This post will try to convey information needed to make the most complicated part of this mould maker's loom. It's very long but the amount of detail should help the aspiring loom builder. For those not interested in actually making a loom skimming the photos and text may give a better understanding of these parts. Their functions are explained more clearly in earlier posts.
The making of two new spindle racks and matching wire troughs are documented here. These are the major parts of the twisting mechanism, both made of wood. When finished and equipped with the usual additional parts (weights, spindles etc.) this loom will be able to make two new chain wire spacings 7/8" and 13/16" apart.
Layout
Blanks are prepared with dimensions of 3" wide and 1-1/8" thick for the spindle racks and 1-1/4" wide and 1" thick for the wire troughs. These should be made with care; straight without twist, sides parallel and angles square. The full-length version (the only kind I've made before) uses two pieces cut to exactly the same length (42" for this loom). I'm trying something new with these two new ones. Both are only long enough to make a mould facing 24" wide. But the principles are the same and the methods can be used for any length. These two wire troughs are longer than the spindle racks and stick out at each end. This will simply make it easier to feed the laid wires in from the end.
These blanks are yellow birch, a medium density, even grained, easily worked wood. Other suitable woods might be soft maple, cherry or walnut though this is not critical; my original loom, used for years, had parts made from pine.
The chain wire spacing is carefully laid out on top of the spindle rack using a square and sharp pencil. Here the wire trough has been laid on its side and clamped in place while the marks are transferred to it from the rack.
Preparing for Attachment to the Loom
Three bolts will attach the rack to the loom. Acetal plastic plugs are embedded into the bottom, then drilled from the side and tapped for the bolt threads.
A 1/2" brad point drill has bored a blind hole in the bottom of the spindle rack.
An acetal plug is tapped into place.
A 1/4" diameter hole is drilled to the edge of the plug. This is followed with a #7 drill to make a hole through the plug.
These holes are then threaded with a 1/4-20 tap.
The part can now be securely bolted to the traveling beam of the loom. A full length twisting mechanism would use all five bolts; this shorter version uses only the middle three. The angled ends are the somewhat random result of cutting a long piece of wood in two at a 45 degree angle to get just a little more length along the front edges. This way I was able to make two spindle racks; both long enough to make a facing for a 18" x 24" mould, a fairly standard size.
Boring the Spindle Holes
A fence is clamped to the drill press table to drill a line of holes centered exactly 1" from the front of the spindle rack. The holes aren't drilled all the way through since part of the front will later be cut away. If you look closely you can see that I pre-drilled tiny starting holes with a very small drill/countersink. This made it easier to get the holes centered right on the marks. The points of these wide, flat Forstner drills are not easy to see.
The rack is held firmly against the fence and down against the table. A 5/8" high quality Forstner drill is being used to bore clean holes for the spindles to turn in.
You can see that I was barely able to squeeze in enough spindles and needed the extra length created by the 45 degree cut. Identical cuts were made at the other ends for balance, more visual than functional.
Laying out and drilling for 'Reel Posts' and for attachment of the 1/8" brass rod
Holes are drilled for two pairs of 1/4" steel posts. These will brace the reel that winds up the weighted strings to drive the spindles. The reel is made of 3/4" acetal rod. This is perfect for this application but would be pulled forward too much by the weights if these posts weren't here. A competed spindle rack with posts installed is shown at the back. The posts don't need to be steel; brass or plastic would be plenty strong.
Pairs of small holes are placed at intervals along the front to secure a 1/8" diameter brass rod there. This elevates each weighted cord at the front so that it won't tend to cross over the previous wraps around the spindle. The cord starts low at the back and winds around the spindle in an ascending counter-clockwise spiral. After three turns it leaves the spindle higher up and is kept there by the height of the brass rod. The cords pass over the front of the rack and down where each is tied to a lead weight.
Later on brass escutcheon pins will be driven into the holes to secure the rod as shown above.
Indexing Holes for the Wire Trough.
1/8" diameter holes are drilled about 3/8" deep into the top of the wire trough blank. These should be exactly centered front-to-back (with the help of the fence) and carefully drilled exactly on the pencil lines. I use magnification and sit low to the drill press table to 'split the line'. Extreme care here will pay off many fold. I count nine different operations that will be performed for each spindle location; all will depend on the indexing holes and single pin to insure accuracy. This adds up to about 550 separate operations on these two wire troughs! (60 plus spindles x 9 operations each)
These index holes will be used to precisely line up a bunch of different holes and saw cuts. They need to be 'perfect'.
1/8" diameter and 1/4" diameter brad point drills, a 3/4" diameter Forstner and a 3/4" diameter 135 degree twist drill will be used in making the wire trough.
For the drilling operations an index pin must be set in the drill press. A piece of smooth, flat plywood is clamped to the table. Then a 1/8" diameter hole is drilled partway through with a brad point drill. A number drill a few thousandths smaller is then selected to drill a smaller hole the rest of the way through.
