Stainless bolts etc

[cholmondly]

I would like to replace all/most of the various bolts and screws on my 600s with stainless ones, is there such a thing as an 'inventory list' of the sizes etc required, has anyone got such a list or seen one online?
Thanx in advance
Jim

[CD]

The last engine I did - took out each bolt measured it and put it back then went to the fasteners factors with a list. Some had to be cut down and deburred. Its not that time consuming and at least you know they will (should) all fit.

Be careful on brake caliper bolts they use fine threads that are not so easy to come across.

[cholmondly]

And you didnt keep the list ?

[CD]

Not much point, mine was done and most MZ riders dont care what their bikes look like.

[pilgrim]

Isn't there a strength issue with SS bolts?

When I use SS (wood) screws at work they often break off at the heads if over-tightened..................

[CD]

Stainless is tough but has a tensile strength similar to mild steel, fine for engine casings but carp for anything that needs a high tensile strength. Its also solid stuff so the threads stop dead and dont spring together, making them shake loose (much) more easily.

I have stainless socket head screws on the front discs. I reasoned that all the load is in shear with minimal tensile load so should be ok - and its screwed into aluminium. I'd argue the same for the brake caliper bolts, but thread-lock is a must.

Where's Gurninman Dave when he's needed?

[cholmondly]

I was looking for one of these 'dress up' kits that you can get, these are mainly in areas like engine covers, fairing screws, I've seen them on other bikes (usually the coloured anodised type, and mostly alloy), was just wondering if the kit could be bought in polished stainless

[CD]

They probably can (try fleabay) but would almost certainly be cheaper from a fasteners factors. I use Pugh & Sanders in Derby but there will be similar around the country.

One issue will be hex headed bolts and nuts. They use 13mm and 15mm AF sizes where the Japanese use the (neater I think) 12mm and 14mm. Socket heads are same either way.

[pilgrim]

I'd be happy with the 'dress-up kit' in stainless steel. OK

CD, I'd be less assured with SS on front discs and brake caliper bolts.

I get an un-easy feeling with phrases like:

".......... so should be ok"

and

".......but thread-lock is a must"

Am I just a little bit too worried......or is this a technical part of my life I don't understand (most likely).

[m40man]

Aug 21, 2009 18:56:42 GMT pilgrim said:

I get an un-easy feeling with phrases like:
".......... so should be ok"
and
".......but thread-lock is a must"

I'm currently working towards removing the gearbox of my K100RS. Lots of the bolts on this bike have been replaced with stainless, including the brake caliper bolts. They were not loose, nor were they stuck. They each had evidence of copper slip on them. I seriously don't think you need to worry - but if worry you must, then your regular check around the bike will show up any issues, won't it ?

[pilgrim]

Sir m40man, thanks for the assuring comment.

"Lots of the bikes bolts on this bike have been replaced with stainless, including the brake caliper bolts."

My point was not really if the threads were stuck or not; just that SS is weaker in 'shear' and therefore vulnerable if over-tightened.

Are they acceptable replacements to BMW? If yes, then ok, no doubt in my mind.

If not then who put them on, and why are they acceptable if not the norm.

[teejayexc]

Aug 21, 2009 20:51:25 GMT pilgrim said:

Sir m40man, thanks for the assuring comment.

..........why are they acceptable if not the norm.

I would suggest the fact that the caliper bolts were still there on a bike in M40mans stable would answer that one

[cam7777]

Its good practice to use threadlock on caliper bolts.

[pilgrim]

Very techincal response teejayexc! ;D

Joking aside, where do BMW stand on this bolt swap,

or Sir m40man?

Edit: sorry cam7777, that's only a problem if you want to undo them. ;D

[teejayexc]

Aug 21, 2009 21:33:23 GMT @cam7777 said:

Its good practice to use threadlock on caliper bolts.

Or in Martin's case a blob of weld

[Tigger]

Have a look here................

www.tastynuts.com/Products/Yamaha_XJ600S_DIVERSION_9204

Matt

[pilgrim]

Tigger, nice kit but can you put a torque wrench on them, or are they just pretty?

[beeblemaster]

Aug 21, 2009 21:35:46 GMT pilgrim said:

Joking aside, where do BMW stand on this bolt swap,

or Sir m40man?

I don't think BMW would give a rat's bottom about a K100RS

You worry too much ;D

[Padster]

It is very common for BMW owners to replace the engine casing bolts with stainless.

[CD]

There's two sides to the tensile strength story - the fasterner and what its fastened into.

Brake calipers (especially on the front) are aluminium alloy bolted to alloy forks. Even though stainless isnt the high tensile strength its got to be loads stronger than the aluminium parent metal.

I hardly ever use a torque wrench, prefering to "feel" the bolt tighten and spring when its tight enough. Apart from the fine and coarse pitch, some threads are tight some are slack and all feel that little bit different. A torque wrench can trick you into thinking all is ok when really the threads are being over-done.

With stainless from that point where the threads start to bite you feel them go solid with shorter turning angle. But like any other they are tight enough when they feel tight enough. A torque wrench should be ok but as said I've always been happier feeling the spanner. If you are used to giving an "extra 1/2 turn" (or whatever angle) its easier to over tighten stainless.

