Stainless Spring Bolts
I have a rusted solid bolt in the sleeve of one of my rear spring bushings, happens to be in the leading fixed end. These are normally I think SAE grade 8 or JIS 12.9 bolts.
Has anyone ever thought about using stainless? I know they use them on boat trailers that get dunked all the time but not sure stainless would be sufficiently strong on a vehicle.
One justification I can see is people often use greaseable bolts where are line bored and cross drilled. This takes away some material in the bolt, might be that removing 20% of the cross section of a grade 8 bolt is closer to a full cross section 316, which is similar to grade 5 in equivalency.
Personally I don't think I'd trust stainless for that application on a vehicle the way we use them. I Have had good luck with anti-sieze applied to most all chassis hardware to prevent corrosion. That or replace with a grease-able bolts I have those on my 40. Not sure if the material or size is changed for material removal? But I see your argument.
I haven't done any math or anything, just hip shots here.
I hate the way stainless fasteners gall. I wish I never had to touch the stuff but I am forced to use it...
I'd be curious what the reduction in cross section because of the cannulation does to the shear strength and how it compares to something like 316 or 17-4 at H900. Could you source some bolts made from 440C or any 400 series? that might be worth trying..
I'd probably do 17-4 before I did 316 though. 316 kinda sucks... 17-4 should be available enough right?
The bad thing about the bolts Corbet posted is the fenestrations get full of crap and clog the whole thing up if you aren't on top of the greasing (like me) then they turn into regular bolts.
Either way I almost feel like the stainless stuff is just gonna gall when you go to take it apart unless you use something like the 400 series stuff that has so much carbon in it it will probably rust eventually. And I think something made from 316 would be too soft for a spring pin.
edit, from my Carpenter book:
316 - 82ksi UTS, Rockwell b 80
17-4PH - cond h900 198ksi UTS, Rockwell c 44
420 - hardened 1900 f oil quench, tempered 400F 250 ksi UTS, Rockwell C 55
440C - hardened 1900 f oil quench, tempered 600F 285ksi UTS, Rockwell C 60
well crap, I was thinking grade 8 stuff was magic.... maybe stainless would be fine in terms of strength....
google being my friend and all:
Grade 8 bolt (not cannulated) UTS is like 150ksi..
Get some 17-4 ones... see how they do. At least you'd have a fighting chance of taking them apart. I'd avoid 316 though.
Yeah, anti-seize is mandatory on assembly with stainless to prevent galling. Figured that out the hard way some time ago.
I have greaseable bolts now, so you can see how on top of maintenance I've been. I think I tried pushing grease in at some point but it must not have had anywhere to go because it mostly just ended up pushing out around the zerk.
I'm no metallurgist, but I think it all boils down to alloy selection and picking one that is somewhat corrosion resistant but that can be hardened. That is the problem with the 316 stuff at the hardware store, it's not heat treated plus actually doesn't perform all that good in the absence of air. I've pulled out bolts from rails of WilderNests that have a ring of rust around them where the bed rail foam had trapped gunk.
Like you say a 17-4 or maybe 4xx series stainless.
I think there is a stainless that will work, they use stainless fasteners all over in ships and breweries. Obviously cost is a major reason why you don't see them used normally. Just takes the knuckleheads once in a while pulling out bolts and recoat them to keep them from rusting in place.
Neglecting for the moment the question of size and length availability. I've only been able to find 14mm in 18-8, which is not hardened but generally rated at 100 ksi. That's probably too low.
These are 14mm bolts or 0.551 inch in diameter. Cross sectional area is 0.238 sq-in, so selecting a 17-4 like H 1150 gives YS of 150 ksi. Something like a single shear of 35,700 lbf, so using a FS of 0.2 (5 times factor of safety) is still 7,140 lbf or 14,280 lbf in double shear. Although if memory serves something like this would not be a double shear joint due to the relatively large void between the side plates and the twisting of the spring in the hanger.
why do you have sleeves in your bushings?
anyways, tons of antiseize or greaseable if you have metal sleeves. some say greasable is prone to breakage, but i've never had an issue or been with someone who did
if no sleeves and poly bushings, just regular bolts.
if rubber bushings, greaseable pins.
In the back I'm running aftermarket shackles with greaseable 18mm bolts at both the frame and spring, bushings have 30mm OD and 18mm ID, no sleeve necessary.
The factory used sleeved bushings at both ends of the springs with 14mm bolts. The frame side shackle bolt was 18mm.
Yeah I always forget you can use anti-seize in the real world :)
I think if you can find them some 17-4 bolts would be your best bet if you wanted to go stianless....
but I am having trouble finding any of the shelf.
We custom machine all our stuff unless we use 316 or 18-8, in which case we do McMaster..
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