Norton factory (special) thread form(s)

Previously wrote:

Hi All,

I have just been reliably informed by 'the highest authority', that some of the enginestud/shaft threads on my Mark 3 Interstate are not, as popularly believed, BSF or Cycle thread, but a special factory Whitworth form thread which fits nothing else at all!!!!

In particular, the exhaust valve cover studs and corresponding nut threads, the rocker adjuster threads,the drive side crankshaft thread and corresponding alternator rotor nut thread, the clutch centre nut and corresponding gearbox mainshaft threads, the tachometer drive take off and its corresponding cable sleeve nut threads.

Purpose of this message is to see if anyone out there is aware of the use of this special Norton only thread, and if taps and dies are available in any or all of the relevant diameters and threads per inch across the range of sizes.

Apparently, this mysterious 'Norton' thread (as I have come to refer to it) has a 55 degree thread angle - the same as BSF, BUT - with a different 'core diameter' - so 'Norton' thread will not fit BSF thread. Cycle thread is ruled out because that has a thread angle of 60 degrees - so 'Norton' thread won't fit that, either.

It would be of great benefit to know exactly what 'Norton' thread is officially called, and, as mentioned above whether taps and dies are still available anywhere.

Food for thought? Anyone got any ideas? Cheers Ken Weeks.

There is a summary of Norton threads in the technical section Screw Threads

The Norvil catalogue which can be downloaded here Norvil Catalogue has the bolts, screws, etc listed from page 40.

There is an American stainless supplier with a comprehensive list here Stainless Bits

There are a number of threads about threads on the Access Norton board. A recent one is here Access Norton

Completely rely on none of them! Get good quality thread gauges and check whenever unsure.

Alan

Previously wrote:

There is a summary of Norton threads in the technical section Screw Threads

The Norvil catalogue which can be downloaded here Norvil Catalogue has the bolts, screws, etc listed from page 40.

There is an American stainless supplier with a comprehensive list here Stainless Bits

There are a number of threads about threads on the Access Norton board. A recent one is here Access Norton

Completely rely on none of them! Get good quality thread gauges and check whenever unsure.

Alan