How the heck do you cut a super-ellipse? (1 Viewer)

LotsOfChips

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Hey all,

So I've been researching my first poker table build, and I'm going back and forth a bit about the exact shape and dimensions for the table. I was thinking of 96 x 48 oval, but a few people here (especially @Taghkanic) are big proponents of the Super-Ellipse, largely due to the improved sight-lines and easier reach for collecting cards, pots, etc.

I've looked around, and there are several different router jigs for cutting ellipses and circles, but so far I haven't seen anything for cutting super-ellipses.

I'm guessing that I would probably have to draw out the line on the wood and then free-hand the router or jig-saw (and I'm really crappy at freehand cutting). I have seen a few online calculators that allow you to specify the length, width and "n", but I'm not sure how to go about transferring the resulting drawing from the computer screen to the table surface and rail sheets.

Any suggestions, or should I stick with the simple and easy to cut oval?
 
Imo, a combo elipse/oval design is the best of both worlds -- it's essentially an elipse design (for better sight-lines) but with half-circle arcs at each end (for improved player elbow- and foot-room).

Just superimpose both the elipse and oval dimensions on the wood, and cut the larger of the combined images.

There's at least one thread here on PCF detailing how to make a router jig for an elipse table.
 
I've looked around, and there are several different router jigs for cutting ellipses and circles, but so far I haven't seen anything for cutting super-ellipses.

My method was crude, but it worked:

1) Designed my shape using an online plotter. There are an infinite variety of super-ellipses, so you may want to tinker with the exact shape;

2) Blew that shape up to my actual size in an image editor;

3) Cropped the full-size superellipse to just one quadrant (say, the upper left 1/4 of the shape);

4) Printed out the full-size “quadrant” template using the tiling feature of my printer menu, taped it together, and cut the curve.

5) Traced the template four times on the plywood.

6) Cut it freehand with a jigsaw and sanded it smooth with a palm sander.

I’ll try to find and post the link to the site with the image plotter and the options I used.
 
http://www.procato.com/superellipse/

Settings I used:

superellipse-240x120-jpg.138592


For the rail I just traced my cut tabletop on another piece of plywood, and measured a few inches on either side of it at multiple points to draw the wider outside and narrower inside edge. But you could instead make separate templates for those, I suppose.
 
I went with an elliptical table, and I think its worth the effort, I didn't like the super elliptical table, I wanted a dealer cut out and the super ellip would make it too wide.

This looks complicated, but its not and again I think its worth the effort.

Youtube Vid
 
However you do it, make sure it's reproducible to a high degree of accuracy because you're gonna repeat it for the rail.
This is the crux of the matter. I want the cuts to be as accurate as possible (OCD issue). Ideally I would like it if the rail and table cutouts were symmetrical to the point that I could install the two pieces of the rail in either direction and it would still be flush, and that I could install the rail over the table in either direction and it would still fit.

An oval may not be optimum for sight lines, but with a simple circle jig and an edge guide, it seems fairly simple to use a router to get a clean, accurate cut that is pretty much symmetrical and reproducible.

Did I mention that I suck at free-hand cutting (with either a router or jig saw)?

I built a jig for an elliptical table once. It didn't work. For the jig to work properly the length and width had to be closer in size. I ended up free handing it with a jig saw. Here's the link to that thread if it helps any.
https://www.pokerchipforum.com/threads/taking-a-crack-at-an-elliptical-table.26094/
The commercially available ellipse jig that I saw only allowed maximum difference between major and minor axis of 8". It looks like even the home built ones suffer similar issues (plus I'm not sure if I have the technical skills to build my own router jig).

Did I mention that I suck at free-hand cutting (with either a router or jig saw)?

My method was crude, but it worked:

1) Designed my shape using an online plotter. There are an infinite variety of super-ellipses, so you may want to tinker with the exact shape;

2) Blew that shape up to my actual size in an image editor;

3) Cropped the full-size superellipse to just one quadrant (say, the upper left 1/4 of the shape);

4) Printed out the full-size “quadrant” template using the tiling feature of my printer menu, taped it together, and cut the curve.

5) Traced the template four times on the plywood.

6) Cut it freehand with a jigsaw and sanded it smooth with a palm sander.

I’ll try to find and post the link to the site with the image plotter and the options I used.
Thanks for this. I was wondering how to get the desired image onto the table. As you say, crude, but it works.

Did I mention that I suck at free-hand cutting (with either a router or jig saw)?


http://www.procato.com/superellipse/

Settings I used:

superellipse-240x120-jpg.138592


For the rail I just traced my cut tabletop on another piece of plywood, and measured a few inches on either side of it at multiple points to draw the wider outside and narrower inside edge. But you could instead make separate templates for those, I suppose.
Yes, I found this (or something similar) online. Loved how you could adjust the "n" value to fine tune the shape! If only there was a router jig that could reproduce this!

Did I mention that I suck at free-hand cutting (with either a router or jig saw)?

Imo, a combo elipse/oval design is the best of both worlds -- it's essentially an elipse design (for better sight-lines) but with half-circle arcs at each end (for improved player elbow- and foot-room).

