White Elephant Handbrake Help

[wedgeman]

We are trying and struggling to identify the nut (26 on the Jaguar diagram) which secures the handbrake lever on the White Elephant. It is the same umbrella handbrake from what we can gather, as used on some of the SEACs and was originally Series 3 XJ12.



We are pretty sure the thread is 16tpi and of course the nut will be imperial, but more than that we cannot establish.

Does anyone know?

Thanks in advance

[Wedg1e]

There are plenty of thread charts around that should help, like this UNF one:

http://www.carbidedepot.com/formulas-tap-standard....

Just need a Vernier caliper or similar to get dimensions.

[phillpot]

wedgeman said:

We are pretty sure the thread is 16tpi and of course the nut will be imperial

What is the od of the thread?

[stainless_steve]

3/8 UNC would be my bet

[wedgeman]

On the vernier the OD measures very close to 18mm depending on where you measure it, which equates to nothing precise in imperial from what we can see.

[phillpot]

3/4 unf is 16tpi , could your 18mm be a very worn 19mm ?

[stainless_steve]

3/4 unf is close

[wedgeman]

Sounds good, we'll give it a go

[wedgeman]

Ok 3/4 UNF is too big, so any other ideas?

[stainless_steve]

wedgeman said:

Ok 3/4 UNF is too big, so any other ideas?

[Wedg1e]

M18 x 1.5? As you say, I'd expect it to be Imperial but if 3/4 UNF is too large, then maybe the pitch isn't 16tpi - unless you've had a thread gauge on it?

Might be just as quick to machine a bit of 25mm round bar into a hex and internally thread it on the lathe...

[stainless_steve]

Howard,are you sure it's off a Jag.
Could it be off a Toyota Hiace

[wedgeman]

Wedg1e said:

M18 x 1.5? As you say, I'd expect it to be Imperial but if 3/4 UNF is too large, then maybe the pitch isn't 16tpi - unless you've had a thread gauge on it?

Might be just as quick to machine a bit of 25mm round bar into a hex and internally thread it on the lathe...

Might end up doing that Ian if we can't sort it out. Apparently the pitch is meant to be 16tpi but I think we will be getting it checked out on Monday.

[wedgeman]

stainless_steve said:

Howard,are you sure it's off a Jag.
Could it be off a Toyota Hiace

Could be Steve, if so then it might be a metric thread not imperial...

[The Hatter]

I had this problem on my rescued SEAC. I had to cut this nut off to get the mechanism off the car; and as you've found replacements are not available! It appears to be a special for wherever the handbrake came from; I thought Jag but haven't confirmed that - in my case the lever/mechanism has been modified by TVR anyway. I think I found somewhere that it's actually a conduit thread; but it's now obsolete.

It's on the TBD list still for me... the original nut with a suitable repair has been pressed back into service in the meantime.

[hallsie]

The Hatter said:

I had this problem on my rescued SEAC. I had to cut this nut off to get the mechanism off the car; and as you've found replacements are not available! It appears to be a special for wherever the handbrake came from; I thought Jag but haven't confirmed that - in my case the lever/mechanism has been modified by TVR anyway. I think I found somewhere that it's actually a conduit thread; but it's now obsolete.

It's on the TBD list still for me... the original nut with a suitable repair has been pressed back into service in the meantime.

If its a conduit thread then itll be NPT or BSP, I might have some knocking about in the garage, whats the internal diameter?

Stu

[wedgeman]

Sorted it - it is a UNF 11/16 16tpi. Very odd thread size which has even had the East Lancashire engineering shops baffled, so we've ordered a die set and we're going to make one.

Appreciate all the input guys. Many thanks

[adam quantrill]

Surely it's taps you'll be needing?

[wedgeman]

adam quantrill said:

Surely it's taps you'll be needing?

Yes sorry - a tap & die set

[adam quantrill]

Good idea - I have a tap set for Metric and wanted to buy dies as well to go with - but it seems impossible to buy just dies (at a reasonable price) so definitely get both at once!

I suppose I could buy a full set then sell the taps on the flea....

Sod it! Gave up the struggle and bought full set of taps and dies for a fiver, will sell the taps on.

Also don't forget you might not even get your strange diameter in the standard set, so it might be better to just buy the single one from an engineering shop.

Edited by adam quantrill on Tuesday 2nd July 08:28