g741.org

Some how I miss placed the bolts for my running boards.Are they a special bolt or can I buy them locally?
Thanks,

I believe we got them from either Fastenal or Granger. I may be able to find out what number they were later today.

They are just a carrage bolt aren't they? The parts manual should list them with their size etc.

Hi Guys,

The ORD I have is blank for the diameter and head size of this bolt, but it does say it's a Square Neck (ie, Carriage Bolt), 18-NC-2 (Course Thread), steel, with either cad or zinc plating. Looking up the part number online it says this bolt is 5/16" thread diameter, 3/4" long with a 1" head diameter. Seems it's a pretty common bolt accoring to the part number (128412) and online hits I got. It looks like this;


gm-128412 by w30bob, on Flickr

regards,
bob

They are not a "carriage" bolt, but instead a "step" bolt. A step bolt has a larger diameter/ lower profile head than a carriage bolt. When looking up bolts make sure to get measurements from the seller before buying as some suppliers don't know the difference between a step bolt and a carriage bolt, and will sell you the wrong parts.

Steve

Hi Steve,

Thanks for that info......you're right, these bolts are "step" bolts, not carriage bolts. But you have to be careful, because with everything it seems, there are different step bolts. If you look in the McMaster catalog their "step" bolts have heads that are flat, with no curvature. The bolts originally used on the M37 had curvature, like the one in the pic above. The following pics are of the correct original bolts in the running boards of my AF M37. If you search on the bolt part number you can get the full dimensions from one of the many NSN sites on the web, which is where I got the specs below.

regards,
bob


5306-00-012-8412 ( 128412, 00-012-8412 ) Characteristics Data

MRC Criteria Characteristic
THSD THREAD SERIES DESIGNATOR UNC
AHYM NOMINAL THREAD DIAMETER 0.312 INCHES
CMLP THREAD QUANTITY PER INCH 18
AAJD THREAD CLASS 2A
AAJF THREAD DIRECTION RIGHT-HAND
AASA THREAD LENGTH 0.406 INCHES MINIMUM
AASB FASTENER LENGTH 0.750 INCHES NOMINAL
MATT MATERIAL STEEL OVERALL
MDCL MATERIAL DOCUMENT AND CLASSIFICATION QQ-S-633, CANC FED SPEC SINGLE MATERIAL RESPONSE OVERALL
SFTT SURFACE TREATMENT CADMIUM OR ZINC OVERALL
AASK HEAD STYLE C31 OVAL
AASL HEAD DIAMETER 1.000 INCHES NOMINAL
AASU HEAD HEIGHT 0.156 INCHES NOMINAL
AGQB NECK LENGTH 0.156 INCHES MINIMUM AND 0.187 INCHES MAXIMUM
CWXQ NECK WIDTH 0.307 INCHES MINIMUM AND 0.324 INCHES MAXIMUM


. by w30bob, on Flickr


DSC05328 by w30bob, on Flickr

Gerry, how many do you need? I might have some take-offs here. I can look to see
Rick

Thanks for all the replies. I unfortunately need all of them for both sides. If I remember correctly I had to cut them to get them off

Gerry,

Looks like Fastenal has pretty much the exact step bolt you're looking for. They seem to have some raised letters on the head........but you can grind them off. Otherwise it matches up dimensionally with the original 128412.

http://www.fastenal.com/web/products/_/ ... categoryl1: Fasteners"|~ ~|categoryl2:"600001 Bolts"|~ ~|categoryl3:"600033 Step Bolts"|~ ~|attrdiameter:390|~ ~|attrlength:950|~

regards,
bob

Thanks Bob

w30bob, McMaster-Carr can't tell the difference between a "step" bolt and an "elevator" bolt. Don't get me wrong I buy a lot of stuff from them, but honestly I wonder who does there catalog listings.

I think the replacement bolts I bought for my steps came from fastenal, and I don't believe the short ones had markings on the heads. I bought longer ones for the bow corners and they had markings on them.

Steve

I stock the running board bolts.
Just call the shop.
John
MWM