Bolt/screw thread gauge

Post by **wibble_puppy** » Wed Oct 12, 2005 5:19 pm

hi guys

where do i get one of these from? my local tool supplier is asking all sorts of difficult questions as they are standard (woodworking etc) tool suppliers. Local motor factor doesn't stock them. Any ideas? Somewhere online maybe?

Cheers!

juliet xxxx

Post by **Alec** » Wed Oct 12, 2005 5:29 pm

Hello Juliet,
I guess this is to do with your post about nuts and bolts?, the place to find thread gauges is an engineering tools supplier. One source on line is RS components, (rswww.com) and search for RS Stock no: 387-0183.
Another useful item is a small book with engineers data called Zeus Tables. These used to be sold by good booksellers (even Smiths) but mine is many years old so it may not still be readily available. Amongst other things it gives bolt references i.e thread pitch for a given type and size of fastener.
I suggest you contact a nut and bolt supplier as most general tool shops don't stock even UNF\UNC fasteners much less BSW\BSF that you will need for your Minor.

Alec

Post by **wibble_puppy** » Wed Oct 12, 2005 6:00 pm

wow thanks alec, what a fabulous and extremely useful answer

juliet xxxxxxx

Post by **bigginger** » Wed Oct 12, 2005 6:03 pm

They generally sell them with Tap 'N' Die sets - Is it worth checking if Machine Mart do them seperately?

LATER I did it, and they do - http://www.machinemart.co.uk/search.asp?q=screw+gauge

Post by **wibble_puppy** » Wed Oct 12, 2005 6:12 pm

firstly: isn't "gauge" a stupidly spelt word??

secondly: what does it mean when it refers to 55% or 60% thread angle?

thirdly: which characteristics of the thread is it important for me to identify, and do these gauges identify them? I'm thinking: distance between each section of thread (obvious), depth of incut between each part of the thread.... and maybe other factors? For instance, are all Morris Minor bolts n screws single threaded, or are some double?

don't want to know much do i

juliet

Post by **wibble_puppy** » Wed Oct 12, 2005 6:13 pm

PS forgot to say THANK YOU ANDREW

Post by **wibble_puppy** » Wed Oct 12, 2005 6:20 pm

have found out that "pitch" means the distance between adjacent thread peaks

and "TPI" is threads per inch

http://www.modelfixings.co.uk/thread_data.htm

*note to self: get out more*

Post by **wibble_puppy** » Wed Oct 12, 2005 6:23 pm

http://www.colinusher.info/Livesteam/mewdata.html

Post by **bigginger** » Wed Oct 12, 2005 6:27 pm

The gauges (you could always move to America, where they don't mind spelling it 'Gage" ;) ) are shaped like a saw blade. You find the one that accurately fits the thread you're measuring, ie the teeth fit into/over the thread. I've always found them very hard to use, mind...

Post by **wibble_puppy** » Wed Oct 12, 2005 6:35 pm

cheers andrew

think i'm getting the hang of it now. To identify a screw thread it seems that you need to know:

the pitch

the TPI

the angle of the thread peak (in our case, (Whitworth - NOT UNC) 55%)

and for more esoteric applications:

the shape of the ditch between each thread peak

the shape of the thread peak

The gauges measure the first two and you need to know the third in order to buy the right gauge lol

phew

why do you find them hard to use, andrew dude?

juliet xxxxxx

Post by **wibble_puppy** » Wed Oct 12, 2005 6:40 pm

oooh check this out thread fans:

P = Pitch = 1/Number of threads per inch (tpi)

h = Angular Depth = 0.960491 x P

D = Depth of Rounding = 0.073917 x P

h/6 = Shortening = 0.160083 x P

d = Actual Depth = 0.640327 x P

r = Radius at the Crest & Root = 0.137329 x P

C = Core diameter = Major Diameter - 1.280654 x P

Effective or Pitch Diameter = Major Diameter - .640327 x P

Post by **Alec** » Wed Oct 12, 2005 6:52 pm

Hello Juliet,

I think that this is getting overly complicated, basically all you need is to know the diameter, length and thread. E.g. 5\16" x 1 1\2" BSF bolt (By the way a bolt has a plain shank with some thread and a screw or sometimes set screw is threaded all the way to the head)

Most body/suspension fasteners on the Minor are BSF and most engine, gearbox, axle etc threads are UNF with some UNC.

Where you may come unstuck in identifying bolts is if in past times a UNF or worse a Metric bolt has been substituted.

Alec

P.S. isn't gauge and guard confusing?

Post by **wibble_puppy** » Wed Oct 12, 2005 7:00 pm

Alec wrote: I think that this is getting overly complicated

i like it like that

but yes you are probably right - ENOUGH!!!

Alec wrote:basically all you need is to know the diameter, length and thread. E.g. 5\16" x 1 1\2" BSF bolt

yup, agreed. I just got interested. Blame my slightly autistic-spectrum father's genes

Alec wrote:By the way a bolt has a plain shank with some thread and a screw or sometimes set screw is threaded all the way to the head.

Oh, ok, I thought a bolt had a stubby end and a solid faceted head, and a screw had a pointy end and a slotted or Phillips head?

