# Fibonacci gauge

 Project by Dave Polaschek posted 03-17-2019 05:15 PM 1503 views 4 times favorited 31 comments

After wrapping up the spring swap, my workbench was a mess, and one of the things in the way was a box of shorts I had received from EarlS. Rather than actually clean anything, I decided to dig through that box and see what I could find. There were a bunch of smaller strips of wood that were about a foot long, and most of them were 3/4 wide or more (and down to 1/4 thick).

I decided to make a Fibonacci (or golden ratio) gauge, but the plan I found online called for long legs that were 340 mm long (which is more than a foot). But none of my scraps were more than a foot long (they had all fit in a square large flat-rate USPS box, which is 12×12, so that wasn’t surprising). Rather than trying to stretch the wood (I’m told that doesn’t work real well), I decided to do some math.

My first attempt was to multiply everything by 0.8, which gave me all sorts of measurements that were in 64ths. Nothing that lined up with an eighth anywhere in sight. Scratch that plan.

OK. Let’s back up and think a little. The plan online has pieces that are in the ratio of 1:1.618. If I whack that in half, I get 0.5 : 0.809. Multiply that by 10 and I’ve got 5 inches and 8 3/32 inches almost exactly. That’s something I can work with!

So I drew up the plan that’s picture 5 above. My drafting skills are pretty awesome, aren’t they?

The long pieces are 8 3/32 from the pivot to the tip. The short leg is 5 inches from the pivot to the tip. And the connecting piece is 3 3/32 between the holes. In fact, the holes on all the pieces are 3 3/32 between the holes.

So I put a 5/32 drill bit in the post drill (because that’s the size of the brass rivets I have) and drilled a hole through about an inch from one of the ends of a stack of four pieces. I dropped a rivet through to keep everything aligned and drilled another hole 3 3/32 from the first (measuring from the centers, as best I could), then cut out the pieces and shaped them on the belt-sander. I even avoided sanding me this time!

With the pieces more or less the right shape, I riveted them together, not being especially careful in cutting the rivets to the right length. After peening them enough that they’d hold together I headed back to the belt sander to “trim” the rivets to length. And discovered that I had put one in backwards. Oops! Sand them down a little, then peen them over again, and things are looking good. The gauge is a little stiff, but it’ll loosen up with use.

Throw on a coat of BLO and call it done. And the shop is STILL a mess!

Note, there’s a good writeup on Fibonacci gauges here for the curious.

-- Dave - Santa Fe