Any experts on hydraulic union threads?
Discussion
I am confusing myself rotten here... hopefully someone who knows how to measure threads can confirm.
I am attempting to use a land rover clutch slave cylinder on the 400SX. If I can make it fit, it'll provide us all with an alternative part which is much cheaper and more readily available than the standard slave.
Where I am stuck is finding a union which will fit the thread on the slave.
This slave cylinder is supplied with a bleed nipple, and the nipple fits both ports on the cylinder - they seem equivalent.
The nipple measures 11.0mm across the thread ridges, and also has an 11mm AF hex drive. The thread pitch appears to be 1.25mm.
I have got an M10x1mm union which is far too small, and an M12x1mm union which is too big.
The "standard" union on the end of the wedge clutch pipe is also too big to go in, and I suspect it's an imperial size, maybe 9/16"?
Ideally I would like a female union to attach straight onto this, so I can make a short adapter pipe, but I can't find one that will fit either!
So it looks like I need an M11x1.25mm male union? Which seems impossible to find. Any pointers gratefully received.
I am attempting to use a land rover clutch slave cylinder on the 400SX. If I can make it fit, it'll provide us all with an alternative part which is much cheaper and more readily available than the standard slave.
Where I am stuck is finding a union which will fit the thread on the slave.
This slave cylinder is supplied with a bleed nipple, and the nipple fits both ports on the cylinder - they seem equivalent.
The nipple measures 11.0mm across the thread ridges, and also has an 11mm AF hex drive. The thread pitch appears to be 1.25mm.
I have got an M10x1mm union which is far too small, and an M12x1mm union which is too big.
The "standard" union on the end of the wedge clutch pipe is also too big to go in, and I suspect it's an imperial size, maybe 9/16"?
Ideally I would like a female union to attach straight onto this, so I can make a short adapter pipe, but I can't find one that will fit either!
So it looks like I need an M11x1.25mm male union? Which seems impossible to find. Any pointers gratefully received.
Yeah the nut sizes are almost no indicator of thread size with these things - I have some where the nut end is barely bigger than the thread diameter, and others where it is much bigger. In my posts I've been very careful to say which I'm measuring (I hope).
Thanks, I'll send you a mail,, if PH mail is working....
One mystery solved though - the standard one on our V8 wedges with the Girling slave is indeed an M12 x 1. I think this is what was putting me off as it's a bit unexpected.
Thanks, I'll send you a mail,, if PH mail is working....
One mystery solved though - the standard one on our V8 wedges with the Girling slave is indeed an M12 x 1. I think this is what was putting me off as it's a bit unexpected.
Edited by adam quantrill on Sunday 9th November 23:09
Sooo - just received a 7/16" x 20 tpi nut wot I bought off the flea.
It's very close - but no cigar! Still doesn't fit.
Here's a piccie of the fitting one (bottom - the bleed nipple) up against the non-fitting one.
The number of turns per inch/mm seem to be the same. However the thread angle appears to be different.
The overall thread crest diameter is the same to within 0.1mm. (11.9mm)
The other oddity is that I also acquired a female union which purports to be 7/16 x 20 tpi, the new 7/16 one doesn't fir that, but the bleed nipple in the picture does fit it. I wonder if this is the difference between 20tpi and 24tpi? But I can't see a difference in the picture (apart from the helix angle)
It's very close - but no cigar! Still doesn't fit.
Here's a piccie of the fitting one (bottom - the bleed nipple) up against the non-fitting one.
The number of turns per inch/mm seem to be the same. However the thread angle appears to be different.
The overall thread crest diameter is the same to within 0.1mm. (11.9mm)
The other oddity is that I also acquired a female union which purports to be 7/16 x 20 tpi, the new 7/16 one doesn't fir that, but the bleed nipple in the picture does fit it. I wonder if this is the difference between 20tpi and 24tpi? But I can't see a difference in the picture (apart from the helix angle)
It's a Britpart FTC5071
The metric thread could explain a lot.... trouble is it might be M11 and I haven't found these anywhere, the nearest I can get is an M11 tap or die, then cut my own....
Looking at those threads they are not much help, I have M10x1 and M12x1 nuts which don't fit, and the 7/16" one is close but no cigar.
The metric thread could explain a lot.... trouble is it might be M11 and I haven't found these anywhere, the nearest I can get is an M11 tap or die, then cut my own....
Looking at those threads they are not much help, I have M10x1 and M12x1 nuts which don't fit, and the 7/16" one is close but no cigar.
