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 Post subject: Knob Reinforcement
PostPosted: Jan Sun 28, 2018 8:41 pm 
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Location: Groveland MA
I recently removed a plastic knob by using a plastic prying tool, unfortunately I cracked the hub of the knob. I usually pry at different spots around the perimeter of the knob to avoid damage, but I guess I was a bit heavy handed.
I glued the knob back together, but was concerned that the pressure of the spring would cause the crack to open back up. This is a "D" cut shaft with a leaf spring.

I picked up a 1/2" spring type hose clamp and modified it a bit. Using a Dremel, I cut off the tabs that are used to open the clamp, and cut some notches in the clamp to allow for the ribs of the knob.
In this case, the spring could be pressed on to the knob without needing to open the clamp.

The clamp came in a pack of 8, with 4 different sizes, but perhaps it is possible to buy only 1 of the size you need. This was not an option at the store that I went to.

Russ


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 Post subject: Re: Knob Reinforcement
PostPosted: Jan Sun 28, 2018 9:30 pm 
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Joined: Mar Sat 14, 2009 5:56 pm
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Location: RI, 02885
I have a few sizes of the spring clamps for reinforcing knobs that have split. Let me know the exact diameter of the knob rear and the width to fit without modifying the clamp and I will see if I am able to help.

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 Post subject: Re: Knob Reinforcement
PostPosted: Jan Sun 28, 2018 10:49 pm 
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Location: Charleston, W.Va.
Good advice on using spring clamps to reinforce knob shafts. These were often used by knob manufacturers back "in the old days".

As another alternative, I have often used thin-wall brass tubing (available at good hobby stores in various diameters), selected for a snug fit and glued onto the knob shaft with epoxy.

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 Post subject: Re: Knob Reinforcement
PostPosted: Jan Mon 29, 2018 2:42 am 
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^ Couple of good ideas here!

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 Post subject: Re: Knob Reinforcement
PostPosted: Jan Mon 29, 2018 3:39 pm 
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Location: Charleston, W.Va.
Poston Drake wrote:
As another alternative, I have often used thin-wall brass tubing (available at good hobby stores in various diameters), selected for a snug fit and glued onto the knob shaft with epoxy.

To elaborate more on my above post: As I mentioned, select a size of thin-wall brass tubing which is a snug fit. If this is not possible select the next smaller diameter and cut a lengthwise slot in it with an Xacto saw or thin cutting disc in a Dremel tool, then spring it over the shaft, bedded in epoxy.

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 Post subject: Re: Knob Reinforcement
PostPosted: Jan Mon 29, 2018 4:43 pm 
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Location: S. Dartmouth MA 02748-1225 USA
I have used a compression spring of a small 22 ga. wire size, just a bit smaller ID than the OD of the hub of the knob. Takes a bit of doing forcing the spring over the knob hub but it has a good strong tension even over a cracked hub.

Great idea Russ, I've got a bunch of those clamps, leftover auto parts from the early days of emission control. There "was" a tool to install them so they wouln't go flying, but without "ears" the tool can't work.

Chas

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 Post subject: Re: Knob Reinforcement
PostPosted: Feb Sun 04, 2018 8:04 pm 
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Cracked / broken plastic is pretty common where self tapping screws are involved. Just epoxied three pieces of Weller soldering gun screw hub back together, then wrapped it w/ a few turns of thin gauge steal wire, twisted the ends tight, and coated the wire / hub w/ more epoxy..... keeping epoxy out of threaded hole.

After a 48 hrs of hardening, it's much tougher then original. Method is kinda messy and looks bad, but if hub is in pieces it has to glued anyway, is usually out of sight, and will work w/ any size hub. On a knob there would have to be a little clearance for the wire wrap and, after hardenng, one can Dremal off the twist ear if needed.


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 Post subject: Re: Knob Reinforcement
PostPosted: Feb Tue 06, 2018 6:48 pm 
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Location: Groveland MA
Thanks to Bugman, I now have a spring clamp made for radio knobs. It is a better fit, and thinner too.
Still in the future, should I need one again I at least know how to make one.

Russ

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 Post subject: Re: Knob Reinforcement
PostPosted: Feb Thu 15, 2018 2:16 am 
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Location: Florida
The clip is a good idea to remember.

Just as a side note I use a couple of methods to remove knobs:

Barbecue forks of various sizes from the thrift store.

Two L-shaped pry bars made by bending and filing old screwdriver shanks (same tool used to remove clock hands and some wheels).

In either case the idea is to get equal force on two opposite sides.

RRM


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 Post subject: Re: Knob Reinforcement
PostPosted: Feb Thu 15, 2018 3:18 am 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: The Old Dominion VA 23518
We kept cotton thread and Duco cement in our TV service caddy - take the split knob shaft and douse it with some cement, wrap a layer of cotton thread tightly around it, and then add a veneer layer of cement. Dries in a minute, lasts a lifetime, and no tools required...

Note that Nylon and Polyester thread just don't work well - the cotton absorbs the cement and hardens nicely. The "thinness" allowed use on concentric knobs. And i know of one or two Navy test stations that have knobs that I repaired in just the same manner.....

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 Post subject: Re: Knob Reinforcement
PostPosted: Mar Sun 04, 2018 10:10 pm 
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Location: Mecosta MI
Retired Radio Man wrote:
The clip is a good idea to remember.

Just as a side note I use a couple of methods to remove knobs:

Barbecue forks of various sizes from the thrift store.

Two L-shaped pry bars made by bending and filing old screwdriver shanks (same tool used to remove clock hands and some wheels).

In either case the idea is to get equal force on two opposite sides.

RRM


Check for set screws. :lol:

Wrap a heavy gauge wire around the pot shaft if you can & start pulling. :shock: This technique works well on hard to pull hood releases on older vehicles without breaking one side of the handle off.:wink:

If you have broken knob, that you can get glue to meld, use a bread twisty tie or small zip strip to secure it while the glue sets up.

If it's a D shaft *position* pot knob you can wrap a couple of turns of small gauge wire around the outside of the knob, with the two ends twisted together. You can also embed that with epoxy for additional strength.

YMMV,
Lloyd
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Advice-It's like Cooking. You have to Taste it First, before you Feed it to Others.


Last edited by CrumblingWires on Mar Sun 04, 2018 10:19 pm, edited 1 time in total.

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 Post subject: Re: Knob Reinforcement
PostPosted: Mar Sun 04, 2018 10:14 pm 
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Joined: Sep Tue 15, 2009 9:38 pm
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Location: Mecosta MI
Dupe :oops:


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 Post subject: Re: Knob Reinforcement
PostPosted: Mar Mon 05, 2018 3:24 pm 
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Joined: Feb Thu 24, 2011 3:13 pm
Posts: 852
Location: Ironwood, MI
Great suggestion radioalfa! I'll now pry knobs with renewed confidence.
Thanks.


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