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Tap & Die Sizes

Can anyone tell me what the numbers that refer to tap and die sizes
mean e.g. 0-90, 0-80 etc.

I’m trying to make a screw out of 10 gauge silver wire and I’m not
sure which tap & die I need to buy.


Bob, The sizes you refer to are thread sizes. If you are familiar
with 4-40, 6-24, etc. You know that the diameters of machine screws
are numbered (2, 4, 6, 8, etc). The “0” os the smallest size I know
of. The second number is the number fo threads per inch. 4-40 is
40 threads per inch as you may know. 0-80 is 80 threads per inch.



the numbers refer to screw thread size & dia.

In any case, I would forget trying to thread silver, its to soft for
either operation. If you can substitute, use silver steel (English
term for American tool steel), while not silver, it looks OK
alongside it.


Hi Bob,

The 1st number is the size of the metal the screw is made from. The
second number is the number of threads per inch.

Small screws are available in following sizes:

Screw #       Diameter in Inches
0000             .021
000               .034
00                 .047
0                   .060
1                   .073
2                   .086
3                   .099
4                   .112
5                   .125
6                   .138
8                   .164
10                 .190
12                 .216

The odd numbers aren’t used very often, if at all.

For your 10 ga wire (1.02) I’d suggest using a number 3 if you can
find it. Depending on the amount of stress that’ll be applied to the
joint & the number of times it’ll be opened & closed a 4-40 may


   forget about trying to thread silver, its to soft for either

Just as well the Swiss dudes who made the solid sterling silver
cigarette lighter on the bench in front of me didn’t know that Bob -
they wouldn’t have been able to make it

It has 4 tapped holes from c.a. 5/64" to 3/8" and screws to fit,
none of which show any wear, and was made in the 1930’s.

Al Heywood

.102"/10ga wire falls outside of the miniature taps you are looking
at. You can see those numbers in our References pages at
<> The closest in American NationalStandard is
1/8" which you can get anywhere. It would be a little lose. #4 “Best
wire” is.093" which would be tight but you could taper the end a
little. My references don’t show anything made for a .102" wire. Bill