Smooth Finish For Bronze Bushing?

[Kroll]

Guys I am boring out my bronze bushing for a shaft and can't get a smooth finish.I tried speeding up rpm's then slow down the rpms.Then hand feed,then power feed at the slowest setting.I don't have a boring bar for HSS so I was trying to make this insert work.Any suggestions,I am getting close to the correct bore size----kroll

 

[Tony Wells]

Nose radius is too big, and it appears you may have more bar hanging out than needed. Generally, you can cut chatter down also by using a slower spindle speed. Probably a combination of things.

 

[dave_r_1]

Um, I can't solve your lathe problem, but I would suggest rigging up some kind of shield/cover for your motor so that fine metal particles don't happen to get pulled through it [as that is either the air inlet or outlet for the motor that is getting sprayed with your swarf].

 

[Kroll]

Thanks guys,that's a starting point.I do have some inserts w/1/64 rad.coming so I may wait till then----kroll

 

[Tony Wells]

That's likely a TEFC motor, so there is not a path open to draw debris in, and the fan is shrouded and will keep light chips like the bronze there blown clear.

And yeah, a 1 radius (1/64") will do better. If you feed too fast though, you will see a "thread" cutting path, so slow your feed for finish passes.

 

[Wreck™Wreck]

That tool while not ideal should work just fine in that material, it appears that you have problems unrelated to the tooling itself.

 

[tertiaryjim]

Many lathes have a large feed rate. You could dis-ingage the power feed which might reduce vibration and feed by hand.
This often improves the finish.

 

[Tony Wells]

Do you get this chatter based spiral pattern in other materials? Naturally, there are many possibilities that could be contributing to this. Spindle bearings? Tool post rigidity? Insert not properly seated? It looks like a harmonic induced pattern, so that could be a clue.

 

[Kroll]

Guys taking ya'll advice and there is a big improvement slowing down the rpm which also slowed down the feed rate.I did give it a try by hand but could see each time that I stop for a second.I did check the other area's and I did set the bar alittle shorter.

 

[Tony Wells]

Looks much better. Just for the sake of mention, you know to chuck pretty lightly on that bushing, right? Either it will spring back tri-lobed and poorly support the shaft, especially back on the end in the chuck, or it will be permanently deformed in a tri-lobed OD, with the bore nice and round....until you press it into a round hole. Then that out of round condition will transfer to the ID.