Hi. I am trying to fabricate an inside thread. The strength and precision are not critical. I came up with the idea of fabricating the thread in a sleeve using a TIG welder and some steel wire. As an experiment, I tried to weld a 1/16" wire to a piece of 1/16" sheet. This was a lot harder than I thought. At an intermediate current setting, the arc was not hot enough to melt the sheet, but if it ever jumped up to the wire, even for a second or so, the wire would overheat and melt through. Filler was no use, since it would just blob everywhere. The current was set to be just too cold to put a decent bead on the 1/16" sheet, but it was way too hot for that little wire.

A lot of folks told me that you can TIG weld a razor blade to an anchor, but it seems to be hard to attain that kind of control here. I sharpened the 1/16" tungsten to a sharp point, but it seems to just either jump to the sheet (no good) or the wire (even worse). Other folks have suggested that this is a good way to make internal threads for a post vise screw, but with brazing instead. Would this work better?

evfreek - are you putting the wire through 2 holes in the plate and then tring to weld from the backside? If so leave some extra stickout on the wire to melt with the torch so as to form a ball bigger than the hole - it will act as a rivit. - JK

1/16th wire is a heck of a lot smaller than any thread I have ever seen on a post vice, and 1/16th sheet metal would have no structural strength anyhow, so I am not sure what you are trying to do. Yes, those sizes are too small to be readily tigwelded, and would lend themselves more to a soldering operation. The type of brazing used to fabricate a postvice box nut is forge brazing, not torch brazing, two entirely different operations.

Sorry for the mix-up - I thought you were triing to replicate a sewn type thread in clothing. Now it makes sense if you said it was for a vise. Here is a link for the same problem that was discussed awhile ago: http://www.iforgeiron.com/forum/f11/leg-vice-reproducing-screw-box-4975/ - JK

Edited February 15, 200917 yr by jeremy k

Hi Jeremy and arftist. I am trying to fabricate a thread for a simple cap. The seal is by o-ring, so the cap need not seal liquid tight. The experiment is just laying a piece of wire on the sheet and trying to weld it with the TIG arc. I can easily weld 1/16" wire and put a decent bead on a 1/16" sheet (or even a 0.022" sheet, but 0.005" gives me the fits). But trying to weld wire to sheet is just not working. I am suspicious that it is a fitup issue. In other words, the wire must lay flat against the sheet to keep the heat from getting out of control.

The idea about forge brazing sounds very interesting. I like the fiddly TIG welding, but it is just too hard here. I can fix snapped umbrella ribs, but this is much much harder.

What type of cap / size? Drilling and tapping a piece won't work?

Hi Jeremy. The cap is slightly over 2" in diameter. Drilling and tapping will work, but I do not have a lathe of that size. Before I impose on a friend, I will try the forge brazing. I think that should get past the fillet problem.

try to heat up the plate with a torch,and than tig. while the plate is hot,melts faster. maybe...

drill holes and plug weld it from the outside. as for leg vise screw boxes (nuts) see here,
http://www.iforgeiron.com/forum/f7/question-about-leadscrews-9883/#post94581

drill holes and plug weld it from the outside. as for leg vise screw boxes (nuts) see here,
http://www.iforgeiron.com/forum/f7/question-about-leadscrews-9883/#post94581

Thanks, Irnsrgn. This is a great idea. It gets rid of the slop and heat problem simultaneously! I'd have never thought of this in a million years.

Can the local machine shop cut the thread for you, as they would cut threads all the time and are set up for this sort of work.