Shopsmith Forums

I just spent the last half hour looking at the threads. I got a stock 3/8-16 nut and bolt out. As has been mentioned they do not fit either of the parts on the fence.

I got out my thread gauge and checked the pitch and it is right on 16 tpi. Major diameter is the same within .0005" which could well be my error since I was using a cheap caliper.

It is not double threaded.

Here is a picture of the two threads lined up next to each other:
While this proves nothing it does snow the differences are pretty minor. If I could get to my Machinery Handbook I would try looking up some of the other options there are in non-traditional treads, but way to deep to dig out.

Best to just leave this at don't try to re-thread at home unless you have a lathe and some better measuring instruments.

Ed

Take another look Ed. The one on the left has a lead twice the one the right.

The thread hill/valleys are the same, but the distance a "hill" moves in one trip around is twice as far. The angle of the threads in thy pix though not obvious, shows up.

Another way to verify is to rotate the wing nut counter clockwise and observe it falling into the threads twice per revolution.

Thanks all the the explanations - I think.

Still not sure why it would be needed.

stew wrote:Thanks all the the explanations - I think.

Still not sure why it would be needed.

In addition to faster lead, it also provides twice the bearing surface since two threads are involved. i.e. Both threads exert force thus splitting the stress between them.

However this comes at the price of requiring twice the torque.[

OK I have to take my comment back. Looking at the end of the screw I can see the two starting spots. So I guess the mystery is solved for sure. Should have just looked for two starting places before I did anything else..... and saved myself the half hour.

Now as to why some seem to be hard to remove, well that is another question that I can't even attempt to answer.

Ed

I am gonna speculate that burrs created during the drilling of the hole for the pin may be a contributing factor.

Ron
Thanks, that I can understand but I think what was throwing me was the difficulty that was being had putting the nut on and why that was and if a different type nut would be needed for a double or triple. This was due to my lack of knowledge for machining and fasteners.