Problem- machining Brass 360

[fenix728]

hello everybody i am making this simple part out of brass 360 and i am leaving .01" per side to finish the ID but i get chatter even when i am going 700 rpm and .004" ipm my boring bar is .5 and is sticking out 4.3" carbide. can anyone please tell me how i can get rid of chatter, should i leave more stock for finish or feed faster or slow the rpm even more, the worst chatter is at the front where the cilindric wall is .065" thick an i am using a .0156" TNR insert, thankyou for all your help and time.

[PoiToi]

Try leaving more stock, going faster, and pushing the boring bar as hard as it will go while holding your surface finish reqs.
A part like that should only need one boring bar pass after the drill.
If you have a bar with a smaller TNR, that will help too. (less pressure in the cut). On that note, make sure your bar is SHARP!!! brass cuts like butter, the sharper the edge, the better the actual cutting action will be, instead of shearing the material.


Also, bore before you turn. this should help too.

[ViperTX]

Are you boring on a mill or lathe. I suspect the problem is the stock is flexing the most where it is unsupported...which is the front.

Paul

[jeffrey001]

For such a light cut, I would use HSS boring bar with a very sharp bit, carbide are not very good taking very light cut in brass.

Jeff

[Crapmuffins]

Your boring bar is an 8.6-1 ratio which is over the standard maximum for a carbide boring bar (6-1) It's possible to go over the max ratio to 10-1 by tuning the rpm to cancel out the frequency of the bar's resonance. http://askblueswarf.com/showthread.php?p=4#post4

[Metalmanti]

Move the boring bar as close to the tool holder as possible so you can still bore the part. Also use a .007 TNR insert. You might also try slowing down your feedrate. Depending on the size of the part you can also wrap rubber or lead around the OD to help damp out the vibrations.

[toolsharpener]

have you tried reaming?