Acme Taps for wood

[Nicholas Lingg]

Does anyone make a tap and die set in Acme or Square thread?

[george wilson]

Acme or especially square threads in wood are the very worst type of threads. They easily shear off. The correct thread for wood is a "V" thread with 90º thread angles instead of the usual 60º angles commonly used in metal threads.

I can't post pictures right now as the "manage attachments" box won't fill out.

[Ray Gardiner]

Hi Nicholas,


There were a few threads (pun intended) a little while ago, that went into some detail as to why square and trapezoidal thread profiles (like acme) are unsuited to wood, the traditional metal thread, that is the triangular 60 degree, is still ok, and most of the taps and thread boxes you find commercially for wooden threads are 60 degree.
If you have a choice then, as George has already said, 90 degrees is preferred.

Regards
Ray

[george wilson]

The "manage attachments" isn't working for me right now,so I cannot put up pictures. We had to replace the 6" diameter screw in the bookbinder's standing press in the Historic Area. It was made many years ago by someone who didn't understand wooden threads. It had square threads on it. Each thread was 1" wide,quite a coarse,heavy thread. None the less,it had gotten chunks of it broken out until it would no longer function. We retained the old press frame,but made a new screw and nut. The new screw we made with 90º "V" threads,and stained it up to match the old part of the press. I have a nice picture of it WHICH I POSTED here last year. If you search my postings you can find it.

P.S.,I just searched "A book press screw we made" and found it at once. Look at the 90º angles of the V threads. This screw will last 200 years if it isn't allowed to be eaten by termites!! The old screw was perhaps made in the 1950's.