Tap Drill size for 8-64 UNS 2B

[Mic6]

I can't seem to find this one. Google-Fu is lacking and so is Machinist Handbook. What you guys got for me?

 

Calculation is showing .148, but I'd like something more definite.

[The Cathedral]

 .164-64 UNS-2B INTERNAL THREAD

 Number of starts...............................  1
 Threads per inch...............................  64.0000

                                     METRIC        INCH
 Decimal lead is.................. 0.396880        0.01562

 Major dia. is.................... 4.16560        0.1640 min.

 Pitch dia. is................from 3.90906        0.1539
                                to 3.98526        0.1569

 Minor dia. is................from 3.73380        0.147
                                to 3.83540        0.151

 Pitch dia. tol. for 2B is........ 0.07620        0.00300
 The helix angle is.............................  1.85099
 Or if you prefer    1 Degree   51 Minutes   3 Seconds
 These are COMPUTER values......................
 5-UP rounding was used.........................
 Run date is 07-21-14
 

[EX-wccprogrammer]

My software says:

 

8-64 UNS 2B.pdf

[Mic6]

Thanks!

[Rocketmachinist]

Oh i misread for a second. I though you were doing a 8" 64tpi tread.

 

My brain went holy cr@p, then after it made more sense.

[Mic6]

Oh i misread for a second. I though you were doing a 8" 64tpi tread.

 

My brain went holy cr@p, then after it made more sense.

Cross thread nightmare!

[The Cathedral]

Cross thread nightmare!

 

That reminds me of an anecdote I heard a while back--someone was talking about machining ultra-precision thread collars for use on the space station, for joining the tunnels people transverse through. He said the tolerances were so tight, that you can spin the threaded parts together by hand but if you put even a single drop of oil on the thread it will seize up. These were four-foot diameter collars.

 

I never did find out if it was bull plop or true. Anyone else ever heard that story?

[Matthew Hajicek - Singularity]

Sounds like bull plop to me... I'd probably specify a tapered thread so it would lock up fine with garage shop tolerances.

[EX-wccprogrammer]

I second the bull plop theory.  

[kccadcam]

Somebody posted this along time ago,,,,,

 

Just subtract the pitch from the major for the tap drill.   Works for all threads.

3/8-16    PITCH = .0625   .375-.0625 = .3125
1/2-13    PITCH = .07692  .5-.07692 = .423

METRIC
M4X.7     PITCH=.7    4-.7 = 3.30
M3X.5     PITCH=.5    3-.5 = 2.50

 

 

 

8-64   PITCH= .015625    .164-.015625 = .148375

[JAMMAN]

Somebody posted this along time ago,,,,,

 

Just subtract the pitch from the major for the tap drill.   Works for all threads.

 

3/8-16    PITCH = .0625   .375-.0625 = .3125

1/2-13    PITCH = .07692  .5-.07692 = .423

 

METRIC

M4X.7     PITCH=.7    4-.7 = 3.30

M3X.5     PITCH=.5    3-.5 = 2.50

 

 

 

8-64   PITCH= .015625    .164-.015625 = .148375

 

Ditto, it's what I've been doing for over 20 years.

 

For the mathematically challenged pitch is 1 divided by the threads per inch on english.

[EX-wccprogrammer]

kccadcam, on 11 Aug 2014 - 1:57 PM, said:

Somebody posted this along time ago,,,,,

 

Just subtract the pitch from the major for the tap drill.   Works for all threads.

 

 

This works for standard 60 degree threads.  It does not work for non standard threads like UNJ, Buttress, or Stub ACME.