Making wooden threads, by any means........

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Making wooden threads, by any means........

Postby veto » Fri Nov 07, 2014 2:31 am

I see that the thread boxes are not so very popular due to the poor quality of the cutters, the heat treating is suspect apparently. The Beal system does not appeal on the grounds of just not being hand tool friendly. And then, there are the chasing tools which unless you have a continuously rotating lathe are out as well. Has anyone explored the idea of using the cutters from Dictum in Munich for the "cheap" thread boxes, it appears the sizing should be appropriate? Dieter Schmid has a set but it requires a mortgage on your house, no doubt of highest quality though. Just asking, are there other options? Ahh, yes cutting by hand after tracing the pattern but I would like it in this coming year. Thanks for any suggestions. Terry V.
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Re: Making wooden threads, by any means........

Postby Darrell » Sat Nov 08, 2014 4:51 am

Veto,

Newer thread boxes may have issues, but some of the older ones are quite good. I picked up a 1 1/2 inch Henry Boker thread box at an antique shop for $10 CAD. Of course it was missing the tap, but I had seen an episode of the Woodwright's Shop that offered a good solution to that problem.

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A "false nut" and a cylinder of the root diameter of the screw, with a spiral saw kerf cut to match the pitch of the thread box. A couple of metal plates that run in the saw kerf drive the tap. The tap cutter is a piece of steel filed to the appropriate shape, and it acts as a scraper to cut the interior threads.

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Not sure if this is clear, but the tap cutter is protruding from the side of the cylinder.

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And here are some threads cut with the tap:

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It's a bit slower than a proper tap, but it does work, and I rescued a thread box from oblivion.

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Re: Making wooden threads, by any means........

Postby Billman » Sun Nov 09, 2014 6:53 pm

This method was used to cut a big 4 or 5 inch diameter thread for a copy of an early Gutenberg printing press on a TV programme a few years ago - the initial male thread was cut by hand with a mallet and chisel, and then used as a tap to cut the female thread....

I think this may be the programme: https://www.youtube.com/watch?v=O6KmzuULPmQ they are cutting the male thread at about 9 minutes and the female thread at about 20 minutes...

Similar methods were probably used on the large medieval wooden cider and wine presses....
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Re: Making wooden threads, by any means........

Postby AlexanderTheLate » Mon Nov 10, 2014 1:45 am

Didn't JRCCAIM do some experiments with different methods a while ago? Have a look at his blog (in his profile).
I fear the day that technology will surpass our human interaction. The world will have a generation of idiots.- Unknown.
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Re: Making wooden threads, by any means........

Postby jrccaim » Mon Mar 02, 2015 6:52 am

AlexanderTheLate wrote:Didn't JRCCAIM do some experiments with different methods a while ago? Have a look at his blog (in his profile).


Sure did. For the record, I own a 19mm/3/4" wood tap and die set, works perfectly well even if it is asiatic; got it (I think) from woodcraft.com. What I was really trying to do was to cut threads on a pole lathe -- supposedly either impossible or very difficult. I had limited success. I really wanted to chase the threads. If you want to see the experts do this, look up "thread chasing" on your search engine. The experts can do it with a thread chaser (which looks like a chisel with saw points on it) in a couple of passes. The real difficulty is starting the thread. I had reasonable success starting the thread "the greek way" (see below), widening out the cut with a specially ground tool, and finallly using my homemeade chaser, which was made by filing. So much for that effort. See my blog, www.chalupyacres.blogspot.com; I believe the label is "thread chasing."

The greeks (ancient, not modern) cut threads the following way: cut a piece of paper of widtn of the pitch you want. For a wood screw this is at least 2mm and not more than 6mm. Wind this piece of paper very carefully around a round dowel. Tape it down. You have a spiral, which is what you want. With a fine saw, very carefully cut about a 2-4 mm groove right at the joins of the paper. Call the groove the "trough" of the thread. Now you have to cut out the ridges. (Cut down to the saw lines.) This is done with a small chisel, and it is painstaking work. The bigger the diameter the less painstaking, so don't try anything less than 25mm first time. You have to cut down to the trough at about 60 deg angle. If you are a Briton you will celebrate Mr Whitworth and cut at 55 deg :). I have done this and "painstaking" is a mild expression indeed. This procedure will give you a male thread.

For the female thread, you have two choices. (1) out of steel and with files, construct a tap in exactly the same way you constructed the male thread. I have yet to do this. (2) build a die box and a cutter. For this I refer you to Roy Underhill; his books and even a couple of videos on the subject.
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