Stainless Steel Bolts

[Brabham]

Would there be any issues with switching some of the external bolts on a car to stainless steel form normal zinc plated steel? I was told stainless bolts were a bit softer than normal bolts. I would only be switching bolts that hold panels on, nothing that requires high tensile bolts. Was going to go to 316 stainless to prevent rusty bolts snapping off.

 

Cheers

[luvemfast]

I wouldn't have thought there'd be any problem with that. Obviously not to replace any load bearing fasteners though.

Have you considered socket head cap screws? I'm a big fan of Unbrako's. You can get all sorts of finishes too 

[Retro Z]

I bought the larger version of this kit from a company called Bolted on ebay for about $90. Has a big variety of bolts that work throughout a s30.

 

http://m.ebay.com.au/itm/161187378755?nav=SEARCH&sbk=1

[C.A.R.]

Stainless into mild steel? Enjoy your electrolysis Alex...

[luvemfast]

Stainless into mild steel? Enjoy your electrolysis Alex...

Would have thought there's plenty other sacrificial metals on the car that'll corrode first

I like to use antiseize on fasteners too. (Ones that don't have loctite, that is)

 

[Brabham]

I was hoping there wouldn't be much of an electrolytic reaction Locky  The headlight housing retaining bolts are stainless and I haven't had a problem there, they came out alright. However, my mate who has a boat said that he has seen some problems with stainless bolts freezing into steel but this is obviously a marine environment. The main areas I was thinking of doing this were along the front guards, the indicator panels to nosecones and the front valance panel, all areas where I have seen the factory bolts rust and snap far too often, resulting in many tears :'(. Surely stainless in those areas would have to be better than zinc plated steel? Maybe a drop of oil on the bolt might prevent any reaction taking place?

 

Still thinking about this. Simon where do you get unbrakos from? The two areas where I was thinking of socket head cap screws were the grill and the nosecone to indicator panel as they look a bit neater than hex bolts. All other areas I would stick with hex bolts as you can get a lot more force on them(until they snap!)

 

Would titanium bolts have the same problem - there is an ebay seller offering these (primarily for bikes, although some of the bolts would suit Datsuns).

 

Obviously unless the compounds of both bolt and panel are identical, there is always going to be an extent of electrolysis, but I was hoping to prevent snapping any bolts in the future, and what about the tensile strength of stainless?

 

Cheers

[luvemfast]

We use stainless allthread on our tensile tester at work. No stretch at all. We take it up to 18kN.

Any bolt supplier will stock Unbrako's, get plated. You won't have any problems with not bring able to apply enough force to undo them either. If so, you're doing it wrong!

As said earlier, I use high temp antiseize. Helps to reduce friction to torque down, then makes it easier to undo in future. Learnt that as a teen working on coastal refineries.

[pauly_adams]

the wurth copper mix anti seize is worth its weight in gold, I highly recommend getting some

[Scottz]

A to Z of Materials - a handy website:

http://www.azom.com/article.aspx?ArticleID=2868

 

Engineering Tool Box - also a handy website:

http://www.engineeringtoolbox.com/stainless-steel-classifications-d_368.html

 

Don't use copper anti-sieze on ss.

To prevent gauling:

1. Reduce torque (not always possible)

2. Mix ss parts EG; 316 screw with 304 nut.

3. Use lubricant made for ss.

 

Save the hassle and cost. Use carbon steel with anti-sieze compound or buy cadmium plated fasteners, if you can find a supplier, as cad coating is getting phased out.

[Brabham]

Just came across this, all you ever need to know about fasteners, may be handy as a sticky. Stainless bolts will marginally increase the corrosion rate of the base metal, however zinc plated ones also corrode leaving bare metal, often resulting in seized bolts as I am sure we have all experienced. However the corrosion will only occur in the presence of an electrolyte ie water or high humidity.

 

http://www.fastenal.com/content/documents/FastenalTechnicalReferenceGuide.pdf

 

Scott what anti-seize do you use? I was looking at INOX with a machine oil base, light grease may also work.

 

Titanium also looks ok for racecars, however is getting up there in terms of the potential difference between the two metals and exy at about $5 for an M6 bolt. Has anyone here used Ti bolts on their racecars, Porsche used to do this at Le Mans.

[Scottz]

Hi Brabham,

I use the following:

Anti-Sieze Compound A (Known in America as LED-PLATE)

Spanjaard Copper Compound

Spanjaard Chrome Compound

Loctite Silver Grade Anti-Sieze, part No. 76741

 

For very high temperature and pressure I always used Led-Plate, until a few rather stubborn reactors and heat exchangers made me look for something better. That's when I changed to the Chrome Compound.

I use the Loctite 76741 for all stainless steel threads.

Copper compound is for general purpose stuff. Low temperature and pressure, not in contact with liquid / vapour.

http://www.spanjaard.co.nz/

 

[Brabham]

Thanks Scott,

 

sounds like the Loctite might be the go, will have a look at that. Assuming it also prevents electrolysis too?

 

Cheers