Originally Posted by dmfa200
I just used a step bit to get the hole close, and used a flapper wheel on an end grinder to get the fit snug enough that the coupling would stay put with out tacking. You can use a file, but power tools speed up the process.
On the half couplings I play it safe and thread a nipple with teflon tape in the coupling to make sure the coupling stays round until the welding is complete. Remember what I said about welding on small short pieces?
The teflon tape insures that the threads don't gall from the heat. Stainless steel threads are notorious for galling.
I've mentioned this in another thread. A center drill works better than a drill bit or step bit for starting a hole in stainless. I learned this from my machinist boss.
So you used a flapper wheel small enough to fit inside the hole?
I'm familiar with galling. I had to cut a 2" plug out of a fitting when I had my kegs welded... what a pain.
I know I put WAY too much heat into the purge I made and that is probably part of why it distorted so much. But actually, it becoming kind of oval is a benefit. GreenMonti suggested I make it oval (he meant after it was welded), so it would fit the contour of a keg a little better. I didn't do it on purpose, but didn't worry too much about it. I have a lot to learn about heat distortion and working with it. I work with wood, so I'm used to material movement, but not so much while in the assembly process.
I read somewhere about heating one side of an object causing distortion. If I had pre-heated the entire purge with a propane torch prior to welding, would it have distorted less?
Edit: Sorry for the off topic post, forgot what thread I was in.