Learning to Cut Threads

[SLK001]

Try cutting a 64 TPI thread with a piece of 1/32 rod and you can see the problem. The thread becomes a spiral "U" shaped groove around the screw rather than a "V" shaped thread. In most cases, I grind threading tools from HSS. Carbide is a fair, general, turning tool. But if I'm doing threads, I need more "right" than mass produced carbide can provide. At least in my price range. There may be finer tips at a higher cost. . . I don't know. It's a lot easier to just grind it.

Although they probably exist, I haven't seen a carbide insert for a thread with a greater TPI than 44 TPI, so at 64 TPI, you're going to have to use HSS. I use HSS for materials that carbide just can't handle - like threading plastic. I can get my HSS bits much sharper than any carbide bit that I have seen.

 

[Bi11Hudson]

For the most part, the biggest thread I have ever cut was 16 TPI. There have been a few "one offs" larger, but rare. I use HSS for threading always, I did try carbide once on 16 TPI but didn't like the results. I do a lot of 56 TPI, and some rare occasions have tried 80 TPI. For 90 or 120 TPI, I depend on taps and dies alone. I know 000-120 from memory, but my gauge only goes to 80 TPI. Optical screws are now metric, have been for some years. I don't know the thread pitch, but they are a little larger than 00-90, which is 0.047. The screws in my glasses are around 0.052. For reference, a 000-120 screw is 0.034. My lathe will cut 120 TPI but I'm not up to it. I'm just babbling, this doesn't mean anything.

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