The boxes I started on holiday have gone on hold for a while as I need to get on with making a birthday present for my Mum. It's going to be an "Inkle Loom": my home-brew version of this (bought) one that Carolyn has:
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I wanted to add some curves to make the design more interesting and open up the hole (I've seen designs on-line with an open hole, so hopefully it'll be okay
). I thought I'd also add a couple of extra pegs to allow it to be used for longer weavey things (that's the technical term
).
As there seem to me to be some subtleties in making sure that the warp (?) doesn't crash into itself or any of the pegs, I thought I'd start with a CAD model, with a fairly complicated driving sketch:
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With that done, it was fairly straightforward to turn it into a model for a 3D printed template, on which I can base the real mccoy:
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I'm not sure how clear it is in that image, but the template is made of four main parts, with some rectangular keys to make everything line up properly. More on that in a minute.
The first job was to draw round the template (on some 18 mm birch plywood) and go round with a jigsaw to rough-out the shape (cutting a few millimetres outside the line, which isn't visible as it's on the other side of the plywood here):
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I then stuck the template down to the plywood with some double-sided tape (crossing my fingers that it would come off easily enough later!) and used some wood filler and masking tape to fill in the small indents that resulted from the template being made in four parts rather than all as one big piece.
Then it was time to set up the router table and install a pattern following router bit to finesse the shape:
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With that done, I could use the holes in the template to mark the positions of the holes for the pegs and also mark the location of the slot for the tensioning peg with a knife mark:
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The template peeled off fairly easily thankfully. Once that was off I took it to the pillar drill and continued the 3 mm pilot holes all the way through the plywood.
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I then drilled a little way in with a 6 mm bit, flipped it over and drilled through with the 6 mm bit and then countersunk all the holes to an equal depth:
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I then cleaned up the outside of the countersunk holes with a chisel, but didn't take a photo as it didn't look that different really!
The next job was to get on with the pegs. I'd previously bought some lengths of beech dowelling for just this purpose. I started with my bench hook thing with a stop set to make it easy to cut them all to the same (somewhat arbitrary) length:
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All the dowels cut:
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I don't have a woodworking lathe and I don't really like turning wood on the metal lathe (sawdust is great at soaking up all that protective oil
), but I couldn't think of an alternative so I put a rag over the slideways and got on with it
I started by making some quick soft plastic jaws out of some acetal bar I had in the drawer. These screw onto some two-part jaws I made a few weeks ago out of some commercial one-piece soft steel jaws. I could then bore a 16 mm hole in the plastic jaws to hold the dowels nice and concentric without risk of marring them.
It was at this point that my brain caught up and I realised that an M6 threaded hole in a 16 mm piece of wood is a bit optimistic really. It's plenty of material in a bit of aluminium or steel or whatever, but a threaded insert would need a 9-ish mm hole drilled in the dowel and it would be very likely to crack when the threaded insert was screwed into place. I tried an offcut (thankfully!) and proved this was true, so I had to stop and think of a plan B (as I'd already made all the holes in the body a nice fit for an M6 countersunk screw).
After pondering for a little while I came up with a plan to use rivnuts instead of normal threaded inserts.
I drilled a 20 mm deep hole and counterbored it 1.2 mm in each dowel, then set a depth stop in the lathe and faced them all to the same length, rounding the outside corners with a file.
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The holes were a tight fit for some M6 rivnuts, but I added some superglue for extra security. This probably isn't necessary: in the test piece I made, I didn't glue the rivnut in. I put an M6 cap screw into the rivnut and put the head of the cap screw in the vice. I pulled as hard as I could on the peg and it wouldn't come off the rivnut! Nevertheless, the superglue seemed a wise precaution.
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Next up was the tensioning peg. A quick re-bore of the soft jaws meant this could be held in the lathe, faced and drilled through 8 mm:
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I then used an 8 mm chisel to open the hole up slightly at the outer end to accept the square bit of a coach bolt:
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The coach bolt I found in the drawer isn't in the best condition, but the head should clean up okay and the rest will be hidden in the peg:
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At that point my stomach told me it was dinner time, so that's as far as I've got this evening. More to follow...