Remove stripped set screw on front panel knob

[matthuszagh]

I'm trying to remove the knob from the front panel of an HP 8566A. However, one of the 2 set screws is stripped. I've attached an image showing the knob and the hole for the screw. If you'd like me to attempt to image the screw let me know. How can I remove this? I'm a bit nervous to take a drill to this. If possible, I'd prefer not to damage the knob. But, if that is necessary I expect the knob is probably replaceable.

[jdragoset]

You have not said if it is an Allen set screw.
If it is, get a correctly sized easy-out (grind the end if it bottoms out), back the opposite side of the knob with some mass (so the knob shaft is not stressed) and drive the easy out with a small ball pein hammer before trying to turn the easy out.

[xrunner]

Yea it's tough. I restore test equipment and I've had to leave on knobs like that or risk destroying it to get it off - drilling the screw out and sweating it. If I didn't see a replacement knob I've just left it alone.  If there are any jagged areas in there you can try sacrificing a small screwdriver to turn it if you can get some solvent down there for 24 hours.

That knob + encoder is available on Ebay for $27.

I don't know how bad you want it off ... 

[matthuszagh]

You have not said if it is an Allen set screw.
If it is, get a correctly sized easy-out (grind the end if it bottoms out), back the opposite side of the knob with some mass (so the knob shaft is not stressed) and drive the easy out with a small ball pein hammer before trying to turn the easy out.

My mistake. It is indeed an allen set screw. Size #4. About 150mil length. Thanks for the advice!

[Miti]

I have a Craftsman set with 15 sizes in inch and 15 in metric. If I were you, I would try the next size up from either inch or metric. Literally next size up, measured with a caliper. Maybe is not completely rounded.

[matthuszagh]

If it is, get a correctly sized easy-out (grind the end if it bottoms out), back the opposite side of the knob with some mass (so the knob shaft is not stressed) and drive the easy out with a small ball pein hammer before trying to turn the easy out.

I'm not too familiar with this process. Does something like https://www.mcmaster.com/5054A11/ look like it would work?

[matthuszagh]

Yea it's tough. I restore test equipment and I've had to leave on knobs like that or risk destroying it to get it off - drilling the screw out and sweating it. If I didn't see a replacement knob I've just left it alone.  If there are any jagged areas in there you can try sacrificing a small screwdriver to turn it if you can get some solvent down there for 24 hours.

That knob + encoder is available on Ebay for $27.

I don't know how bad you want it off ... 

That's a fair point. It is just for personal use and the reasons are purely cosmetic (cleaning the front panel). But, my perfectionism is getting the better of me. A $27 mistake doesn't sound too bad though. Anyway, thanks for the advice.

[matthuszagh]

I have a Craftsman set with 15 sizes in inch and 15 in metric. If I were you, I would try the next size up from either inch or metric. Literally next size up, measured with a caliper. Maybe is not completely rounded.

This is one of the first things I tried and unfortunately I didn't have any luck. It's possible that I just didn't have the right next size up.

[xrunner]

But, my perfectionism is getting the better of me.

I completely understand. 

[bdunham7]

You can try wedging a sharp Torx driver of the appropriate size in there and seeing if it will grip.  Failing that, I have left-hand drill bits for difficult cases, but that takes some care.

[Runco990]

I'm an HP test gear whore....  so am extremely familiar with the dreaded set screws.

What has worked BEST for me after much grief and trial and error:

Heat up the set screw with a fine tip soldering iron and THEN try a filed down to fit allen key.
Most of the time they come right out when they will absolutely NOT without heating them first.

Good luck!   

[matthuszagh]

You can try wedging a sharp Torx driver of the appropriate size in there and seeing if it will grip.  Failing that, I have left-hand drill bits for difficult cases, but that takes some care.

I tried the Torx driver technique to no avail. Good to know about the drill bits.

[matthuszagh]

I'm an HP test gear whore....  so am extremely familiar with the dreaded set screws.

