What nut and bolt material?

I’ve been building my Fire King for a year now. I notice that many of the nuts and bolts that have been in for a while are starting to look a bit tarnished as if starting to go rusty. That’s not pretty to me. So, I hit upon the idea of replacing them with stainless steel ones. Is this a silly idea or are there any alternative solutions?

Bob

Stainless certainly will resist corrosion better. But too much bling can look overdone. I see over restored classic motorcycles full of stainless fasteners quite often and they don't look authentic.

Gun blueing or chemical blacking or Parkerizing etc of mild steel fittings might look more in keeping perhaps? Kits are available. 

But its your engine so go with what you prefer. It is the kind of model that lends itself to bright work so stainless might fit right in if that is what you like.

A bit of Never-Seize on stainless threads helps minimise galling between stainless-on-stainless which otherwise can be a problem. And stainless can be a bit difficult to machine or cut threads on because it tends to work harden so be prepared for that.

Edited By Hopper on 14/01/2021 02:50:12

Your model is a fire engine and they had lots of polished brass, so unless they are under heavy load, brass nuts and bolts .

Paul.

Thanks Hopper.

Paul - that’s a good idea. I like a bit of bling. And I have some brass nuts left over from an earlier job, so I can try those.
Bob

The risk of galling between stainless-steel fasteners can be reduced further by using differing alloys - possibly easier if one part is to your manufacture under your own quality control.

It is increased by the load concentrating on one thread flank as the assembly is tightened.

I once had an M5 screw and 'Nyloc' nut of the same grade of stainless-steel, seize solid before they were fully tight, on an assembly that prevented any other solution than tightening them until the screw broke. Preferably without locally distorting what they held together: a pair of thin stainless-steel plate rings clamping together the inside flanges of two rubber mouldings forming a toroid. This was at work, so something not to my design.

I make and fit a lot of stainless fittings and never have trouble with galling because when assembled all parts are lubricated with either copaslip or hydraulic oil. How blingy they look is entirely up to you, as machined, scotchbrited or polished. Scotchbrited finish is good on vintage bikes as it looks close to nickel. Don’t forget that corrosion resistance is greater the more highly polished it is

I’ve got some shears and they were sold as “black stainless steel” is that really a thing? They are black but I don’t know if they’re stainless ...

I've got a Leatherman multi tool which is made of black stainless steel, or I should say stainless steel which has been blackened. So maybe it is a thing?

Sorry Tony but not all stainless is rustless. Check with a magnet

Edited By bernard towers on 14/01/2021 22:56:03

Law Dictionary: **LINK**

https://thelawdictionary.org/stainless-steel/

i.e. ... it stains less than ordinary steels

MichaelG.

There are several families of stainless steels with different physical properties. The magnetic properties of stainless steel are very dependent on the elements added into the alloy. A basic stainless steel has a ‘ferritic’ structure and is magnetic, formed from the addition of chromium – it can be hardened through the addition of carbon, making it ‘martensitic’. However, the most common stainless steels are ‘austenitic’ – these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it theoretically non-magnetic.

304 stainless steel contains chromium (min. 18%), and nickel (min. 8%). It is an austenite steel and is only slightly responsive to magnetic fields. It also contains 18 – 20% chromium and 8-10.50% nickel, and lesser quantities of some other elements. It is relatively easy to machine and less expensive than 316.

316 stainless steel is a molybdenum-alloyed steel. The fact that it is also negligibly responsive to magnetic fields means that it can be used in applications where a non-magnetic metal is required. It also contains a number of other elements in varying concentrations. 316 can work harden and make machining difficult. It has a much better corosion resistance and is used for marine fittings.

I recently inspected the spindles on some model globe valves which I made about 18 months ago out of 304 S/S because they were not sealing properly and found that the seats were pitted and coroded. Now have to make them again, this time out of 316 grade.

Paul

Any stainless steel will rust if the conditions are right, it is the chromium oxide on the surface that helps to reduce corrosion. Look up passivating of stainless steel, its only a google away.

Tony - just don't look too closely at silver steel.

What we call things is not always clearly related to what they look like or what they do. Consider, for example, a carbon brush from an electric motor, and the points we used to adjust to set the timing. Nothing like brushes and never pointed.

Cheers, Tim

This are of corrosion is complex. A good guide is the PRE no which is a guide to pitting and crevice corrosion resistance

As a guide

304stst is about 18

316stst is about 24 so 30% better but if at elevated temperatures would not be considered marine.

Generally if there was a problem on a swimming pool or sea water I would look for a PRE >40

This takes us to super Duplex such as SAF2507 or 254SMO which is like 316 but with more chrome and molly.

Steve

Never dreamt that my simple question would provoke such a heated discussion. But apart from Hopper’s suggestion about a bit of brass bling not many other posts address my initial issue 🙁