Okayyyy - finding myself once again in that realm where it seems blokes are just BORN with knowledge... since I can't find an explanation for things anywhere... so...

Males of the species... please impart your knowledge:

BOLTS:
1. WHY are some bolts on a bike allen/socket heads and other hex - and yet others screw heads?

2. WHY can't I just change ALL the bolts to allen heads - that way, I only have to carry ONE ALLEN KEY in my toolbox?

3. WHY are there different thread sizes/pitches (M4 M5 M6 etc.) to fasten things - why not just use the same pitch?

4. DOES the size of the ALLEN HEAD change with the size of the pitch? Or WHY are there different sized ALLEN HEAD BOLTS - why not just have one size?

5. If A2 stainless steel has less tensile strength than 8.8 carbon steel bolts.. why am I changing all my bolts to stainless steel?

NUTS:

1. IF NYLOCK nuts are so wonderful - why not change ALL the nuts on the bike to NYLOCK?

2. WHY are some of the nuts on my KTM "flange" nuts? Is this to make the surface of the fastener bigger... for bigger holes?

WASHERS:

1. What is the real purpose of washers - WHY are they not used on EVERY bolt? Do they act as SPACERS? Or do they act as seals? Or WHAT?

2. If SPRING WASHERS are shake/vibrate proof - WHY not use them on all fasteners?

3. If SHAKEPROOF WASHERS (the ones with teeth) are shake/vibrate proof - WHY NOT USE them on all fasteners?

4. If WAVEY WASHERS are shake proof...

Which is REALLY shake proof: Spring, toothy or wavey??

JARGON:

What is the difference between:

Stainless Steel UNC Fasteners

and
Stainless Steel UNF Fasteners

and
Stainless Steel Metric Fasteners

__________________

OK, I have an engineering degree and can't answer all the above off the top of my head, but here's a start.

Allen heads be they square topped or buttons need access from the end, hex's can be got at from the side. The bigger the hex (external is biggest), the more torque (turning force) you can apply before you break something. You can replace most with standard Allen heads, but the manufacturer is thinking about control on a production line and so picks what works best for him.

Sizes (M4, M5 , M6) etc. are the size of the hole/rod you start with. The pitch is the angle of the spiral. An M6x1.5 will take a bigger load than an M4x1.5 simply because it's thicker. Having finer pitch means more spirals over a given length, hence more contact area and more grip. It also vibrates loose at different frequencies. An M10x1.0 is typically a stronger joint than an M10x1.5, but will fit in a space where you can't fit the M12x1.5. Fine threads are easier to wreck by rough assembly, hence the standards tell you to try and use course pitch if you can. If everything on the bike was M10x1.5 it'd be rather heavy, hence the size variation! The only people who built a vehicle you can take to bits with one spanner worked for the Russian Army!

I hope you are NOT changing ALL your bolts to stainless. Stainless is fine when properly lubed on assembly and used where ultimate strength is not an issue. OK, replace the engine cover bolts with copper-slipped stainless, but think twice about the luggage rack and don't even think once about the brake calliper bolts! If in doubt fit new standard bolts every couple of years as they start to look nasty.

A washer can do two things properly and one as a bodge. It spreads the load to prevent the head pulling through and acts as a spring to keep the bolt in tension and prevent the head turning through vibration. It's shape decides how well it does which. As a bodge it fills an oversize hole. The type of washer needed depends on the load, fastener load, vibration frequency etc. For Yamaha it is actually worth testing every component to see if it needs a flat washer, nyloc, spring washer, wavy washer etc. If they save 2p on every engine by using a standard nut rather than nyloc or wavy washer it soon adds up. Production engineers and design engineers actually come to blows over one wanting a single gun-on nyloc and the other wanting wavy washered and wired!

UNC and UNF are imperial/US sizes where the design is set by different parameters. Metric is the world standard. Vehicle wise everything after about 1990 should be metric. This means all fasteners are to designs held in Paris and designated as M (for metric), Size (in mm), x, pitch (as a ratio). The spanner and allen key sizes for each type are defined in the spec and there is a design book listing which you should pick first. The problem is that for years the US was clueless and had the manufacturing strength to simply ignore all standards and the Japanese big export market was the US where everyone had inch size tools. As a result you get abominations like an M10x1.3 bolt with a 7/8" AF flange head and built in Torx security bit hole! (That was on a Russian built valve for a US owned company, so we guessed if was a mistake in the translation!)

