My daughter restores looms and relies on me to help make replacement parts. She is restoring a loom made in 1956 that has dobby bars that act like a punchcard or music box cylinder to "program" the loom shafts.



Dimensions are at the bottom, the widest part of the bevel.

She is asking for 200 of these. I am looking for suggestions about how I might make that tedious process easier.

My thoughts so far:

Cut long 5/16" thick maple strips to width on table saw set for 45 degree angle using rip jig and zero clearance blade guard.

Create a sliding bed crosscut jig and trim (multiple) strips to length on table saw set for 45 degree angle.

Create a jig (with a recess for the beveled piece) to "bed" the pieces narrow side down and drill holes on drill press. Devise a "tongue-in-slot" or "pin-in-hole" mechanism/fence to move the jig uniformly and position it for each hole.

Use screw eyes in place of the "S" shaped attachment points. (I have not done any destructive investigation, but I think those are inserted through the piece and the opposing side bent after.) If the screw eyes pull out use some epoxy to strengthen them.

Assuming the original strips are 36 inches long, this scheme will require about 500 saw cuts and 2800 drills (and maybe 100 passes through the planer to achieve the original thickness.)

Any ideas about automating?

I also have a 9 inch bandsaw and a router table.

I wish there was a way to drill multiple holes simultaneously.

Thanks.

 

Should the 4 15/16" length dimension in the second picture be 36"?

You can drill multiple holes simultaneously if you stack the pieces. Or, you drill the holes in thicker stock before cutting them into 5/16" thick strips.

If using screw eyes I would look for ones with machine screw threads. Since the wood is only 5/8 wide and you have two screws coming in from opposite sides that only leaves 5/16" they can penetrate into the wood. With a machine screw thread you can tap the wood all the way through. Then cut the threaded portion of the screw eye down to 5/16 and run one in from each side.

 

The 4 15/16 inch pieces will be cut from the 36 inch stock bevel ripped in advance. Avoids having to rip many small pieces and is a better length to work with on the table saw. Then those long pieces will be crosscut to 4 15/16 inch dimension pieces.

I think I can offset the holes for the screw eyes so they won't meet and I can get longer purchase in the wood.

Thanks for the suggestions.

 

I don't think screw eyes are going to work there.
They use what looks suspended ceiling grid hanging wire.
Shouldn't be too hard to bend in place.

Cutting isn't the problem..... it's the precision drilling location.

I figured someone must make/have these. They do but they are expensive.
Dobby bars

 

She knows that they are available but is looking to keep the cost down. I don't charge her.

They can also be 3D printed but the cost is similar.

Edit: She informs me that those AVL bars are a different size and will not fit on her loom.
Also hers was built in 1981 not 1956. She has so many I can't keep them straight.