Trojan Boat Forum

A while back we had a discussion aoubt using stainless bolts on my exhaust manifolds being a bad idea due to galling with Stainless.

I took heed and used grade 8 bolts with anti-sieze and am glad I did, not because of my exhaust but because:

I was installing a hydraulic jack plate in an outboard I have and used 1/2 inch stainless bolts, course thread with stainless aircraft type nuts. Well all was fine for the first two bolts. The third when using impact wrench siezed half way on, I mean Siezed, could not turn the nut either way. Had to break the bolt, whew. The fourth one I attempted to tighten using a ratche wrench, about three turns and a squeak and it was totally siezed same as first, had to break the bolt.

Word of caution, it is a good idea to put a drop of lube oil in a stainless bolt as a precautionary measure. Me I am going to be very sparing where I use them.

Word to the wise and thanks to Prowlerfish and the others that warned me earlier, I would not have bet a bolt that big would have siezed but two of them did.

7 Rules for Stainless Steel Bolts/Nuts (if both bolt and hole or nit are stainless) to prevent galling:

1) Chase the bolt with a die to clean it up
2) Chase the threaded hole/nut with a die to clean it up
3) Use dissimilar types of stainless if possible (18-8, 304, 304L, 316 or 316L for example) for the bolt versus the nut or threaded hole
4) Use plenty of lubrication during assembly
5) Tighten slowly to avoid generating heat through friction - stop and wait to cool if it is getting warm at all
6) Use plenty of assembly lube
7) Do NOT over-tighten

Al of out products are stainless and galling is the only real problem this poses for us. If you follow these rules, stainless works well, although I would not use it for manifold bolts.

Been there! When unbolting, if you run into more resistance than you should, stop and assess, and take measures at the very beginning if you need to take the bolt out in one piece so it doesn't break in something. Split the nut, or add heat or freezing spray, lubrication etc, then retry. Ya you will deffinitely sheer the bolt before bad threads give up that nut.