If you are worried:

Only use stainless if you are sure.
Replace like for like or go up (ie nyloc and washer replaces nut and spring washer).
If you do have weird sizes (fine pitch, Imperial/US mixed) get a thread gauge.
Never force a fastener.
Always use copperslip unless told not to.
Don't reuse old fasteners unless you are sure they did not stretch.

If you have a workshop available buy yourself a block of aluminium, a tap and a selection of bolts. Learn to feel when a thread is about to strip. This is way safer that having loose bolts or messing about with uncalibrated torque wrenches. I once took a torque meter round some UK workshops. The average uncalibrated torque wrench was 15% out. Vehicle fitters got within that by feel alone. They didn't like my idea that service instructions should get rid of the numbers and replace with Tight, Very Tight, ****** tight, ******* tight, ****** ******* tight etc. but we did add the word CALIBRATED

BTW, the best fastener engineer I know is a Woman. This probably shows who was listening in Uni and who was thinking about Trucks/bikes/planes etc.

Andy

Andy,
Interesting what you say about torque. I have a torque wrench, but never use it. You get a feel after time for how tight to tighten something. I used to be a bicycle mechanic and only stripped a couple of things in several years of doing that work, both early on in my 'career'.
I've also seen bolts stripping threads after being tightened to the recommended torque by people with torque wrenches.

To be honest, XT Girl, I think you are worrying too much about stuff that doesn't matter. In general bolts that need to be nyloc/have a spring washer etc. are so because they have a tendency to rattle loose due to their low torque setting/postion on the bike. Other bolts are the size/pitch/head they are because the manufacturer thinks that is the most appropriate for the site. Generally people replace standard fixings with weaker stainless so they don't rust. The alternative is keeping your bike clean. (Or, like me, do neither!)

Matt

__________________
http://adventure-writing.blogspot.com

http://scotlandnepal.blogspot.com/

*Disclaimer* - I am not saying my bike is better than your bike. I am not saying my way is better than your way. I am not mocking your religion/politics/other belief system. When reading my post imagine me sitting behind a frothing pint of ale, smiling and offering you a bag of peanuts. This is the sentiment in which my post is made. Please accept it as such!

Just a word of warning - DO NOT use nylocs near heat - they will melt!

I don't know about the XT but some exhaust manifold nuts are slightly squashed off round to lock in place and aren't really reusable - they are also made from a soft metal alloy that can absorb the heat and vibrations.

__________________
Chris
-----------------
"Never have a stupid argument with an idiot - he gets a lot more practice than you"
there I go again
not too hard really

Sorry to admit it but thanks for posting the query and answers – I found that very interesting! I’ve had a car and mountainbike for years. I’ve never done anything with them in terms of fixing stuff. Having had a bike for almost 4 months I really feel I should be able to do more – probably as I hope to do bigger and longer rides in the future and want more knowledge (erm, thus the reason I frequent these forums!). I never even knew what half of these things were called (good old google images has sorted that out though) or that number on the bolt packets were pitches,. It has got me a bit worried about heading down to B&Q and replacing my snapped, overtightened SW Motech rack nut and bolt with the Zinc plated one….since erm, B&Q never had stainless ones.
(Hey you’re talking to someone who has been well pleased to be able put on panniers then change the screen, clutch lever (no cables on my bike!) and numberplate after a first spill !!)

I don’t want to hijack the thread, but when should you use (or not) loctite on bolts – is this the same as copaslip / copperslip or is one to keep them there, and the latter one to stop them seizing?

And is a waterproof grease the same as waterproof grease, or should I not have used copper grease to keep that thing my hydraulic brakes ‘piston’ thingy that sticks into my clutch lever greased – should I have used something else…..?

Not trying to hijack but I thought they were kinda related – keep the education coming!

It makes me take a bit more interest in the fasteners company my mate runs though! I would put a shameless plug but that’d probably go against forum rules.

Cheers

I have found the best way to replace nuts and bolts is to go to my local components shop and hand over the old one sying "Can I have a couple of these please?"

B&Q is almost never the best/cheapest place to buy anything. Same with Halfords!

Matt

__________________
http://adventure-writing.blogspot.com

http://scotlandnepal.blogspot.com/

*Disclaimer* - I am not saying my bike is better than your bike. I am not saying my way is better than your way. I am not mocking your religion/politics/other belief system. When reading my post imagine me sitting behind a frothing pint of ale, smiling and offering you a bag of peanuts. This is the sentiment in which my post is made. Please accept it as such!

