Author Topic: Remove botched screw from tuning dial knob  (Read 2379 times)

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Online langwadt

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Re: Remove botched screw from tuning dial knob
« Reply #25 on: February 13, 2019, 10:18:28 am »
Sheding some light in the hole, revealed what I was afraid of.

?? But it looks like just a plain slotted grub screw, intact. Or is one side of the slot broken off? It's hard to tell from the pic.
Is it possible your flat bladed screwdriver was just too fat to fit in the slot?
If so, sacrifice some cheap (but tough)  screwdriver by grinding it down till it just fits. Don't let the metal get hot while grinding. Veeery gently, lots of water for cooling.

Anyway, it also looks like the knob can be rested on a bit of soft wood on the opposite side to the screw, while you...
Get a small pin punch that fits in the hole. Put it against the screw top. With a small tack hammer, strike the punch firmly. The idea is to do two things: shock-break any oxides/corrosion/metal contact welds between the screw and the knob, and also drive the screw point into the shaft a little. Thus leaving it a bit loose.
Then try the screwdriver again.


I have a similar but worse problem atm. A toothed-belt drive cog, with a small hex head grub screw. Except the hex has been well rounded off.  The shaft has a mating hole, so I can't just forcibly drag the cog off with a puller.
Fortunately I don't have to preserve the cog, so as a last resort can just angle grind it down to near the shaft, then split it with a chisel.

if the screw is steel and the cog something else like aluminium you could try etching it out with alum

https://hackaday.com/2015/08/03/dissolve-steel-drill-bits-in-alum-from-the-grocery/
 

Offline frozenfrogz

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Re: Remove botched screw from tuning dial knob
« Reply #26 on: February 13, 2019, 10:23:48 am »
Slightly OT:

This thread is driving me nuts! The tension is killing me!

 :scared: :scared: :scared: :scared: :scared:

Will he succeed? Will he be beaten by a set screw?
Why does it take for forever for the OP to get it done?
Am I impatient? Is it much more complicated then usual?
How can we help this guy to just get it done already?

Oh the horrors of being damned to merely watch and wait for someone to just do it. xD
He’s like a trained ape. Without the training.
 

Online Ian.M

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Re: Remove botched screw from tuning dial knob
« Reply #27 on: February 13, 2019, 10:30:16 am »
if the screw is steel and the cog something else like aluminium you could try etching it out with alum

https://hackaday.com/2015/08/03/dissolve-steel-drill-bits-in-alum-from-the-grocery/
Yes, but I'd hesitate to try that if the shaft is also steel.

Maybe in the O.P's situation I'd consider it as a last resort short of cutting the knob away.  I do have a few ounces of alum sitting on the shelf . . .   Also, if you do use alum,  pack behind the knob with well greased string to keep the alum out of its bearings, or you'll probably FUBAR it.
« Last Edit: February 13, 2019, 10:33:00 am by Ian.M »
 

Offline frozenfrogz

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Re: Remove botched screw from tuning dial knob
« Reply #28 on: February 13, 2019, 10:52:49 am »
I have a similar but worse problem atm. A toothed-belt drive cog, with a small hex head grub screw. Except the hex has been well rounded off.  The shaft has a mating hole, so I can't just forcibly drag the cog off with a puller.
Fortunately I don't have to preserve the cog, so as a last resort can just angle grind it down to near the shaft, then split it with a chisel.

Try force-feeding it a slightly oversized TX or slotted head driver.
This has helped me out several times.

The driver/bit should be decent quality though!
He’s like a trained ape. Without the training.
 
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Offline 6PTsocket

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Re: Remove botched screw from tuning dial knob
« Reply #29 on: February 13, 2019, 12:43:56 pm »
There are bits By Alden calked Grabit. One end drills just a dimple and the other end grabs the screw. With a hex or torx  drive setscrew you probabably wouldn't even have to drill. Use a hex bit extension to get the drill away from the front panel. The pilot dimple (I wouldn't even call it a hole) and the extraction are both done with the drill in reverse. They come in small sets. It was hard to tell in the picture but I hope the setscrew is not too deep in the knob.

Sent from my SM-G900V using Tapatalk

 
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Offline michalism

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Re: Remove botched screw from tuning dial knob
« Reply #30 on: February 14, 2019, 07:47:28 am »
Hello!

thank you all for your comments and advice...this is a little bit overwelming with so many options to try :p

Slightly OT:

This thread is driving me nuts! The tension is killing me!

 :scared: :scared: :scared: :scared: :scared:

Will he succeed? Will he be beaten by a set screw?
Why does it take for forever for the OP to get it done?
Am I impatient? Is it much more complicated then usual?
How can we help this guy to just get it done already?

Oh the horrors of being damned to merely watch and wait for someone to just do it. xD


LOL!!! :D
Sorry for creating so much stress to you! Not in my intentions at all!

