[Elecraft] K2 knob mod

[Wallace, Andy]

I don't like the drag of the felt washer (even lightly) so I
removed it from my K2. However, on doing so, it became clear the 
knob was not balanced. At some positions, it would slowly drift
and spin to the balance point...

The knob seems to be molded with a brass insert. The insert
has a hole drilled through it and positioned about evenly between
the two set screw locations. 

The insert does pull out. The knob itself has molding channels running
along the setscrew lines, so it looks like that side would have more
plastic, and therefore, be heavier. So to balance the knob, they've
drilled a hole in the brass and put it between the setscrews. 

OK...I tried moving the side with the hole to the opposite side -- which
made it worse.

I put it back the way it was and marked two drill locations in the brass,
opposite to where the setscrews are. In other words, if you hold it so the
setscrews are at 9:00 and 12:00, then the drill marks are at 3:00 and 6:00.
I pulled the brass out again and used a 1/16" drill to take out some metal
at those places. I only went down 1/16" at most, not all the way through.

I then put the knob insert back in, with the through-hole again centered 
between the setscrews. 

It could probably be improved further by making my drill holes just a bit
deeper, but the balance is now almost perfect, with no felt pad. The
knob spins very freely and does not move on its own. 

... 

As for comfort, I think someone could have more pleasing results than 
the broccoli-band trick by chucking the knob in a lathe and cutting a 
v-groove just behind the face of the knob, and then slipping a 1.5"
black rubber O-ring into the groove. 

The substitute knob via Mouser (Alco/Tyco brand) would not be the
same size as the K2 knob -- it's bigger and would have to be left further
away from the front panel, with the edge hanging over the LCD bezel. 

Andy