Monday, 5 April 2010

How to talk about screws politely...

I bought this set of thread cutters recently on eBay, thinking I got a real score as they are a matched set of four and relatively old.
A couple are marked, "Henry Boker", with "Germany" underneath a symbol of an arrow, two crossed lines and a couple of stars. I did some research before I bought them and the only inference that I could find about this manufacturer was on the Davistown Museum web site. There they stated that the Henry Boker company was a prolific exporter of tools from Germany, many landing on the shores of the Americas. Nothing special there, except to me, a matched set of four average tools is much better than four different ones. I said this before in this blog, I think this comes from being raised poor and having a kitchen cupboard of mismatched glasses, cups and the like. The one shinning star in the whole kitchen was my father's matched set of beer glasses. Go figure. Anyway, I grew up with a penchant for all things matching.

Anyway, back to these thread cutters.

I need a number of adjusting and locking screws for my new shooting board so I thought this would be the perfect answer. The listing and the tools are marked; "1 1/8", "1", "3/4" and "1/2", which I assumed was the size of the d0wels used to make the screws. When they arrived, I noticed they are also marked with a second set of numbers, those being; "13", "36", "6" and "2". They make no sense to me.

The other day I stopped off a Lee Valley (just down the street from the college, tee-hee) and picked up some maple dowels, one 1/2" and one 3/4", just to give them a go. Nope, wouldn't fit. All four have sample threads or test pieces, so I measured them to try and figure things out. Just for an example, the one marked 3/4" has a test thread of 11/16", that is a measurement of the none-threaded area above the thread.

If anyone out there can enlighten me on these sizes, I would truly appreciate it.




  1. Well having turned wrenches for a few years, I know that the 13mm and 1/2" are pretty interchangeable. Would think that the 1/2" dowel would have worked on it. Don know if you knew this but there is a "wider" end on the thread cutters to star the cut on.

    I found an existing German Thread cutter:

    Looking at this the now-fractional numbers could be the pilot hole sizes, but the "2" would have to be tiny.

    Remember to soak the dowel in water to ease the cutting.

    I don't know if that helps or not...


  2. Mitchell,

    That is a problem everyone has even with the new screw boxes. The turned dowel part for threading needs to be just under the actual size of the stated size. The holes for the internal threads need to be drilled with a smaller hole as well.

    Here is an entry from my web site that may help: