trick is to mount the tool below center, remembering that on a CNC with the tool at the back upside down raising the tool puts it below center from the point of view of the cutting action.
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An open mind is a virtue...so long as all the common sense has not leaked out. |