What has worked BEST for me after much grief and trial and error:

Heat up the set screw with a fine tip soldering iron and THEN try a filed down to fit allen key.
Most of the time they come right out when they will absolutely NOT without heating them first.

Good luck!   

Thanks for the advice. I assume heating the set screw damages the RPG?

[Runco990]

Sorry... the RPG?

Heating the set screw makes it expand and then contract.  This often breaks it loose and then lets you extract it without a lot of force.  Don't overdo it, or you'll melt the knob.  Just get the set screw hot for a few seconds and then try. 

[matthuszagh]

Sorry... the RPG?

Heating the set screw makes it expand and then contract.  This often breaks it loose and then lets you extract it without a lot of force.  Don't overdo it, or you'll melt the knob.  Just get the set screw hot for a few seconds and then try.

Sorry, the whole knob assembly (saw RPG in the manual, so that's what I though it was).

I got you now. That makes more sense. Thanks!

[jdragoset]

Maybe this one.
https://www.mcmaster.com/easy-outs/socket-set-screw-extractors-6/

[tkamiya]

As far as I can remember, the rotary encoder has mostly plastic internals.  If I were to do this, at this stage, I will be making decision as to if I want to destroy the knob in order to remove it without hurting the rest.  I can nibble away at the plastic knob to expose the brass collet and set screws.  At that point, you can dremel your way in.  The whole front has to come out before you can change it out.  It's pain in a butt to do that.

[langwadt]

dissolve the steel screw with alum or acid?

[tkamiya]

How do you do that in reality?  The knob, thus the whole collet, is stuck on the front panel.  It will take an incredible luck to pull that off (ha!) without damaging the rest....  Let me actually look at one of mine to see how they are actually mounted.  I'm curious now.  Somehow, I recall seeing very fragile piece of construction in there.

[Runco990]

Geez, I just "RE-looked" at that image.  No, you cannot get a soldering tip in there.  That only works for the small knobs that you can see the set screw.  But keep that in mind for the next one.

The best shot is to file a slightly larger key at a taper and tap it in.  Then try to turn it.  It has to be a tight fit.
I bought an entire cheap set just to "make" HP set screw extraction tools. 
You'd think they used an impact gun to put them in. 

Now if you already stripped it... all bets are off.  May HAVE to drill it out.   

[David Hess]

Heat up the set screw with a fine tip soldering iron and THEN try a filed down to fit allen key.
Most of the time they come right out when they will absolutely NOT without heating them first.

Filing down a slightly larger Allen wrench to fit what remains of the set screw tightly has always worked for me.  I have never needed to heat the screw up.

Another recommendation I have seen is to put cyanoacrylate glue on the end of the Allen wrench before inserting it into the worn screw.

[Microdoser]

Mechanics have access to some quite strong metal glues/fine metal fillers.

I would think about putting some on the end of an allen key nearly the right size, waiting until it is really cured, then carefully trying to put *just* enough force to undo the screw.

[tkamiya]

I took one of mine and looking at it closely.  Actually, took it apart to see how both the rotary encoder and the knob is made.  Yes, one pair was sacrificed in name of science and just pure curiosity!

The knob is unusually heavy.  Cutting into it showed it is mostly made of metal.  It is a machined and plated brass pressed into a plastic.  Front gray/creme circle is a thin aluminum which you can pop off once it is removed.  Shiny ring visible from front is NOT a plated plastic like in cars from 1980s but it is part of aforementioned plated brass piece.  Drilling into it will be a significant effort.

Shaft of the rotary encoder appears to be made of a stainless steel.  So drilling THROUGH it while it is still on the panel is close to impossible.  Drilling the set screw out may be possible but then burr and all that will likely cause it to bind even harder.  Getting that off will require too much prying force for the rotary encoder to survive.

If I were you, I'd stop right there and not attempt to remove the piece just for cleaning.... 

[tkamiya]

I have pictures but forum is not allowing me to upload them.  Weird!

[Gregg]

Before screwing it up with heat or glue, try a left hand drill bit.