Adjustable boring bar bearings

**Frank S** · May 10, 2025, 12:53 AM

last year when I made my DC powered boring bar I just made simple quick bearing mounts for the job I needed at the time. I didn't bother with making them adjustable for centering the boring bar. Mostly since I was pressed to complete the job at hand.
I had used it a couple of times and it was always a royal pain to get centered. A couple of things needed to be altered. #1 the bearing mounts once tack welded in place made it difficult to remove the boring bar to remove the aligning cones. #2 it was impossible to try the shafts or pins for fitment after line boring without cutting the mounts off. Then if I needed to take another few, thou out of the bore.
With these new bearings and mounts I can micro adjust the alignment and remove the bearings and the bar without losing the alignment I can also pass the pin of shaft through the mount rings for double checking the bore.

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**DIYer** · May 10, 2025, 04:12 PM

Thanks Frank S! We've added your Adjustable Boring Bar Bearings to our Metalworking category,
as well as to your builder page: Frank S's Homemade Tools. Your receipt:

Adjustable Boring Bar Bearings by Frank S

tags: adjustable, boring bar

**Saltfever** · May 14, 2025, 10:09 PM

Frank, I'm trying to understand your drive mechanism. I see the fine threads that appear to be 10 to 12/in? A feed of 0.100" per rev seems to be a "heavy" cut for a turning operation? What kind of surface finish do you get on the bore? Is that the drive end of the boring bar? Is the vise grip holding a temporary alignment bushing?

**Frank S** · May 15, 2025, 12:23 AM

Originally Posted by Saltfever

Frank, I'm trying to understand your drive mechanism. I see the fine threads that appear to be 10 to 12/in? A feed of 0.100" per rev seems to be a "heavy" cut for a turning operation? What kind of surface finish do you get on the bore? Is that the drive end of the boring bar? Is the vise grip holding a temporary alignment bushing?

The threaded cylinder with angular contact bearings inside allowing the boring bar to rotate. The feed 12 TPI the chain vice grips make a convenient handle to turn the cylinder with. The power to rotate the boring bar is accomplished via a 36 VDC gear reduction motor Connected to my battery charger using the 25amp 24V setting without batteries this time.
battery powered line bore machine
This is how the bores turned out