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Discussion Starter #1
Build Instructions and animations:
http://www.instructables.com/id/Trammel-of-Archimedes/

This mechanism consists of a base with two slots intersecting at right angles. Two sliders are confined within the slots and are attached to a handle by pivots (screws) at fixed positions along the handle. The mechanism can be used for drawing a perfect ellipse. This is done by positioning a writing utensil at the end of the handle while making a full revolution.

With that said, it is often sold in novelty shops with interesting names like Bullsh*t Grinder, Bullsh*t Masher or Do-Nothing Machine. Interestingly, most of the names are preceded with state names such has Arkansas, Kentucky, etc. I guess that’s how locals make fun of their neighbors.

Video of Build
 

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Discussion Starter #3
I think I would improve on it and put an end on it that goes down to the base level.
I'm a woodworking novice. From the work I've seen on this site, I bet others could build a much nicer version. I would like to have used a dovetail but that's beyond my ability. I did make a 3D print that looked nicer.
 

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Discussion Starter #7
There might be too much friction with the groove doing it with a dove tail.
I was wondering about that as well. However, it looks like others have done it and they look pretty nice. The 3D print version I made slides great due to coefficient of friction.
 

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Totally off topic: I know a guy from Mt. Airy...
 

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Someone please tell that guy that spade bits suck, they make feather boards for a reason, and you are not supposed to use a SMS like that.
 

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Spinner of Wood
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Someone please tell that guy that spade bits suck, they make feather boards for a reason, and you are not supposed to use a SMS like that.
You could tell him yourself, that guy and this guy (MtAiryMD) are the same.
 

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Man, I wish I still had my shop. I had built larger ones on plywood that had a router at the end. I could cut just about size elliptical top I needed to. I forgot where the measurements were taken from the two slides had different register pins on them. You can be determine the shape of the ellipse, that is - both the long and short sides by where you set the register pins. This info can be found all over the internet.
Just search for Ellipse Jig, Elliptical Jig or anything similar. They work remarkably well.
 

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Discussion Starter #13
Someone please tell that guy that spade bits suck, they make feather boards for a reason, and you are not supposed to use a SMS like that.
You just told me :). I understand spade bits aren't great but the hole did come out very nice. I agree on the feather board - need to buy/make one. I'm not sure what I did wrong with the SMS.
 

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Discussion Starter #15
Man, I wish I still had my shop. I had built larger ones on plywood that had a router at the end. I could cut just about size elliptical top I needed to. I forgot where the measurements were taken from the two slides had different register pins on them. You can be determine the shape of the ellipse, that is - both the long and short sides by where you set the register pins. This info can be found all over the internet.
Just search for Ellipse Jig, Elliptical Jig or anything similar. They work remarkably well.
Good to know...thanks.
 

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mtairymd said:
You just told me :). I understand spade bits aren't great but the hole did come out very nice. I agree on the feather board - need to buy/make one. I'm not sure what I did wrong with the SMS.
I didn't know you were the same guy or I would have been nicer about it. On a SMS you are supposed to pull the saw out and lower it and push it back in to make the cut. The way you cut it can climb cut. When that happens the saw can pull itself rapidly toward you. Your board as a feather board works pretty good. I do it sometimes, but it would make me feel better if you used a longer board.,I have also heard the devise you made called a smoke grinder. I used to have a cheap plastic one. I discovered putting a little liquid soap in the track made it work much smoother. Oil would have worked, but soap doesn't stain anything.
 

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Discussion Starter #18
I didn't know you were the same guy or I would have been nicer about it. On a SMS you are supposed to pull the saw out and lower it and push it back in to make the cut. The way you cut it can climb cut. When that happens the saw can pull itself rapidly toward you. Your board as a feather board works pretty good. I do it sometimes, but it would make me feel better if you used a longer board.,I have also heard the devise you made called a smoke grinder. I used to have a cheap plastic one. I discovered putting a little liquid soap in the track made it work much smoother. Oil would have worked, but soap doesn't stain anything.
Thank you...learn something new everyday.

Yeah, it took a little sanding to make it rotate smoothly. I plan to try alternate versions.
 
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