How to Make Lost Knobs of Antique Radio




Introduction: How to Make Lost Knobs of Antique Radio

Antique Radios found in Auction site or flea market are hardly maintain their original exterior. Especially tuning or volume knobs often would have been lost. Such radios lacking some parts often trade cheaply. So if you don't strictly stick to originality, you can restore complete receiver economically.

Step 1: Ingredients

Plarepair(TM)(Plastic repair kit) is one of resin casting kit, same as "Super-bond" that is popular for dentists.

This time we are going to use these ingredients:

1) Plarepair (TM) powder (black)
This is 100% acrylic powder.

2) Plarepair(TM) liquid
This is Methyl methacrylate

3) "moulage you" (型取り君›). mold plastics
It is low temperature deforming material, a kind of polyethylene resin.

3) Another old radio's knob for a prototype

4) A new general-purpose knob
It should be about 5mm smaller than prototype knob, and the hole diameter must be match the shaft of VR or rotary switch.

You can buy Plarepair here. And perhaps there are other products similar to it in your country.

Step 2: Molding

Molding is very easy.
Prepair hot water, dunk moulage in it, and wait a moment.
After it is softened enough to mold, spread it over the prototype and press well. Wait several minutes till it cools down. Then take it off.

Step 3: Casting Resin

Now we have got a mold. Put and drop resin in the mold with the dedicated needle for Plarepair, then the resin spreads on inner surface. With holding against the light keep uniform thickness. After several minutes it consolidate and form a hollow shell.

Step 4: Put Them Together

Put a new knob in the center of hollow, and 
fill the gap between new knob and shell with Plarepair powder, then drop Plarepair liquid on it. Be careful not to deviate central axix.

Step 5: Polishing

After taking off the mold, there may be some burrs. Cut them and polish.

Step 6: Weathering

The new cast must look too new and shiny, so it would better be weathered. I splayed gold (or other) paint on cloth, and rub the knob with it.

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    7 years ago on Introduction

    Love this idea, and you're correct about if you are not a stickler about
    getting original (read VERY expensive) replacement parts it keeps the
    who restoration effort in saner territories. Just one other suggestion
    - polymer clay. It's cheap, ready to mold or hand craft to match other
    knobs, and can take on almost any color of finish (something I'm sure
    many Steam Punker types already know about). And there is a lot of info
    out there on how to make this stuff resemble almost anything. Just
    whip it up and bake it (but test the plastic parts for this first - and
    maybe use metal knobs as the base). Got a few projects myself to test this out on, maybe an 'iable or two waiting to be written?


    9 years ago on Introduction

    Very nicely done and you've solved a big problem among collectors.