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7/8 shank boring bars (nearly) non existent??

You could try this, but it will be very expensive. Purchase a 1" carbide shank boring bar that holds the insert geometry that you plan to use. Chuck it up in a lathe, and use a PCBN/CBN or PCD tipped turning insert to cut it down to Ø7/8. I'd start with the RPM at 200-300, feed .0015-.0025 IPR, and a DOC of .015. I've had to use this method to turn down shanks on carbide shank boring bars & solid carbide round tools before and believe it or not, it really does work. The first time I tried it, I was like, "Holy S#/T it actually works!"
Hi again Hvnlymachinist:
Man that bore does look awfully gnarly in the places where it hasn't cleaned up yet.
Kudos to you for finding a way to make it work without turning the making of the tooling into its own elaborate project.
That bore looks pretty good considering you bored it on a radial drill with no outboard support...I'm impressed.
Are you going to run a hone through it to make it cylindrical and shrink fit a sleeve into it or will it be good enough to just press a sleeve in and maybe stitch weld it at each end?


My plan depends on the actual finish quality, I got....... Edit; this line changed from" held up" to "sent on errands, and made phone calls" ........ today so I'm still working on it.

If it's good I won't have to hone. But I do hope to shrink fit a sleeve into it. I like to use liquid nitrogen, then follow up with a weld at the head end. I doubt I can reach the inside for a weld there but the sleeve will be pretty heavy.
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