[tab10672]

not sure if this is the right place to post this thread but I wanted to share with everyone how easy it is to reproduce any knob you may need. first, and most expensive is the mold making kit bought at hobby lobby, it was $41 after coupon and you could make around 100 or more knobs with what comes in the kit and replacement plastic mixture is around $19 with coupon downloaded online.    
First affix the knob or knobs you want to reproduce onto a smooth surface by hot gluing or anything that will keep them from moving.    
Then make a cardboard box around the knobs leaving about 1/2" on either side. make sure it is sealed around the bottom to keep mixture from leaking out.    
then follow mixing directions and pour over knobs, with 1/2" above tallest knob.        
when it hardens, remove knobs and you have a perfect mold. the kit can make a mold to reproduce about 10 to 13 knobs but I wanted a mold for all hex and rosette with any configuration needed so I could pour an entire set at once.

[morzh]

OK, how do you reproduce the bottom part of the knobs?

I used to do silicon rubber molds for epoxy potting - it would consist of two halves. We also had to make holes for air to escape.

[tab10672]

   
you can drill and thread for a set screw, insert a shaft spring or make a two piece injection mold to make them identical to the original. I use springs cause these are for my own personal radios and who will ever know but me.
after you remove the original follow plastic mixing direction, add what ever color dye you need and pour        
when they dry I sand the bottom level, leave it in the mold, drill the hole for the spring, glue the spring in and that's it.    
which one is the real thing    

[tab10672]

this photo shows the detail on a small rosette the color isn't right but I just poured it with left over mixture the closest one is the repro    
the entire reproduction set installed on my 89    

[skyscraper]

That looks fantastic, great work! I almost wish I were missing some now

[tab10672]

A two piece injection mold will reproduce the bottom identical to the original but it uses more mold material and like I posted earlier these are for my personal use so I didn't care what the bottom/back looked like. the directions in the kit shows you haw to make the two piece mold.

[Jayce]

This might be a good way to reproduce knobs on rare radios that are basically impossible to find replacements for and a lot cheaper than a 3D printer!

[Bob Andersen]

Excellent! I'd heard about alumilite a few years ago but never followed up on it.

[OldRestorer]

Those hex knobs are exactly what I needed! I just paid $25 on ebay.
I would have rather paid you for them.

[tab10672]

"Those hex knobs are exactly what I needed! I just paid $25 on ebay.
I would have rather paid you for them."

You could use the same kit to reproduce the grill you mentioned.

[jerryhawthorne]

Thanks for the journey, those came out exceptional.
Jerry

[Warren]

Tap Plastics also sells mold making supplies. You can use it to make one sided molds or 2 sided if you want the back the same as original also. I have used it to make some little parts that you cant buy... works pretty well.

[tab10672]

Hobby lobby sells a variety of plastic mix, they even have crystal clear for knobs like on the sundial radios. The mix I have very closely resembles bakelite, you can even marble the color by lightly mixing/swirling the dye in last and when you have the dye mixed right you absolutely cannot tell which is the reproduction "unless you look at the shaft end"

[Jamie]

That's just a fantastic tip. I can't tell you how many radios I've walked away from because they were missing one rare knob, and I didn't feel like chasing it down.