Bolt head sizes

[double_entendre]

So I'm looking for a couple of bolts that I took off the bike and can't find. Whoopsie. Just standard 4mm bolts, but of course the Yamaha parts catalog only has a part number, not something useful (i.e., thread pitch and length).

I could go to my local Home Depot and get bolts that would fit, I'm sure, but the heads on the bolts there would be "off-size." The factory bolt probably has a 10mm head, but if I buy 'em at Home Depot or the like, it's going to have a 9mm head. Or 11mm. Something inconvenient and different from every factory bolt.

WHY?????

Why make the head size an odd size? I'm going to guess that the answer is that when you make 10 million bolts and save one-ten thousandth of a cent on each one by using a smidge less metal it adds up, but does anyone know?

Off to order the right bolts, I guess. :glare:

Rancho

 

[Ignacio]

Or go to a true "fastener" store and get one that's far more correct than the urban Lowes/Home Depot. Don't presume that it's odd-sized if they don't have it.....there are catalogs out there with TONS of fastener choices.

I've found after looking through my local Yellow Pages at least two good ones in my community of 150,000. One or more is in our industrial area of town and one recently opened called Tacoma Screw that has a gaggle of nice stainless fasteners that are nearly identical to the various Yamaha fasteners...and maybe even of better quality. It helps if you take in an example of one, but not necessarily a requirement.

 

[DailyCommuter]

.......one called Tacoma Screw.....

Tried that move on the Mrs.; man my ears were ringing for a week!



Must have done it wrong!

:rofl:

 

[charismaticmegafauna]

<snip>I could go to my local Home Depot and get bolts that would fit, I'm sure, but the heads on the bolts there would be "off-size." The factory bolt probably has a 10mm head, but if I buy 'em at Home Depot or the like, it's going to have a 9mm head. Or 11mm. Something inconvenient and different from every factory bolt. Why make the head size an odd size? I'm going to guess that the answer is ... a cent on each one ...

Maybe? There have been attempts to standardize fastener sizes -- I.S.O. (Japan) and there exist general conventions: 5mm hex hd bolt has a 8mm head; 6mm=10mm hd; 8mm=12mm hd; etc.

The U.S.of A. (even) passed a law in the mid-'70s to go metric, nationally -- never happened!

but does anyone know?

I think the reasons for different heads are many: sometimes to save weight (dimpled); looks (you're so vain); sometimes (I would guess?) engineering/structural reasons.

One of those classic 'structural reasons' would be to make a bolt with a smaller head than standard (8mm hd instead of 10mm on a 6mm bolt -- for instance) in order to keep (those who have trouble with wrenches) from using too big a wrench and over-tightening/stripping, etc.

The factories probably initiate this as much, or more, than the aftermarket.

Off to order the right bolts, I guess. :glare:

Nothing like a new factory part.....

'Ignacio': ... Tacoma Screw that has a gaggle of nice stainless fasteners that are nearly identical to the various Yamaha fasteners...and maybe even of better quality

Be forewarned that, although lookin' good, stainless may not be your 'fastener of choice'? Stainless threads tend to 'gall' and are often given a looser/'sloppier' fit because of this (MamaYama does this on the FJR where stainless fasteners are used). If you're serious about what your bolting together -- you may want to skip the stainless?