5040 Tap and die??????????

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Deck Dog

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Does a 5-40 tap and die even exist? So far everywhere I have asked about it they look at me as if I came from Mars. A model steam engine I am building actually says "use a 38 drill and a 5-40 tap" and says it twice for two different holes. Even the large tap and die sets seem to skip the 5040 taps and dies.
 
5-40 screws have the added advantage of being exactly 1/8" in diameter. I'm surprised it isn't a more popular size.

Chuck
 
Gun shops would be another source for that size. Micro Mark (do a Google search) carries them, American Model Engineering Supply is another (tel# 850-729-8549) That particular size is not widely used except in gun and clock repair as well as model engineering.

BC1
Jim

 
I know this has been answered before but can someone remind me what the 5-40 actualy stands for ? Presumably the 40 is the TPI but not sure about the 5

Also what thread standard does this come under eg BA, UNF, ME etc

Cheers

Jim
 
The USA, always in search of idiotic nomenclatures meant to conceal true dimensions, uses a numbered screw system. The numbers extend from zero to 14 (well sort of - see below).

The major diameter of the screw, the real number of interest, is obtained from the formula:

MD = 0.060" + N * 0.013"

where N is the screw number.

However, since the numbering system is not open-ended, one ends up with idiotic designations such as:

00-90
000-120
0000-160

for screws smaller than 0-80. To use the formula for these screws, one must use:

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

Wouldn't it be nice to have a system where the first number indicated the MD and the second number indicated the pitch? Like, for instance, what is done in metric thread nomenclature?
 
Even though I have a 5-40 tap and die, along with a bunch of other goofy micro fractional size taps and dies from an ancient Greenlee set I don't bother with using them. When the plans call for a 5-32 I'll determine if a 4-40 or 6-32 is more appropriate.
 
5-40 is one of those sizes you won't find in local stores, but is very useful for model work (as somebody said above, it goes right onto 1/8" material.

It's probably a casualty of the great de-oddification of the hardware store-- #2,4,6,8,10 no problem, #1,3,5,7,9 ???
 
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