Bolt & screw tester set for the wall

I wanted a way for people at Robots and Dinosaurs to quickly figure out what fasteners were what, without having to go to the trouble of using thread gauges or calipers.

Wall mount bolt sizers aren’t exactly new, of course, but the cheapest ones I could find online were >$100 delivered. After a couple of hours of measuring and lasering I had this knocked up and installed at the space.

Bolt and screw sizer

The fasteners weren’t exactly cheap, but buying a small packet of each allowed me to make a few sets at once:

3 sets under construction

One for home, one for the space, and one for a friend.

Files are up on Thingiverse if anyone’s interested: http://www.thingiverse.com/thing:1037990

After going through all the different types of screws, it got me thinking. I remember a couple of times going through the junk bin to find a match, and getting one where one bolt size was just close enough to another that it’d go in a turn or so before jamming. How often does this occur?

I drew up this graph to help visualise it. Two different bolts types only have a ‘collision’ if not only the diameter is close, but also the pitch (distance the bolt travels per revolution) as well. So it’s really a 2 dimensional issue:

Screw pitch vs diameter

Blue is the standard metric range, and purple is the special metric ‘fine’ (which is rare to the point of being almost unheard of). The other two are UNC (coarse) and UNF (fine), the two most popular US standards.

Judging by the graph, I’m going to guess the pair I had issues with previously were M10 and 3/8″ coarse.  Nifty!

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