Navigator threads

Sholto,

My advice would be to get a thread gauge covering imperial threads.

On you Navigator you will find Whitworth threads, BSF threads, Cycle threads, UNF threads and BSP threads. A thread gauge and digital measuring caliper will be a very worthwhile investment. You will soon recover the costs by not wasting money on attractive, shiny, incorrect stainless fastenings.

Regards

Peter

Previously sholto_humphries wrote:

As you will gather from my latest posts I have started work on my 1961 Navigator.

Silly question perhaps, but as I strip the bike down and think about stainless steel fixing replacement, what thread types will I encounter and will they be mixed?

I ask the question as I have a BSA Bantam which is a mixture of Whitworth and British Cycle (or somthing simillar).

Any advice would be appreciated.

regards

Sholto

Previously peter_holland1 wrote:

Sholto,

My advice would be to get a thread gauge covering imperial . You will soon recover the costs by not wasting money on attractive, shiny, incorrect stainless fastenings.

Regards

Correct, as I have learned, it's not so much the cost but the annoyance! !

dan

Previously sholto_humphries wrote:

Previously Dan Field wrote:

Previously peter_holland1 wrote:

Sholto,

My advice would be to get a thread gauge covering imperial . You will soon recover the costs by not wasting money on attractive, shiny, incorrect stainless fastenings.

Regards

Correct, as I have learned, it's not so much the cost but the annoyance! !

Thanks Gentlemen.

Without sounding silly where would a chap purchase a thread gaauge?

Try Tracy Tools - they have everthing associated with threads

Regards

Derek Ambler

Previously sholto_humphries wrote:

As you will gather from my latest posts I have started work on my 1961 Navigator.

Silly question perhaps, but as I strip the bike down and think about stainless steel fixing replacement, what thread types will I encounter and will they be mixed?

I ask the question as I have a BSA Bantam which is a mixture of Whitworth and British Cycle (or somthing simillar).

Any advice would be appreciated.

regards

Sholto

Hi Sholto,

On the Navigator, as Peter Holand says, you will find a mixture of standard ( and non-standard) British thread forms.

A thread guage is an indispensible tool.

Even better, if you can get one, will be a thread chaser/restorer, like the one in my picture. Make sure it has at least 20TPI & 26TPI (Threads per Inch) on it - by far the most common sizes. That way you can both measure and repair damaged threads. A set of taps & dies will be useful too. Tracy Tools of Newton Abbot in Devon can help with stuff like this.

Am doing this next bit from memory (so check first).

Common thread forms you will encounter:

Almost all screws that screw into aluminium and hold a cover in place (eg primary chaincase) are all 1/4" Whitworth. I think 1/4" UNC is a very close replacement.

Most of the studs holding the frame together are 3/8" Cycle thread.

The cylinder head studs are 5/16" Whit into the crankcase & 5/16" Cycle to hold the cylinder head down.

The Oil Feed Banjo & Head Steady bolts on the cylinder head are 5/15" BSF. (The Oil Feed bolts are the same as for the big twins).

Enjoy!

Don't use stainless on highly stressed parts. E.g. cylinder head and barrel nuts, bolts or setscrews. No need to use them anywhere inside the engine or gearbox either - they are full of oil! Safest to use them on tinware for show.

One of the threads on my 1961 Navi is 7mm! Obviously not original, which is why a thread gauge is absolutely essential. Over the year bodgers may haver been at work or just used whatever was to hand and nearly fitted!