I am no metallurgist but I have worked in precision
engineering and know a little about industry practice. Some of my Yamaha's
fasteners are a bit rusty and they need replaced. I once had a good friend who
swore by D Middleton, but rather than stick to one place I posted a question on
the Thumper Forum asking for recommendations. This and doing a search on Google
unearthed an amazing wealth of information and this is where this article comes
from.

Stainless Steel

The alloy known as 'stainless steel' is a British invention
which has been around since the 1920s. It consists of steel mixed with varying
quantities of chromium, nickel and molybdenum which give differing properties
and hence the various grades of strength and corrosion resistance. Its undenied
strength is of superb corrosion resistance and long term value.

Motorcyclists should be interested in A2 (aka 304, 302hq
etc) or A4 (316). A1 (303) is for less demanding applications. Fasteners are
usually marked with things such as 'A2, 70'. This makes it A2 stainless that
meets class 70 strength according to ISO 3506. Anything below this, class 50,
is not recommended in critical areas. Fasteners with no identification marks or
not bearing at least the 70 mark are most likely to be class 50. Probably okay
to hold the licence plate holder on with. Some suppliers polish off these marks
for looks, in which case you will have to trust their reputations on the
quality.

I requested or downloaded catalogues from 5 suppliers:

Mr Fast'ner
(download) www.mr-fastner.com 02476 688000

Their range includes anodised, chrome plate and gold plate
fasteners as well. A good selection with the cheapest prices. Metric and
imperial stocked. Good value assortment buckets. Low on technical information.
Also at M+P. The website was quoting slightly lower prices than M+P for a
while, they have probably equalised.

Molnar (download)
www.manx.co.uk 01772 700700

Purely stainless and definitely one of the places to go if
you have a British bike, and if it is a Norton even more so. A very
comprehensive list. They do also have a
good metric selection too. Amal parts, bezels, handlebars also. *Reasonable
prices, but no mention of finish quality or much technical background.* Does
monograde 40 oil and Castrol R too.

D Middleton 01924 470807

The man for some people. Top faces finely machined from M6 upwards. Very comprehensive imperial
and metric selection. Most pricey of the bunch, but presumably also the
shiniest. Good range of starter packs even including things like split pins.
Good advice and technical information. Screw thread gauge for £3.80 - only
really needed if you are dealing in imperial threads.

Superior Stainless
01375 644744

Big British bike
specialist. Very comprehensive list including a good range of metric fasteners.
Also do classic tyres and oil as well as other sundries aimed at old British
bikes. Flat head bolts are faced and chamfered so their prices reflect some
added value and in some areas they are quite reasonable.

Inox
www.inoxgrp.co.uk 02380 586805

A lot of good background and technical information. They
only do metric fasteners claiming speciality in Japanese machines. They sell
crankcase kits for popular models as well as good value 200 and 400 piece
assortments. Braided hose and brake bolts also available here. Prices are
lowest except for Mr Fast'ner. That is unless you specify either their
Electropolishing or Bright polishing services. In which case we come up to a
similar price level to Mr Middleton whose fasteners are polished too. You get
what you pay for.

I ended up ordering from Inox but I must stress that all the
companies above were recommended by others who had used them with success. If I
was restoring an Imola 750 then I think it would be Middleton or Molnar. But
for the day to day and the SRX mill finish is fine from Inox.

As it turned out
Inox made a bit of a cock up with my order but completely salvaged their
reputation by giving me some free parts to make up. I had pointed the
discrepancy out to them more with other customers in mind so it was very
refreshing attitude to come across. I will go back. The order arrived quickly
enough, I phoned it through mid afternoon and it was on my doorstep at 10am the
following day.

I bought one of their 400 piece Allen Assortments for
£30.95. I counted at least £41 worth if bought separately so it's a good deal.
Anyone who wants to know exactly what is in the kit I'll email you the Excel
file I saved. It's all marked A2 70 as well so I know its good stuff.

Here is a table comparing some of the companies attributes

* HT steel as recommended by Mr Fastener

Here are some other things you should know about Stainless Steel

• Always lubricate the threads with good quality copper
  grease. This serves two purposes. It prevents galling or seizing especially in
  stainless to stainless joints at high torque settings. It also prevents the sacrificial
  corrosion that can take place between
  alloy crankcasings and stainless fixing screws which could lead to the
  seizing of the screw.
• Graphite is much more noble than Stainless meaning it will
  make Stainless corrode so keep it away.
• There is a passive layer that forms on the surface of
  stainless which is measured in angstroms - very thin. Funnily enough if this
  layer is discouraged by excluding oxygen then stainless will rust and pit like
  ordinary steel. So keep it clean.
• Hydrochloric acid doesn't do stainless any favours but the
  cleaners it used to be found in are now 'greener'.

More technical information and links at www.assda.asn.au