Lathe Boring Bar Holder

I find boring bars exciting.

I have a boring head for my milling machine, which is excellent (indispensable) for milling holes to a certain diameter in square stock. But for round stock in my lathe I’ve been messing around with various cutters with mixed results while trying to cut the inner diameter of various projects.

Boring bars are the correct tool for the job on a lathe, but I don’t have any. Even if I did, I don’t have a holder.

I decided to rectify this situation by making a holder that would accept the cutters from my boring head set.

When I made my quick-change tool post, I milled a dovetail into a large block of steel. The idea is that I can cut off chunks as needed to make various tool holders without having to mill a new dovetail.

I sliced off a chunk with my portable bandsaw, cleaned up the shavings, and then milled it down to a more appropriate size.
Boring bar holder for lathe
I drilled a starter hole  in one end and through the full length of the workpiece.

Then I used my boring head to bring the diameter to fit the boring bars’ 1/2-inch shanks snugly.
Boring bar holder for lathe
Boring bar holder for lathe

In order to check by progress while boring the hole, I had to move the workpiece out from under the cutter and fit some calipers into the hole. My DRO proved very helpful for this: I could set the axis to 0, move the table to get the workpiece to a measurable location, and then  move it back till the DRO read 0 again. It perfectly relocated the hole under the boring head every time.
Boring bar holder for lathe
Boring bar holder for lathe
Boring bar holder for lathe
Boring bar holder for lathe

Once I had bored out the hole to the proper depth and diameter,
Boring bar holder for lathe

I set the workpiece on its side and drilled 2 holes through to the 1/2-inch hole, which I then tapped out with 1/4-20  threads for set screws (i once again use the DRO to relocate the holes after changing the drill bit out for the thread tap)
IMAG1Boring bar holder for lathe069
Boring bar holder for lathe
Boring bar holder for lathe

In order to tap the threads perfectly straight, I like to lock the tap in the drill chuck, and then use my lathe chuck handle to turn the chuck manually.
Done!
Boring bar holder for lathe
Boring bar holder for lathe

I slapped the new boring bar holder on my lathe and bored out the inside of a couple of my lathe feed gears as an inaugural project. The boring bar performed perfectly in its new holder.
Boring bar holder for lathe

I win.

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