Small screw thread standard 1

[Tunalover]

Folks-
You know how a #4(.112)-40 UNC-2B machine screw thread callout defines the nominal size (.112), pitch (40 thds/inch), series (Unified National Coarse), tolerance class (2), and gender (B=internal)?

What about 00, 000, and 0000 threads? How would one call out, say, a 0000 internal machine screw thread in a part? I've been having a devil of a time determining what to use for the series, tolerance class, and gender. Also, what (if any) is the governing standard for these oddballs?



Tunalover

 

[drawoh]

Tunalover,

I use 4-40 threads all the time. My callout for a tapped hole is...

4-40UNC-2B

Some people prefer .112-40UNC-2B, but I am not certain this is written on the tap or the thread gauge the worker has to select. The B is internal. See the Machinery's Handbook.

The above specification completely defines the thread as per the Unified National specification.

JHG

 

[Tunalover]

drawoh-
You're preaching to the choir. How about my question?


Tunalover

 

[Pressed]

          Inches   UNC     UNF     NUT       
Gauge     Decimal  TPI     TPI     Size       Millimeter 

No.0000  0.021     160 	  - 	 - 	     0.53
No.000   0.043     120 	  -  	3/32" 	   0.86
No.00    0.047 	 90 	  - 	3/32 	   1.19
No.0 	0.060 	 - 	  80 	 5/32" 	   1.524
No.1 	0.073 	 64 	 72 	5/32" 	   1.854
No.2 	0.086 	 56 	 64 	3/16" 	   2.184
No.3 	0.099 	 48 	 56 	3/16" 	   2.515
No.4 	0.112 	 40 	 48 	1/4" 	   2.845
No.5     0.125 	 40 	 44 	1/4" 	   3.175
No.6     0.138 	 32 	 40 	5/16" 	   3.505
No.8 	0.164 	 32 	 36 	11/32" 	   4.166
No.10 	0.190 	24 	 32 	3/8" 	   4.826
No.12 	0.216 	24 	 28 	7/16" 	   5.486
1/4" 	0.250 	 20 	 28 	7/16" 	   6.349

Heres to ya Tuna!

_______________________________________
Feeling frisky.........

http://www.tailofthedragon.com

 

[drawoh]

Tunalover,

Oops! Sorry.

There is a standard in the Machinery's Handbook for Unified Minature Screw Threads, but it is metric. The intruction paragraph states that existing minature screw threads are "improvised and unsystematized".

If your standard is not official, would it be acceptable to call up the tap and inspection gauge by manufacture and part number?

JHG

 

[Kenneth]

http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=53606

http://catalog.asme.org/Codes/PrintBook/B110M_2004_Unified_Miniature.cfm?IMAGE.X=18

 

[Tunalover]

Pressed-
What's your source?
Kenneth-
Machinery's Handbook talks about UNM threads and they are different from 00, 000, and 0000 screw threads. In fact I have the ASME standard for the UNM and they don't mention those sizes.
Drawoh-
I suppose it would be OK to do it that way but it effectively sole-sources the tooling to one mfgr. For high-volume production that's not a good thing. That's the good thing about standardization!




Tunalover

 

[Kenneth]

Haven't checked these, but take a look at the callouts on the page tabbed "ANSI Unified Screw Threads" at

http://www.invent.dk/ubbthreads/upload/1053-Thread.xls

http://www.ring-plug-thread-gages.com/ti-N-vs-UN.htm

 

[Pressed]

zytrax

_______________________________________
Feeling frisky.........

http://www.tailofthedragon.com

 

[Tunalover]

Pressed-
What in the world is "zytrax"? Just wondering...


Tunalover