Posted by Alan Bowes on February 26, 1998 at 16:53:40:
In Reply to: Re: Military nuts and bolts posted by Steve Ostroski on February 26, 1998 at 15:57:37:
Zinc iridite plating is basically just zinc plating with a yellow chromate conversion coating, which enhances both corrosion protection and paint adhesion. This is typical of what you'll find on many fasteners of recent manufacture, especially the higher-grade fasteners. Chromate coatings can vary in color, depending on the process parameters. For example, one variant is an olive-drab finish, which is slightly better than the yellow chromate in terms of corrosion protection, but it may cost a bit more, since the OD chromate finish is less popular and a plating shop might have to make a special run.
If you do bead blast the old fasteners, use a fine glass bead media and moderate air pressure to minimize any damage to the surface of the fastener.
You can probably get some used script bolts off some parts vehicles in salvage yards. Some places may have a pile of them lying about, in which case you might be able to buy them by the pound. Maybe if you order something more expensive, they'll just throw in a handful or two.
If there is any sign of stretching from over-torquing, don't reuse the bolts. As Bill mentioned, the softer bolts will tend to twist or stretch more noticeably before they break. I pulled off some bolts from a hub flange recently, and one of them was stretched nearly 1/8 inch into an hourglass shape. That is unlikely with harder bolts. Fortunately, in this case, it probably saved the forging from damage from overtorquing. However, I'd still opt in favor of bolts that are as strong or stronger than the originals, being careful not to torque them beyond the technical manuals specs, especially if they bolt into forgings or castings.