An 1/8" diameter drill is picked out whose blunt end fits snugly but not too tightly in the index holes. It is rounded slightly with a belt grinder and buffed smooth. Here it is being forced into the 'too small' hole that has been prepared for it, using a drill bank chucked into the drill press. The drill press is switched off and is only being used as a press here.
The butt end of the 1/8" drill has become the indexing pin and is now firmly imbedded and exactly in line with any hole that is drilled above it.
Attachment of the Wire Trough to the Spindle Rack.
After the indexing holes have been drilled several pairs of holes are drilled for screws that will attach the wire trough to the spindle rack. #4 flat head wood screws will pass down through these holes and into the top of the rack. I use the indexing pin for this operation, too. First, correctly spaced 1/8" holes are drilled from the bottom, out of sight here. Then larger holes are drilled from the top using the indexing pin as a guide. The heads of the screws will be sunk about 3/8" below the top in the larger holes.
Boring Clearance Holes for the Spindles.
The reason the wire troughs have such an elaborate shape is simply to prevent the weighted cords from slipping off the tops of the spindles during use. This is a real headache when it happens. The extra time and trouble taken in making this design are well worthwhile. These 3/4" diameter holes leave plenty of room for the cords to wrap around the sides of the 5/8" spindles. Since the clearance holes completely cover the spindles notches will be cut to allow room for the cords in a later step. The tops of these notches will be just above the cords to prevent them from shifting upwards if the lead weights are accidentally bumped.
The wire trough is flipped on its back and 3/4" clearance holes are drilled into it using the indexing holes and pin to line the holes up perfectly. The spindles will stick up from the spindle rack and into the trough exactly 3/8". These holes need to be just a bit deeper so the spindle can rotate freely. I add about 1/32" which indicates a total depth of 13/32".
This shows how the indexing pin is used. The wire trough blank has been laid on its side with the index holes exposed. After blowing off the shavings the blank will be placed flat on the table with an index hole engaging the pin. When a new large hole is drilled from the top it will be precisely in line with the index hole below.
These clearance holes are very close together for the new twisting mechanisms. This is about as close as 5/8" spindles can get without seriously weakening the wooden parts that hold them.
Earlier on I put in 1/8" diameter dowels cross-wise every four spaces to strengthen the parts so they wouldn't crack between the large holes. The dowels were driven into the drilled holes without glue. You can see the end of one of the in the photo above and five in the photo above that one.
A completely drilled rack lying alongside a completed spindle rack to help show the direction things are going.
I next drill 1/16" diameter holes a little deeper into the wood. Later these will show as a small opening where the V groove of the wire trough intersects the conical spaces over the spindles. The small holes will be also used to help gauge the fine saw cuts which will be made to create the wire engagement slots.
The 1/16" holes are not yet drilled in the bottom piece.
Making the flat bottoms conical.
Forstner bits leave a flat bottomed hole. To give the wires room to twist above the spindles a shallow cone-shaped space must be drilled into the flat 'bottom' of each hole (which will become the top when the part is turned right side up). This conical space does not need to extend all the way to the sides since the wires leave the top of the spindles less than 1/2" apart. A narrow rim around the edge of the hole is left flat.
I purchased this 135 degree twist drill to create the cone spaces. The wide angle allows the chain wires to splay widely as they twist around the laid wires. This makes it possible to use heavier chain wire for a given laid wire spacing. A less obtuse 118 degree drill would likely be fine also. A 60 degree countersink would create a conical space far too pointed; laid wires in the trough would end up far above the top of the spindle and the twist angle would be very steep. In researching this post I learned that countersinks are available with angles as wide as 120 degrees. A 1/2" diameter 120 degree countersink would work since the wire holes in the spindle are less than 1/2" apart.
If the large twist drill leaves a small flat at the middle it can be judiciously removed with a countersink. This is visible in the photo above; slight flats are visible on the right and have been corrected on the left.
Aligning the Wire Trough to the Spindle Rack
The drilling of the wire trough is finished. Now the two wooden parts of the twisting mechanism are carefully aligned while extending the small holes for the attachment screws.
I made these two plastic parts to align the wire trough directly above the spindle rack while marking the small screw hole locations with a brad point drill as shown above. Careful measurement would also suffice. The centers of these barely started holes are carefully drilled to allow for the #4 screws.
Cutting Cord Slots in the Wire Trough
For each spindle location this area needs to be removed from the bottom of the wire trough to make space for the weighted cords that will drive the spindles. The narrow part indicated in black will be removed first; it is the start of hand sawn 'wire engagement' slots that will be cut further up into the trough.
The drill that was embedded in the drill press table as an indexing pin has been removed and is now used to index slots being cut on the table saw.
The drill is moved to a new hole and pushed against the stop for each saw cut.
You can see how these slots are the beginnings of very fine cuts that will cut farther up into the trough. The top part is a completed wire trough.
