Making a Rigid Heddle for a loom - Router Forums
 
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post #1 of 3 (permalink) Old 11-10-2011, 08:49 AM Thread Starter
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Default Making a Rigid Heddle for a loom

I think this may be a jig/fixture question. I am not really interested in making a whole lot of these but it would involve making a whole lot of cuts to make one.

Here is a picture of the part I am going to describe:



You can see it in use on this page: Backstrap Weaving – What IS backstrap weaving? « Backstrap Weaving

For scale they are about 24" long in the first image. What you see amounts to a giant comb. It is referred to as a rigid heddle or a reed. Originally these were probably made by lashing many basket reeds together and burning a hole through the centers of each of them. In weaving (simplified) a thread either goes between two reeds or in the center hole of a single reed. When this is done, every other one, then lifting or lowering the reed will separate the threads so that you can pass threads between them in one motion as opposed to doing the over-under-over-under thing. Depending on the size of your thread/yard will determine the pitch you want to use. Common sizes are between 6 and 12 dpi (dents per inch).

I have played with some ideas, some of which are good, others are bad. Up to this point, the major idea is to do this on the table saw with a jig somewhat like a box/finger joint jig. The idea being that I would take a piece of wood/masonite cut to final size and glue two boarder boards top and bottom. When the glue was dry and set, I would box joint it with the initial board face down. I would set the blade height to just pass through the initial wood and not into the boarder boards. When completed I would glue on 2 more boarder boards opposite the existing ones to sandwich it. I like this idea except that limits me to the width of my saw blade, and it depends on a surface glue joint (scary especially if I were to use Masonite). Many of these appear to be made from plastic, likely injection molded and probably done in china at some ridiculous low price. However, I would like to do it myself regardless of cost.

I have seen smaller ones of these (tape looms) made with a comb saw, and I have seen other hand tool methods for doing these tool, but I neither have these tools not the patience/discipline to manually do 216 of these cuts by hand

If I could do this in Masonite as a single piece, with consistent indexed cuts that would be great! I know I can simply set up a perimeter to handle the stop cuts, but what would be the best way to accurately and repeatably index a straight cut? I assume if I can come up with a way to do the long cuts, the centered holes would be something similar.

Each reed in the system should be 3 times the size of the hole in the middle and the space between them. So if i wanted to work with 1/8" cuts I would have 4 dpi. To get to 8 dpi I need to deal with 1/16. For an example there would be a groove 1/16 wide, followed by 3/16 of solidness with a 1/16" hole in the center, followed by a 1/16" groove and so on down the line. One can quickly see the tedium involved in doing this manually or without a jig.

Last edited by Absinthe; 11-10-2011 at 08:56 AM.
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post #2 of 3 (permalink) Old 11-10-2011, 12:03 PM
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Quote:
Originally Posted by Absinthe View Post
I think this may be a jig/fixture question. I am not really interested in making a whole lot of these but it would involve making a whole lot of cuts to make one.

Here is a picture of the part I am going to describe:



You can see it in use on this page: Backstrap Weaving – What IS backstrap weaving? « Backstrap Weaving

For scale they are about 24" long in the first image. What you see amounts to a giant comb. It is referred to as a rigid heddle or a reed. Originally these were probably made by lashing many basket reeds together and burning a hole through the centers of each of them. In weaving (simplified) a thread either goes between two reeds or in the center hole of a single reed. When this is done, every other one, then lifting or lowering the reed will separate the threads so that you can pass threads between them in one motion as opposed to doing the over-under-over-under thing. Depending on the size of your thread/yard will determine the pitch you want to use. Common sizes are between 6 and 12 dpi (dents per inch).

