TR2/3/3A Does this fitting need a Whitworth wrench?

[karls59tr]

The fitting is for the copper vacuum tube at the bottom of the front SU. carb,,, 5/16th dosn't fit. I've heard that the TR3 has a few nuts and bolts that are Whitworth and I was wondering if this was one of them?

 

[mctriumph]

You are on one of the few metric fittings Tr's have. try 9mm.
Mad dog

 

[karls59tr]

You are on one of the few metric fittings Tr's have. try 9mm.
Mad dog

Why would the British use a metric fitting in 1959?

 

[PAUL161]

Probably leftover parts in the nut & bolt bin?

 

[JHaydon]

I just went out and tested mine, a 1/8 W - 3/16BSF wrench is correct.

According to my crossover lists, 1/8 W measures 0.340" across the flats and 9mm measures 0.354" so a 9mm could maybe work in a pinch, as long as the nut isn't too tight. A 9mm wrench will be a looser fit than, say, an 8mm wrench on a 5/16" hex 0.014" larger vs 0.0025" larger). On top of that, wrenches are typically a hair oversized (which is why a 19mm socket fits 3/4" lug nuts, despite 19mm being 0.002" smaller than 3/4").

If this is your first time removing that nut, I'd be very concerned about rounding off the hex with a 9mm wrench.

 

[karls59tr]

I just went out and tested mine, a 1/8 W - 3/16BSF wrench is correct.

According to my crossover lists, 1/8 W measures 0.340" across the flats and 9mm measures 0.354" so a 9mm could maybe work in a pinch, as long as the nut isn't too tight. A 9mm wrench will be a looser fit than, say, an 8mm wrench on a 5/16" hex 0.014" larger vs 0.0025" larger). On top of that, wrenches are typically a hair oversized (which is why a 19mm socket fits 3/4" lug nuts, despite 19mm being 0.002" smaller than 3/4").

If this is your first time removing that nut, I'd be very concerned about rounding off the hex with a 9mm wrench.

I carefully used needle nose pliers and I had the carb removed enough to turn it upside down for easier access.

 

[François]

Don't know whitworth much. Thought it was a function of threads

 

[mctriumph]

My Morgan had whitworth , Most of which are now in the re-cycle bin. Hate them. Nothing
will rust as solidly as a whitworth(more surface area on each thread) /
Mad dog

 

[JHaydon]

Don't know whitworth much. Thought it was a function of threads

Whitworth does indeed refer to the thread size, but in the Whitworth system the hex head size is consistently matched to the thread size. This is partially so that the wrench you use will be the appropriate size (length) to apply "correct" torque for the thread size.

In SAE and metric, there's no standard hex size for a given thread size. You may encounter a bolt with one hex size and a matching nut with a different hex size.

So, instead of calling out the hex size (as SAE and metric systems do), Whitworth wrenches call out the thread size.

Conversion charts as on this page are extremely helpful, I keep laminated copies in each car and in each toolbox:
> Convert,compare all Imperial tool,nut,bolt and spanner sizes to metric. <

And amplifying on MD's reply, Whitworth threads are easily confused with SAE UNC (coarse) threads because the diameters and (most) pitches are the same. The problems are in the thread angle (55 degrees vs 60 degrees) and the thread root (generous radius vs squared-off). You can thread an SAE nut onto a Whitworth bolt and vice-versa, but it will take effort and will usually ruin both pieces of hardware.

 

[donbmw]

On my 59 it is 5/16.

 

[DrEntropy]

And amplifying on MD's reply, Whitworth threads are easily confused with SAE UNC (coarse) threads because the diameters and (most) pitches are the same. The problems are in the thread angle (55 degrees vs 60 degrees) and the thread root (generous radius vs squared-off). You can thread an SAE nut onto a Whitworth bolt and vice-versa, but it will take effort and will usually ruin both pieces of hardware.

And: "Cross-threading is Nature's LocTite!"