Loctite and Copperslip are different. Loctite is a bit like glue. It stops bolts working loose by sticking the threads together. It comes in different strengths for different applications. Threadlock is the strength you want. Don't use too much. Use it on bolts that are likely to shake loose. Because it effectively excludes water and air from the thread it prevents corrosion, therefore you don't use it in conjunction with grease. While it stops bolts shaking loose it does not prevent them from being undone when required.
Copperslip is essentially grease with copper in it. It provides a very water resistant and long lasting lubricant for threads. Good for most nuts and bolts that do not require loctite.

Matt

__________________
http://adventure-writing.blogspot.com

http://scotlandnepal.blogspot.com/

*Disclaimer* - I am not saying my bike is better than your bike. I am not saying my way is better than your way. I am not mocking your religion/politics/other belief system. When reading my post imagine me sitting behind a frothing pint of ale, smiling and offering you a bag of peanuts. This is the sentiment in which my post is made. Please accept it as such!

If you look up your local engineers merchant in the yellow pages or yell.com they will sell you the right replacements at sensible prices - diy chains make their profits from packaging inferior quality fastenings.

__________________
Chris
-----------------
"Never have a stupid argument with an idiot - he gets a lot more practice than you"
there I go again
not too hard really

I cant speak for Grant and Susan, but if you think that your mate's fasteners company would be a good resource for HUBB members to know about, stick the link up here. You can always add the caveat "Moderator: Please remove link if this is not appropriate."

I for one would love to know of a good fasteners company that does online retail in small quantities, if that's the kind of stuff he does, get that link up!

Matt

__________________
http://adventure-writing.blogspot.com

http://scotlandnepal.blogspot.com/

*Disclaimer* - I am not saying my bike is better than your bike. I am not saying my way is better than your way. I am not mocking your religion/politics/other belief system. When reading my post imagine me sitting behind a frothing pint of ale, smiling and offering you a bag of peanuts. This is the sentiment in which my post is made. Please accept it as such!

Ok, here is the link to my mate's fasteners company as discussed above - a fasteners company that also supply the motoring industry - e.g. supply the MSS Discovery Kawasaki team, local riders popping in to change their nuts (my poetic licence used there) and to suppliers helping some Dakar riders.

Like an earlier poster said please remove if this post breaks the rules and apologies.

motoGF and Beta Tools – quality / motorsport / performance

He said they don't have individual fasteners listed as there are way too many combinations etc but to give them a call. The website currently focuses on Beta and other tools I think. Based in Aberdeen, Scotland.

Cheers

This should give you a good idea of whats behind the usefulness of bolts and screws...

Screw - Wikipedia, the free encyclopedia


How a bolt works...
Keeping It All Together, Part 1
Keeping It All Together, Part 1

And the usefulness of torque wrenches...
Keeping It All Together, Part 3

__________________
edde
93 BMW K75s
www.motoedde.com

Stagonset - Stainless Nuts and Bolts, Screws and Fasteners

Very good point! I'd forgotten about all that vibration out there, and me an ex enfield owner

The one to avoid is permanant loctite (red?). That's the superglue of threadlocks and needs a blowtorch to get it out. The others are like gel or powder when set and fill the gaps as Matt says.

Copperslip's main use is with stainless fasteners going into mild steel or alloy. The water resistance prevents the other thread rotting to match the stainless which is then a real pain to drill out. Talking of which, anyone care to add to the following for getting a stuck fastener out:

1. Penetrating oil and leave overnight.
2. Heat
3. Impact gun (Argos/RAC in the UK do a very effective electric one)
4. Rock back and forth with a long bar.
5. Drill out and/or use stud extractor.
6. Spark erode to get out broken stud extractor

For a rounded hex, hammering on an undersize (Imperial) socket or welding on another nut or socket can work. This is harder with a rounded allen key socket.

As you can see I've done my share of bodging

Andy

Learn where this limit is. Just takes some time and experience on the wrenches.

__________________
Patrick passed Dec 2018. RIP Patrick!

A couple of things:-
good quality tools will fit the bolt head better than cheap ones - less chance of rounding.

use hex (6point) sockets where you can rather than bi hex (12point) - again less chance of rounding.

the open end of a spanner will do less damage to a corroded bolt head than the closed 12point

on stuck bolts a slight tightening before loosening sometimes works to free the corrosion but be gentle

__________________
Chris
-----------------
"Never have a stupid argument with an idiot - he gets a lot more practice than you"
there I go again
not too hard really