Alec wrote:Most body/suspension fasteners on the Minor are BSF and most engine, gearbox, axle etc threads are UNF with some UNC.

Oh so not Whitworth then?

Alec wrote:Where you may come unstuck in identifying bolts is if in past times a UNF or worse a Metric bolt has been substituted.

surely, surely no one would...... yeah you're right

juliet xxxxxx

Post by **Alec** » Wed Oct 12, 2005 7:31 pm

Hello Juliet,

different trades use different terminology, but in engineering a bolt or a screw is purely part threaded or threaded respectively, and the type of head is irrelevant.
BSF is a Whitworth thread, just the finer threaded variant i.e.more t.p.i. . Whitworth spanners, confusingly are sized with the BSW being smaller than BSF although they both fit the same hexagon, e.g. 5\16" BSF\1\4"BSW. Post war BSW and BSF fasteners are the same across flat dimension, it was pre war that they had a larger (by 1\16" head)
You probably know that BSW spanners refer to bolt diameter and UNF(C) and Metric spanners are the across flat dimension of the fastener.

By the way, an important point about fasteners is that they have grades, as far as strength is concerened. look for 8.8 for suspension or any thing else that is stressed.

Alec

Post by **wibble_puppy** » Wed Oct 12, 2005 7:36 pm

thank you again, alec!

so i need to get a BSW gauge (can't find any BSF ones

) and a UNF one?

with your engineering knowledge, do you know the best place to look for buying screws and bolts once I have made a list of the ones I need?

juliet xxxxxxx

Post by **bigginger** » Wed Oct 12, 2005 8:52 pm

As an aside (and an answer) I could never persuade myself that I've actually got it right - see the seemingly endless variations to choose from ^^^^^

Post by **Alec** » Wed Oct 12, 2005 9:11 pm

Hello Juliet,

thread gauges are either Imperial or Metric as thread form isn't the criteria. I don't think that you really need one, however. A simple way, and as you will need the spanners anyway, is to determine whether the fastener you need to replace uses a Whitworth or an A\F spanner.
There are a few suppliers that advertise in the Classic Car magazines, or you could try a web search for nut and bolt suppliers?

Alec

Post by **bigginger** » Wed Oct 12, 2005 9:19 pm

There's a company in Weston-Super-Mare called (go on, guess...) Nuts and Bolts who will sell you whatever sort of bolt you want. I don't know if they do mail order though, but they're extremely friendly.
Nuts and Bolts
Unit 10 Longton Industrial Estate
Winterstoke Road
Weston super Mare
BS23 3YB
Somerset
Tel: 01934 416765
Fax: 01934 418704
http://www.nuts-and-bolts.co.uk/ - still under construction...

Post by **rayofleamington** » Thu Oct 13, 2005 12:47 am

Oh, ok, I thought a bolt had a stubby end and a solid faceted head, and a screw had a pointy end and a slotted or Phillips head

The woodworking / building trade use the term 'screw' for anything with a thread and a pointy end and 'bolt' for any fastener with a thread and a stubby end.
Unfortunately everyone has to un-learn and re-learn the terms to get it engineeringly correct. I've still not learnt how to spell guage though ;-)

Alec's info is very neat stuff. Personally I would rather go for a collection of nuts and bolts. If you remove a bolt and it fits your x/X" UNF nut, then that'll be ok...
As your Van is pretty Modern by Morris standards, you shouldn't need to stress too much. For things like 'wing bolts' I have just ordered a load of wing bolts from a Minor centre. They didn't have the nice tapered point (helps to centralise a captive/caged nut) but they certainly fit

[note to self - having raided the stash of wing bolts to replace the 10 that vanished from Monty I ought to thing about getting more...]

If you have something like an MM, then you need to take a lot of care to find the right stuff, but with a later Minor I wouldn't think it is so hard (or am I missing something?)

Post by **wibble_puppy** » Thu Oct 13, 2005 9:05 am

thanks everyone!

andrew - can see what you mean.... am sure i'll have the same problem

Alec, the sites selling gauges seem to sell them in either metric, American standard, UNF or Whitworth. Just thought that as they are selling these different types then it must make a difference which one I buy

Already have me spanners (and sockets)

- the spanners are extremely venerable ones which belonged to my grandfather donkey's years ago, so I'll need a new set I think at some point, to avoid chewing up the heads of the bolts.

andrew cheers for the company info

ray, it's more that i wondered if there is a cheaper (and as good) place to get me fixings from - I know I can get 'em from ESM but didn't know how their prices matched up to other sources.

I take your point about there not being much need to stress lol

I thought thought that as I was making this list, which I would like to make available to other members if they would find it useful, I wanted to get my info complete and correct

I read some scary stuff on that web site about needing to make sure the thread pattern of your nut and bolt fits exactly, as otherwise you are putting strain on the peaks of the threads rather than on the sides of them, which concentrates the strain on the weaker parts of the thread (makes sense) - they said for instance not to mix up Whitworth and UNC fixings.

Why have wing bolts disappeared from Monty?

cheers all and have a good 'un!

juliet xxxxxxxxxxxxxxxxxxxx