Fork stanchion 1 1/8" inner thread top

[rudelan_LAPSED]

Here is my question: on a 1954 fork stanchion 1 1/8", what are the characteristics of the inner thread at the top of the tube?

15/16" x 20 tpi ?

Thanks Ruddy

[rudelan_LAPSED]

I got the answer from a top nut manufacturer for this 1 1/8" fork.
it's 15/16" 20 tpi but BSF, BSW or? I don't know.
I'm looking for a pipe thread pad to redo this inner thread.

[Greybeard]

Hello, Rudelan.
It sounds like it would be a Whitform thread (55 degree thread angle like BSW) at that size - dies available here, though at that size I would do the initial thread cutting on the lathe and use a die to clean it up if necessary. Whilst they don't list taps in that size, it can still be worthwhile contacting them as they do have some second hand stock. I have found them to be very helpful in the past.

https://www.tracytools.com/taps-and-die ... ct_id=1146

Steve

[rudelan_LAPSED]

Hello Steve,

Many thanks!

Rudelan

[Andy51]

Almost certainly whitworth form thread - UK standard unless otherwise specified, e.g. BSC or BA. BSA and possibly others also used 20 tpi Cycle thread, but AMC to my knowledge only used 26 tpi BSC, hence forks likely to be whit form. If you are cleaning up existing thread, die is fine, but as Steve says, if you are cutting a new thread, do most of the work in a lathe, just using die to finish. Andy

[bitza]

Surely the member would need a Tap if wanted to clean up the internal thread at top end of fork stanchion.

[56G80S]

I'm pretty sure I did this with a thread chaser a very, veryyyyyyyyyyyy, long time ago. Unfortunately, as I'm in lockdown following youngest's illness I can't go to the lock up to check out.

I'll second the comment about Tracy Tools.

I also recall that I couldn't undo them and had to cut the top to fit a large "C" spanner on rather than use the allen key. I used one of the "scrap" nut to make a leg puller for re-assembling . If I find the other one, would it clean up the threads if you ran a hacksaw at right angles to the threads on my scrap nut where the two flat parts are? Feedback from others welcome and if would work I would post to you when I find it. But not supposed to be out of the hutch until a week tomorrow.

EDIT - oops, I forgot about the two sizes. Mine's a 1956 G80S, perhaps my nut is the wrong size? The brain inside it clearly is.

Cheers

Johnny B

[rudelan_LAPSED]

It 's the inner thread of the tube that is damaged. When the top cap is screwed on, at one point it turns in a vacuum and therefore cannot be tightened. I contacted Tracy tools, he doesn't have this tool anymore... thread tap 15/16 20 tpi whitworth.
Rudelan

[56G80S]

I probably confused the issue when I referred to a "nut" when it is in fact a bolt. It was that inside thread that I used a thread chaser on. In my thread substitute "bolt" for every reference to "nut".

Cheers

Johnny B

[Andy51]

Re my earlier post, for die read tap. My apologies. Andy