Hole cutting advice

[whistlerface]

Hi. I'm looking to get a pot from Powell brewing. I've bought a weldless tri-clamp bulkhead to fit to the pot.
The seller of the bulkhead said it needed a 41mm hole to install. Not sure why they couldn't have made it 40, but that's the problem I now have.

The place I bought the bulkhead just happen to also sell a 41mm Tungsten Carbide Tipped Holesaw for £6 .
PowellBrewing kindly said they could punch a 40mm hole for nothing. I think the thread of the bulkhead would possibly screw ok in to the pot with a 40mm hole, but not 100% sure.

I'm worried about messing up the pot with the holesaw. Would it be worth trying with the 40mm hole and risk having to widen it somehow a mm, or just bite the bullet with the holesaw and do it myself. Any advice would be welcome

 

[Richie_asg1]

I would go with their suggestion of the 40mm hole punched.

It's a lot easier to open it out half a mm than start with a holesaw - and it's free!

A dremel and small grinding wheel would probably be best to shave a bit off, but may not be needed at all.

 

[Dutto]

Apart from the above (which I agree with) a copper washer inside and out will ensure a perfect seal.

 

[whistlerface]

So I got the hole cut and the weldless triclamp bulkhead fits in ok. Could do with some advice about getting a good seal.

This is the bulkhead fitting I'm trying to install.


At the moment I have the silicone seal on the outside of the pot, and went to tighten the nut on the inside of the pot.



I didn't realise..duh..how much the curvature of the pot would affect the fitting. Should I get a silicone seal for the inside of the pot too, and maybe a large steel washer. It didn't come with one but I feel like it should. The nut on the inside of the pot is really going to scratch the surface I think, getting it tight enough to pull the front in to the seal.

Any suggestions or advice would be most helpful, before I scuff up the pot.

 

[Dutto]

Silicone and nylon can both melt when exposed to a naked flame!

Because of this I use two copper rings (one inside and one outside) to seal the tap on my Boiler.

They are available from here ...

https://www.amazon.co.uk/slp/copper-washer/evczh6co37k68my

My only tip is that before use it helps if you heat the washer to "cherry red" with a blow-lamp and then quench it in cold water.

Copper is unusual in that it becomes a lot more malleable after it has been heated to "cherry red" and then quenched. It is important to make sure that it will deform enough to seal the Boiler against the curvature; and more than one copper washer may be used if the ones you buy are too thin to seal properly.

 

[Gulpitdarn]

and then quench it in cold water.

Are you certain about that? It's a constant argument on the BSA motorcycle forum that I also partake in concerning cylinder head gaskets. To quench or not to quench, that is the question. I've always allowed copper to cool naturally.

 

[whistlerface]

Silicone and nylon can both melt when exposed to a naked flame!

Because of this I use two copper rings (one inside and one outside) to seal the tap on my Boiler.

They are available from here ...

https://www.amazon.co.uk/slp/copper-washer/evczh6co37k68my

My only tip is that before use it helps if you heat the washer to "cherry red" with a blow-lamp and then quench it in cold water.

Copper is unusual in that it becomes a lot more malleable after it has been heated to "cherry red" and then quenched. It is important to make sure that it will deform enough to seal the Boiler against the curvature; and more than one copper washer may be used if the ones you buy are too thin to seal properly.

There will be a electric element going in to the pot, so there wont be any direct heat outside the pot.

Does this look ok? It's the closest copper washer I could fine with a 40mm internal diameter.

https://www.ebay.co.uk/itm/50mm-x-4...135745&hash=item54598004be:g:vMcAAOSw629atrNV

 

[foxbat]

A bulkhead with a 'shoulder' like that should be the easiest to seal even with the curve of the pot. A fat o-ring instead of flat silicone washer would work better. Alternatively you can stack the flat type.

On the inside just a stainless nut is required tightened just enough to not totally deform the silicone on the outside. Your seal is the silicone on the outside.

[Edit] you can also try fully tightening it up with just the nut and no washers. As long as the stainless walls aren't too thick then they will be drawn flat by the pressure. Leave it like that for a while and they'll stay flat. Yes you'll make marks on the inside. No it doesn't matter.

 

[Dutto]

There will be a electric element going in to the pot, so there wont be any direct heat outside the pot.

Does this look ok? It's the closest copper washer I could fine with a 40mm internal diameter.

https://www.ebay.co.uk/itm/50mm-x-4...135745&hash=item54598004be:g:vMcAAOSw629atrNV

Looks okay to me - but "Whew!" on the cost!!

In view of that, I agree with @foxbat above and suggest that you try a nylon washer to start! (Pennies from Wicks, B&Q etc.)

 

[BarnBrian]

Are you certain about that? It's a constant argument on the BSA motorcycle forum that I also partake in concerning cylinder head gaskets. To quench or not to quench, that is the question. I've always allowed copper to cool naturally.

Definitely cherry red and quench for copper.

 

[Richie_asg1]

Going to stick my neck out and say a fibre washer on the outside would also work.

 

[BarnBrian]

True, fibre would work but not easy to sanitize.

 

[Cwrw666]

Can you not flatten the curve out of the boiler at that point?

 

[Richie_asg1]

It will pull in and flatten out when you tighten the fitting. Not a problem. If you can turn the fitting and keep a spanner on the nut then it should do it without scratching the inside. Just protect the outside fitting if you are using pipe grips.

 

[Dutto]

"To quench or not to quench?"

Copper is an unusual metal in that it softens and gets more malleable after being heated and quenched; as opposed to steel which hardens and gets more brittle after the same process.

Anyone who did metalwork at school will have made either an ashtray or a fruit bowl out of a copper sheet and those who failed to heat and quench the copper often enough always finished up with cracks; and a rollocking off the teacher!

 

[Druncan]

I have a similar Powell set up. He cut 3 x 40mm no problem and as @foxbat says I just use a nitrile o'ring ,it seems to work so far,,, and ok for boiling temp;
temperature range of -35°C to +120°C (-30°F to +250°F), Nitrile/NBR is the most widely used elastomer in the seal industry today.