Standard pot and jack holes are 0.3750 (3/8) inches in diameter (9.53
mm). What if some people want to use large bushing pots and others want
small bushing pots, like the Alpha? No need to worry about hole sizes.
I learned this trick from Larry Hendry (R.I.P.). Fit a #5 rubber O-ring
to the Alpha pot bushing and it neatly fills the gap and fits snugly
into a 1/8-inch thick panel. The #5 O-ring is a standard plumbing item,
easily found at hardware stores, at least in the U.S.. I never worry
about mounting Alpha pots, as long as I have a box of #5 O-rings, which
I buy from Lowes. I use 3/8-inch holes universally for pots. If I
change my mind and want to replace an Alpha pot with one with a larger
bushing, it's a snap.
Richard Brewster
http://www.pugix.com