# Where can I get a conic section of wood slices?

I am trying to help a math teacher spruce up a barren basement classroom that currently looks like a prison cell.
I gave her an 18-inch WiFi antenna for her to put posters on saying it's a parabola and showing the focal point.
But I want to find a conic section that shows that when you slice a conic, you get circles, elipses, and hyperbolas.
https://www.andrews.edu/~calkins/math/webtexts/conicsl.jpg
If I were a great woodworker, I would just make one. But I'm not that good and I don't have a lathe. All I have is a circular chop saw.
Do you know of an easy way to make or buy conic sections (wood or plastic)? https://www.andrews.edu/~calkins/math/webtexts/numb19.htm
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Here is one:
http://www.didax.com/shop/searchresults.cfm/Keyword/conic%20sections.cfm
On 8/20/16 1:47 PM, Aardvarks wrote:

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On Sat, 20 Aug 2016 13:54:09 -0400, Retired wrote:

That is good for the math class. http://www.didax.com/shop/productdetails.cfm/Keyword/conic%20sections/Sort/Item/Order/Asc/StartRow/1/ShowAll/No/ItemNo/333311.cfm
At \$30, it's best for the teacher to expense it. So I'll see if they'll let her do that. She's new to teaching and is shy and far too timid (IMHO), since this is a good request, I think, for a math teacher.
I'm just trying to help her out.
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On 08/20/2016 12:47 PM, Aardvarks wrote: ...

...
Somebody (actually, I gargled and found quite a number) has already beat you to it...
<http://www.eaieducation.com/Product/532031/Dissectible_Conic_Section_Model.aspx
Now, what they're asking for them may not fit the budget...
--

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On Sat, 20 Aug 2016 12:55:28 -0500, dpb wrote:

I was hoping to figure out a cheap way to just give them to her, but the ones you showed at that site were gorgeous! http://www.eaieducation.com/Product/532031/Dissectible_Conic_Section_Model.aspx
At \$100 each, they're a bit pricey for *me* to spend just to help someone out, and maybe she'd even have a problem expensing them at a public school, but they *are* perfect (and gorgeous!) and made out of wood, which is fantastic.
If I had a lathe, I'd just take a light colored wood and a dark colored wood and make two single-napped cones.
Then I'd slice each cone four ways with a thin jig saw blade (I only have a hand-held jig saw though), and that would be what you see in that picture you found.
http://www.eaieducation.com/images/products/532031_L.jpg
So, with a lathe and a jig saw, it would be easy. But without a lathe, I'd need the cone to exist in a material I could cut (plastic or wood most likely) with a hand-held jig saw or circular saw.
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On 08/20/2016 1:47 PM, Aardvarks wrote:

You are half way there with the chop saw.
If it would be me I would go down to Lowes and buy a piece of round wood stock and just cut it at different angles to show how a round circle can be come can become the other pieces.
If you can not find a piece of round wood, you could do the same thing with a piece of PVC pipe. After cutting you could sand the rough edges and actually use the Pipe as a stamp; ink it and print the circles, , elipses, and hyperbolas.
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It can't. If you cut a cylinder perpendicular to its axis, you get a circle. If you cut a cylinder at any other angle, you get an ellipse. It is impossible to make a single cut through a cylinder and get either a hyperbola or a parabola.

No can do. You can cut hyperbolas and parabolas from a cone, but not from a cylinder.
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On Sat, 20 Aug 2016 21:06:46 -0000 (UTC), Doug Miller wrote:

You just gave me a great idea!
My original (and main) goal is to figure out where I can find a cheap cone to slice into conic sections.
However, at the same time, I can get a similar diameter "dowel" and show exactly what you just said!
I think, I might try a 2-inch diameter soft wood fence post.
What I can do is put my belt sander into a vise and then use that belt sander to sand the soft fence-post wood into a cone.
It might look fugly - in which case I'll have to scrap the idea, but if it works, I can then slice the resulting cone into the conic sections.
Then I can slice the original fence post into sections to show that what you get out of a cylinder is different than what you get out of a cone.
I think this is a GREAT IDEA as it has to be cheap (my time is not worth much, but my money is).
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On Sat, 20 Aug 2016 14:12:53 -0400, Keith Nuttle wrote:

