Strange chatter on part off tool

[horst007]

I am so unsure of what to do with this. I am running these parts that are made out of a custom made steel that is pretty hard (probably around 40hrc) and have been parting them off with no problems until the corner of the insert chips which is to be expected. Now with a new insert in the part off tool I have very fine chatter happening on th .045 x 100 deg chamfer that I make with the parting tool. So here is the question why did it work for 30 some parts with no problems and then when a new insert is put in play does it start chattering I have tried several inserts and even a new holder for the inserts and the chatter wont go away now. What could be the cause because I am stumped. Also the chatter is only on the chamfer and not on after it is so fine you can hardly hear it whistle when it happens, but it is still too bad to keep letting it happen.

[Geof]

Sometimes when you put in a fresh insert you get chatter because the new cutting edge is so sharp. Was the previous insert that did not chatter used before you started this job?

A possible fix is to stone the sharp edge of the insert to put the most minuscule chamfer on; a couple of swipes with an oilstone might do it. The idea is to take of the extremely sharp edge without dulling the tool and destroying its cutting ability.

[horst007]

Geof thanks for the reply. Yes I had thought of that. I will try that on the next run on those little &%$& of a part. I also though that as hard as the steel was it would take but a part or two to dull it up, but who knows.

[leggazoid]

The material could change from bar to bar. The chamfer operation puts a different tool pressure than a straight cut. The amount of overhang on the tool will adversely affect this. A possible solution is to reduce the tool overhang, or produce chamfer with a grooving or a steep turning tool.

[Karl_T]

You might try to feed your way out of it. Turn the feed way up.

Karl

[horst007]

leggazoid - It was all ran off of one bar. I think Geof is on the right track.

Karl_T - The material is very hard and I am certain it would eat the tool in a heartbeat even if I increased the feed by 50%.


Thanks for the input though I appriciate the in-site from everyone

[chadwiggan]

i agree with geof... ive used a scotchbrite wheel on inserts before and took chatter away. amazing that you gotta dull em to get em to cut lol