Identify boring bar insert

[Clunker1]

I've acquired a small boring bar that has been very useful. The indexable carbide insert it came with only had one corner left uncapped. I am trying to id the insert so I can purchase new inserts for the bar but having a difficult time with id charts. My inert is 60 degree triangular(T), 7 degree clearance (C). The thickness is 0.128, 0.250 inscribed circle, and cuts top face only since positive rake. The hole is cylindrical halfway like for a socket head bolt with a camfer at the bottom half of the hole. The screw is the same with top of head cylindrical and bottom of head camfered like a wood screw. The corner is rather sharp but can see a tiny facet on the corner edge.

I thought this might be a tcmt220 but this seams to be unusual and pricey. I thought i might be interpreting the table wrong. More common is the tcmt21.5. Can this work? And what corner radius should i use? Ill use this for mildsteel and up to 4140 (no additional heat treatment).

Thanks

 

[Eddyde]

Posting a picture might help. Or maybe our resident expert, davidpbest, will be along to help.

 

[davidpbest]

Assuming your measurements are correct, the ANSI designation would indeed be TCMT22XX where XX is the nose radius in 1/64th" increments (01 = 1/64, 02 = 1/32, etc.). However, that 0.128" thickness looks suspicious to me since triangular inserts with an I.C. of 1/4" are typically 5/32" thick (0.156").

The ISO equivalent insert would be a TCMT1103XX. The 11 is the length of one side of the triangle (rather than the I.C.), the 03 = 3.18mm thickness (0.125"), and XX would be the nose radius in tenths of a mm (08 = 0.8mm). While that insert size does exist, it's not very common.

As far as nose radius goes, to get consistent cutting and surface finishes, you want the depth of cut to be at least 1/2 the nose radius.

I'm suspicious of your measurements, and it is possible you could mount a TCMT22.51 in that boring bar (5/16" thick) which is a much more common insert size. I have a Dorian boring bar that takes TCMT22.5x myself. You might want to call carbide depot and discuss this with them: https://www.carbidedepot.com/

If I were in your shoes and unsure, potentially investing in an expensive insert that doesn't fit, I would either:

• buy one cheap TCMT22.5x insert for a test fit (example), or
• I'd toss that boring bar and buy one where I know what exactly what it is and the required insert type (like one of these).

Hope this helps.

 

[Clunker1]

Since I was eye balling the I.C. I assumed it may not be accurate. I calculated it after double checking measurements ( r= side x (sqrt 3)/6. I have other triangular inserts with same thickness and cutting edge length but double sided G type for comparison.

I belive the I.C. to be 1.8 which might be even more weird as that would make it TCMT1.82x. I don't think a tcmt 22x would fit the bar.
Thanks a bunch for the inputs.