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Looking for recommendation for type of carbide inserts for boring small holes (steel-1/2") with a boring head


Cast Iron
Mar 7, 2018
Kansas City
I know boring bars have been discussed extensively on the forum, but I can't find any topics recommending carbide inserts for small holes. I have a Criterion boring kit with 3/4" dia. carbide faced bars, but prefer bars with carbide inserts.

I have a few 3/4" bars which take either TPGB-321 inserts or CCMT 32.51. But I'd like to get some 3/4" bars for smaller holes. Insert and corresponding boring bar recommendations would be appreciated. Thanks.
I would look at a PCD insert. But first, I'd like to see how you're going to bore 1/2" holes with a 3/4 bar/
Sorry for the confusion. Criterion head accepts 3/4" bars, but the bars for smaller holes neck down. The Criterion set (with the 3/4" head) goes from 1/2" to 1-1/4". Each bar is 3/4" dia. at the big end, with a flat to hold it parallel with an allen screw in the boring head. The smaller bars neck down an hdave small pieces of carbide faces. Bigger bars are obviously thicker and contain bigger carbide faces.

As mentioned, I have bars which accept big inserts. Looking for bars which are smaller dia. at the head and accept smaller inserts.

This isn't my photo, but this is somewhat similar to the set I own, but bigger boring head.

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Often a problem with boring is that the cutter/insert heal rubs below the cutting edge. Quick check it to just hold the boring bar to the bore and see that the heal clears. Going to a small bore (ID) may need more clearance below the cutting edge.