Multiple cuts are made to creat the shallower part of the notch. It makes room for the weighted cords that drive the spindles but also prevents the cords from 'riding up'.
A third cut completes this operation.
The older version of these slots (at the top) were symmetrical and could be used to make counter-clockwise twists if desired. (I have never done this and probably never will) Since these new parts pack the spindles so closely together the slots are made one-sided to keep the trough from getting too weak. As more and more wood is removed the wire troughs become fragile and somewhat flexible. I always store them screwed to the spindle racks when they are detached from the loom so they don't get broken.
In the back a completed older version, in the middle the slots are complete, and at the bottom the shallower cord slot has not been finished. You can see how the asymmetrical version leaves more of the bottom surface intact.
Sawing the Wire Engagement Slots
Once again, the indexing holes prove invaluable! A rounded bit of brass rod sticks up from the middle of this crude sawing jig and will be used to locate the saw cuts precisely.
A lot of head scratching and playing around with a set of feeler gauges yields a jig in which the trough can be lifted and repositioned to index the saw cuts precisely. The jig yields right angle saw cuts directly through the centers of the small holes. (It would have been smart to make an extra, scrap wire trough blank to help adjust the sawing jig.)
A partially sawn blank with some of the tools that are used. A strip of wood is clamped to the top of the Japanese style saw to stop the cut at the right depth.
Here the stop rests on top of the blocks, showing where the cut would be stopped.
The beginning of the cut.
The cutting action has been stopped by the wooden strip riding on the blocks. The cuts are about .025" wide. The heaviest wire that will pass through these slots is .015"
The wire trough is nearly completed.
Final shaping of the Spindle Rack
The back of the spindle rack is left thick to provide a strong attachment to the loom. The front edge needs to be thinned to 1/2" to support the spindles at that level.
The waste has been partly cut away leaving the front edge exactly 1/2" thick.
The back edge is cut at a 45 degree angle.
The front edge is rounded with a small radius router bit.
The piece on the right is now completely shaped.
Final shaping of the Wire Trough
A V shaped groove will be created in the top of the wire trough to guide and support the laid wires as they are inserted one at a time. The bottom of the V should be just deep enough to intersect the tip of the cone shaped clearance holes above the spindles.
First the waste is roughed out with the table saw set at 45 degrees.
The indexing holes are gone and the hand cut slots and the 1/16" diameter holes have become visible in the bottom of the trough.
Final smoothing of the V groove is made with a 90 degree router bit. A slight flat will be left at the bottom of the trough. This is fine; the twisting action of the chain wires lift laid wires slightly and pull them to the center each time one is twisted into place.
Spindle Support Strip
A 3/4" wide strip of polycarbonate supports the front 1/16" of the spindles; holding them level. Screws are placed every three inches or so.
Final Details
A brass rod is cut to length and fastened in place by escutcheon pins driven into the previously drilled holes.
Short lengths of smooth rod are fitted into the holes to brace the reel.
Several corners needed to be chiseled off where escutcheon pin heads kept the trough from centering on the rack.
For the same reason shallow grooves were cut at the back to make room for the reel posts.
Now the wire trough is free to align correctly and be screwed down to the spindle rack.
A cross section working drawing showing the parts we've been making and how they relate.
Installation and Testing
The finished 13/16" twisting mechanism is installed along with a few spindles and weights for testing.
This shorter version required me to make new parts to hold the reel at the ends.
Here is the end with the fixed and adjustable stop to limit the turn of the spindles. If I had thought of this earlier I might have designed this loom so that the reel stayed on the loom all the time. The earlier twisting mechanisms require the reel to be re-installed each time a different chain wire spacing is required. (Which isn't very difficult)
The lead fishing weights nearly touch and I had to make new wire slides that are smaller than the old wooden ones. These would have interfered with each other at this close spacing. The white plastic discs at top and bottom are 3/4" diameter. 1mm fiberglass rod was used for the narrow splints that prevent twisting.
I have to hang every other weight on a longer string for these closely spaced chain wires. The weights are slightly magnetic and want to stick together.
Conclusion:
I hope that this is helpful for anyone wanting to make this type of mould maker's loom. I now have seven chain wire spacings possible ranging from 1-3/16" to 13/16". I am looking forward to making a small mould with these very close chain wires and ribs. I am attracted to the (largely theoretical and mostly unrealized) subtle interplay between laid and chain wire sizes and spacing as incorporated into finished paper.
If I were designing a new loom I would likely separate the structures of the reel from the twisting head so that the reel could remain permanently in place as different twisting heads were installed. This had never occurred to me before this project.
Being able to make smaller twisting mechanisms could make it easier to produce moulds with custom rib spacing. In-between sizes, metric, or irregular spacing would be possible and full length mechanisms would not be required. A mould maker could keep dedicated twisting units on hand for standard size moulds.
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