As said, I am working full time and these days I finish late at nights. I also have a 3y.o. son, that is taking a lot of my attention :D

I hope that I will have some results during the weekend for you!

Thanks again!
 

Offline frozenfrogz

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Re: Remove botched screw from tuning dial knob
« Reply #31 on: February 14, 2019, 09:01:24 am »
No worries! :)
I might be over-exaggerating a bit.  ;)
He’s like a trained ape. Without the training.
 

Online SilverSolder

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Re: Remove botched screw from tuning dial knob
« Reply #32 on: February 14, 2019, 05:15:14 pm »
I guess we all feel your pain...   stuck screws,  and 3 year old kids, are not always quickly dealt with! 
 

Offline michalism

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Re: Remove botched screw from tuning dial knob
« Reply #33 on: February 15, 2019, 07:39:35 am »
OK then!!

Up for the great Finale!  :popcorn:

The screw is out!
Much easier than expected, although this thing is sitting on my shelf for more than two months now, and I had several previously failed attempts.
What I did now: I lightly heated the knob, and then use a light hammer to tap it. A couple of days ago I had sprayed the hole with penetrating oil. After it colled down, I used 4-5 different flat headed screw-drivers trying to "feel" if the screw was moving. Then as I was getting ready to go to the epoxy-drop solution, the screw come out as if it was never stuck!  :palm:

As you can see from the pictures, this is not a botched screw, it's just a piece of screw that a technician or ex-owner put in place to keep the knob on the shaft, because he had lost the original piece. That's my assumption.

Now that I see the extracted part, I consider myself extremely lucky that this turned out like it did...

I am also including pictures from the inside, as promised. I would be terrible to mess that up...

Anyway, thanks for all your help, and sharing my agony!!!

I promise to come back with more questions 8) ;D
 
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Offline tggzzz

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Re: Remove botched screw from tuning dial knob
« Reply #34 on: February 15, 2019, 08:45:01 am »
The screw is out!

It is good to see:
  • you've successfully extracted the culprit
  • someone that listens and thinks :)
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline Chris56000

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Re: Remove botched screw from tuning dial knob
« Reply #35 on: February 15, 2019, 02:03:17 pm »
Hi!

Well d;ne!

You should ne able to locate a replacement no problem –an M1.5 x 8 or M2 x 8 grub–screw should do to replace it and you can get these in packs of 10 from fleabay!


Chris Williams

It's an enigma that's what it is!! This thing's not fixed because it doesn't want to be fixed!!
 

Online Ian.M

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Re: Remove botched screw from tuning dial knob
« Reply #36 on: February 15, 2019, 03:13:24 pm »
I wouldn't trust a fleabay grubscrew.  If it isn't properly hardened it wont bite on a steel shaft and if it even slightly over-hardened, it will be too brittle and if it jams again the head is likely to break.  You already know its a PITA to remove so unless you are planning to flip the item for cash as a private seller as soon as you've fixed it, cheapening  out on small parts is a false economy.

Incidentally, if you ever have to fabricate a grubscrew from a bolt, (Not recommended.  Least evil is if you shape it to a point to match a drilled dimple in the shaft) don't cut the slot too deep.  Otherwise the leverage from the screwdriveer will break it
 

Offline michalism

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Re: Remove botched screw from tuning dial knob
« Reply #37 on: February 15, 2019, 07:54:16 pm »
I already have a small set of such screws, which I bought from a reputable local hardware store.
These are so cheap, it makes no sense to get them from China, IMHO.
 

Offline TerraHertz

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Re: Remove botched screw from tuning dial knob
« Reply #38 on: February 15, 2019, 10:46:27 pm »
Mine is out too. Turned out the reason the grub screw hex socket rounded off, was that the grub screw was not hardened at all. And some form of thread-locking compound had been used.

As a last despairing attempt before destroying the pulley with an angle grinder, I finally tried drilling the screw. Expecting to get just a blunted drill. Surprisingly the drill cut in and went down the center of the screw easily. After going right through it cut off enough of the screw's end to free the pulley from the shaft.
The hollow remnant of grub screw was _still_ solidly glued in the pulley. Using a larger drill bit, it finally came free and screwed inwards, into the empty shaft hole. And was short enough to come completely free and drop out in the center.

Edit to add: speaking of grub screw sets, they are very cheap from Aliexpress. Pic: a couple I bought in 2017.
Store name: Son Day Day Up Store
200pcs Stainless Steel Hex Socket Set Screw Grub Screws Cup Point Assortment Kit M3-M8 With Plastic Box
$ 4.99 per box.
« Last Edit: February 15, 2019, 10:55:17 pm by TerraHertz »
Collecting old scopes, logic analyzers, and unfinished projects. http://everist.org
 


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