How do you measure bolt/nut sizes?

[Droopy Dick]

I'm puzzled.

I need to sort out a few stainless bolts, washers, nuts, nylock nuts, but I can't work out what size I need.

Length is obvious, so I'm OK with that.

For example, I've just bolted on the BMW engine bars and found that I needed a 5mm (it may have been 6mm, but I'm not going back out to the garage to look) Allen-key thing, but a 13mm spanner to hold the nut.

Are nuts measured across the flats?

Then again, looking at some catalogues I'm being baffled by different thread pitches for the same size bolts ....

Is there an easy way to work it all out?

Or am I terminally stupid?

 

[cookie]

nuts and bolts: they're not measured across the heads (A/F across flats). they are grouped by diameter M5, M6, M8, M10 are the usual suspects.

measure the diameter of the threaded or shouldered section of a bolt*, round it up to the nearest 0.5mm and that is the bolt size. so if it measures 4.8mm odd it's an M5.

countersunk lengths are for the whole screw. hex heads and cap heads (that's allen heads) , don't include the head.

if you don't ask specifically, you generally get given metric course thread pitch. bikes generally use the common pitches, but sometimes don't. buy a thread gauge or take a sample to the fastner shop.

A2 stainless is fine for most things**. A4 is corrosion resistant for marine use and much more dear.

i tend to buy clear zinc plate now. much cheaper & they look right on a modern bike.


* if it's got a shoulder, it's a bolt, if it's threaded all the way, it's actually a machine screw.


**lots of opinion on that i bet i'd use it mostly anywhere but wheel spindles.

 

[dazco]

all as cookie said, dont be too worried about size of the thread
The majority of threads used for fixings on your bike will be a standard size.
just for you the following standards should apply

M5 (5mm diameter)=0.8mm pitch
M6 (6mm diameter)=1.0mm pitch
M8 (8mm diameter)=1.25mmpitch
M10(10mm " )=1.5mm pitch
M12(12mm " )=1.75mm pitch

The size of the head on the bolt will also be a standard size as will be the size of allen key slot if its a cap head

Also if you want washers just state that you want the washer for the size of the bolt, ie a 30mm long M6 caphead would need an M6 washer

Hope that helps a bit

 

[Droopy Dick]

nuts and bolts: they're not measured across the heads (A/F across flats).

Thanks for all that.

And here was me thinking AF = American Fine, BSF = British Standard Fine, etc etc etc.

I think I go and buy a small handful of all the normal looking sizes in different lengths and varying tops.

 

[cookie]

AF = American Fine

it means that as well

 

[Droopy Dick]

all as cookie said, dont be too worried about size of the thread
The majority of threads used for fixings on your bike will be a standard size.
just for you the following standards should apply

M5 (5mm diameter)=0.8mm pitch
M6 (6mm diameter)=1.0mm pitch
M8 (8mm diameter)=1.25mmpitch
M10(10mm " )=1.5mm pitch
M12(12mm " )=1.75mm pitch

The size of the head on the bolt will also be a standard size as will be the size of allen key slot if its a cap head

Also if you want washers just state that you want the washer for the size of the bolt, ie a 30mm long M6 caphead would need an M6 washer

Hope that helps a bit

Ta very muchly.

I shall be scouring a couple of websites later this evening.

Oh deep joy.

Or, as my youngest has just said, what a sad life to be looking at bolt sites and thinking it's interesting.

 

[Tarka]

Rough and ready Metric spanner/bolt size ( Some Euro manufacturers differ )

Spanner size 8mm.....Bolt Size M5......Allen Key Size 4mm


Spanner size 10mm.....Bolt Size M6......Allen Key Size 5mm


Spanner size 13mm.....Bolt Size M8.....Allen Key Size 6mm


Spanner size 17mm.......Bolt Size M10.....Allen Key Size 8mm

The awkward sods sometimes put 12mm spanner size heads on M6 or M8 bolts.

Sometimes 14mm spanner size head on M8 bolts.

Sometimes 15mm spanner size head on M10 bolts.

Caliper banjo bolt heads may be 12mm or 14mm and sometimes 15mm.

The above Allen key sizes are for Allen 'cap' (socket head) screws. Button headed or countersunk Allen screws will require either one half size smaller Allen key or one full size,depending on manufacture.

 

[Droopy Dick]

Rough and ready Metric spanner/bolt size ( Some Euro manufacturers differ )

Spanner size 8mm.....Bolt Size M5......Allen Key Size 4mm


Spanner size 10mm.....Bolt Size M6......Allen Key Size 5mm


Spanner size 13mm.....Bolt Size M8.....Allen Key Size 6mm


Spanner size 17mm.......Bolt Size M10.....Allen Key Size 8mm

The awkward sods sometimes put 12mm spanner size heads on M6 or M8 bolts.

Sometimes 14mm spanner size head on M8 bolts.

Sometimes 15mm spanner size head on M10 bolts.

Caliper banjo bolt heads may be 12mm or 14mm and sometimes 15mm.

The above Allen key sizes are for Allen 'cap' (socket head) screws. Button headed or countersunk Allen screws will require either one half size smaller Allen key or one full size,depending on manufacture.

Now printed and encapsulated and pinned to the edge of the shelf above my bench in the garage.

 

[Greg Masters]

nuts .....: they're not measured across the heads (A/F across flats).

?



Greg

 

[Greg Masters]

Rough and ready Metric spanner/bolt size ( Some Euro manufacturers differ )

Spanner size 8mm.....Bolt Size M5......Allen Key Size 4mm


Spanner size 10mm.....Bolt Size M6......Allen Key Size 5mm


Spanner size 13mm.....Bolt Size M8.....Allen Key Size 6mm


Spanner size 17mm.......Bolt Size M10.....Allen Key Size 8mm

The awkward sods sometimes put 12mm spanner size heads on M6 or M8 bolts.