Just superimpose both the elipse and oval dimensions on the wood, and cut the larger of the combined images.

There's at least one thread here on PCF detailing how to make a router jig for an elipse table.
That's an interesting idea. One of the big problems I have with a true ellipse is the "pointed" ends. That is why the super-ellipse appeals to me. You can adjust the "n" value to get a more desirable shape. But your idea of superimposing the half-circle and the ellipse seems to open up some other opportunities.

I did a couple of searches using "jig", "ellipse" and "elliptical", but the only results showed people ending up free-hand cutting the wood. Did I mention that I suck at free-hand cutting (with either a router or jig saw)?

_____________________________________________________________________________________________

TLDR: Sounds like there is no jig for cutting super-ellipses, or even for larger (48 x 96) ellipses. The consensus seems to be to trace the desired shape onto the first sheet (or onto one quadrant), and then use that cut as a template for all remaining cuts. Either that, or buy a CNC machine and learn how to program it!

Did I mention that I suck at free-hand cutting (with either a router or jig saw)?
 
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or buy a CNC machine and learn how to program it!

Or get it cut by someone else with a CNC machine.

I don't have the correct tools, or the space, so I got my tables wood parts cut for me by someone few miles away - and that included getting 76 bolt holes drilled extremely accurately. Could have probably done it a tad cheaper another way but wouldn't have saved that much at the end of the day and I have something that I wouldn't have got close to quality wise.
 
You’re never going to see the cut on the table top itself, as it will be covered by the rail.

The rail will be covered with foam, and then by fabric or vinyl or leather. So those coverings are going to hide a world of small flaws.

Which is not to say that you don’t want to be as precise as humanly possible… Just that it’s unlikely anyone is going to notice very small flaws.

The other thing is that you will have the opportunity to sand everything. Sanding is a slower and more forgiving process. So if you’re really aiming for perfection, I’d say that’s where you’re going to get closest.

Unless this were C&C’d. Then it can be perfect. But then your upholstery job is likely to be less perfect than the carpentry.

As far as reversibility of the rail, that will have more to do with the precision of the locations of the holes you use for fastening the rail to the surface than the perfection of the edge, I would think.
 
I was just going to say, maybe you can hire a shop to do a quick CNC guided cuts. Maybe Tony?
LOL, I thought about that for about 3 seconds. I’d either have to transport the wood into the city, drive into the city to buy the wood, or pay Tony to buy the wood for me, then transport everything back to Chilliwack after it is cut.

Plus the goal is to build the entire table myself. If I would consider farming out any portion of the build, it would be covering the rail. But even there I would rather learn how to do it myself, for the experience and the satisfaction.

I suppose that if there is a local shop that would cut the pieces for a reasonable (cheap) fee, then perhaps that might be an option.

Oval is sounding more and more appealing.
 
You’re never going to see the cut on the table top itself, as it will be covered by the rail.

The rail will be covered with foam, and then by fabric or vinyl or leather. So those coverings are going to hide a world of small flaws.

Which is not to say that you don’t want to be as precise as humanly possible… Just that it’s unlikely anyone is going to notice very small flaws.

The other thing is that you will have the opportunity to sand everything. Sanding is a slower and more forgiving process. So if you’re really aiming for perfection, I’d say that’s where you’re going to get closest.

Unless this were C&C’d. Then it can be perfect. But then your upholstery job is likely to be less perfect than the carpentry.

As far as reversibility of the rail, that will have more to do with the precision of the locations of the holes you use for fastening the rail to the surface than the perfection of the edge, I would think.
I hear what you’re saying. If I can develop my cutting skills a bit more, then maybe I’ll attempt something like that. But my last attempt at cutting plywood with a jigsaw pretty much wasted the entire sheet of wood. (When I say that I suck at cutting free-hand, I mean I REALLY suck at cutting free-hand)
 
Some math wizard might know how to rig up a combination of strings and nails to plot a super-ellipse with a pencil… Which could then be turned into a jig.

A basic ellipse is drawn with just two points and a string, with the dimensions determined by how far apart the nails are and how much play is on the string:

 
As far as the jigsaw goes… Not sure what went wrong for you.

I helped my s.o. jigsaw a decorative headboard for a photo shoot yesterday. It was quality birch plywood, and as long as we went slow it was easy with just a basic jigsaw. (I’d love to get a Festool one of these days.)

I was surprised how little splintering there was… Sometimes putting down painter’s tape prevents this, but with better wood and a good blade, tape wasn’t necessary. It only required very light, quick sanding after.

The cuts went quite slowly, but that helped with accuracy.

Don’t do it if you’re not comfortable. But getting a scrap piece of plywood and just practicing a bit might make you a lot more at ease doing the final cuts.
 
Some math wizard might know how to rig up a combination of strings and nails to plot a super-ellipse with a pencil… Which could then be turned into a jig.

