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So after a couple of days playing with the design, I’ve managed to get to a point where I can cut either loose or extremely tight fitting box joints quite easily. 🙂
The ‘proper fit’ is one that I still haven’t mastered. But I’m getting closer.
The design has been simplified in a few ways from what I originally posted. I’ve dropped the drawer runners for the lateral movement – I didn’t take into account that all the runners I have are the ‘self closing’ type. Basically they are angled to help an open drawer shut itself. And once I started test cuts using a simple piece of wood balancing against the jig, it made no sense to complicate things.
The real issue is in finding that perfect fit. The original turret template I made was poorly done, the fingers were different widths and were just too inaccurate. So instead I made a 2cm x 2cm template in Sketchup and printed it out, then cut that carefully on the scrollsaw. Results were better, but again using calipers I could see that there was a real width variation on each finger.
So I came up with this method which has given me the best results yet; I sliced up some 2cm (3/4in) stock into small blocks, in two different sizes. By placing these blocks next to each other in an alternating pattern, I can create a very accurate template for my key to follow. Each block is 2cm thus each slot will be 2cm. And as a bonus, this method will make it easy to knock together a different design of box joint in the future. I can simply swap the block positioning around to create joints twice as wide or cut new ones to make them different sized but still accurate.
What is stopping me from perfect fitting joints now is my ‘key’. I used a screwdriver originally which was 5.8mm in diameter, my blade leaves a kerf of around 3.4mm. I didn’t stop to think and realise that this meant if I moved my key all the way to the left, the blade would move 1.2mm less than it. Ditto on the right. So each time I cut, I was making a finger 2.4mm wider than it needed.
I swapped out the screw driver for an allen key that measured 4mm and instantly the results were better, but the allen key also wobbled slightly as it could not be mounted tightly enough. Looking around I found a woodworking screw that measured 3.9mm, driving that straight into the jig as my key yielded the best results of the day. But still, not good enough to use.
It’s after 9pm now so I can’t play around with the saw tonight, but I did find a different screw which measures 3.4mm. It’s all set to try out first in the morning.
Overall, I think this is time well spent. I know a box joint jig is pretty simple and rudimentary, but I only avg 1-2 hours a week in the workshop these days;
If I can cut joints out with a jig in just a few minutes, it will do wonders for me!
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