Sanke Keg - hole drilled slightly too big, need advice

I had ordered this Blichmann Brewmometer beforehand thinking I was going to get a Polarware kettle with a threaded insert BUT then I got a Keg instead and tried to make this work. I can't get a good seal because the hole was drilled slightly too big I think and now I'm trying to get washers and o-rings to fill the gap.

My question is these threads are 1/2" NPT. I'm tightening this into a copper 1/2" coupler inside. On McMaster Carr they have stainless steel (18-8 or 316) with washer sizes like .5,.501,.503,.515,.531, etc.
McMaster-Carr

What would you guys say would be a tight fit but fit over the threads. I will use a washer or two on the outside and inside plus some o-rings around 11/32size to hopefully seal this up for good.

Thinking bout these O-Rings:
McMaster-Carr

Any thoughts?

Here is the temp probe I have.


As always I appreciate the help!

If you have a Lowes near you, they have stainless washers in the specialty drawers. Get the 3/4" ones. However, you will probably find that you have to pack the heck out of the threads with teflon tape to get it to seal because orings don't seal against threads. Instead of washers, you might want to go with a locknut on the thermo, sealed to the threads with teflon, and backed all the way down.

The Oring you're looking at is way too small. You'd want something like an ASTM number 313. You can probably do it cheaper by getting some silicone baby bottle nipples and use the mounting ring with the nipple cut off.

Yea - drill out to 3/4" and use a reducer coupling like this one then just order the right o-rings...

Ok so 3/4" washers should fit snug?

The normal locknut with nylon threads is rated above boiling temps so maybe I'll try that. Thanks guys!

Contact your local Homebrew shop or club. Ask them if anybody in the shop or club TIG welds stainless.

I found a guy here that welded my 3 keggles for the ball valve, temp fitting (same one you have there) and the sighttube for 10.00 a fitting IF i supplied the fittings and predrilled the holes.