More parts coming in, solder problems and a fail

A project log for cheap versatile High vacuum chamber

A Modular vacuum chamber that can be outfit

rbalsan1rbalsan1 01/28/2019 at 03:040 Comments

So, I made a lot of progress with sanding disc/ angle grinder drill press and ball bearing , but this technique was very frustrating.  I caved and gave the base plate to a friend to face in their lathe: They look great.

I also have a couple of stainless steel KF40 flanges that I plan to solder to the plates.  

The soldering is the main issue.  Stainless is a major hassle to solder.  I had reasonable success using a rotary tool to wire brush the outside, applying  zinc chloride flux and then dipping the fitting in molten solder  solder in my kiln at roughly 340 C.  All this just to pre-tin the parts so I can join them more easily.

In the photo you can see incomplete wetting on the outside, but a complete ring of wetted solder on the inside.  If I come up with a better technique I'Ill post.

Lastly my chamber came in.

I got 6 inch OD heavy wall pyrex tubing.  The supplier shipped it to me pre-cut in 4 equal pieces from a 5 foot tube.  You can see in the picture that the edges are smooth in some places, but still have some rough spots and some sharpness.I opted not to have the 4 pieces  fire polished for an extra $200.  That seemed reasonable I can fire polish glass tubing.  So I rapped up the tubing like a mummy and put it on my hand rollers and got out a big ole oxy-popane torch and got to work.

For starters, I wrapped the tube so my steel rollers wouldn't scratch the glass.  After trying to rotate the glass with the rollers under the tape I quickly found out that there was too much friction and had to move the rollers into contact with the glass.  Then I found I wasn't getting the edge of the glass red hot with my single burner so I moved the torch closer heating the outside and inside edge of the tube until this happened:

The tube shattered at the edge I was polishing.  I assume I heated a little close on the inside to one of the cool rollers on the outside causing a massive thermal gradient causing the break. Bummer.  but the biggest disappointment was that the edges I was polishing were still nowhere near as smooth as I needed.  This will probably take multiple torches and a lot of patience.