72 replies to this topic

[Spider]

The best thing for bleed nipples I think (and also the brake adjusters, for which I did once have a special square spanner but which I can't seem to find) is the small Knippex wrench pliers. They're actually gripping the thing with positive force and not relying on just being the right size so you get a much better purchase and no risk of rounding.

 

My socket set dates from the 90s and has a full set of metric and imperial everything, and before getting my Mini sorted a few years ago, I got some imperial ratchet spanners (very useful for the hard-to-reach things like the fuel pump and exhaust clamp) and some imperial open/ring spanners, although I had a few from back in the day. They're perfectly easy to get hold of in UK.

 

Here is a conversion table. A 19 is actually within the lower tolerance for a 3/4 (the lower tolerance is usually about 0.05mm), so they are really interchangeable, but at the upper end, according to ISO, spanners are allowed to be about 0.2mm too big (the exact amount varies according to the size). That means a 5 on a 3/16 is just about OK, an 8 on a 5/16 is fine, as is a 16 on a 5/8-- if you have a 16, 17 is a much more common size. You might get away with a 13 on a 1/2, but I don't like it. YMMV.

 

inches      mm          rounded-up  too big by (in mm)

3/16    4.762   5       0.238
1/4     6.350   7       0.650
5/16    7.938   8       0.062
3/8     9.525   10      0.475
7/16    11.112  12      0.888
1/2     12.700  13      0.300
9/16    14.287  15      0.713
5/8     15.875  16      0.125

11/16   17.462  18      0.538
3/4     19.050  20      0.950

 

 

That's a great little chart, thanks for posting it here.

 

What also needs to be kept in mind is that spanners aren't vernier accurate either, they are purposely made a wee bit over size to allow for some light corrosion, gunk, small burrs and an easy fit, ie, if you tied to fit say a 1/2" spanner to a 1/2" Hex and these were exact sizes or even if they had 2 thou clearance, you'd curse the spanner every time you picked it up. I've not looked in to it too closely to see what the rule of thumb for these clearances are, but it's there and on a sliding scale depending on the sizes.

[mbolt998]

 

The best thing for bleed nipples I think (and also the brake adjusters, for which I did once have a special square spanner but which I can't seem to find) is the small Knippex wrench pliers. They're actually gripping the thing with positive force and not relying on just being the right size so you get a much better purchase and no risk of rounding.

 

My socket set dates from the 90s and has a full set of metric and imperial everything, and before getting my Mini sorted a few years ago, I got some imperial ratchet spanners (very useful for the hard-to-reach things like the fuel pump and exhaust clamp) and some imperial open/ring spanners, although I had a few from back in the day. They're perfectly easy to get hold of in UK.

 

Here is a conversion table. A 19 is actually within the lower tolerance for a 3/4 (the lower tolerance is usually about 0.05mm), so they are really interchangeable, but at the upper end, according to ISO, spanners are allowed to be about 0.2mm too big (the exact amount varies according to the size). That means a 5 on a 3/16 is just about OK, an 8 on a 5/16 is fine, as is a 16 on a 5/8-- if you have a 16, 17 is a much more common size. You might get away with a 13 on a 1/2, but I don't like it. YMMV.

 

inches      mm          rounded-up  too big by (in mm)

3/16    4.762   5       0.238
1/4     6.350   7       0.650
5/16    7.938   8       0.062
3/8     9.525   10      0.475
7/16    11.112  12      0.888
1/2     12.700  13      0.300
9/16    14.287  15      0.713
5/8     15.875  16      0.125

11/16   17.462  18      0.538
3/4     19.050  20      0.950

 

 

That's a great little chart, thanks for posting it here.

 

What also needs to be kept in mind is that spanners aren't vernier accurate either, they are purposely made a wee bit over size to allow for some light corrosion, gunk, small burrs and an easy fit, ie, if you tied to fit say a 1/2" spanner to a 1/2" Hex and these were exact sizes or even if they had 2 thou clearance, you'd curse the spanner every time you picked it up. I've not looked in to it too closely to see what the rule of thumb for these clearances are, but it's there and on a sliding scale depending on the sizes.

 

 

This was the chart I found:

 

https://cdn.standard...SO-691-1983.pdf

 

I thought at first that the "min" column meant your spanner was allowed to be a tiny bit smaller than the nut is supposed to be. But now I'm wondering if that's right. When it says "0.04 min and 0.24max" for the 1/2", it might mean that the 1/2" spanner must be between 0.04mm too big and 0.24mm too big. As you say, if it was too small there's a real risk it wouldn't fit at all.
 

[68+86auto]

 

 

The best thing for bleed nipples I think (and also the brake adjusters, for which I did once have a special square spanner but which I can't seem to find) is the small Knippex wrench pliers. They're actually gripping the thing with positive force and not relying on just being the right size so you get a much better purchase and no risk of rounding.

 

My socket set dates from the 90s and has a full set of metric and imperial everything, and before getting my Mini sorted a few years ago, I got some imperial ratchet spanners (very useful for the hard-to-reach things like the fuel pump and exhaust clamp) and some imperial open/ring spanners, although I had a few from back in the day. They're perfectly easy to get hold of in UK.

 

Here is a conversion table. A 19 is actually within the lower tolerance for a 3/4 (the lower tolerance is usually about 0.05mm), so they are really interchangeable, but at the upper end, according to ISO, spanners are allowed to be about 0.2mm too big (the exact amount varies according to the size). That means a 5 on a 3/16 is just about OK, an 8 on a 5/16 is fine, as is a 16 on a 5/8-- if you have a 16, 17 is a much more common size. You might get away with a 13 on a 1/2, but I don't like it. YMMV.

