I need some ideas... The set screws are seized in two of the knobs on my PAS-3. Steel screw in an aluminum knob--bound to be trouble. I tried DeOxit soak and Liquid Wrench soak. Screws are still seized. Obviously I want to avoid damaging the soft aluminum knob.
4 posters
Seized set screws
j beede- Posts : 473
Join date : 2011-02-07
Location : California
Bob Latino- Admin
- Posts : 3262
Join date : 2008-11-26
Location : Massachusetts
I remember a situation like this years ago with a PAS-3 that I had. As I recall what I did was similar to what you did. I turned the knob until the set screw channel was facing near up and sprayed WD-40 until the little screw channel was filled with WD-40. I left it alone for a few days to soak in. Next I found a screwdriver that fit the screw slot just about perfect and slid it down the channel and did a series of LIGHT taps down on the screw to try to break up any "bond" between the steel screw and the aluminum knob. I sprayed in some more WD-40 and let it sit a couple of hours. I turned the screwdriver by hand and it STILL would not come out. Finally I put some lock grip pliers on the shaft of the screwdriver and with the extra leverage of the pliers was able to break the screw free and get it out. You have to be careful that the screwdriver fits the slot in the screw really well. You don't want to bung up the slot in the screw. If you do ruin the slot with an ill fitting screwdriver, you will probably wind up drilling the screw out to get the knob off. If you have to drill the screw out, you wil then have to retap the aluminum knob for a larger thread and use a somewhat larger set screw.
Bob
Bob
j beede- Posts : 473
Join date : 2011-02-07
Location : California
I was able to wriggle the two problem knobs off the PAS. They have soaked overnight in penetrating oil. I'll be able to be a little more aggressive with some hammer taps with the knobs off their potentiometer shafts. A couple cycles through my ultrasonic cleaner may do something--besides cleaning the knobs I hope. Yes, finding a screwdriver that fits that tiny slot well is part of the problem. I'll try vise grips on the shaft of a jeweler's screwdriver.
sKiZo- Posts : 1530
Join date : 2013-04-01
Location : Michigan USA
Dissimilar metals can pretty much weld in place. Now that you've got the knobs off, maybe dremel shallow slots in the control shafts to fit the set screw's protrusion tight enough so you can still wiggle them on ... that would at least minimize visible damage to the knobs.
Short hits with the dremel, as you wouldn't want to heat the control shaft ... I'd think a grinding disk, worn down to minimum diameter so you can get up close to the panel if necessary, would do the trick with a couple light passes.
No dremel tool, just file the shafts flat so the screws can slide down tight and still lock on without spinning. You'd want to take it slow with plenty of test fits and make sure you line up the markings properly.
Short hits with the dremel, as you wouldn't want to heat the control shaft ... I'd think a grinding disk, worn down to minimum diameter so you can get up close to the panel if necessary, would do the trick with a couple light passes.
No dremel tool, just file the shafts flat so the screws can slide down tight and still lock on without spinning. You'd want to take it slow with plenty of test fits and make sure you line up the markings properly.
j beede- Posts : 473
Join date : 2011-02-07
Location : California
Good ideas. Thanks. I was able to loosen one screw after getting the knob and screw pretty hot with my heat gun. The other seized screw would not submit to heat. I tried to drill the set screw out but the bit "walked" around too much and I ended up elongating the hole in the knob a bit. I happened to have a set of "diamond dust" bits from Harbor Freight. The 1/8" spherical bit in my Dremel cut through the set screw in about a minute. I tapped the resulting hole to 6-32 and used a 3/16" long set screw where the factory 4-40 x 1/4" screw used to be. I will use the repaired knob for the balance control--that way the repair will be at the (least visible) 6 o'clock position.
sailor- Posts : 269
Join date : 2011-04-04
Flitz metal polish is great stuff for cleaning almost any metal without damaging it. It has no abrasives and is very fast acting. Don't use it on painted surfaces.
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