How to identify / sort a box of random taps?

[julianf]

So, i have a few kilos of random taps, all sizes, threads.

A lot are without any marking, and then some have, as an example "1/2 S 20"

Now this is obviously 1/2 inch, 20tpi, but a quick google suggests UNF or UNC - how would i know which one?

Also, for taps that have no markings whatsoever, i can measure the TPI using a gauge, and the OD with some verniers, but, in the case of a taper thread, at what point should i measure the OD? Mid point?


Ive not yet found a website with all the charts on one page, so swapping between sites just adds to my confusion - im sure im missing somthing, and it cant really be this difficult!

Suggestions welcomed!

 

[AndyStobbs]

You can't have 20tpi for both unf and unc. Its either fine or coarse.

 

[julianf]

Further confusion -

Ive just dug out 5 taps, marked 1/2...

24
20
12

 

[MattF]

The 1/2" 12 is BSW. Print these sheets off and stick them to the wall for quick reference.

http://mdmetric.com/thddata.htm

 

[julianf]

You can't have 20tpi for both unf and unc. Its either fine or coarse.

Ok, thank you - i may have made a mistake - im sure i googled the numbers and got both options. Ill look again.

 

[julianf]

Further confusion -

Ive just dug out 5 taps, marked 1/2...

24
20
12

12 is bsw
24 is (according to this auction) unf - http://www.ebay.com/itm/1-2-24-HSS-Right-hand-Tap-1-2-24-TPI-/110784713431
20 is unf according to http://mdmetric.com/tech/thddat9.htm#uf

so i have two sources telling me both are UNF...

I dont know much about imperial threads, outside of BSP, so they have me somewhat confused.

 

[ford34/2]

1/2 X 24, not that popular, seen it on bench grinder spindles, MG Bumper bar bolts, some obscure Motorcycle forks, 1/2 X 20 is the more popular one.
Heres two more charts.

http://www.gewinde-normen.de/en/index.html
http://www.watchman.dsl.pipex.com/thread.html

Or get yourself a Zeus book or an Old Moore and Wright ref book

Stan

 

[Bill Edwards]

I have yet to find a thread not listed on this site:

http://mdmetric.com/thddata.htm

Should make it all quite easy for you.