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

[cculp]

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?

 

[btrueblood]

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.

 

[WKTaylor]

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

 

[cculp]

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.

 

[monkeydog]

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.

 

[Heckler]

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
Sr. Mechanical Engineer
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(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[cculp]

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

 

[mtharp]

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?

 

[monkeydog]

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

 

[mtharp]

Thanks.