I have played with some ideas, some of which are good, others are bad. Up to this point, the major idea is to do this on the table saw with a jig somewhat like a box/finger joint jig. The idea being that I would take a piece of wood/masonite cut to final size and glue two boarder boards top and bottom. When the glue was dry and set, I would box joint it with the initial board face down. I would set the blade height to just pass through the initial wood and not into the boarder boards. When completed I would glue on 2 more boarder boards opposite the existing ones to sandwich it. I like this idea except that limits me to the width of my saw blade, and it depends on a surface glue joint (scary especially if I were to use Masonite). Many of these appear to be made from plastic, likely injection molded and probably done in china at some ridiculous low price. However, I would like to do it myself regardless of cost.

I have seen smaller ones of these (tape looms) made with a comb saw, and I have seen other hand tool methods for doing these tool, but I neither have these tools not the patience/discipline to manually do 216 of these cuts by hand

If I could do this in Masonite as a single piece, with consistent indexed cuts that would be great! I know I can simply set up a perimeter to handle the stop cuts, but what would be the best way to accurately and repeatably index a straight cut? I assume if I can come up with a way to do the long cuts, the centered holes would be something similar.

Each reed in the system should be 3 times the size of the hole in the middle and the space between them. So if i wanted to work with 1/8" cuts I would have 4 dpi. To get to 8 dpi I need to deal with 1/16. For an example there would be a groove 1/16 wide, followed by 3/16 of solidness with a 1/16" hole in the center, followed by a 1/16" groove and so on down the line. One can quickly see the tedium involved in doing this manually or without a jig.

If I were going to make one of these, I'd do it on a table saw using a thin kerf (1/16") blade. I would make a comb by settind up a stop block (using the 2 miter slots) to prevent the blade from going all the way thru. I would set the fence at 1 inch (or thereabout - make a layout first), make a cut, move the fence 1/4", make a cut, etc. This would take about 96 cuts but it would pretty fast (at least on a unisaw with good fence). You'd have to layout the comb so you have about an inch extra all around. Once I had the comb, I would glue on a hardwood frame (or border) that was 3/8" thick and 1" wide. I'd use a half lap joint for the corners of this frame. I'd glue a frame to both sides of the comb, then use wood screws to clamp them together, trapping the comb inbetween. I'm not sure what glues will bond to masonite but there must be something that will do, especially with the added screws. After this, I'd make an indexing fixture to use on a drill press to drill the 1/16" diameter holes in the cemter of each comb element.

Instead of a table saw, I imagine that you could use a fixture similar to the Oak Park (and other) box joint fixture (for the router table). The main difference is that the workpiece is laying flat. There's also a "universal' fixture that was posted (on this forum) a year, or so, ago. This one used a router table with a guide bushing and had a fence that coul be set perpendicular, or at an angle. Someone else might be able to find it (I couldn't). With a router, however, the cutting forces are mostly lateral. This could result in breaking the combs. Table saw cutting forces are toward the table and should not result in breakage (with appropriate feed rate).

“The single biggest problem in communication is the illusion that it has taken place.”
George Bernard Shaw

Robert
Redondo Beach, CA
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post #3 of 3 (permalink) Old 11-10-2011, 01:00 PM Thread Starter
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I even considered trying to raise the blade up through the material. But again doing that 96 or more times would be painful.

When you say that you would move the fence 1/4" each time. Are you meaning via the tape and the readings of it? I was more hoping for a trick to consistently move it without relying on my ability to count 1/16ths and line up a thick red line with a thin black line

The reason I was considering the router for this is that I could come up with a completed panel that would be structurally secure even before I added the framing to it.

I had the idea of shaping a piece of wood thicker at the top and bottom and then slicing it into enough pieces to glue together. Still seemed like too much little fiddly stuff to deal with.

At some point I may want to come up with something that would be even smaller than 1/16 (not that I would want to run the threads through it, but in general I was hoping to come up with a solution that I could apply to many multiple thicknesses.

I have looked at fluting solutions as that would seem like a related problem. But then again most of those I have seen rely on visually doing the measuring.

If I can make a base plate and then mortise in a small 1/16 x 1" or so registration pin I could use that like people do the box joint jigs.

Still open to other ideas.
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