Jigs for making chairs

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rscrawford
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Jigs for making chairs

Post by rscrawford »

I had a couple questions asked a while back about the jigs I use. So I thought I'd start a thread about jigs.

Here is a YouTube video I just made, showing my vacuum jig for cutting the curved back slats for chairs in action.

http://www.youtube.com/watch?v=VUrHXJCuVUE

I've posted about my aluminum vacuum table before, but I thought I'd put all the pictures on one thread, and maybe get some others to post their jigs.

I'll post a couple pics now and then some more, with explanations, later.

Here is the jig for making the top rail with mortises for the slats. Its a two sided vertical jig - the flat blank is placed on the front and one side of it is cut, and the mortises are cut. Then it is placed on the back of the jig, with the curved surface against the jig, and the other side of it is cut.
IMG_0658.JPG
The jig for the back slats is the same concept. This one is shown in better detail in the YouTube link above.
IMG_0644.JPG
These jigs are held to the table with vacuum pressure. The fit tightly over the grid in the aluminum vacuum table, with a foam seal. This enables me to place them in the exact location on the table every time, which is VERY important with these kind of jigs (or the pieces will not cut properly). There is a hole up through the bottom of the jig, that goes to the sides so the vacuum can hold the blanks in place. A foam gasket forms the seal to hold the blanks tightly to the jig, and there are little rubber pads to create a surface for the blank to suck up against (so the foam doesn't compress all the way - gives a positive stop for the blank so it compresses the foam seal the same amount each time, making it more accurate).
Russell Crawford
http://www.cherryleaf-rustle.com

moto633
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Re: Jigs for making chairs

Post by moto633 »

Nice Russ,
Critique, ...to long on the cut video, not enough on the assembly portion. Just me being picky on your video. It was certainly better than I could do!!!!!!!!!!!!

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Ms Wolffie
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Re: Jigs for making chairs

Post by Ms Wolffie »

I STILL cannot get my head around how it works.
Old timers disease :mrgreen:
I guess you are using a compressor and a venturo (sp?) valve?
Cheers
Wolffie
Cheers
Wolffie

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zeeway
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Re: Jigs for making chairs

Post by zeeway »

Thanks, Russell. I learn something every time you post. Also liked the video. I was thinking of cutting the top rail horizontally until I saw your setup, but now I can see the advantage of the vertical cuts, in that you can do a profile cut rather than a 3d cut. Hmm, now I have to check the real z travel on my machine.

Angie

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Re: Jigs for making chairs

Post by Bob_S »

Russ
What are you using to great your vacuum? I want to start making some production style jigs and wondered if a Venturi type system would be able to keep up with the inevitable small leaks
Bob
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rscrawford
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Re: Jigs for making chairs

Post by rscrawford »

I haven't assembled these chairs yet. I'll post more on the rest of the parts when I make them.

I use a venturi for this. I think it requires 10cfm @100psi. On my corian jigs, I usually get 15-25"hg, but on these MDF jigs I was only getting 8-10"hg. As you can see in the video, that was still enough to hold it firm with some pretty aggressive cuts. The secret is to have the closed cell foam around the border to create a seal, and then a stop so the foam can only compress so much. I use 1/8" window gasket (because its so readily available), and .05" thick rubber pads (just cut it from rubber sandblast mask). Sometimes I'll just use the rubber mask and and no foam, but the wood has to be completely flat in order for a seal to form.

I set my venturi up to turn on and off with g-code. Its connected to a MAC valve, which is connected to a pressure switch. I just ran power to the pressure switch through a relay in my control panel, that can be controlled with g-code. It sounds complicated, but was actually very simple. I just set the jig in place, put the wood blanks on it, and run the file. The venturi turns on and sucks the jig down hard onto the aluminum grid (so even if my jig warps, it is always sucked down flat to the aluminum) and sucks the blanks tightly to the jig. When the cut it over the venturi turns off and everything can be lifted off.

Here are the jigs I use for the seats (I've posted these pictures before on someone else's thread). They allow me to cut the whole seat out, two sided cuts, with no tabs or clamps needed. I can cut a seat out in 30 minutes.
chair seat 1.JPG
I need the jig flat for the first side cut (for the square blank), but I need indexing blocks for the second side - the seat fits tightly over these blocks to index it perfectly to the jig for the second side cut. I cut the bottom first and engrave my name and date, then flip it over and carve out the top.
chair seat 2.JPG
chair seat 4.JPG
Russell Crawford
http://www.cherryleaf-rustle.com

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rscrawford
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Re: Jigs for making chairs

Post by rscrawford »

Just finished a set of dining chairs using the jigs. These came out pretty good, so I don't have many changes left. These pictures were taken after the first coat of finish (had to do it in my garage because my 'dust free' room in the shop was too small to work on all 8 chairs at once - I don't have a spray booth, so I finish by hand).
cherrychair 1.JPG
cherrychair 2.JPG
cherrychair 3.JPG
Russell Crawford
http://www.cherryleaf-rustle.com

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Re: Jigs for making chairs

Post by WoodEraser »

Russel, Those look great!
Great choice of wood.
Thanks for sharing.
Eric
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zeeway
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Re: Jigs for making chairs

Post by zeeway »

Those chairs look good, Russell. Love the cherry. Also, quite amazingly all chairs look identical... :D

Angie

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