How did they make this back in the day? Wooden radio knob.

[Perry]

My neighbor asked if I could 3D print a couple of radio knobs for her old Electrohome 216B radio. After seeing the knob my CAD side of my brain started whirling along thinking about how I was going to sketch this up. The lazy doughnut side of my brain starting thinking that looks like a lot of work. How the hell did they do this back in the day. It is wood with a brass insert( with a set screw.....you can just see the hole for it in the bottom view). The bottom curve of the knob follow the shape of the tray that it is set in. It's the curved splines that are tapered as they come from the base of the knob up to the top that has me wondering? These would have been mass produced back in ~1940 in Kitchener, Ontario.



I did make a post on canadianvintageradio.com incase someone has these in their collection of parts. They are pretty unique.

Cheers, P.

 

[Perry]

Ok.....lol. The typo in the title is because I'm thinking of treats. Doughnuts, apple pie, butter tarts.....lol...I need a fix.

And it looks like there is no way to correct the typo. My name is Perry, I am a bakery addict.

 

[David]

Ok.....lol. The typo in the title is because I'm thinking of treats. Doughnuts, apple pie, butter tarts.....lol...I need a fix.

And it looks like there is no way to correct the typo. My name is Perry, I am a bakery addict.

Fixed it for you

 

[David]

That was made with an ornamental lathe like a Holtzaffel.

Dale's Woodturnings - My Home Built Rose Engine Lathe

For many years I've been fascinated with the Rose Engine Lathe. This is my version of the Rose Engine Lathe

www.winburn.com

Ornamental Turning | Jon Sauer

www.jonsauer.com

 

[Perry]

Fixed it for you

but.....I still have cravings for a snack.

 

[trlvn]

I think it is more likely that the features that appear to be 'carved' on the knobs were actually made by a steel die and pressure. Same as "press back" chairs. For info, see:

The Press Back – The Art of Chair Decoration without Carving - WorthPoint

What is it? What's it Worth? Find out at WorthPoint, the comprehensive antiques, art, and vintage collectibles research site. Home of the biggest pricing database plus marks, patterns, expert advice, and more.

www.worthpoint.com

Craig

 

[trevj]

I think it is more likely that the features that appear to be 'carved' on the knobs were actually made by a steel die and pressure. Same as "press back" chairs. For info, see:

The Press Back – The Art of Chair Decoration without Carving - WorthPoint

What is it? What's it Worth? Find out at WorthPoint, the comprehensive antiques, art, and vintage collectibles research site. Home of the biggest pricing database plus marks, patterns, expert advice, and more.

www.worthpoint.com

Craig

Yeah, I'd go with this! Factor in for some steam or simply heat in the equation, and you can make wood do all sorts of wonderful things!

Same method was commonly used for clock cases in mass production. No money in it, if you need an expensive Ornamental Turning Lathe, plus a LOT of factory time, to make something as cheap and simple as a knob for a radio!

 

[Tom O]

There are lots of antique dials and reproductions online

 

[Perry]

Yeah, I'd go with this! Factor in for some steam or simply heat in the equation, and you can make wood do all sorts of wonderful things!

Same method was commonly used for clock cases in mass production. No money in it, if you need an expensive Ornamental Turning Lathe, plus a LOT of factory time, to make something as cheap and simple as a knob for a radio!

I think you nailed it. This makes a lot more sense to me. The base circumference of the carved splines seems to be a little bit lower than the area outboard of this circumference. Learning something everyday.


This is as far as I got last night.....

No splines yet. 3D printed to test the basic dimensions. I'm off a little and will clean that up first.

 

[Perry]

Sorry Craig. I replied to the wrong thread. I'm sure you came up with the correct process. Thank you.

 

[Perry]

Tried 3D printing the first model.......you can see the shape was a little off.


The underside was a little rough. Printing on air isn't the best. Did not want to add supports. No one will see the bottom of the knob, but I have an idea.

Splitting this into two pieces. Right where the splines end they are recessed a little and a joint would kind of replicate the edge.

Tonight I spent a little time to correct a few dimensions and add some splines. This is where I am tonight.


The problems I see.....CAD is too perfect. The slight imperfections on the original will be hard to copy.

Second problem. The printer might not be able to do a clean job on the splines.

Will try a test print tomorrow evening in my spare time.

Have a great night!

 

[djberta]

You could play with trying to 3d scan the original knob. Also you could vinamold or rtv the original and then cast it in resin paint to match if you want an exact copy. This is a great thread on how some of the older components were manufactured.

 

[Gennady]

if you have resin 3d printer to you disposal (or friend with one) you can try it printing in resin. You will get much more precise and detailed print without layers and filament artifacts, and paintable

 

[Perry]

Had a little time to play this evening. Like most 3D prints, this looks much better in real life. The dish on the top of the original looks bigger in the photo but in real life they look the same. Used a 0.4 mm nozzle with 0.2mm layer height. Probably could have got better detail with a 0.2mm nozzle. Might switch out the nozzle on the final prints. Will pass the sample by my neighbor first to see if she is happy with it. Hoping she will be happy with a full set of black charcoal knobs. (That way they will all be matching.)

Now the interesting side of the fun. Had the file drawn up a couple nights ago and finally had some time to print it tonight. Bambu studio choked on the stl file. Apparently 340 million + triangles in the STL was a lot to handle for Bambu studio. Reduced the parameters and saved it again. This time there was some strange artifacts showing up in Bambu that did not show up in the CAD file. Where the recesses are for the spline there were little raised wing sections on some of the splines. Played with that for far too long. Redrew the whole thing from scratch. Saved it. Seemed to fix the issue. Not sure where the problem came from.