That does not mean that 'anything will do'. There is a difference between thinking something is Ok and knowing it is Ok, and that is particularly true when looking at critical components.
Arquebus, thank you for your elequent reply, shame you feel the need to resort to insults. You need to understand what context is. I made the comparison between a M6 bolt and a M8 bolt because as pointed out by myself and others, Honda use M6 bolts for retaining the discs on some Fireblades. This is a six bolt arrangement not dissimilar to some Ducatis, however Honda with all their engineering prowess have concluded they are strong enough. Dukedesmo quite correctly points out the over engineering and change in Ducati's later designs.
Look, just change your name to Lethal Mouse and learn about metals, metal stresses and metal fatigue..........F**k knows why you keep bringing up M6 Honda bolts when the OP was asking about bolts for Ducatis........ ........you have your opinion, as incorrect as it may be.............and I and other well qualified persons have theirs...........as I said earlier, my reasoning won't get anyone killed. For FS Matt, close this bl**dy thread before I die please...............................(from laughing). AL
And I bet you use Copaslip on stainless bolts in aluminium threads when you should be using moly grease...........:wink:
the way I see it.. schwwarzzzenneggerrr in terminator 2 was found to be made of Ti and he was as hard as f*ck there must be a reason he wasnt made from stainless..
You definitely don't understand what context is do you or how to have a logical and justified argument.
Correct..............Not when the 'context' put forward is like comparing the tensile strength of a plastic drinking straw with a raw chipolata.
I referenced no expert rather pointed useful technical information based on science. There is quite a lot of information on the site, I am surprised you were able to read and digest in it in a few hours. Bolt Science is a business specialising in bolted joints, you would expect that they knew what they were talking about. In fact they conduct training and seminars to industry. I maintain the disk bolts are in tension not shear and that the disk is prevented from rotation against the hub by friction. Bill Eccles reply confirms this which you conveniently ignore “Normally joints are designed for friction grip which rely upon the clamp force created by tightening the bolt. The joint carries the shear by friction between the joint plates rather than shear going through the bolt.” How is that being shot down? Shear loads are defined as loads perpendicular to the axis, as the joint is clamped no movement between the parts can occur, a perpendicular load and therefore a shear load on the bolt does not exist. The shear mentioned by Bill Eccels, is in relation to a joint that is not clamped sufficiently to prevent movement, another point you ignored and was subsequently pointed out to you by another poster. But you seem obsessed with the word shear. Tensile strength is the maximum stress that a material can withstand while being stretched or pulled before failing or breaking. Tensile strength is not the same as shear strength. Indeed the tensile strength of both stainless and titanium is less than steel and for the same tightening torque the stretch would be greater. The question is one of magnitude. Torque and therefore tensile load (and any resultant stretch) is limited by the strength of the weakest material in this case aluminium which as I have pointed out will fail before the UTS of the bolt is reached. To put this into perspective, the UTS of an aluminium alloy is about 450MPa whereas the UTS of a 10.9 grade bolt is 1000Mpa Clearly the bolt will operate at a tensile load lower than 450MPa, this is important as the stretch is linear and bolts will operate at the lower end of their modulus. Given the tensile load, properties of the materials and safety factors involved, stretch (and any differences between materials) would be insignificant at the recommended torque which is calculated to effect the required clamping force of the joint and would also include a substantial safety factor that would provide for among others, variations and inaccuracies in torqueing procedures and possibly a sufficient clamping force with one bolt loosened. FACT. The joint is secured from movement by the clamping force exerted by the tension of the bolts which are loaded in tension. Confirmed by Bolt Science FACT. The aluminium hub is the weakest point of the joint and is the limiting factor in the amount of tension that can be applied to the bolts. FACT. For the bolts to be loaded in the shear plane, the disc would have to move in relation to the hub, this is impossible with the bolts torqued to the correct figure. The proof of the pudding is in the eating, there are thousands of motorcycles using stainless or titanium disk bolts (as pointed out by another poster) I’ve yet to hear of a failure and would endorse their use in this application. Take my advice and stick to building garden sheds
Been on Google twice, I see............ I shan't deign to provide a detailed answer other than using stainless bolts in lieu of the correct strength bolts makes a friction joint substandard before it is under any load, even it is at the correct torque, which you don't appear to be able to comprehend. You endorse what you want; people can make up their own minds; I will disagree with your endorsement. Take my advice and go to university to study basic engineering instead of Google.
Wow, jeez guys . Is there anyway we can agree to disagree on this subject. I don't know enough about the strengths of one metal over another, so I'm not going to comment, but can we please refrain from throwing insults around over something that could be perceived as being fairly trivial on the grand scheme of things. :smile:
The thing I find interesting is given that the wholesale cost (units of 20000+) of a SS bolt is no different (actually, probably cheaper) than a zinc coated bolt with a coloured treatment and an anti corrosion and release surface treatment which mainstream automotive road vehicle manufacturers use, and the pro stainless advocates argue that the properties are suitable for purpose, then for a mainstream volume manufacturer like Honda it would make perfect sense from an engineering and moreover a longevity/ lifecycle/ duty and financial sense to go for stainless... so why haven't they? - Personally for the cost, I'd rather renew my furred up bolts with new if they need them. For personal reasons I don't do stainless on structural applications and the only way I can justify titanium is bragging rites as I'd be better off getting off my fat arse and walking round the block once a week and pocket the cash. In respect of the debate for Shear or tension, I believe that it's both, depending on load. I've seen brake disk bells with thread wear on the bolting seats after some heavy abuse - but in perspective it's the sort of abuse a road rider will never see or want to see, as in disk glowing red hot and fluid boiling in the reservoir. Now those were tightened to the specific torque, and the tolerance margin and variable was reduced as NAS bolts were used throughout, which as a point of reference were torqued to anything up to +60% greater than a stock fastener. Interestingly ! have seen the same wear attributes even with conical seats - read into that what you will. I'd love to get Eccles into our place, to 'train' us. We, like the crew that Ricky X works for obviously have a huge amount to learn. But then again the sheds we build are pretty large. Should you or shouldn't you? - Its your bike, its your neck and in truth 99.9% of the riding public will never, even though they may think you do, abuse your brakes enough to ever find out, so fill your boots. The overriding thing seems to be that those who want to use stainless fasteners have already made up their mind that they will. So lets make it easy- A4 stainless is pretty much nearly on par with an 8.8 bolt, so should be absolutely fine if that's what you want and that's what probolt / Eccles / man down pub told you was ok. See... Simples.
I think it certainly does come down to application versus material and its pointless looking at a bolts strength in isolation for example there is only so much force a sportsbike can generate whilst braking before either you skid or the rear will overtake the front. it is then a matter of deciding on those ultimate forces and using a material sufficienty strong to secure the discs (for example) discs will try and create a shearing force on the bolts. the torque settings are so low on my carbon bst wheels hubs/discs securing bolts that it cannot possibly rely on clamping forces alone....but they are alloy hubs and obviously cannot tolerate a high torque before stripping the threads
I know this thread is about bolts so I apologise in advance for taking it off topic.....but now the bolt issue is sorted What's the best type of nuts to use on these bolts? And is it best to use a grease with a low coefficient of friction, say 0.11? ;-)
