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 Post subject: Wood knob repair
PostPosted: Jul Tue 16, 2019 5:57 am 
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Joined: Apr Thu 10, 2014 3:29 am
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Location: Oak Harbor, WA 98277
What’s the preferred method of repair for a wallered out set screw hole on an original knob?

1929/30 Majestic Model 91 if it matters.


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1990D912-E2B7-4C2D-9A64-1379230D5536.jpeg [ 281.17 KiB | Viewed 733 times ]
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 Post subject: Re: Wood knob repair
PostPosted: Jul Tue 16, 2019 8:08 am 
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You might be able to re-tap the hole in the old insert to a slightly larger set screw, which is certainly the easiest option. Might look into a metric screw size if sae is too large.

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Last edited by processhead on Jul Tue 16, 2019 8:41 am, edited 1 time in total.

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 Post subject: Re: Wood knob repair
PostPosted: Jul Tue 16, 2019 8:15 am 
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Joined: Dec Sat 21, 2013 5:15 am
Posts: 427
Location: Puyallup, WA 98371
Or maybe glue in some wood veneer, stuffing in toothpicks to make it fit the inside of
the oblong hole, then use a needle file to enlarge and round out the opening.

Or find another knob...

Dale

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 Post subject: Re: Wood knob repair
PostPosted: Jul Tue 16, 2019 10:25 am 
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Location: Montvale NJ, 07645
Coat what remains of the threads with a thin layer of epoxy- a little will go a long way. Use a toothpick to apply. Use a release agent on the set screw and insert it. Release agent can be several layers of wax, though it will be a pain to remove excess wax from threads, or WD40 or even PAM cooking spray. Best would be a spray graphite lubricant.
Back screw out when the epoxy is cured. If it is at all difficult, use some heat from the tip of a soldering iron on the screw head and heat up the set screw and it will back out fine.


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 Post subject: Re: Wood knob repair
PostPosted: Jul Tue 16, 2019 3:09 pm 
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I'll add this - instead of using your set screw to form the epoxy, use a bolt with the same thread.
Also, as well as epoxy resin you can use a fiberglass filler like Bondo, or glazing putty, and don't use too much. Excess will be forced out into the shaft hole and need to be cleared away.

And who told you it was wallered? Is that in the dictionary? :lol:

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 Post subject: Re: Wood knob repair
PostPosted: Jul Tue 16, 2019 3:56 pm 
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Location: 06457
Tap the whole out to the next size larger aka 8/32. :)


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 Post subject: Re: Wood knob repair
PostPosted: Jul Wed 17, 2019 3:26 am 
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Joined: Dec Sat 21, 2013 5:15 am
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Location: Puyallup, WA 98371
westcoastjohn wrote:
And who told you it was wallered? Is that in the dictionary? :lol:


Yeah, I think I misunderstood what the term meant. Looked to me like the issue was the elongated hole in the wood due to using too big a screwdriver or something.
If it's the threads that are at issue, then never mind what I said...

BTW, an alternative to epoxy, etc would be "Magic Mender for Steel". It's machinable, so you could drill and re-tap the hole.

Dale

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 Post subject: Re: Wood knob repair
PostPosted: Jul Mon 22, 2019 1:24 am 
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Location: Oak Harbor, WA 98277
Take 2...

I failed to provide enough information the first time. The knob uses a brass insert which is loose on the knob. I believe this originally was a press fit with flutes on the insert. It is loose enough to rotate but doesn’t readily want to pop out of the knob itself.
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1. Should this be glued in?

Due to the loose insert, the head of the set screw has substantially damaged the surrounding wood in what I believe should have been a significantly smaller hole. The knob has what I consider to be excessive play when tuning despite the set screw being tight on the shaft of the tuning condenser.
Attachment:
A43FF65C-A9CC-42EB-BF7C-B3E58A9A7FC6.jpeg
A43FF65C-A9CC-42EB-BF7C-B3E58A9A7FC6.jpeg [ 280.62 KiB | Viewed 431 times ]

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5461E08F-F539-434A-9550-8ACB3D5DE1AF.jpeg [ 352.06 KiB | Viewed 431 times ]

2. Once the insert is solid in the knob, how to repair the enlarged set screw hole?

I’ve considered both the filler option or possibly gluing in a piece of dowel and re drilling the hole.

Thanks for all of the replies thus far. I’ll choose my terms (wallered) a little better in the future.


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 Post subject: Re: Wood knob repair
PostPosted: Jul Mon 22, 2019 1:51 am 
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I would try and remove the insert. You could try and thread a bolt into the 1/4 inch insert opening just far enough to catch and then try pulling out the insert while holding the knob.

Once the insert is out, address the loose set screw threads and then epoxy the insert back in the knob.

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 Post subject: Re: Wood knob repair
PostPosted: Jul Mon 22, 2019 12:24 pm 
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Location: Montvale NJ, 07645
Looks to me like someone possibly drilled the hole in the wood out larger to fit the wrong screw in there. If it was damage from the insert rotating, the hole would be oval- it doesn't look all that bad to me, especially in your picture at the top of the thread. Normally, these set screws don't have heads on them like the screw in your picture, but maybe these knobs do.

Also, it sounds like your insert rotating is the problem and not the threads messed up on the set screw?

If it is also the insert threads messed up, just drill and tap a new hole in a different spot on the insert and use that for the set screw.

If the insert is loose and rotating, it will come out. I would just get it out and glue the insert in and call it a day. I see nothing worthwhile coming from inserting a dowel, redrilling, etc. The endgrain will never match anyway.

I always try to put the set screws facing down where possible so they are the least visible on the radio.

The first picture you posted at the top of this thread looks decent and I would not go messing with the wood on the knob to try to improve that.


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