[apalm]

I have been having a lot of trouble with what im thinking is my guide bushing. Just recently got Star swiss a couple months ago and just recently have been having issues with the guide bushing. I am using 1/4 inch 304ss and it seems like the guide bushing is getting tighter as we run. I took it out and lapped it to try to clean up and chips in it but still seem to be having the same issues. The drill will go in and when the machine pulls the stock out of the drill it gets stuck, then when it goes up to bore it snaps the carbide dill thats stuck in the stock and then snaps the boring bar. If any one has any advice it would be great!

[uperez]

Is your material and tool getting properly cooled? Sounds liike thermal expansion.

[MCImes]

Sounds like you have a burr from facing on your stock; thus preventing the stock from retracting into the bushing. Are you putting a .002-.010" chamfer or radius on the bar when you face? If not, add that. Be sure to ramp in
Try something like;
G0 [STOCK +.05] Z.03
G1 [stock+.004] F.005
G42 [stock-.0005] Z.01 F.0005
G3 U-.020 Z0 R.01
X-.02 F.002

The bushing would have to be REALLY tight for it overpower the main collet on its own. Or your main collet is set very loose. The stock would be scratched/galled to hell if your bushing was that tight.. If your stock is not severly scratched with 3 evenly spaced perfectly straight lines then the bushing tension is probably not your issue. It sounds more like a burr preventing retract to me.

[DPMINC]

Your bushing is not getting tighter. Your material is expanding. Especially since your drilling 304SS. Go slower on your drilling (both speed and feed). When you get to depth back off a few thousandths and add a dwell before retracting that way you have a chance to cool down and decrease diameter.
Another thing to do would be to leave the bushing a little on the loose side that way if your material does expand it wont get hung up in the bushing when retracting.
Another thing you can do (if your hole is less than .600 deep) is to take a skim cut on the OD before drilling.

[dookie2022]

If your machine is a Star do you have the optional Guide bush magic installed
If you do have this system then the air pressure is too high so the setting needs to be lower
Also do not forget to purge air in system by commanding M150/M151 to stabilize
Now in some case by using a cermit type of guide not a carbide type can solve this issue but they are expensive and there are not too many manufactures in the world that can supply.
If you have a standard guide bush system in most case the guide bush is too tight or the material used is not round or varies in diameter too much.
Coolant can also have an effect are you using oil or water soluable.

Regards