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Old 09-27-2005, 01:33 PM
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Fasteners ... 18.8 Stainless or Grade 8 ?

Hi,

I've ordered and received a whole bunch of 18.8 stainless-steel bolds, nuts, and washers in a few of the popular sizes.

Most of the chassis hardware that I have removed has a Grade 8 headmark on it, and now I'm having second thoughts on using the stainless to replace them.

I've been told that the 18.8 specification is a pretty good grade of steel, but then again ... I've had someone tell me that stainless galls up the threads really easy when you tighten it ... indicating to me that it's too soft?

I'd really like to use the stainless, for both it's anti-corrosive and appearance properties. Painted bolts are OK I guess ... apperance wise ... but we all know that wrenches/sockets don't fit right and that it chips off when you try to assemble it, right?

The other possibility might be to use all new cadmium-plated grade 8. Can anyone attest to the anti-rust properties of the cad-plated fasteners?

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Old 09-27-2005, 02:47 PM
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Quote:
Originally Posted by 66GMC
Hi,

I've ordered and received a whole bunch of 18.8 stainless-steel bolds, nuts, and washers in a few of the popular sizes.

Most of the chassis hardware that I have removed has a Grade 8 headmark on it, and now I'm having second thoughts on using the stainless to replace them.

I've been told that the 18.8 specification is a pretty good grade of steel, but then again ... I've had someone tell me that stainless galls up the threads really easy when you tighten it ... indicating to me that it's too soft?

I'd really like to use the stainless, for both it's anti-corrosive and appearance properties. Painted bolts are OK I guess ... apperance wise ... but we all know that wrenches/sockets don't fit right and that it chips off when you try to assemble it, right?

The other possibility might be to use all new cadmium-plated grade 8. Can anyone attest to the anti-rust properties of the cad-plated fasteners?
Stainless is good for things like exzaust clamps but, By my chart I have, a 7/16"-20 stainless has a max torque spec of 28 ft/ lbs and a grade 8 will take 95 ft/lbs. Go with painted bolts, use a high heat paint, then heat it up gently with a torch, it turns hard and will not chip. The cadium and zinc plated bolts are designed so the plating will corrode off b4 the metal rusts, extending the time b4 the bolt forms rust. Stainless will also lock into regular steel threads as time goes by.
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Old 09-27-2005, 04:36 PM
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18-8, aka 304, nominally has 18% chrome and 8% nickel. While it's ultimate tensile stress is fairly high, it's yield strength is fairly low (70K and 30K if memory serves). It will gall unless you you anti-sieze on the threads. Even then it is suspect.

I would limit it's use to cosmetic, low stress environments. Stick with cad plated grade 8 hardware for you suspension and chassis if you have a driver. When the cad plating starts to deteriorate, replace them.
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Old 09-27-2005, 04:40 PM
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I just did a suspention lift on my Toyota pick up, and I have agree with everyone on this. Grade 8 all the way. There is just less risk involved, espeially considering that your entire vehicle is riding on these bolts, at least it was for me.
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