Archimedes Trammel

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Stray Feathers
Posts: 767
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Archimedes Trammel

Post by Stray Feathers »

I am going down future rabbit holes; thinking ahead about making a flat-top (radiused) mandolin. I see lots with oval/elliptical soundholes and rosettes and wondered how that is done. Some are hand cut, some use router bit templates (this would require changing the bit or template piece several times). I was hoping for something as easy as an adjustable circle-cutting jig. Lots of online references to Archimedes Trammel (AKA Ellipsograph, and other less-flattering) to draw it, and larger versions to cut one out, like a table top say.:

https://www.instructables.com/Trammel-of-Archimedes/;
https://woodarchivist.com/3372-elliptic ... jig-plans/

But my dim mind bogs down when I try to figure if one could be made that was adjustable equally in both directions, and mounted to a mini-router base, to make small rosettes. Anybody any experience? Bruce W.
starbuc2
Posts: 12
Joined: Wed May 29, 2024 4:54 pm

Re: Archimedes Trammel

Post by starbuc2 »

Search for "Rockler Ellipse/Circle Cutting Jig". You would need something like that but smaller.
-David
Stray Feathers
Posts: 767
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Re: Archimedes Trammel

Post by Stray Feathers »

Yes, I did come across the Rockler tool in my digging, and as you point out, it needs to be smaller. I wondered if it could be made to work to produce a much smaller ellipse, in the same way you used to (pre-digital aids) enlarge or reduce an image using a pantograph:

https://www.leevalley.com/en-ca/shop/to ... ograph-set

For all the hassle, and given the increasing availability of CNC products, it may be no surprise that no one has bothered to try! A round hole for my first mandolin is looking pretty appealing . . . Bruce W.
MaineGeezer
Posts: 1808
Joined: Wed Aug 13, 2014 12:14 pm

Re: Archimedes Trammel

Post by MaineGeezer »

My friend Carter made an elliptical sound hole:
https://submusicworks.com/wordpress/wp- ... 8x1024.jpg
I'll inquire how he did it.
Don't believe everything you know.
Anything is possible if you don't know what you are talking about.
When things are bad, try not to make them any worse, because it is quite likely they are bad enough already. - French Foreign Legion
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