is it possible...

[Tarkin]

Having compleated my mortice jig (see the projects thread), and sticking 2 fingers up at Trend (£170 my backside), I've been inspired to go further. I've always wanted a Leigh dovetail jig, the adjustability is a big plus (I currently have a cheapo SIP fixed one), and it would be nice to be able to do through dovetails withough risking using the saw (once ruined a whole lot of walnut with a dovetail saw... ).

Anyway, I've had a few ideas of just how you'd go about making a Leigh style jig. The actual base of the jig and the clamping mechanism is the easy bit (or at least it seems that way IMO). The difficult bit is how to fix the fingers. At the moment,, my idea to to make the leigh style fingers out of 1/4" acrylic, and double them up. By routing a grove in them, centered, this would give a hole through which to pass a bar (probably 1/4" or 3/8" aluminim with a slot in it). A machine screw could then fit through form the top and fix into a bolt fixed to the under piece (with epoxy or something). Here's a diagram....since my explanations are typically rubbish.

Thoughts and suggestions greatly appreciated.

Cheers, Ewan.

 

[SketchUp Guru]

Hmm.. Might work but I wonder if acrylic would be too brittle for those pointy ends.

I suppose you could stack all the blanks for the fingers and mill the slopes and radii all at once.

 

[jasonB]

Hardest part will be making 24+ identical acrylic fingers unless you have a small CNC router/milling machine.

As Dave says acrylic may be a bit fragile maybe tufnol or similar that has some fibres in it.

Jason

 

[Scrit]

I'd agree with that. Acrylic will be likely to chip in service and will be difficult to machine without running the risk of shattering at the point, or making a fancy jig and machining in 2 or 3 passes. I'd also agree with Jason that if you want to machine these in plastic go for fabric-reinforced phenolic plastic (Tufnol, etc). The fabric re-inforced variety is much more durable than the paper-reinforced variety. You may need to buy a specific cutter to machine it, though, as it can be very hard on wood cutters (you need to produce chips when machining it, not dust, to get a clean, burn-free edge). Tufnol and acrylic can both be threaded, although for durability I wouldn't recommend it with either material. Tufnol works well if threaded brass inserts are bonded in using a cyanoacrylate adhesive ("superglue")

BTW, have you looked at the way Porter Cable do their Omnijig variable spacing? A different approach.

Scrit

 

[Tarkin]

Good idea about the tufnof! Only reason i would use acrylic is that I have loads of the stuff lying about. I would cut them using a router jig, that way they would all be identical.

Scrit, don't suppose you have a source for said router bits. Or tufnol for that matter? Only things i can find made from tufnol are router table inserts, and I don't think they are suitable.

I've bee thinking more about this, and I dont think it will be that difficult (famous last words!!!). unfortunatly, I've got uni finals coming up, so it'll be a couple of months before I get time to make the bloddy thing...

Cheers.

 

[jasonB]

Small amounts of Tufnol etc from here

Trend do a couple of cutters in their pro range

Jason

 

[Scrit]

As Jason says Trend do some Tufnol and acrylic cutters, so do Titman. Another source of acrylic cutters is Clico in Sheffield. Go for HSS on acrylic as they're cheaper and will last a long time. Tufnol needs carbide.

Another source of Tufnol offcuts, sold by the kilo, is A1 Plastics in Walkden, Manchester.

Scrit

 

[lugo35]

why not use ali for the fingers. routes as easy as plastic and will give you he strenght

 

[Tarkin]

why not use ali for the fingers. routes as easy as plastic and will give you he strenght

I'd had the same thought. I've routed it before with a TCT Spiral cutter, and it works like a charm. That would give 1/2" aluminium fingers, which should be plenty strong....

Cheers for the suggestions everyone.