How do I cut off the BOTTOM of a keg

[SenorWanderer]

I'm working on an e-HLT/HERMS build and I'm thinking it would be nice to have a bottom dump valve because I'll be whirlpooling and chilling in the HLT. I used the pvc coupler in the hole method to cut the top of one of my kegs and it worked brilliantly but I'm drawing a blank on how to cut a hole in the bottom. I want the cut to be just as nice and perfect as the top cut I've made. I really don't want to free hand it and I don't want to have to make such a big pilot hole to use the pvc method.

Has anyone one done this? Any ideas? I obviously have an angle grinder, and I have access to a machine shop but I'm a novice there so I can't even begin to think of what tools/machines would be useful. I also have access to a plasma cutter, but I'd like to avoid using it on this, even if I could fab a functional compass jig. I'm not opposed to a SMALL pilot hole as a last resort.

 

[ahave]

When I converted my keg into a keggle, I simply used the guard on the grinder against the rim of the keg to make the circle. You need a little bit of a steady hand, but it came out looking pretty good.

 

[IrregularPulse]

I've freehanded my two kegs and with a circle drawn first got very round circles.

 

[shroomzofdoom]

I was thinking of doing the same thing-cutting the bottoms.
I was going to make a jig out of wood blocks then strap that to the angle grinder. The idea being that I should be able to ride the bottom skirt like a rail...at least that's how it works when I imagine it anyway.

 

[Ohio-Ed]

Here is a jig I built. With a couple blocks on the base to keep it centered inside the keg skirt, should work fine. In these pics, I was making a very small hole so I needed to clamp a block behind the grinder to change the angle. The last pic is before I touched the hole with a file or sandpaper.

 

[TheZer]

np

 

[SenorWanderer]

Ed, thats nice work. Looks like you were cutting off the top, while i'll be cutting the bottom, but your concept has my wheels spinning and I think I can work out a solution. Thanks for sharing! I'll post what I come up with!

 

[GillandCo]

You could start with a drill bit in the center, open it up with a step bit, then use the same concept as Ohio and build a jig with something in the center to hold it in place...Thats what I would do.

I know this is the top, but mine looks easier to build than ohio's...but his looks sturdier! Whatever gets the job done! How big is that hole 10"'s?

https://www.homebrewtalk.com/f51/jig-i-made-195299/

I free handed 2 of my kegs...one im still using, the other retired!

 

[Ohio-Ed]

You could start with a drill bit in the center, open it up with a step bit, then use the same concept as Ohio and build a jig with something in the center to hold it in place...Thats what I would do.

I know this is the top, but mine looks easier to build than ohio's...but his looks sturdier! Whatever gets the job done! How big is that hole 10"'s?

https://www.homebrewtalk.com/f51/jig-i-made-195299/

I free handed 2 of my kegs...one im still using, the other retired!

I kinda overbuild most things

It is adjustable both ways and the "base" keeps it from moving when the cutout becomes loose.

The keg in the pictures is now a fermentor. I made the hole small enough that I could clamp another keg's cutout over it with a big o-ring to seal. So yea, it's probably about 10".

The stepbit hole in the bottom is a great idea.

On the other end of the threaded "T" handle is an upside down holesaw that fits in the keg valve opening which could easily be changed.

 

[Dwain]

I've got an idea. I'm pretty sure it will work with a minimum of jig building. I can't explain it well but I will go to the shop now and mock something up. I'll post pictures in a little while - Dwain

Well, so much for that. Long story short, by the time I got mine to work for "any" keg, it's as much to build as the other jigs.