Cheers guys, seems I am not alone here! The inserts are ccgt, sharp, positive rake, designed for aluminium. 0.4mm rad on the tip, I am using the same cutter for roughing and finnish, just reducing the feed speed.
Hu, I am fairly certain the chattering is caused by a damaged tip, which has suffered due to the swarf getting wrapped around it, then the cutter pushes it int othe side of the part. Although the facing op leaves an almost mirror finnish on the internal face of the part, it is just the sides that are screwed. Perhaps a different style of bar?
I am starting with an 18mm drilled hole, then facing around 2mm off of the piece before it gets to work inside. The bar is a 12mm diam, and is not suspended any further out than it needs to be. I guess I could switch to a larger bar, but that means using a boring motion, rather than facing, and there is where the problem is with the chips.
Perhaps I will take a smaller cut, and play with feed speeds to get those chips to form a little better. Thanks guys, I will let you know when I get it sussed out!
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