Tiny thread checker

**mklotz** · Mar 23, 2018, 12:44 PM

If you make miniatures you certainly don't have to use a lot of material making a thread checker plate. This one...

is 1.25" long and covers most of the sizes encountered in my model making. From the left, the threads are:

5-40, 4-40, 3-48, 2-56, 1-72, 0-80, 00-90. The screw lying on the (0.75" diameter nickel) is a 00-90. Missing are the 000-120 and 0000-160, both of which are watchmaker size. I try to avoid them.

For the benefit of the folks unfamiliar with the nomenclature idiocy of the inferial system, the diameter formula,

OD = 0.013*N + 0.060

for numbered screws can still be used form screws smaller than N=0. "Simply" count the number of leading zeros, subtract one and apply a minus sign. This leads to:

00 => N = -1
000 => N = -2
0000 => N = -3

so a 0000-160 screw has a nominal diameter of 0.060 - 3*0.013 = 0.021" or about half a mm.

This is why you should never construct a nomenclature system that's terminated at either end unless that termination represents a physical limit. Naming things by size is permissible because nothing can have a negative size. Arbitrarily setting the zero at 0.06 or labeling drills with letters of the alphabet will lead to confusions like the 0000 debacle.

**Moby Duck** · Mar 23, 2018, 10:12 PM

Does anyone know how they manufacture the threads on these very small screws? ( 0.021" and smaller)

**Frank S** · Mar 24, 2018, 12:29 AM

Thanks for the thread checker idea.
The smallest screws I ever had to work with was the 0-80. And I got a baptismal in them. it was at a company that built custom wire-line geological logging equipment. This 1 client wanted all of the gauges and instruments to be installed with polished brass bezels with from 12 to 20 counter sunk stainless 0-80 screws in them Tapping into a 3/16" thick chromed consul using the recommended #46 or 3/64" drill bits meant we were breaking a lot of taps Doug and I spent more time extracting broken taps then mounting instruments. Fortunately I ran out of the proper sized bits and decided to use a #55 .052" With as many screws as each item was to get we figured what the heck use blue locktite to keep them from loosening if need be. So I drilled and Doug taped we went from breaking a tap 1 in 10 holes for the first 10 items (15 taps in 160 Holes)to nearly zero breakage for the remaining 30 only 5 taps in 400 holes we used more taps than that but 5 was all that broke.
I can only imagine trying to use 00-90 or 000-120 even if in .030" brass.let alone anything thicker. 0000-160? forget me. 0-80, 00-90 and 000-120 are popular in electronics like computers