Alpha pot solid shafts

Did you bend the detent tab over?

 

Aren't the Alpha available with longer threaded shanks like CTS are? Some CTS are too short to use a lock washer also... You need 3/8" long bushing.
I guess they are not available from Alpha.

I try to save those really thin lock washers to use with those short bushing pots and use the thicker normal star washers for longer pots.

These are thin, (switch size, will work on pots though) but there are also pot size ones that are super thin with a 3/8" ID.
https://www.cedist.com/products/lock-washer-carling-internal-tooth-toggle-and-foot-switches

 

I was under the impression Alphas came in short-shaft (like for guitars) and longer shaft (like for amps). Speaking of long shaft, many folks like to use star washers under their pots, even if they don't do the old-style ground to the pot case. Prevents pot rotation, don't ya know.

As an idle observation, it's funny how slagging on product B in a question about product A can turn a 'request for help' into a bit of a flame fest...

 

I normally buy all of my Alpha pots from Valvestorm. They don't give the exact length but they have never come up short on any of my builds with a steel chassis/plexiglass faceplate.

http://valvestorm.com/Products/Components/Potentiometers/Amplifier

Edit; This store focuses mainly on Marshall circuits so they may not have some of the values needed for other amp brands.