[Closed] Buying specialist bolts over the counter

Google fasteners.

You are in Cardiff aren't you?

[url= http://www.f-e-s.co.uk/about.php ]Clicky [/url]

Most fastener places will sell to you in lower numbers but there is often a minimum charge of a fiver or something.

Specialist High shear strength ? For a rack.

Really ?

Oh, on that other page it does say retail yes, bamboo, didn't see that.

Specialist High shear strength ? For a rack.

They have to stick out past some kind of cowl on the fancy dropouts. Means they need to be long, means they need to be much stronger than usual.

Have often found eBay useful for buying small quantities of fasteners - usually more than what I need but still, maybe 20 or 30 instead of 500.

I use these people, always quick and have a good range:
[url= http://www.westfieldfasteners.co.uk/ ]Westfield Fasteners[/url]

Any engineering suppliers locally?

These are close to me, give them a call?

http://www.riponeng.com/adhesives-fixings-hardware/bolts-nuts

Whoever you contact, they're gonna love you ringing up to talk about purchasing half a dozen high shear strength bolts. 😀

My thoughts too, darcy!

what size and grade are you looking for?

Like rack mount bolts but about 10-15mm longer.

[url= http://www.tritoncycles.co.uk/accessories-c11/pannier-racks-c136/salsa-lower-mount-kit-for-alternator-rack-p2555/s6580?utm_source=google&utm_medium=cpc&utm_term=salsa-lower-mount-kit-for-alternator-rack-salrk8031&utm_campaign=product%2Blisting%2Bads&gclid=CjwKEAjwka67BRCk6a7_h_7Pui8SJABcMkWR6Q7qlZAZYpUePllfMFyGh5gN5YZfSpME4QXpoiv8gBoCWJXw_wcB ]Like these, probably a pair of some of the middle ones.[/url]

are they m5 or m6?

M4 I think.

if you let me know what length you need i'll have a look tomorrow

Ta, but I wanted to get something sorted this weekend...

They have to stick out past some kind of cowl on the fancy dropouts. Means they need to be long, means they need to be much stronger than usual.

Making them longer won't change the shear stress. It'll crank up the bending (tensile) stress though.

In my experience of a similar rack setup, its fatigue that'll kill them - high bending load acting on a threaded fastener is a terrible, terrible design. I actually keep a rack bolt that failed in this way for demonstration purposes, it's textbook!

I have done similar with racks to clear disk calipers.

Not once ever have I sheared a bolt that holds my pannier on.

I do however only use good quality steel bolts. No fancy light Ali or even stainless.

What do you do to your racks to fatigue them Mr curtain.

Maybe that explains why Salsa quote such a light weight for their rack and then claim it's the only one you can use. Maybe it's the fittings..?

The spacers should limit bending though? Looks like on my frame protrudance will only be about 10mm or so if that.

Salsa say this about the fasteners they sell with their own rack: (M6 size in fact)

All the Alternator rack models mount to Salsa frames with Alternator dropouts via the upper pivot bolt of the dropout/frame plate. This fastener is a partially threaded M6x10 SHCS with a 12.9 grade. Compared to the smaller, fully threaded M5x0.8 fasteners traditionally used to attach racks, the upper pivot bolt of the Alternator dropout has greatly increased shear capacity. We’ve fully tested this connection beyond the rated load and cycled beyond normal testing limits (all the way to failure) and never had this fastener be the failure point!

What do you do to your racks to fatigue them Mr curtain.

Dunno, cycle them?

Badoom tish, etc.

This fastener is a partially threaded [b]M6[/b]x10 SHCS with a 12.9 grade. Compared to the smaller, fully threaded [b]M5[/b]x0.8 fasteners...

They're mainly saying that the partially threaded 6mm bolt is stronger than the fully threaded 5mm bolt (no sh!t, Sherlock!)

12.9 is very common for SHCS (aka allen bolts). You may not be able to get the correct partially threaded length, but any decent M6 x 10 allen bolt will see you through the weekend.

FYI the grade will be marked on the head of decent quality fasteners:

[img] [/img]

(A lower grade - 8.8, may actually offer more protection against fatigue, but that's a bit of a can of worms.)

Thanks Tilly. I went back to that website posted above and noticed that all their listed socket head bolts are 12.9. only available in packs of 100 however almost 1/3 the price of the kit from Salsa 🙂

Just need to find spacers by should be able to bodge that.

Wiki disagrees but in UK I was always taught (apprenticeship, college and uni) fully threaded is a screw and partially threaded is a bolt.

One major cause of bolt fatigue failure is faces that aren't flat / square. So thick paint, hacked off bits of spacer tube or heaps of washers can all cause problems. Poor quality plated 12.9 bolts can also fail due to hydrogen embrittlment.

So quality black 12.9 socket head cap screws / bolts with a machined spacer will be the most reliable option (which is pretty much what Salsa is selling in that link ^). Spacers - a few minutes work for a friendly guy with a lathe. Pretty much any local engineering supplies place will sell you bolts in small quantity over the counter.

Not critical for this application but on fatigue rigs at work I've generally found Holo-Krome to be the best brand.

...fully threaded is a screw and partially threaded is a bolt.

Yeah, me too, but I lapsed into the vernacular 😉

So two of us think Wiki is wrong 🙂

Making them longer won't change the shear stress. It'll crank up the bending (tensile) stress though.

This. Even just adding a couple of washers can cause a large increase in bending moment on the fastener.

tbh having loads carried perpendicular to the fastener by the fastener is generally bad and when you are talking about rack loads on bumpy rides through little M4/5 bolts I am thinking "poor little bolt". You would often use the bolt to provide enough friction in the interface to have that carry most of the load - as you do with car wheels where the bolts/studs dont take the torque loads but the wheel to hub interface.

fully threaded is a screw and partially threaded is a bolt.
Yeah, me too, but I lapsed into the vernacular

It matters not whether it's fully threaded, it's about whether or not it's used with a nut. Used with a nut, it's a bolt. An identical fastener used with a tapped body (eg a dropout) is a screw.

I don't think anyone actually bothers making the distinction though.

It matters not whether it's fully threaded, it's about whether or not it's used with a nut. Used with a nut, it's a bolt. An identical fastener used with a tapped body (eg a dropout) is a screw.

Mmmm. . . Not bad, but I go with:

Fully threaded, with an equal thread is a [b]machine[/b] screw. That distinguishes it from a wood screw or similar. Partial thread is a bolt.

IMHO of course.

Back to OP. Just get down to Screwfix. They'll have something that will last a weekend and then get the proper ones.

Marko

LBS had some stainless bolts - it says A2-70 on the top which has a tensile strength of 700 N/mm2 as opposed to the 1220 N/mm2 for 12.9. So just over half of what Salsa supply.

Any of you engineers want to work out how much load this bolt can take when it sticks 13mm out from where it's bolted?