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Threads per MIL-S-8879 (J-series)
3

Threads per MIL-S-8879 (J-series)

Threads per MIL-S-8879 (J-series)

(OP)
I am trying to find standard (MS?) bolts that use "J" series threads.

I can't seem to find any stock bolts that use this thread.  I did a Google search for "threads per MIL-S-8879" and all that came up was an earlier thread on this forum (that unfortunately didn't answer my question).

Any ideas?

RE: Threads per MIL-S-8879 (J-series)

You'll need to get a listing of specifications for fasteners from the SAE, a sample:

AS9696C Bolt, Machine - Double Hexagon Extended Washer Head, PD Shank, Corrosion and Heat Resistant Steel, UNS N07001, 165 ksi min,
.1900-32 UNJF-3A
AS9576B Bolt, Machine - Double Hexagon Extended Washer Head, Drilled, Pd Shank, Silver Plated, Corrosion and Heat
Resistant Steel, Uns S66286, 130 Ksi Min, .3125-24 Unjf-3a

etc. etc.

There were also a NAS series of fasteners using UNJ threads, NAS1351 comes to mind.  Hmm, now that I check (type NAS into IHS site), those were UNR series threads, not J.

RE: Threads per MIL-S-8879 (J-series)

2
CCULP..

SAE AS8879 thread spec replaced MIL-S-8879 and MIL-S-7742  in most instances... with a few specific exceptions. FAA AC21-41A "REPLACING MIL-S-8879C WITH SAE AS8879" discusses the subject in-depth.

Virtually all fine-thread  AN, MS [NASMxxxxx spec] and NAS Bolts/nuts use these (3) thread specs. NOTE: for large diameter parts this spec probably wont apply.

For a relatively complete listing of common aeropace fasteners [bolts, screws, nuts, etc], with good illustrations, go to the following SPS website and download the "Aerospace Fasteners" file [7+Mb]. NOTE: in the back of the document are references to "very old-technology" and obsolete part specs.

http://www.spstech.com/aero/prod_lit/index.html

Regards, Wil Taylor

RE: Threads per MIL-S-8879 (J-series)

(OP)
Thanks for the info! I was reading the AS8879 RevC, as well as an article on the changes from MIL to AS while you were writing the response, Wil.  I grabbed that fastener guide from SPS, that should come in handy.

I am probably looking at 1/4" hex bolts/nuts; although if I can get down to .190 and maintain the fatigue strength (and everything else), I will go with the smaller size.

I appreciate the pointers from both of you, and I can now continue my calculation scribblings.

RE: Threads per MIL-S-8879 (J-series)

Be careful, not all fine/course threads are the same.
There are still threads made to MIL-S-7742 (which are cut threads) as well as the MIL-S-8879 (which are rolled threads).  
I cannot quite remember off the top of my head, but in a tolerance stack-up a male/female combination will not fit.  I don't remember if it is 8879male/7742female or the other way around.

RE: Threads per MIL-S-8879 (J-series)

Quote:

I am trying to find standard (MS?) bolts that use "J" series threads.

MS9556 Double-Hex .190-32 UNJF-3A
MS9555 Double-Hex .164-36 UNJF-3A
MS9111 Double-Hex .250-28 UNJF-3A

Heckler
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RE: Threads per MIL-S-8879 (J-series)

(OP)
Thanks for the tips.  I guess I should close out this thread saying I've found what I'm looking for.  

It looks like I need either:
MS9783 or MS9784

RE: Threads per MIL-S-8879 (J-series)

I am designing a threaded part with .2500-28 UNJF-3A threads.  The threads need to be rolled and I'm not sure which spec I can/should use to define the rolling process.  I was going to use AS8879 to define the threads.  Any thoughts?

RE: Threads per MIL-S-8879 (J-series)

Rolled threads are the "controlled root radius" threads,
AS8879,

RE: Threads per MIL-S-8879 (J-series)

Thanks.

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