1" to 10 mm boring bar adapter

[Frank S]

In Needing to cut an internal snap ring grove in a .625" bore I discovered that I still hadn't gotten around to making a boring bar adapter for 10mm boring bars. Since this bar is 6" long I wanted to use the BXA#4 250-204 1" bore tool holder, as I have a few of these bars in varying insert configurations I also have a couple of 3/8" bars I was hoping the bushing would be able to squeeze down to hold them as well,
Here is what I did I started with 1" 1018 cr round drilled it to 10 mm set up my change table to make my band saw a vertical saw then cut 3 groves part way through the length of it and one all the way through the length of 1 side

[DIYer]

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

Boring Bar Adaptor by Frank S

tags: adaptor, boring bar

[Frank S]

I tried a 3/8 shank boring bar in the adapter today. I think I will just make a separate one for the 3/8" long shank boring bars
The short shanked one work great in the precomposed brazed carbide took shank

[metric_taper]

I like this idea of making a collet to fit in the boring bar holder. Curious why you would not use the 250-201 holder for holding what appears to be an internal threading bar.
That seems to be the way I end up holding these smaller shank tools. For round, I use the 250-202 holder with the groove machined to trap the round shank.
I have the small 100 series for my 10x24 lathe, and the 400 series for my 18x40 lathe. I have run out of adjusting range (for tool center) on that larger size QCTP system for very small diameter shanks.

[Frank S]

I like this idea of making a collet to fit in the boring bar holder. Curious why you would not use the 250-201 holder for holding what appears to be an internal threading bar.
That seems to be the way I end up holding these smaller shank tools. For round, I use the 250-202 holder with the groove machined to trap the round shank.
I have the small 100 series for my 10x24 lathe, and the 400 series for my 18x40 lathe. I have run out of adjusting range (for tool center) on that larger size QCTP system for very small diameter shanks.

Actually I reground a triangular insert to be used to make a snap ring groove. I have a limited number of the 201s and always keep them loaded with square shank cutters. Not even sure if any of them might be 202s instead of 201s it has been so long since i have removed the cutters from them.
This collet adapter fits in the holders I have for 3 of my lathes 1 being a CXA 2 being BXA tool posts
In my original post I wrote it as a BXA but in looking this morning that holder was actually a CXA.
with the number of lathes I have it is sometimes easy to mix up the numbers and sizes of the tooling.
I don't do much internal single point threading any more and almost never any internal threads on anything under 1inch. I just don't have the patience for the fiddly little flexible shanks. Snap ring grooves in a 5/8 inch bore try my patience enough.

[Toolmaker51]

Commercial tool holder bushings are made same way; at WAY higher cost per unit, none over the counter in area, so solution is DIY.
Along with spring cuts, prefer a small flange at one end, and splitting one side is required. Using low carbon material says they'll fatigue, eventually flexing to collapse and break.
So...... while it's still chucked in lathe, cut what passes for a snap ring groove, to one side, not within center of length. Later, when it breaks, a small coil (3-5 turns) of music wire is rolled up and wound into groove. Tying two halves together with original concentric alignment means no clamping is lost OD or ID, and eliminating hunt for matching parts, or mixing two that only appear to match. When there are sets similar in size, take a minute to stamp that ID.