Whe replacing bolts....

[Arthurdaily]

Hi all, now as my restoration begins I realise I'm going to have to replace nuts and bolts - but with what? Stainless Steel yes, but what type - BSF, Whitworth, AF Metric, good lord.... I think it might be easier to replace with what is there, ie original, do you think?

Also, how do you measure a nut and bolt? You need the head size yes? So that would be say 12mm for metric or whatever, and then what? JUST the shank length is it?

Cheers.

[Arthurdaily]

Some nuts and bolts, for example on ebay, are listed m16, 70mm - does that mean it is a 16mm head and nut with a 70mm shank???

[Alec]

Hello Arthur,

I stick with mild steel rather than stainless, but if you do go the stainless route, don't use them on high stress applications like the supension, they are not strong enough. Use plated 8.8 fasteners (This is a strength rating and is stamped on the head)
The Minor has a mix of Whitworth (BSW and BSF) and Unified (UNC and UNF) fasteners (There are no Metric bolts on a Minor), and they are categorised by thread diameter and length. Also there are bolts and screws, the latter being threaded all the way to the head. You want to use bolts where there is any length of the shank, through a sleeve, for example, and screws where the item to be fastened is quite thin, e.g. wing to body. The other type is B.A. which are identified by number e.g. 2B.A. such as hockey stick nuts, so another set of spanners.

Alec

[Arthurdaily]

Thanks Alec, is unc and unf the same as af?

[Arthurdaily]

Oh, and where do you buy these from - esf and bull motiff type suppliers?

[Alec]

Hello Arthur,

better to go to a fasteners specialist, one well known one is Namrick, but there are many others.
A.F refers to across flats and is used for unified threads so a common size is 5\16" and the spanner size is 1\2" which is the across flats measurement (Metric is the same 8mm is a 13 mm A.F spanner size). Whitworth is slightly more complicated a 5\16" BSF is a 1\4" Whitworth spanner, but usually marked 1\4" BSW 5\16" BSF.
There is quite a bit to fasteners that at first is apparent. As I said earlier the tensile strength of the fastener can be critical so you need to be aware when buying, specialists sell good quality ones.
Also,, as I said I stick with mild steel but coat them in Copperslip which makes removal easier even many years down the road.

Alec

[Arthurdaily]

I sort of begin to understand... but in spanner sizes section only whitworth and AF are really mentioned... so to confirm IS unf sort of the same as af? Or do you need unf spanners as well?

At the moment I have metric and af and have been doing okay with these... but today, for example, I had problems taking the wing off, so think I need at leat a few whitworth... but are unf DIFFERENT?

Might have to actually find a nut and bolt shop to go through all this lol

[bmcecosse]

DO NOT use 'stainless steel' fasteners. When used in close contact with mild steel they form an electrolytic cell -and guess what - the mild steel around the stainless fastener rots away........

[Arthurdaily]

Hi BMC - Will do, or rather won't do - mild it is... but is unf same as af lol... must know or won't sleep! lol

[Alec]

Hello Arthur,

forget about A\F, it is not a fastener size merely an aid to what spanners you need, which you quickly pick up anyway. Whitworth spanners are the only ones to my knowledge that are sized in shank diameter, all else went to head dimensions i.e A\F. (B.A excepted)

Alec

[Arthurdaily]

lol - so, when buying a new nut and bolt forget about the had size (unless whitworth... ) and concentrate on the shank size?

[Alec]

Hello Arthur,

they are all categorised by shank diameter, except B.A., including Whitworth then by the length. The length is measured from the end to the bottom of the head except for countersunk which is measured as overall length.

Alec

[bmcecosse]

So - a 'half inch' AF(across flats) bolt head, will have a 5/16" diameter thread........which can be UNF (Unified Fine) or UNC (Unified Coarse)

[mogbob]

Arthur
Recap time... your AF spanner set will "work" on tightening/loosening all UNF or UNC bolts/screw threads.
( The usual disclaimer..your Morris nuts and bolts will be covered in rust/dirt/underseal.crud,etc after several decades and will need attacking with a wire brush/penetrating oil,etc to clean them before you attempt to use the right size spanner).
Whitworth and BA spanners for the rest on a Minor.
Bob

[mike.perry]

A set of thread gauges, a bit like feeler gauges with teeth, is useful for checking and comparing threads. UNF is a slightly finer pitch than BSF, eg 7/16 UNF = 20 TPI, 7/16 BSF = 18 TPI.
When working on a Series MM or early Series 2, especially the brakes and suspension it is important to check the threads as there was a changeover from BSF to UNF during the production span of the Series MM and incorrect components could have been fitted on previous repairs. Do not to try to force two threads together, the result will be stripped threads and a ruined component.
To correct an earlier statement, there are metric threads on a Minor, the side valve engine has metric fine threads but in order to reduce the number of tools required for assembly they are fitted with Whitworth heads, hence the importance of checking the threads.

[Alec]

Hello Mike,

good point, I'd forgotten about the early engine. Can you get replacement whitworth headed bolts for them or do you have to put up with metric headed replacements?

Alec

[Arthurdaily]

I think it is all a little clearer... interesting that in the driver's handbook, original bmc, it lists only AF sizes to keep with you for emergencies... however I'm going to start looking for Whitworths on ebay now

[mike.perry]

The correct nuts, bolts or studs should be available from specialist component suppliers or they can be made. The threads are metric fine, not the standard metric

[beero]

... however I'm going to start looking for Whitworths on ebay now

Car boot sales are a good source of whitworth spanners