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 Post subject: question : Repairing a Bakelite knob
PostPosted: Jan Sat 27, 2018 9:25 pm 
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Location: Buffalo NY
Does anyone have a tip or method for repairing a stripped set screw hole in a Bakelite knob? I thought of maybe going with a bigger set screw, but worry about breaking the knob...

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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Sat 27, 2018 10:27 pm 
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Try putting a piece of string in the stripped hole and set screw over it.

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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Sun 28, 2018 1:23 am 
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Find a bolt laying around that is a little bit bigger. Tap the hole in the knob to fit the bolt. Cut off a section of the bolt as long as the old set screw. Cut a slot in the top to fit a screw driver. Presto! Your new set screw will hardly be noticeable if done neatly. Done it many times....


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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Sun 28, 2018 4:08 am 
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Location: Plymouth, MI
I have found from my experience that replacing the old screwdriver slotted setscrews with hex socket setscrews makes things a lot easier. The setscrew will stay on the hex wrench when your going into a recessed hole and the setscrew will tighten easier and tighter without slipping out. A good smaller hardware store will carry many sizes. I use 8-32 setscrews 5/16 long on many of my radios.

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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Sun 28, 2018 5:03 pm 
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Wrapping a few turns of Teflton plumbers tape around the set screw works sometimes.

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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Sun 28, 2018 8:43 pm 
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Location: Sunbury, Ohio 43074
And if all of those ideas fail, fill the stripped hole with epoxy, let it set for 24hrs, then drill and tap it. If the control shaft is flat on one side, this will probably work. If it's a 100% round shaft, 50/50 since your setscrew would have to be very tight.

If you get truly desperate you could drill the knob all the way through, and the shaft, and use a small roll pin :-D

Truly, the 'slightly larger' bolt or screw idea should work fine

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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Sun 28, 2018 10:58 pm 
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You could also drill a fresh hole in the opposite side and tap it to the size you need. Use correct drill size for tap. Then fill bad hole.


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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Sun 28, 2018 11:58 pm 
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Location: Buffalo NY
Thank all of you for your advice. The knob is for my Grunow 1181 tone control with half round shaft and indicator dot on top...The string and pipe dope tricks failed, so I'm going to try to tap a larger screw into it. I hesitate, because someone did that sometime in the past on one of the other knobs and cracked it. failing that, I'll have to hunt down a couple of good knobs....


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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Mon 29, 2018 3:13 am 
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These knobs are very common. They were not only used on several Grunow models, they were also used by other radio manufacturers in the late 1930s. You should have no problem finding a good knob at a reasonable price.


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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Tue 30, 2018 2:31 am 
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If you are going to tap it for a larger screw, get the correct size drill to make the correct size hole for that tap. That will minimize the stress on the knob.

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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Tue 30, 2018 5:54 am 
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Location: Buffalo NY
Once again, thank you all for your input. Unfortunately, redrilling and tapping the hole wound up being a huge fail. As slow and careful as I tried to be, the drill chipped the knob around the hole (which I probably could have lived with, seeing it's on the bottom), but the tap cracked the interior boss portion of the knob. I guess this thread is now moving to the classifieds. :cry:

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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Jan Tue 30, 2018 5:54 am 
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Joined: Mar Thu 13, 2014 1:29 am
Posts: 707
Location: Buffalo NY
Once again, thank you all for your input. Unfortunately, redrilling and tapping the hole wound up being a huge fail. As slow and careful as I tried to be, the drill chipped the knob around the hole (which I probably could have lived with, seeing it's on the bottom), but the tap cracked the interior boss portion of the knob. I guess this thread is now moving to the classifieds. :cry:

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 Post subject: Re: question : Repairing a Bakelite knob
PostPosted: Feb Fri 16, 2018 4:18 am 
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Location: 253 Blanche St. Plymouth, MI USA
lorenz200w wrote:
These knobs are very common. They were not only used on several Grunow models, they were also used by other radio manufacturers in the late 1930s. You should have no problem finding a good knob at a reasonable price.


There are other generic knobs that look like these, they dont have the face design, and are very common. However, this type with the face design are only for Grunow to my knowledge. There is only one size I know of, its about an inch diameter. I have some, and the other knob dealers usually do also as they are not rare.
Mark Oppat


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