Another project (80's JB-Player neck-thru)

[Granny Gremlin]

Alphas are 6mm.  Don't remember if coarse or fine knurls, but it may be neither (metric).  Though as Psycho suggested, you're supposed to use press on knobs on split/knurled/spline shafts (whatever one calls them), colletted ones with a set screw work fine and have play in them so you don't have to sweat the sizing so much.

[dadagoboi]

Don't fit how: too big or too small?  What kind of pots did you put in there?

US made stuff (and older British) will be 1/4" shaft.  Everything else (metric) will be 6mm which is just a hair bigger. 

6 MM is SMALLER THAN 1/4" (~6.35mm).  Import pot shafts are smaller than US ones.   Typically Asians scale everything down to the closest mm (at least).

US sized knurled knobs should fit on knurled 6mm shafts with a little coaxing.

[Granny Gremlin]

Yes, sorry, wrote that backwards.  Thanks for the correction.  0.23" = 6mm

Press on knobs are such a PIA/bad idea I don't even bother anymore.  Colletted for everything on my end.

[dadagoboi]

Using set screw knobs limits the possibility of what you can use: no bell, speed, witch hats, or reflector for example.  The correct size push on knobs work very well in the right place, have for many decades.

4 of 5 of these knobs are press on, the 6mm P/P for active/passive volume pot has a set screw. 

[Granny Gremlin]

Yeah, but the kind of knobs he has on that bass (like yer TBird pic there - that one looks real nice BTW; one of yours? Just too bad about that bridge ;P) come in both varieties.  The reverse could also be said (e.g. some Davies style knobs etc)