Tap and die set - which??

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Another Q patient people!

when I removed the carburettor fixing screws -the ones that fasten the carburettor spacers to the head (part no. 062536 for those of you with a parts list) I noticed that the threads on one were pretty bunged up. I do not have a tap and die set, but have been meaning to buy one for ages, so this is a good time.

However, will the standard generic set that can be purchased in most auto stores, and has both metric and inch sizes work on commando threads? Is there such a thing as whitworth threads?
 

L.A.B.

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skippy said:
However, will the standard generic set that can be purchased in most auto stores, and has both metric and inch sizes work on commando threads? Is there such a thing as whitworth threads?

Metric taps and dies will be of no use on a Commando.

A range of various different thread forms were used on Commandos that can include the following:

Many threads are SAE UNF/UNC (and the odd UNEF I think?)

BSW (British Standard Whitworth) Studs/screws into alloy before 1972. After 1972 many BSW replaced with UNC (hydraulic brake fittings are UNF).

BSF (British Standard Fine) Used for various things like AA unit retaining bolt and head steady to cylinder head retaining screws

CEI (Cycle Engineer Institution later known as BSC) not many on a Commando = some carb threads.

BA (British Association) = Electrical screws and carb screws.

BSP (British Standard Pipe parallel thread) = fuel tap fittings

ME (Model Engineer) = Carb cable adjusters.

Metric = Spark plug threads and spin-on filter thread.

So a UNF/UNC kit would probably be the most useful?

Unless you are able to learn what every threaded part is, then you need to proceed with caution when cleaning any threads, and identify what the thread type is first.

A couple of sets of thread gauges (BSF/BSW and UNF/UNC) are very handy tools for this, and there are plenty of websites to enable you to identify a thread by its diameter x tpi.
Example
http://www.britishfasteners.com/threads/index.html
 
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Of course, why should it be easy?

Yeah I knew metric was out, but to get the inch sizes the only kits (easily) available come with metric too.

As these bolts go into aluminium, and mine is a 1969 model, i guess i need BSW? can't get that on a weekend ;)
 
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