 

inches      mm          rounded-up  too big by (in mm)

3/16    4.762   5       0.238
1/4     6.350   7       0.650
5/16    7.938   8       0.062
3/8     9.525   10      0.475
7/16    11.112  12      0.888
1/2     12.700  13      0.300
9/16    14.287  15      0.713
5/8     15.875  16      0.125

11/16   17.462  18      0.538
3/4     19.050  20      0.950

 

 

That's a great little chart, thanks for posting it here.

 

What also needs to be kept in mind is that spanners aren't vernier accurate either, they are purposely made a wee bit over size to allow for some light corrosion, gunk, small burrs and an easy fit, ie, if you tied to fit say a 1/2" spanner to a 1/2" Hex and these were exact sizes or even if they had 2 thou clearance, you'd curse the spanner every time you picked it up. I've not looked in to it too closely to see what the rule of thumb for these clearances are, but it's there and on a sliding scale depending on the sizes.

 

 

This was the chart I found:

 

https://cdn.standard...SO-691-1983.pdf

 

I thought at first that the "min" column meant your spanner was allowed to be a tiny bit smaller than the nut is supposed to be. But now I'm wondering if that's right. When it says "0.04 min and 0.24max" for the 1/2", it might mean that the 1/2" spanner must be between 0.04mm too big and 0.24mm too big. As you say, if it was too small there's a real risk it wouldn't fit at all.
 

 

 

The fasteners also have a specified tolerance.

There are brands like Nepros (KTC) who sell tools which are even smaller than the standard specifies in order to get the best fit possible.

[mbolt998]

The fasteners also have a specified tolerance.

There are brands like Nepros (KTC) who sell tools which are even smaller than the standard specifies in order to get the best fit possible.

 

Interesting, I didn't know that. You might also have better luck with a 19 on a 3/4 for this reason, or even a 12 on a 7/16. Sometimes if something is stuck and you're running out of options just bashing on whatever you have that's a bit too small can be a last resort.

[68+86auto]

 

The fasteners also have a specified tolerance.

There are brands like Nepros (KTC) who sell tools which are even smaller than the standard specifies in order to get the best fit possible.

 

Interesting, I didn't know that. You might also have better luck with a 19 on a 3/4 for this reason, or even a 12 on a 7/16. Sometimes if something is stuck and you're running out of options just bashing on whatever you have that's a bit too small can be a last resort.

 

 

12mm is nowhere near close enough for 7/16. But yes, there are combinations which can give a tighter fit than the correct tool.

Edited by 68+86auto, 03 July 2025 - 06:20 AM.

[Steam]

One thing not mentioned yet is POB, or what I call Previous Owner Bodges.
Randomly, today I had to use both a 3/8 and a 10mm on the same item with 2 bolts.

[sonscar]

I have imperial and metric vice grips and adjustables.Steve..

[Ethel]

If bleed screws are likely to put up a fight you're better off with something like a tommy bar to get equal and opposite torque. The hollow centre gives 'em less resistance to shearing. A manual impact driver could be even better, but it'd be difficult to get it to impact the screw and not the caliper or cylinder.

[sonscar]

I like a socket on a bleed nipple to start it.Steve.

[DeadSquare]

@ Ethel & sonscar.

 

The man on the Girling stand at the 1961 Earls Court Motor Show, told me that Bleed Nipples should only be nipped tight.

Brake fluid loves water, and the water in the fluid in the threads is a catalyst for rust.

If you can slacken your bleed nipples without shearing them, a job for the weekend is to clamp the hose, remove the nipple, Copaslip it, wrap it twice anti clockwise in PTFE tape, reinsert it and bleed the cylinder, on each wheel.

[mbolt998]

If bleed screws are likely to put up a fight you're better off with something like a tommy bar to get equal and opposite torque. The hollow centre gives 'em less resistance to shearing. A manual impact driver could be even better, but it'd be difficult to get it to impact the screw and not the caliper or cylinder.

They're also a lot easier if you get the whole cylinder out of the car and in a vice. Mine all came out fine after 20+ years (but I ended up replacing all the cylinders anyway, because a couple of them were weeping a bit after I first put it all back together).

[unburntfuelinthemorning]

It doesn't matter whether you call it 5 pence or a shilling, governments counterfeit them and then compensate themselves to our disadvantage by taxing the devaluation as a capital gain.

 

 

Never trust the government.

 

You sound like someone who understands that it's not that prices are rising but that the pound is rapidly being devalued.

[DeadSquare]

 

It doesn't matter whether you call it 5 pence or a shilling, governments counterfeit them and then compensate themselves to our disadvantage by taxing the devaluation as a capital gain.

 

 

Never trust the government.

 

You sound like someone who understands that it's not that prices are rising but that the pound is rapidly being devalued.

 

Off topic.

 

Because of this hot dry summer, Cattle Farmer's winter fodder is in short supply and poor quality, so it will need to be supplemented with extra Barley, but although Barley yields were also affected, the price of a tonne is only £140-00.

 

In 1953, at just about this time of year with Coronation banners and Union Jacks fluttering from lamp posts I can remember going round the corn merchants in the market and my uncle getting £17-50  a ton for his Barley.

 

In 72 years, the value of the pound has sunk.  For Mars bars and petrol, 30 times.  For beer, 50 times, thanks to Thames Water, but for Barley it has only sunk 8 times.

 

I don't know the relative price of Mini parts, but unless Barley somehow catches up 4 times its price, I won't ever be able to do up my Minis.