Edited by adam quantrill on Thursday 13th November 08:51
At last - some progress. I have purr-chased an M12 x 1mm female union, that fits the original TVR one perfectly, so I can begin to make a short adapter pipe.
I also got some 7/16" x 24tpi nuts, which start to screw into the slave cylinder, but then the thread gets tight after a few turns, so maybe not exactly correct.
I'll compare them with the other 7/16" one next (which was billed as 20tpi). Almost there - but no cigar....
Well the 24tpi ones are obviously too-fine thread.
The 20 tpi one looks much closer to the bleed nipple to the naked eye, but still it doesn't go in.
The bleed nipple does 5 exact turns in 6.2mm which is 1 turn = 1.24mm so 20.5 tpi.
I think the bleed nipple is looking more like 1.25mm pitch - which is metric, for sure. It's under 1% difference which is within my measurement accuracy.
So that's it - I have exhausted all possibilities, except M11 x 1.25mm. Time to order a die, then, as I don't think I have that in my metric set. £7 on the flea...
Latest update:
Hhmm well this is a turn-up! While the britpart slave has two of these "unknown" possibly M11 threads, the other one I bought before only has one M11, and one slightly smaller one ostensibly for the bleed screw. So... nick the bleed screw from the Britpart one, into the M11 hole, that fits, and a smaller union I had hanging about into the smaller hole - that fits.
So now I can make up the adapter pipe and it should all hang together...
That will give me a less leaky clutch until I can get to the bottom of the M11 (or is it?) malarky.
I also got some 7/16" x 24tpi nuts, which start to screw into the slave cylinder, but then the thread gets tight after a few turns, so maybe not exactly correct.
I'll compare them with the other 7/16" one next (which was billed as 20tpi). Almost there - but no cigar....
Well the 24tpi ones are obviously too-fine thread.
The 20 tpi one looks much closer to the bleed nipple to the naked eye, but still it doesn't go in.
The bleed nipple does 5 exact turns in 6.2mm which is 1 turn = 1.24mm so 20.5 tpi.
I think the bleed nipple is looking more like 1.25mm pitch - which is metric, for sure. It's under 1% difference which is within my measurement accuracy.
So that's it - I have exhausted all possibilities, except M11 x 1.25mm. Time to order a die, then, as I don't think I have that in my metric set. £7 on the flea...
Latest update:
Hhmm well this is a turn-up! While the britpart slave has two of these "unknown" possibly M11 threads, the other one I bought before only has one M11, and one slightly smaller one ostensibly for the bleed screw. So... nick the bleed screw from the Britpart one, into the M11 hole, that fits, and a smaller union I had hanging about into the smaller hole - that fits.
So now I can make up the adapter pipe and it should all hang together...
That will give me a less leaky clutch until I can get to the bottom of the M11 (or is it?) malarky.
Edited by adam quantrill on Wednesday 26th November 23:03
Well I bit the bullet - made up the adapter pipe:
(sorry about the focus but you get the idea)
whipped out the old clutch slave, whacked in the Landrover one, connected the pipe, job's a good 'un!
So I am now Landrover master and slave - and they are cheap as chips! And a nice firm clutch. Happy days.
I'll still order that M11 die to cut some threads just out of curiosity...
(sorry about the focus but you get the idea)
whipped out the old clutch slave, whacked in the Landrover one, connected the pipe, job's a good 'un!
So I am now Landrover master and slave - and they are cheap as chips! And a nice firm clutch. Happy days.
I'll still order that M11 die to cut some threads just out of curiosity...
Yeah one day I'll invest in a digital one ;^) It's actually quite accurate - or at least easily accurate enough to tell the difference between 9, 10, 11 and 12 mm....
I've been using it to measure up bike parts for the son's carbon frame and I haven't ordered anything the wrong size... yet.
I also have my grandad's old Starret micrometer as backup - just have to convert from inches back to mm....
I've been using it to measure up bike parts for the son's carbon frame and I haven't ordered anything the wrong size... yet.
I also have my grandad's old Starret micrometer as backup - just have to convert from inches back to mm....
Bump for rockettvr.
Also I now have digital calipers at last - £7 from chinese ebay.
Also note that this mod has been on the car now for 5 years. I was going to support it with a small bracket off a sump bolt, but never got around to it. The pipe is obviously man enough to support the extra weight of the union.
Also I now have digital calipers at last - £7 from chinese ebay.
Also note that this mod has been on the car now for 5 years. I was going to support it with a small bracket off a sump bolt, but never got around to it. The pipe is obviously man enough to support the extra weight of the union.
Edited by adam quantrill on Monday 13th May 10:59
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