in response to a message on the NCRS # 315184
.1970 weld-nuts: should I paint my nuts, or before painting get a mask

If you understand how those nuts are welded on, then you will understand why these assemblies are either completely painted or completely bare, but would probably never be painted with its bare nuts exposed so there is no need to mask them or use lacquer thinner as this girl thought.

The welded on nuts of the C1-C2-C3 era I have seen, and used and purchased in bulk for various repro’s are products called “weld-nuts”. Prior to welding in fixtures, these nuts possess small tit like projections in each corner of the lower surface. On the upper exposed side opposite these tits, the corner is lowered to engage a special designed electrode with 4 protruding terminals. These 4 protruding terminal mate with each corner right above those little tits. When the electrical current flows those little tits are melted and the nut then drops flush with surface of the substrate welded in place.

If the substrate or “weld-nuts” were painted before assembly, the current would not flow properly and you nuts may fall off. Those C1-C2-C3 ones are always unpainted until after assembly. I have never heard or seen these nuts with evidence of any mask or disguise. You can save those q-tips for the make-up mirror and do not inhale too much lacquer thinner.

This type of welding is referred to as Resistance Welding. Thankfully I was corrected by another. in my terminology for this type of welding. Although an experienced reproductologist, I am merely a lay welder compared to many others. That well known ecclesiastical welder, the Right Reverend Dale Pearman has rightfully informed me of the following

" The process by which your nuts melt into another piece in all four corners when under an automated fixture such as you describe is called RESISTANCE WELDING, not arc welding. The rate at which such nuts fall off afterward is much higher than if other forms of welding had been employed but resistance welding is VERY cost effective."

It goes without saying and may even explain why your nuts fell off and other didn't.