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Product and Tech Info

This section deals with the following issues:


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Origins

The first grade of 'Ferritic' (magnetic) Stainless was accidentally invented by Harry Brearley in Sheffield UK in 1913, although Krupp of Germany produced the first austenitic (non magnetic) grades a short while later. In metallurgical terms it is still very much a ‘new’ material. Essentially stainless works because it’s surface is covered in a passive film which provided it is not deprived of oxygen will prevent corrosion of the material substrate. If the the passive film material is scratched or impacted it repairs itself immediately as it does when exposed to mild acids and saline solutions.

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The Benefits

Stainless steel is the ultimate 'fit and forget' material. The benefits of stainless can be appreciated best when the disadvantages of the alternatives are briefly considered:

  • Original equipment (steel) - very expensive, poor quality substrate material, painted or very thinly plated, maybe the reason you are looking at this site!!
  • Anodised - low strength material with finish liable to fail very quickly if exposed to weather or salt air.
  • Titanium(Ti) - approximately the density of Alu overall strength roughly the same as stainless - at a price.

Unlike Aluminum, Stainless will not corrode or become brittle as Titanium can. The material can be finished to a degree to suit you. If a bright polished surface of a stainless fastener becomes scratched or suffers minor impact damage it can be taken off the machine and refinished there and then. In terms of price most stainless fasteners cost far less than Aluminium and a fraction of the cost of Ti. Generally speaking stainless is available in a greater range of sizes compared to Al or Ti. There is no other material suitable for motorcycle fasteners providing these benefits.


Quality assurance

All of the A2/A4 fasteners we sell conform to the relevant EN/ISO specification which is shown in each product section. All items we sell fabricated from 300 series stainless rod or hexagon bar conform to the relevant EN or ISO alloy specification.

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Product Finish

Information on finish and finishing options are covered here

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Physical Properties/Material specifications

All of the products we sell are manufactured are made from materials conforming to the relevant BS/ISO standard. The fasteners we supply will be from one of the following groups:

  • A2 Class 70-80
  • A4 Class 70-80
  • T303S31 [EN1.4305], T304S31 [1.4301], T316S31 [EN1.4401] & T431S31 [EN1.4057]

The grades explained in brief:

A2 Class 70-80 (BS970 bar & hexagon equivalents T303S31[EN1.4305], T304S31[1.4301] & T316S31[EN1.4401])

The 'A2' denotes the alloy type. A2 is commonly referred to as 18/8 (18% Chrome/8% Nickel) or T304S31[1.4301]. T303S31[EN1.4305]is simply a free machining version of T304S31. This is the most common form of stainless steel fastener fabrication, it offers excellent general corrosion resistance and is the minimum specification we supply. Class 70-80 refers to the strength range. There are two strength ranges available, Class 60 and 70-80. Unlike many of our competitors we sell only fasteners made from the higher strength range.

A4 Class 70-80 (BS970 bar & hexagon equivalents T316S31 [EN1.4401])

A4 is also referred to as 18/10/3 (2% extra Nickel added 3% molybdenum) or Type316. This is regarded by specifiers as 'marine grade' or 'enhanced corrosion resistant' stainless and is designed for constant immersion in salt water or 'stronger' acids.

T316S31 [EN1.4401]

As described under the category above. More expensive than T303S31 [EN1.4305] & T304S31 [1.4301] and, because of the added Molybdenum, machining times are typically longer which typically contributes to an item machined from T303S31 [EN1.4305] often being significantly more expensive than an equivalent fabricated from T304S31 [1.4301] or T316S31 [EN1.4401].

T431S31 [EN1.4057]

A Martensitic magnetic high carbon stainless alloy with improved shear resistance used only for socket disc bolts and for short studs where necessary. Because of its hardness T431S31 [EN1.4057] is the most expensive stainless alloy to machine and is not suitable for electro-polishing.

Important Installation note

It is ESSENTIAL that either a Copper Anti Seize compound or anaerobic threadlocking compound be applied to stainless fasteners before use and that all threads are cleared of corrosion and debris using a 'plug' or ‘bottom' tap. For customers unable to source copper anti seize, anaerobic threadlocking compound or plug taps we can supply these products see the 'Threadlocking & Anti Seize' & 'Misc Items' sections of the main product menu to the top left of this page.

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Mechanical Properties

Stainless is not generically a tensile material; no form of standard 18/8 or 18/10/3 stainless alloy possesses the tensility of grade 8.8 steel (the benchmark HT std) beware of any claims to the contrary. Many but not all steel bolts fitted to motorcycles are made from high tensile steel principally because HT steel is cheap and easily available. For the same reason ie cost the factories often use flanged bolts (fastener/washer fused together) ie to save assembly time not having to fiddle with washers and spacers etc.

The fact is that with many applications on a motorcycle - fork castings, disc rotor bolts, engine covers etc the material the steel bolts are threaded into is cast aluminium/magnesium alloy. Al/Mg castings are invariably low density and have little crystalline structure - not a feature of high tensile alloy. If you have worked on a Japanese bike you will know how easily the alloy threads 'pull' - again not really the behaviour of something 'strong' in tensile terms. Stainless might not be as tensile as 8.8 but it is certainly way stronger than those alloy threads - in fact often the shear resistance (resistance to cutting action) of stainless is greater than that of tensile steel and Ti. This issue is also referred to in our FAQ section. It should be made clear that if for whatever reason you require high tensile fixings you should use manufacturers original equipment.

Stainless steel requires less stretching to enable it to seat. On the assumption any threads have been cleared and prepared properly you should need no more than 66% of the original tensile steel torque spec when tightening.

There is an article online relating to the properties of stainless steel fasteners by Joe Dille from Philadelphia, USA. It is superbly written using language, terminology and illustrations which convey detailed information without patronising the reader.

Joe's article pretty much covers all aspects of the product but I particularly like it for its explanation of the mechanical properties, if you need clarity or have a question on the subject, this article will almost certainly cover it click here and thanks so much for allowing us to link to it Joe!