Stainless fasteners - advice required

[Jamieg285]

I know there some engineers on here that can probably answer my question.

I added some crash bars to my motorbike and had to buy some longer bolts to make them fit.  I went for stainless cap heads, but found them very soft - 1 rounded out and will need to be drilled out when the time comes.

I want to know what grade of stainless would be more suitable, something that's more comparable to steel than butter.

[F Body]

Sounds like Chinese Stainless ?

You'll be wanting something with a higher tensile strenght, not my area of expertise, but would it be 8.8

[Andy]

Doesn't sound very much like stainless steel, or if it is, its a chiwanese version.

I have been this week, just making some M16 bolts for a customer from 316 (1.4404 - new grade spec), its pretty tough stuff. Its got a higher nickle content iirc which makes it a lot tougher on our tools. This also makes it far better when it comes to polishing up and surface finishes.

http://www.themontrosegroup.com/Products/MONTROSE_SOCKET_CAPSCREWS

[VIPER]

get yourself down to allfast in luton ...Great guys and very helpfull.Just got some Black SS allen bolts this morning...

[Roadkill]

Was you using A2 or A4 stainless fixings ?

Stainless is simply not as strong as an alloy bolt.

An 8.8 grade alloy fixing is comparable (but still stronger) than even a A4 stainless fixing, so if you had A2 you were way-off 8.8 alloy steel.

If you want tensile strength in stainless it HAS to be A4 to compare to 8.8, alloy.

EDIT -

Here you go - this sums it up quite nicely :

http://www.volksbolts.com/faq/basics.htm

:mrgreen:

[Jamieg285]

I've looked up the ebay ad. They were from Falcon Workshop supplies, supposedly A2 304.

Looking at the torque guides on that link from RK, it looks like it may just be me putting too much effort into them.

I have a couple of spares left over, so maybe I'll try one of them with a torque wrench and see how they behave.  I just hope drilling it out isn't too difficult.

[Roadkill]

Quoting: Jamieg285

I just hope drilling it out isn't too difficult

Unfortunately Stainless is quite hard due to the Chromium content so you'll find them harder to drill than normal steel.

Make sure the drill is sharp and "peck" with the drill (to create small swarf chips) as opposed to just leaning on the drill - this'll likely just destroy the drill bit.   Use a lubricant when drilling stainless, too - spit works on steel but you may need something more on stainless.

[art b]

Quoting: Jamieg285

I added some crash bars to my motorbike

[EDGE]

A2 is akin to play dough

[F Body]

Quoting: Jamieg285

Looking at the torque guides on that link from RK, it looks like it may just be me putting too much effort into them.

Just thinking about the application, it may well be that they are designed to be both not that tight or strong

If they are bolted tightly to the motorcycle frame, you could bend the frame with a minor spill

Didn't think that they still made crash bars other than for aventure/off road bikes nowadays ?

I have the crash bungs/mushrooms on mine

Mind you there is a much simpler and cheaper solution

Make sure you don't fall off in the first place  

[Jamieg285]

Quoting: F Body

Just thinking about the application, it may well be that they are designed to be both not that tight or strong  

If they are bolted tightly to the motorcycle frame, you could bend the frame with a minor spill

The bars are mounted in 3 places on each side. These particular ones are the mounting points for the footpegs.  Don't know if that has any bearing on the what's needed or not.

Quoting: F Body

Didn't think that they still made crash bars other than for aventure/off road bikes nowadays ?

Maybe, but then the bike is 13 years old!