Need some hints for removing stubborn knobs plus some...

Thu Jun 8 06:24:47 EDT 2006

There are several styles of setscrews used such as slotted, Bristol (internal 
flutes) or Allen (internal hex). It is a common mistake to try to remove a 
Bristol style setscrew with an Allen wrench because an Allen wrench can be found 
which will seem to fit. If the setscrew its tight the Allen wrench will slip 
and damage the internal fluted wrenching surfaces. If this happened get the 
correct size Bristol wrench and carefully try to tap it in with a small hammer 
to see if you can save the setscrew. Bristol's fit snug anyway and when I find 
it necessary to do this I keep a Bristol wrench here that I have ground and 
polished the end so my attempt will not be hampered by a sharp edge or a burr 
which is often present due to manufacturing. Setscrews are hardened steel with a 
sharp cup shape formed on the end which is designed to bite into the shaft. 
This raises a ridge on the steel shaft and because most knobs have a brass 
insert any attempt to turn the knob after the setscrew has been loosened just cuts 
grooves around inside the knob preventing you from simply pulling it off. Get 
a surplus setscrew and while holding it on the end on an Allen wrench and 
holding it square carefully grind the cup off until you have a good smooth flat 
surface. Now install this setscrew and rotate the knob while progressively 
turning the setscrew in (a little oil helps) which will roll the ridges back down 
permitting the knob to slip off when the shaft is smooth. I use this technique 
whenever any knob seems to be caught rather than forcing them off which just 
damages the ID of the knobs.

Greg Gore, WA1KBQ

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