What to make a small/long HBM boring bar with?

[Vancbiker]

Seems like a good way to approach the job.
Kuraki is one of the best HBM builders. Nomura is another. Way better than the more common Toshibas.

 

[Garwood]

It worked!

The bar worked fine, but it could have been smaller diameter to help with chips getting packed. I think I could have done 30" in one shot, but at the 20" mark the chips stopped flopping out of the end and stopped rotating with the bar. So I stopped and carefully pulled it out. I was worried about chipping the tool so I followed the table rapids with the quill and used the quill to retract by hand (you can feel stuff with the quill).

I ran 130 RPM and .0065"/rev feed. I didn't want to push anything. Carbide looked great at the end. It was nice to listen to the end of the tube and hear a nice smooth cut. For lube I put a piece of duct tape across the bottom of the outboard end and poured in about a 1/2 cup of cutting oil. I started cutting when the oil made it to the other end. Worked well enough.

This kind of work really is a fun way to make a living. Doesn't seem to be much like this though.

 

[eKretz]

Got 'er done, that's the important part. About the only thing I might have done differently is to change the location of the guide bushing. I'd have put it behind the cutter instead of in front. I would have bored in a short distance to finished size with a short bar, (just long enough to get the cutting tool and the guide bushing behind it in) then switched to the long bar. Then bored to final depth. Kept an air blast going to ensure no chips got between the guide bushing and the finish. The chips would have been able to get out the end that way. Also you know you're generating a straight bore that way, since the bar is guided by the freshly machined surface rather than the DOM tubing ID.

There are other ways too, but that's a good one.

Aaand I just noticed that this was from July of 2021, not 2022. Doh!