Sprangles

I was working on the new shelving for the pantry today and had a bit of problem that stumped me for a while. I ended up coming up with a really simple solution that worked well so I thought I’d share it here.

I’m building the pantry shelving out of white board (particle board covered in melamine resin). The whiteboard is 16mm thick, and where two pieces join I’m routering out a trench so the boards fit together in a snug strong halving joint. Like this:

The problem I discovered today is that the whiteboard sheets aren’t exactly 16mm thick — they’re almost 17mm thick. So after cutting my 16mm wide trench I couldn’t get a board to slot inside the trench. “No problem”, I thought, “I’ll just go and buy a 17mm router bit.” Unfortunately they don’t make 17mm router bits, or at least they don’t sell them anywhere near me. An 18mm bit is too wide.

I ummed and ahhed about it for a while, cursed a little bit, and then did some other things. I didn’t want to widen the trench by hand, so I was going to have to make another pass, but I didn’t want to move my guide — that would be too inaccurate.

When the solution finally came to me, it was really simple: I just stick my rule in front of the guide for the second pass!

Here’s the first pass with no rule:

And the second pass with the rule in front of the guide. This means the second pass will be parallel with the first but the thickness of the rule away from it:

Here you can see how narrow the rule is: just less than 1mm.

With two passes like that I end up with a trench that’s almost 17mm wide, and the whiteboard sheets fit perfectly!