I don't think a cylinder will work but I guess I could put a cylinder against my belt sander and have the belt sander (in a vise) turn the cylinder into a cone.
Then I could slice the cone into the conic sections.
I have an old 2-inch diameter fence post that I might try that on. I was hoping for a large conic section (like 12 inch diameter) but I can't sand a 12-inch diameter dowel with a belt saw.
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On Saturday, August 20, 2016 at 5:09:26 PM UTC-4, Doug Miller wrote:

When did they start popping up t-shirt ads at lmgtfy? It sort of takes away the punch when you have to close the ad first.
Very disappointing.
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On Sat, 20 Aug 2016 21:09:22 -0000 (UTC), Doug Miller wrote:

That totally and completely misses the point. If they existed, in wood, for something like five or ten bucks (at the most), the google search would make sense.
But the wooden ones are in the hundred-dollar range, which is over ten times the price limit.
I guess I didn't state that from the beginning, so, I apologize for not being clear. The goal was to find an existing "something" that can be sliced into conic sections.
The two best existing somethings are that I have 2-inch diameter fence posts lying around, and I have traffic cones lying around.
So both are free.
My current plan is to put my hand held belt sander in a vise to see if I can sand the fence post into a cone. If that works, I can easily slice the cone with the 12-inch circular chop saw - but the kerf might be a bit wide.
If the kerf is too wide, I can probably jig saw it with a hand-held jig saw, but it might not be a good straight edge.
The great thing about the fence post is that one 8-foot length affords me a lot of wasted scrap! And it's free.
The traffic cones are also free, since I have a few lying around, but they're harder to cut - but they're more visually appealing, if I can manage to cut one. I don't think can double nap the traffic cones though.
So double napping will be best done with the fence post.
If I can find a larger-diameter fence post, I will try that, as 2 inches seems too small to be visually appealing to the room (but it could sit on the teacher's desk).
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On Thu, 25 Aug 2016 16:33:00 +0000 (UTC), Aardvarks

Well, they do.
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On Thu, 25 Aug 2016 12:04:21 -0500, Vic Smith wrote:

Wood cones for ten bucks? Where?
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YOu might even find clay free at an excavation, just look where utility work is being done. Or a hobby shop or a potter supply. Mold it by pushing it into the traffic cone. Cut it with a thin wire.
Or candle wax. Candles come 3 inches thick by a foot high, often for 50 cents at yard sales.
If those fail, plaster of paris from home depot is cheap, pour it into the traffic cones to mold it. 25 pound bag for \$11.
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On Fri, 26 Aug 2016 11:35:04 -0700 (PDT), TimR wrote:

I was thinking mostly wood - but plaster of paris should also work just as well as long as I can slice it with a saw into sections.
As a matter of fact, paster of paris seems like the best idea overall, as wood is too expensive (and hard to work without a lathe). Candle wax would work but is too fragile (kids are monkeys).
Plaster of paris might be fragile too - but it's so cheap that I can make extras. I probably need to find a mold which the inside of the traffic cones might supply (except for the sharp tip).
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Aardvarks wrote:

Look up Duram's Water Putty. It's not fragile.
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On Fri, 26 Aug 2016 17:20:44 +0000 (UTC), Aardvarks

I can't be making decisions for you. Just type "wood cones" in the Google search bar. But I'd consider "foam cones" myself.
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On Fri, 26 Aug 2016 16:05:18 -0500, Vic Smith wrote:

I picked up some plaster of paris today and will try to make the cones that way and cut them with a jig saw.
That's the cheapest way I think, and I thank you for the suggestions.
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On Saturday, August 27, 2016 at 6:23:44 AM UTC-4, Aardvarks wrote:

Good luck.
I don't think you'll need a jig saw if you do it soon after casting.
You might need a jackhammer if you wait too long.
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