A basic ellipse is drawn with just two points and a string, with the dimensions determined by how far apart the nails are and how much play is on the string:

Once you have the shape, if you're are using a jig saw you can clamp / screw the pieces together and all 3 at the same time.
 
Imo, a combo elipse/oval design is the best of both worlds -- it's essentially an elipse design (for better sight-lines) but with half-circle arcs at each end (for improved player elbow- and foot-room).

Just superimpose both the elipse and oval dimensions on the wood, and cut the larger of the combined images.

There's at least one thread here on PCF detailing how to make a router jig for an elipse table.

This video makes my head hurt, but I think this might be the shape you mean (which the narrator calls an oval though that may mean something different to geometryheads than to laypeople I think):

 
Some math wizard might know how to rig up a combination of strings and nails to plot a super-ellipse with a pencil… Which could then be turned into a jig.
It's not trivially possible in the general case.

The string and nails trick works because of a neat property of an ellipse: if you draw a line from each focus to a point on the edge, the total length is always the same no matter what the edge point is.

That's unfortunately not true for a Lamé curve (superellipse).
 
What about getting an inexpensive projector and using it to project the template onto your plywood for tracing?

One of those $50-60 numbers from Amazon should be good enough for the job.
Every overhead projector I have ever used distorted the image to some degree. And that includes some that cost >$1000, so I would imagine that a <$100 one would be worse.

However, given my free-hand cutting skills, it probably won't matter if the image is distorted, in fact it might improve the final product!
 
You can buy a 4'x8' CNC Router setup for $600 (plus the wooden frame and the router), better model is around $1200. https://makermade.com/collections/cnc-kits

I'm thinking that this would be fairly simple to program with the Lamé (super-ellipse) formula. Not that I have the room to fit something like this into my garage, or that I would ever be able to justify the cost for the one or two times in my life that I might use it.
 
Every overhead projector I have ever used distorted the image to some degree. And that includes some that cost >$1000, so I would imagine that a <$100 one would be worse.

However, given my free-hand cutting skills, it probably won't matter if the image is distorted, in fact it might improve the final product!
I have one of those cheapies. Now I kind of want to try projecting an ellipse onto a wall and measuring it...
 
You can buy a 4'x8' CNC Router setup for $600 (plus the wooden frame and the router), better model is around $1200. https://makermade.com/collections/cnc-kits

I'm thinking that this would be fairly simple to program with the Lamé (super-ellipse) formula. Not that I have the room to fit something like this into my garage, or that I would ever be able to justify the cost for the one or two times in my life that I might use it.
I looked at one of these because of this thread, and reviews seem to indicate that it has some issues when milling the edges of a full 4x8 sheet (at least compared to better CNCs that cost 5-10x as much).
 
If you’re getting distortion from the projector, presumably that would be because it is not perfectly square to and centered on the board. With some nudging and shimming it ought to be possible to get it right, unless the lens is really low quality.
 
I think job number one should be getting over your aversion to the jigsaw. Saying "Did I mention that I suck at free-hand cutting" is the cowards way out. Learn a new skill.

Use a high quality, very sharp blade. Use a more agressive blade than you think you should. The sander will clean it up.
Use high rpm on the saw, even though this seems counter-intuitive, as it makes it much easier to control and direct.
Use firm downward pressure to keep the base of the saw planted on the material. Don't let it bop around.
Use a SLOW feed speed, patiently making that blade go where you want it to, and don't be scared to back up a bit and re-cut if you start to wander.
Cut a fraction over your line (not much, 1/16" or so) and finish the cut with an aggressive sander.

You got this, just do it and stop limiting yourself. Nobody was born an expert at anything. Take the first step.
 
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I looked at one of these because of this thread, and reviews seem to indicate that it has some issues when milling the edges of a full 4x8 sheet (at least compared to better CNCs that cost 5-10x as much).
I think that you can build the mounting table a bit larger and extend the chains a bit to accommodate milling the edges.
 
I think job number one should be getting over your aversion to the jigsaw. Saying "Did I mention that I suck at free-hand cutting" is the cowards way out. Learn a new skill.

Use a high quality, very sharp blade. Use a more agressive blade than you think you should. The sander will clean it up.
Use high rpm on the saw, even though this seems counter-intuitive, as it makes it much easier to control and direct.
Use firm downward pressure to keep the base of the saw planted on the material. Don't let it bop around.
Use a SLOW feed speed, patiently making that blade go where you want it to, and don't be scared to back up a bit and re-cut if you start to wander.
Cut a fraction over your line (not much, 1/16" or so) and finish the cut with an aggressive sander.

You got this, just do it and stop limiting yourself. Nobody was born an expert at anything. Take the first step.
Thanks coach! (Sincerely)

Yeah, probably a couple of hours of practice on some scrap material would improve my skills and my confidence.

Your tips about speed and pressure are spot on. My last attempt had the jigsaw jumping around, and bending or breaking blades. When I did wander off the cut line, I was several inches into the good material before I was able to stop and correct.

Colouring outside the lines may be something that you want to encourage others to do. Cutting several inches outside (and inside) the lines on your home built poker table, not so much.
 

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