[bobh]

To get a bit technical for a minute, there are in fact several different grades of “stainless” steel. The most common is the austenitic 300-series, sometimes known as “18/8” from the % of chromium and nickel in the mix. These have good corrosion-resistance and weldability and are non-magnetic, and are quite malleable (hence they are good materials for forming exhaust systems, for example). But they are not particularly strong – their ultimate tensile stregth (UTS) is little higher than that of a low carbon steel. I imagine that many cheapish mass-produced fasteners would be made of this type of material. Better quality fasteners will be made of one of the tougher ferritic or martensitic grades.

Another area where stainless differs markedly is its annoying habit of picking-up, particularly against similar materials, so it’s always advisable to lubricate threads on assembly if you ever want to dismantle them again. Also, don’t use it anywhere where there might be relative motion or even slight fretting, unless you are confident that the counter-material won’t pick up (bronzes or polymers should be OK).

Most non-stainless fasteners are not made from low carbon (mild) steel, but from something rather stronger and tougher. Metric hexagon-head screws should have a two-number code on the head which indicates the minimum UTS and % proof stress (roughly equivalent to yield point, those these materials don’t necessarily “yield” in the same obvious way as low carbon steel) of the material, e.g. 8.8 = a material with a UTS of 800 MN/m2 (50 Ton/in2 in old money) and 80% proof stress. This is the common specification for hex head fasteners, while good quality capscrews should be 12.9.

By the way, to all intents and purposes, the shear strength of a material is directly proportional to its tensile strength. So whichever way the fastener is loaded a higher number will give a greater safety margin. In any case, when you actually study a bolted joint in detail you rarely find a case where the load is a simple tension of shear.

Something else to consider is the method of manufacture of the screw thread. On good quality screws and bolts the thread will be finished by rolling, which gives a smooth thread profile and, equally importantly, imparts benficial compressive stresses into the surface. It is easy to detect this on any fastener as the diameter of the plain part of the shank will be smaller than the o.d. of the thread. A fastener made by simply cutting the thread will most probably be weaker, not just because it lacks the beneficial pre-stressing but also because the cutting process may induce microscopic sharp corners that could act as a nucleus from which cracks could propagate over time.

So you can see that stainless fasteners are not necessarily an acceptable direct substitute for the manufacturer’s original ones. But the good news is that in practice only a small proportion of the fasteners on a bike are really critical in terms of their out-and-out strength, and most of those are inside the engine unit. But I would not take a chance with anything around the brake calipers or discs.

And finally, if you should decide to go for chrome plate instead of stainless, be aware that the plating process can generate high surface stresses in the substrate and as a result drastically reduce the effective strength (and ductility) of the finished item. So again be wary of using chromed fasteners in safety-critical locations.

Still with me (ZZZZZ.......)

[Deleted]

Yes I stayed with it all the way through ;D ;D ;D

Correct torquing was a big issue with high pressures in the oil and gas game. No messing about with 'feeling' for the correct torque. The stainless steel thread 'pick up' caused us no end of problems in the early 80's when some very dodgy fittings were supplied to us. We got hold of a lubricant called 'Goop' which helped, but eventually the quality of the fittings improved. One eye opener while on a one day torquing training course was the effect of various lubricants on the amount of torque required. A dry thread could need twice the amount of torque compared to a lubricated one.
Funnily enough I was discussing metallurgy in the pub with my lads g/f last night. They're both artists and she is doing a lot of welding. Her next work involves doing her own iron casting. First time I've had a conversation with a blonde about welding in a pub and she hasn't fallen asleep. ;D

[Deleted]

Yes I stayed with it all the way through ;D ;D ;D

Correct torquing was a big issue with high pressures in the oil and gas game. No messing about with 'feeling' for the correct torque. The stainless steel thread 'pick up' caused us no end of problems in the early 80's when some very dodgy fittings were supplied to us. We got hold of a lubricant called 'Goop' which helped, but eventually the quality of the fittings improved. One eye opener while on a one day torquing training course was the effect of various lubricants on the amount of torque required. A dry thread could need twice the amount of torque compared to a lubricated one.
Funnily enough I was discussing metallurgy in the pub with my lads g/f last night. They're both artists and she is doing a lot of welding. Her next work involves doing her own iron casting. First time I've had a conversation with a blonde about welding in a pub and she hasn't fallen asleep. ;D

[cholmondly]

Rrright, Titanium it is then !
;D

[bobh]

Don't get me started on titanium......

[cholmondly]

Ok, its not Titanium, I've changed my mind

Tell us about it then, read the whole article about different types of steel, very interesting and have book-marked for future ref', cheers bobh,
anyway-Titanium?

[teejayexc]

Aug 22, 2009 17:09:10 GMT @gordy said:

First time I've had a conversation with a blonde about welding in a pub and she hasn't fallen asleep. ;D

She was probably waiting for you to repeat yourself again

[CD]

When I started at the in the power industry routine maintenance scripts required plant mounting bolts to be torque tested every time. Afetr a few years and lots of stud breakages they decided to cancel the idea. Bolts were simply rapped with a small hammer and listen - a dead sound suggested it was loose.

The breakages stopped and we never had any plant shaking off its bed. Even though the whole building vibrated enough to wreck standing toller bearings.

The turbine plant however was always carefully torqued. In the old days the bolts were flogged up tight then heated and turned another x degrees. With the advent of hydraulic spanners they could be torqued, heated and then turned the requisite few degrees.

Dry lubricants were a must-have aznd the bolts were closely inspected. But on very large plant (100 to 660 megawatts) running steam at 570 degrees C and 120bar they had to be done right.

I'm not sure anything on a bike is so heavily stressed.

That said, I keep a close eye on the stainless cap screws I have on my front discs.