What size hole to cut...

[Cully]

What size hole would I have to cut in a plastic bin to take a 3/8" stainless ball valve as used here?

http://forum.craftbrewing.org.uk/viewto ... ?f=9&t=409

[Goulders]

3/8" is 10mm

[Fil]

here is a lookup http://en.wikipedia.org/wiki/British_St ... read_sizes

a 3/8" thread has a major diameter of 16.662mm (if spot on..) so a hole 16-17mm would work fine.
for 1/2" fittings i use a 20mm hole and the occasional fitting needs screwing in, its always easier to file a bit more out (never needed to tho) than try and add some back, a too big a hole can make the job trickier a small/tight hole centres the fitting perfectly making the seal easier..

[Goulders]

I just googled, but I remember my buffalo had a 15mm hole for some reason.
Edit: I did that conversion for my buffalo, but obviously saw your post re the strange hole!

[Cully]

So an 18mm hole would be too big?

[Fil]

So an 18mm hole would be too big?

if u have an 18mm bit/cutter why not try it in the bottom of a 4pint milk carton or similar throw away container.
if you can fit and seal easily enough through a disposable container with an 18mm hole then no problems, in my VERY LIMITED experience cutting holes for my own kit i find the larger 'baggier' holes tricky to keep fittings central while tightening, and orings if used, do benefit from being fitted centrally..

but if you have some snug fitting SS washers (M16)
http://www.ebay.co.uk/itm/A4-STAINLESS- ... 2c880205e5
and use silicone baking sheet
http://www.ebay.co.uk/itm/Large-Silicon ... 234222ea9f
or similar for some diy soft washers, under cut slightly so u need to stretch slightly to fit on the thread barrel, it should seal ok, but i would test before comiting to a brew vessel..

go.. washer, wall. diy silicone sheet washer cut with sharp scissors , 2nd washer, locknut or similar fitting..

you may need to bulk up with 1 or more spacing washers too if the thread used is tapered.. so ??

and dont forget to wrapp the hilt of the threaded thru fitting with lots of ptfe
in 1/2" fittings, with M20 ss washers for thrust and spacing..




ebay links are just the first in the search list not endorsed sellers..

[Fil]

One other think of note when using Stainless steel threaded fittings, unlike softer metals you may have had experience with like steel or brass You cannot just apply a bit more oomph (torque) to your last spanner tightening to line things up, Stainless will just lock.. SO you need to plan and count..

1) dry fit the fittings counting carefully the number of rotations it takes to lock up tight (no need to apply loads of pressure) remember the number, write it down.... lets call it X
2) when fitting wrap the thread of the fitting with a good load of ptfe tape,
3) when fitting turn X-1 turns, and then line up.
If you overtighten its unlikely you can back turn as the sealing ptfe tape is shreaded with each turn and going back will ruin a seal. so undo rewrap and go again..

With enough ptfe ( which is foodsafe heatsafe, almost inert and cheap as chips) it will be a Very snug tight fit..

- Your not having a good time with all this Cully.. i will pm u..