M8 thread pitch on honda motorcycles.

Only M6 & M7 apparently, I bit the bullet and braved the cold and rain to
get an M8 crankcase bolt from the shed, it fits the M8x1.25 die from my tap
& die set, maybe they start using fine threads from M10 upwards.

 

Printable metric bolt gauge:

http://tinyurl.com/dkznex

http://www.boltdepot.com/Fastener-Information/Printable-Tools/Metric-Hex-Bolt-Sizes.pdf

Thanks.

 

I have *never* seen any reference to thread pitch in torque tables.

The tables only address the diameter and grade of the bolts.

 

Exactly -- they assume the correct fastener is used.

And the usage. Looking at the table in a German manual for the
1992 CB-sevenfifty I find these torques for 8 mm bolts just in the section
on brakes alone: 27 Nm, 31 Nm, 23 Nm, 5.5 Nm, 13 Nm, 18 Nm, and 42 Nm.

--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD "You Porsche. Me pass!" DoD #484 JKLO#003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

I can also find a pretty good assortment of metric
nuts and bolts at my local Ace Hardware. A buck
or so buys an assortment of nuts to check with.

 

You will never see a torque table tailored for the idiot who uses mis-matched
fasteners.

Is there a copy of Andy Pugh's Threaded Fastener FAQ online anywhere? I had it
on a website years ago but it's long gone now.

 

Hey! Play nice, now!

 

Blimey. Has anyone heard anything of AtP?

 

Torque tables are related to MAINLY, minor diameter of the bolt, bolt
stretch, and material of the bolt or material threaded into. There can
be many torque specs for an M8- 1.25 pitch depending on the material
it's made from and the material it's threaded into.

There is very little difference in torque specs based on thread pitches,
because the root or minor diameter doesn't change much. Which is one
reason why you don't see references to pitch in a generic torque table.

Also generic torque tables list MAXIMUM torque specs based on bolt
strength ALONE. They have nothing to do with applications

Clay

 

http://www.diyfaq.org.uk/fasteners/fastener.html

 

http://www.geocities.com/motorcity/downs/3837/thrdfast.html

 

Yeah, he's alive and well, rides an R1, lives in Essex & works for Ford.

I'll see if I can find the URL for his FAQ

 

Another factor, sometimes, is the bolt head design. Some heads have serrations underneath and some have an angular undercut of several degrees, but you have to look pretty closely to see it. I think Honda sometimes calls one or the other 'high-tension' bolts.

 

I am familiar with theses, but was under the impression that they were
for SURFACE tension. Hence the High tension designation. Usually
designed into vibration susceptible areas.

It probably effects the torque reading during install.

Clay

 

frijoli wrote:
....

Makes sense. I was trying to think of reasons for different torque values for the same size and same stength bolt. I suppose another reason besides the ones given so far might be thickness of the parts. Then there are those bolts that the manuals say to use some grade or other of loc-tite with.

Another question that the original post made me wonder about is kind of hard for me to put precisely, but I'll try: Given that the effect of a threaded fastener in the first place is to multiply the surface areas under tension (eg., one turn of a thread has less surface area than two turns, and so forth), what factors would favour an M8 with 1.00 pitch versus an M8 with 1.25 pitch? I gather both have an 'angle' of about 60 degrees and if the face of the thread were the same 'height' for both, I guess that would mean the 1.00 mm pitch screw/bolt would have more surface area. Or do the 1.25 mm pitch bolts have 'deeper' threads, giving them more surface (but also reducing the core 'thickness' of the bolt)? Just curious about how the engineers go about deciding this.

(Although I don't know much about fasteners, I've often scratched my head when I saw people buy stainless bolts at the hardware store, then use factory torque values to tighten them even though the stainless steel surely has a different strength than, say, a 10.8 grade factory bolt. I suppose it doesn't matter much for parts like valve covers, but for parts that are under big internal pressures or heavy vibration, it seems a bit dumb to me. Maybe there's not much difference between the strength of stainless bolts and typical high-tensile factory bolts and most of the tinkerers who I happen to know seem to create as many other problems as they solve whenever they take something apart, and even more when they put it back together! Personally, if it's not a spark plug hole and if there's room, I prefer to tap to a larger size rather than use one of the insert coil devices, even if that means mixing SAE sizes with metric. I know one daytime Porsche mechanic who refused to use
a heli-coil on his neighbour's outboard without taking the head off first.)

 

This typically relates to the fastening material toughness. General rule
is The softer the material, the coarser the thread. Because the coarse
thread has a deeper valley, allowing more material to "bite" into, or
hold onto, as the case may be.

I gather both have an 'angle' of about 60

they aren't(see above)

(see above)


Just curious about how the engineers go about deciding this.

Again this relates more to the mating material. Whether that be a nut or
an engine case.

Finer pitch threads allow for more tension with the same torque at
installation. So mating materials and thread pitch are related here as well.

If the torque is specified by the mating material, then it probably
doesn't matter in light to medium applications. Head bolts would be a
different story altogether. The torque specs here, and rod bolts and
such are almost always related to full bolt tension.

There most definitely is! Stainless is much less strong than a typical
High grade bolt! In fact Hardware store stainless bolts are low tensile
strength, sometimes as low as a grade two bolt. Typical socket head
screws are grade 8 bolts. Which is two standard grades above a grade 2
hardware store screw. i would never recommend less than grade five on
any motorcycle, or automotive application, and anything related to
suspension, or wheels, or brakes go with grade 8.

Actually, when you Heli-coil you are going up some in size. One
advantage of a Heli-coils is that you are engaging steel, rather than
twisting your fastener against softer materials like aluminum. You have
essentially one direction of force on the housing, instead of two.


Clay

 

Ah, that's a step up; he was working for Volvo last I saw him, IIRC.
I didn't get along with his R1, tho' -- couldn't adjust the clutch lever to
a comfortable angle.

--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD "You Porsche. Me pass!" DoD #484 JKLO#003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

Thanks for that and the other comments.

 

TRANSLATION: "I DON'T" Thanks for nothing again krusty!

If you have a metric bolt, just lay a metric scale next to it.

1.0mm is a very common pitch.

Typical pitches are 0.5mm, 0.75mm, 1.0mm, 1.25mm and 1.5mm, from one
thread crest to the next.

 

Suck my dick, asshole!

Who *could* give a succinct answer to such a vague question as "Anyone
know the thread pitch on Honda M8 bolts?"

To answer a *stupid* question like that, I would have to know what
thread
Honda selected for *every* 8mm bolt on *every* model they ever built.

Instead, I told the lamer how to measure the pitch on the bolt he had
in his possession, and that's what he did, before spending his money
on a thread repair kit.