Bolt designations for M38

Mateo · Member Joined: Jan 12, 2009 Posts: 9

I am trying to buy bolts for mounting the tub of my M38 to the chassis. Page 292 of ORD 9 SNL G-470 Lists the following bolt for example. BOLT, MACHINE, hex-hd, S. cd or zn-pltd, 3/8-24NF-3 x 1. All is understood in this designation except the -3 x 1 following the NF. Can someone tell me what the -3 x 1 stands for? I've spoken with multiple nut n bolt suppliers and no one seems to know. One guy suggested it was a 3" bolt with 1" of thread, but as an example another bolt is listed with a -3 x 7/8, which doesn't seem a standard. Others are clueless. Any wisdom is appreciated.

idiocrates · Posted: Wed Apr 08, 2009 8:19 pm Post subject:

Just from what I've seen from removing old bolts......the first number is the diameter of the bolt.....the second is the number of threads oer inch.....the third number is anybody's guess.....and the fourth is the length. I've tried to correlate that 3rd number too with no such luck. Might be the grade rating of the bolt but from what I've seen so far what's not grade 8 is grade 5.....and everything else bears no grade markings at all. I'm sure somebody on here knows....fur shure.

Jim

SteveJ · Posted: Wed Apr 08, 2009 9:08 pm Post subject:

If I recall the 3 may refer to the class of fit 3 being medium as per the American National Standard. the x1 would indicate the length in inches. The fit classes were 1 - 4 loose, free, medium, close. Cool

_________________
SteveJ
1986 CDN Armstron MT500 dispatch Motorcycle
1986 arrow 1.75 t cargo trailer
1991 Reynolds Boughton RB44 GS TUH
1952 M38 CDN W/W (Sold)
1953 M100 CDN Trailer
1951 PE95K Genset (Sold)

cody10414 · Posted: Wed Apr 08, 2009 10:17 pm Post subject:

That was a bear to look up because of the updated standards but SteveJ is definitely on the right track.

Class 1 changes to 1A (Loose) for external threads or 1B for internal threads
Class 2 changes to 2A (Medium) for external threads or 2B for internal threads
Class 3 changes to 3A (Close) for external threads or 3B for internal threads

Here are some links that help out:

Note the reference to "military" in this one:
http://www.sizes.com/tools/bolts_inch_threadFit.htm

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

Hope this helps,
Cody

wesk · Posted: Wed Apr 08, 2009 11:08 pm Post subject:

Cody,
Nice work! Wink

_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

Mateo · Member Joined: Jan 12, 2009 Posts: 9

Thank you all. Very helpful. Apparently the body to frame bolts require a higher stress tolerence than others! One last question, though. What is the difference between internal and external threads? Very Happy

idiocrates · Posted: Thu Apr 09, 2009 7:38 am Post subject:

Well that's cool.......so the thrid number defined how tight the hardware went together. Now this begs me to ask.......whenever we're rebuilding something on one of these jeeps.....should those 50+ year old nuts and bolts be replaced (because there's no way they are a 3 anymore) with new stuff......and if so.....how do you get a 3A (or B) fit these days when you just go to the store and get an appropriate nut and bolt and slap em together? Great.....just what I needed....something else to worry about!

So, do I think as confused as you look I am?

Jim

wesk · Posted: Thu Apr 09, 2009 9:26 am Post subject:

idiocrates · Posted: Thu Apr 09, 2009 10:55 am Post subject:

.....and as I understand it......arbitrarily using a grade 8 in place of a grade 5 or a grade 5 in place of a lower grade simply because it seems like a "better" connection is not necessarily true. One of the things that the harness gauge of the original hardware is based on is the anticipated failure of the hardware in lieu of material failure of the components that they attach. Like I guess it would be better to sheer a spring shackle bolt and have to replace it then it would be to rip the shackle mount from the frame or worse yet bend the frame beyond servicibility. Also.....it seems unless you go ballistic and buy the really, really expensive stuff....the harder the grade of the hardware the more susceptible it is to corrosion and oxydization. So replacement of a 5 bolt with an 8 could mean you're looking at having to change it out again sooner then you would had you used a replacement 5.

Cool stuff hardware.......or maybe I just need to get a real life.

Jim

SteveJ · Posted: Fri Apr 10, 2009 12:11 am Post subject:

There are a couple of old publications in the form of small handbooks that are great for this kind of stuff. All the basics for fasteners, tools and hardware.
I am sure Wes has them tucked away somewhere as I do and have since I was an apprentice.

Standard Aircraft Handbook = Leavell & Bungay

Standard Aircraft Workers Manual - Fletcher Aircraft:)
_________________
SteveJ
1986 CDN Armstron MT500 dispatch Motorcycle
1986 arrow 1.75 t cargo trailer
1991 Reynolds Boughton RB44 GS TUH
1952 M38 CDN W/W (Sold)
1953 M100 CDN Trailer
1951 PE95K Genset (Sold)


Create an account	Home · · Forums · · Articles · · Downloads · · Photo Gallery


PHP-Nuke Copyright © 2005 by Francisco Burzi. This is free software, and you may redistribute it under the GPL. PHP-Nuke comes with absolutely no warranty, for details, see the license.