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Home made through dovetail Jigs

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Home made through dovetail Jigs

Postby Robert » 06 May 2019, 15:03

I've always joined the corners of drawer boxes with dovetails and I've always used a dovetail bit on the router table on one piece then struggled to find a way to cut the angle sided pins on the other part.

I don't do hand tools if I can avoid it. So I started thinking about getting a dovetail jig. The cheap ones just seem to do half blind dovetails and I want through joints as I always use fairly thin stock - 13mm thick or less. Maybe some jigs can do it but beyond my understanding.

Then I saw templates for sale on ebay from China and started thinking. The templates were not cheap and the profiles were back to back so switching from one to the other would be a pain.... So I thought why not make my own? Ages ago I did a lot of template mortices when I made our dining chairs and laminate flooring makes good templates.

I did a drawing in sketchup
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For it to work I needed a dovetail bit with a 1/2" bearing and 1/2" bearing guided trim bits. As I wasn't sure if this would work I ordered the cheapest I could find on ebay with long delivery from China.

meanwhile in no hurry I printed the sketchup full size and stuck the paper to some laminate with double sided tape and dug out my rough noisey scrollsaw from the shed. Had to be bolted down tight to stop it vibrating too much but it did the job with only 2 blades used.
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Tape scraped off
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I screwed the templates onto a piece of beech I had lying around. I also bought one of those Katsu trim routers that has been mentioned on here before. Not thought too much about clamping the workpiece yet so for now it is just clamped to the main panel.
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I just used a bit of 12mm MDF for testing and tearout was terrible so I put 2 layers in the jig so the back one had no tearout. The set of trim bits had a problem I hadn't realised before. The jump in sizes was too great between small and middle size. 12mm + a bit of overcut was not possible if I wanted to keep the bearing on the template.
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After thinking i should have made thicker templates I realised all I needed was a spacer to lift the template. I used some 4mm polycarbonate as I had no thin ply.
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The spacer overhangs the front just a little and is enough to space off the workpiece.

The fit of the joined parts is controlled by the position of the template - push it back for looser fit or forward for tighter.
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test pieces together
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So a bit of clamping to sort out with some kind of over centre clamp and possibly a clamp shield to stop tearout but I'm pleased with it as it works and cost next to nothing in materials. Think I made it much too wide but if I never join anything that big at least I have lots of slots to wear out.
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Re: Home made through dovetail Jigs

Postby RogerS » 06 May 2019, 17:40

Very interesting, Robert..great WIP.

I made a Grandfather size jig when I was making those longcase clocks. Designed to be used with a suitably sized guide bush.

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Oh how I miss those high walls with all that racking space :(
If opportunity doesn't knock, build a door.
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