Sometimes 14mm spanner size head on M8 bolts.

Sometimes 15mm spanner size head on M10 bolts.

Caliper banjo bolt heads may be 12mm or 14mm and sometimes 15mm.

The above Allen key sizes are for Allen 'cap' (socket head) screws. Button headed or countersunk Allen screws will require either one half size smaller Allen key or one full size,depending on manufacture.

Yes, when you buy that expensive complete set of spanners, there are some (11mm*, 16mm, 18mm etc that never get used!).

American vehicles generally still use AF sizes, as do a few British items (like the wheel bearings (Indespension) on my trailer.

Some things (like gas fittings and petrol pipes on older cars/bikes) use Whitworth sizes. But these are now very rare. (I recently saw a market trader trying to sell a few somplete sets of very nice but almost useless Whitworth spanners!)

* Reasonable substitute for a 7/16th AF spanner



Greg

 

[Droopy Dick]

Yes, when you buy that expensive complete set of spanners, there are some (11mm*, 16mm, 18mm etc that never get used!).

American vehicles generally still use AF sizes, as do a few British items (like the wheel bearings (Indespension) on my trailer.

Some things (like gas fittings and petrol pipes on older cars/bikes) use Whitworth sizes. But these are now very rare. (I recently saw a market trader trying to sell a few somplete sets of very nice but almost useless Whitworth spanners!)

* Reasonable substitute for a 7/16th AF spanner



Greg

All my early cars were old Fords. Just about everything on a 105E was bolted together with 9/16" AF bolts and nuts.

I'm very fortunate in that I have inherited a very full set of 3/8" drive Britool and King Dick sockets, all in very good nick (my dad was fanatical about keeping his tools clean and slightly oiled). So I have sockets for BSW, AF, BSF, and even a very nice Britool 1/4" drive set of smaller sockets including BA sizes!

I have a mixture of Teng, Facom and Snap-On 3/8" sockets and associated Allen and Torx head tools, as well as a very nice and all but unused 1/2" set of Britool AF and metric sockets. I bought the Teng and Facom stuff. My dad always drilled it in to me that it was a waste of money to buy cheap tools. They're made from spelter barely stronger than chocolate, he said.

Got the full range of spanners too, mostly polished Britool, satin-finished Facom, and some rather dull but unrusty King Dick BSW kit.

One of my lads asked me why I didn't mount them all on a rack-type display above the workbench. I've always tended to keep them oiled and wrapped in oilcloth in a tool chest. Nothing rusts that way. I've been meaning to treat myself to one of those natty rolling cabinet tool things with all the drawers. Couldn't afford or justify a Snap-On chest, but I see Halfords seem to have some decent ones, or even Machine Mart. But, will they stay rust free in a garage that gets a bit damp in winter?

Anyway, I went and ordered a decent range of stainless bolts, nuts, washers, Nylock nuts, spring washers, and the place I got them from is gonna chuck in a 3-drawer storage device thing for them all. I guess that can be wall-mounted - just spray the contents with some WD40, notwithstanding their being stainless.

Anyway, chaps, many thanks for the explanations above. It did make life much easier.

 

[cookie]

?



Greg

if you go to a fastener shop & ask for a 10mm metric bolt, what you get given won't be 10mm A/F.

 

[Steptoe]

Buy your metric snap-on tools off american e-bay - works out very very cheap .

Buy AF tools off UK ebay, very cheap, then re-sell them on american ebay.

I know someone on this site who does it . very successfully ( profitably) ..

 

[cookie]

Buy your metric snap-on tools off american e-bay - works out very very cheap .

Buy AF tools off UK ebay, very cheap, then re-sell them on american ebay.

I know someone on this site who does it . very successfully ( profitably) ..

brilliant

 

[Bigtwin]

Some things (like gas fittings and petrol pipes on older cars/bikes) use Whitworth sizes. But these are now very rare. (I recently saw a market trader trying to sell a few somplete sets of very nice but almost useless Whitworth spanners!)
[/SIZE]



Greg

I recently inhereited my grandfather's toolkit - he was an engineer. I now have amlost exactly 1,439,213,774 Whitworth spanners.

I seem to remember that I did actually use one once, back in the days when I owned a Triumph Herald.

 

[sigmaglider]

All the british bikes use whitworth spaners dont they, so you should make a mint selling them.

 

[Voyager]

* if it's got a shoulder, it's a bolt, if it's threaded all the way, it's actually a machine screw.

Close . .

If its threaded all the way and it has a hex head its a 'Set Screw'.

If its threaded all the way and it has a screwdriver slotted or cross head its a 'Machine Screw'.

That's my understanding anyway.

Bob.

 

[Voyager]

Whitworth and British Standard Fine (BSF) share the same spanner sizes - but one is measured by the shank diameter (BSF I think) and the other by the head diameter (across the flats).

I should go out to the garage and check my Imperial spanners toolbox

Still in use if you are into old British bikes

Confusing isn't it

Bob.

 

[davegs]

Sizes

have a look in Liddles supermarket doing vernia calipers with digital read out for about a tenner, suprising quality not tool room stuff but good enought to check sizes supprisingly good quality.
dave ( Abba Fan see mama mia with out delay) GS

 

[(RIP) Bin Ridin]

BSW and BSF:
I was taught that the spanner size for these threads was the dia of the screw, until WW2 when the head sizes were reduced by 1/16".
I.e. a 5/8" dia bolt will need a 9/16" spanner (which would have suited the full-size head of a 9/16" dia bolt).