Shimming 6mm split shaft pots

[mikeydee77]

I need to replace some pots in a carvin combo. The pots are 16mm, 1/4" solid shaft Alphas. Here in the UK I can't find an exact replacement so I have used 6mm Alphas with a splined and split shaft which are available easily.

With pots like this I have two issues:

1. A 1/4" knob will be a little lop sided. The shaft can be padded with foil tape or electrical black tape, and I did read somewhere that coke can metal is perfect for this. So not a biggie at all.

2. Also, the split shaft will gradually creep in under pressure from the knob's grub screw. Not always as it depends on whether the grub screw hits the gap or ends up 90degs to the gap. I want to find some suitable shim stock (is that even the right term) to fill the gap in the shaft of the pot. It is 6mm across and the length would be in the region 5-15mm depending on whether the shaft needs trimming down. I notice that Orange amps have this very item.

I wonder if anyone has a solution to this. . .

[g1]

I've used wood in the past but it does compress and is not great for the long term. I think a firm plastic would be much better and easy to cut with regular diagonal cutters.

[Richard]

I know they make bushings to convert the knobs for a smaller pot shaft but I can't find them. I believe Allparts makes them. I use guitar picks to fill the split shafts.

[mikeydee77]

I just noticed that Cliff style jacks (Marshall etc) contacts are 6mm across and work perfectly as a filler when you get two pieces back to back.

[J M Fahey]

I live in Argentina and by reasons of availability shim split shafts every day
Any proper plastic which tightly fills the slot will do, itīs kept by pressure alone.

If you want to make perfect, shim all you will use, trim and center so they are even on all aspects and after that apply a small drop of "magic glue" (cyanoacrilate) so by capilarity it is absorbed and firmly glues plastic shim to metal shaft slot.

Mind you, NOT to glue knob to shaft but to make shaft solid.
They become so solid that when dry (a few minutes you can even grind one side to make a custom "D" shaft for Fender amps.

Donīt ask how I had to find that

[drewl]

I use solder wick that is used.
Fills the slot firmly.

[rjb]

Any proper plastic which tightly fills the slot will do, itīs kept by pressure alone.

I use guitar picks to fill the split shafts.

If you happen to be an OCD kinda guy... Dunlop makes several lines of guitar picks that are gauged in mm.
Since the slot for a 6mm shaft is 1.57 mm wide, a 1.5mm thick Delrin or Tortex TIII pick would fit nicely.



Dunlop Manufacturing :: Guitar Picks :: :: Delrin
Dunlop Manufacturing :: Guitar Picks :: :: TortexŪ TIII


-rb

[Mick Bailey]

For shimming I guillotine a strip off the edge of sheet aluminium and clip it into pieces. Older Ashdown amps that use grub-screw knobs use this method. A useful shim material I use for many jobs is the plastic covers from ring binders - the ones that are made from a piece of plastic folded into three and the rings attached to the 'spine'.

I use masking tape to make up the diameter and I have amps from years back where the knob has not loosened.

[Zouto]

I use small clipped off pieces of zip tie, easy to fit, working fine.
Zouto