Re: Half nut restoration
Hi Ed,toggle quoted messageShow quoted text
Thanks for the reply. I had the same thought as you about leaving some room for thread adhesion, but I was also thinking that a sleeve soldered into the half nuts would solve the problem of the two halves wanting to separate. I bored the hole out to about .830 and turned a piece of bronze sprue from the bronze casting class recycle bin to fit. This will leave a thin web between the two halves that I can remove with my dull hacksaw and clean up with my broken rusty file.
I bought a 3/4" x 8 tandem Acme tap on e-Bay a few months ago and I have been itchin' to try it.
--- In southbendlathe@y..., edward4583@a... wrote:
I posted on this around January. I had mine built up with WELCO 14 BARE
nickel silver alloy. I just got my 9" running last week and the halfnuts I
rebuilt with this procedure are as good as a new set if not better. Here are
a few added thoughts in addition to the article.
1. I did all my work on a Bridgeport mill. This procedure can be done on the
lathe as in the article but the mill setup is sturdier
2. I bored the original threads out to .85 dia. I reasoned this would leave
.05 of alloy to act as a "base" for the threads.
3. The halfnuts appear to be made from a single casting and split down the
middle with a 1/8 cutter after all factory machinery is complete. When I
sized and cleaned up the silver solder I left the center portions heavy so
there would be .005 or less between the two nuts when in the fixture. (In the
fixture the nuts are in the engaged position on the lathe.) In hindsight I
believe this step was the basis for my threads coming out as good as they
did. I'll explain. I purchased a new tandem acme tap for this project and
during tapping I had to add clamps over the threaded portion of the nuts as
the casting would flex away from the tap. I tapped about 1/4 turn and backed
out. I did this while advancing 1/8 to 1/4 turn each time. By having a full
diameter of metal around the tap I experienced none of the "breakout" that
would have been felt with the 1/8" gap between the nuts. Also, you can
purchase a single stage acme plug tap for about 1/3 the price of a tandem.
Don't even try to do this with an acme plug tap. I think the nuts would break
from the forces required to remove all the metal with the single thread
former on the plug.
I have spent the last year rebuilding my 9" and at some point in time I plan
to post pictures in the files sections so the group can see my toys. In this
was to be pictures of these nuts and the fixture. If you have any questions
feel free to contact me.
9" Model A