Stainless Steel Automotive Applications

[wildcatmahone]

Hi all new to the forum here. I'm a cnc machinist here in Austin Texas looking for some mechanical advice regarding the use of stainless steel in high strength automotive applications.
Basically, I'm planning on starting up my own little business replicating obsolete and out of production components made of stainless steel for antique motorcycles. I would appreciate some guidance and advise as to what stainless alloy to use for high strength applications, such as wheel axles, engine mounting bolts, suspension bolts and components etc. I know some similar individuals are using alloy 303 for these same applications and another is selling high strength stainless bolts out of 17-4PH for auto applications. 303 doesn't seem to be suitable is it? I am also looking into 15-5PH as well for suitable material to use. Basically looking for a middle ground stainless alloy material between strength and also that would also be affordable to my customers.

Thx in advance

 

[Q_Goest]

Hi wildcatmahone,
Welcome to the board. In my experience, selecting the right material for a job is not as easy as looking for high strength or easy machinability. There are many factors you may want to consider.
- Strength (including strength at actual operating temperature)
- Fatigue strength (different than but often related to strength)
- Machinability
- Weldability
- Corrosion resistance
- Resistance to wear
- Resistance to galling
- Hardenability
- Cost

303 is the easy to machine grade of the austenitic (300 series) stainless steels. It has roughly the same strength as the others such as 304 or 316, but fatigue strength may be compromised slightly. It is also not as easy to weld. Like other 300 series SS it will gall easily and can’t be hardened. If corrosion resistance is an issue, 316 is a better performing material but more expensive and harder to machine.

What parts are you interested in making out of the material? Do they see cyclic loads? Are they highly stressed? Or are you just making relatively ornamental parts like handlebars or brake levers? Even some parts that take considerable load are not under significant stress, so an understanding of what stress the material is subjected to is important.

 

[wildcatmahone]

Hi thanks for the reply, as far what I'm planning to make from the stainless alloy I'm looking for, some components will be mainly decorative. While the other components, such as, wheel components (axles,wheel spacers), steering column (triple trees) components, engine mounting and support bolts and brackets. Basically most OEM parts from antique motorcycles that are no longer produced nor copyrighted, I know there is a market for stuff so starting to get my set-up going. Any recommendations as to what ss alloy would fit these applications?

 

[Q_Goest]

I think as you say, most of those parts are decorative so they aren't highly stressed. Anything made of mild steel could be made from 303 or 304 which has roughly the same strength. Cost may be more or less than 17-4 PH depending on your source.

Axles, bolts and the center post on a triple tree (where the bearings go) might be more highly stressed. If bearings have to run against the part (instead of pressing a race on) then it would need to be hardenable such as 17-4 PH.

There's a nice overview of some common stainless steels on McMaster Carr http://www.mcmaster.com/#stainless-steel/=6rtocq".

I built a bike about 30 years ago but most of the ornamental stuff was chrome plated. I was always kicking myself because it was so hard to keep clean. I saw a bike featured in Easyriders once made of all stainless, frame and everything. Had a brushed appearance instead of polished. Don't know if that was any easier to clean but anything might help. I think the perfect material would be have to be self cleaning!