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I hope you guys don't frown on this post too much but I wanted to ask something pretty basic on spanners..:stupid:

I have a whole box of them some are in MM like 15mm, 17mm others have fractions 11/16 etc... I normally find the best fit and use that one...

How can i decipher the fraction ones and whats the difference between metric and imperial and are all the nuts on are Z's imperial or metric or a mixture??

Another question, i am trying to remove the pipe on the slave cylinder (on the right side of the gearbox). the pipe to the slave cylinder connects via a bolt, i think i need to use a flared spanner... i cant seem to find the right spanner to fit... on the case of the slave cylinder there is an inprint of 11/16, i thought this may be the size of the spanner but it doesnt fit.. what size is it??? :stupid: :stupid:


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All the fasteners on a Z are metric unless they've been replaced by someone (like some that I've found while stripping down my car this week). Anything with a fraction (i.e., 11/16) will be "imperial" in inches. All the metric ones will be even millimeters (although I think I've seen some of the really little ones, like 4.5mm be in half mm). A few of the metric/imperial sizes are pretty close, like 13mm and 1/2 inch. You can convert by using 1 inch = 25.4 mm.

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On my US Spec 240Z's all nuts and bolts (except some for the dealer add-on A/C stuff) has been Metric.

WHen you say "pipe" I assume that you are referring to the fitting where the hard metal hydraulic line (pipe) connects to the rubber hose that goes to the slave cylinder. The fitting on the "pipe" should be for a 10mm spanner, I do not recall the size for the fitting on the hose side of the cionnection.

The measurement you see on the slave cylinder is the diameter of the piston bore of the slave cylinder itself.

Here is a LINK to some information, including two freeware programs for converting to all sorts of metric measurements.

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Carl, Mark - thank you guys :)..

Imperial is Inches, Metric is in MM and 240Z bolts are Metric.... Phew! Got it now..

Carl - thank you for the links... excellent and helpful as ever.

Thanks also for letting me know what the 11/16 meant it really did confuse me!!:stupid::stupid:

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I tried to download the first calculator and it wasn't available, but I put together a couple tables on a spreadsheet. The first gives the decimal inches equivalent for every metric size likely to be on a Z car. The second gives the "imperial" fraction in inches and it's decimal equivalent. Thus, for any imperial size you can look for a decimal equivalent in metric and see how close you are. As an example, look up 27mm and see that it is between 1 and 1 1/8 inches, or 19mm is very close to 3/4 inches, but is a little bigger, so a 3/4 socket probably won't work for 19mm, but just barely. If you have a sloppy 6 point 3/4 inch socket, it might work.

Anyway, hope this is helpful. :classic:

mm inches

4 0.1575

4.5 0.1772

5 0.1969

5.5 0.2165

6 0.2362

7 0.2756

8 0.3150

9 0.3543

10 0.3937

11 0.4331

12 0.4724

13 0.5118

14 0.5512

15 0.5906

16 0.6299

17 0.6693

18 0.7087

19 0.7480

20 0.7874

21 0.8268

22 0.8661

23 0.9055

24 0.9449

25 0.9843

26 1.0236

27 1.0630

inches (fraction) inches (decimal)

1/4 0.2500

5/16 0.3125

3/8 0.3750

7/16 0.4375

1/2 0.5000

9/16 0.5625

5/8 0.6250

11/16 0.6875

3/4 0.7500

13/16 0.8125

7/8 0.8750

15/16 0.9375

1 1.0000

1 1/8 1.1250

1 1/4 1.2500

1 3/8 1.3750

1 1/2 1.5000

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Originally posted by mdbrandy

3/4 0.7500

13/16 0.8125

7/8 0.8750

1 0.9375

1 1/8 1.0000

1 1/4 1.0625

1 3/8 1.1250

1 1/2 1.1875

Not to be picky, but some of those seem to be off. For instance, 1 inch is roughly equivalent to 1.0000, not 0.9375. I'm fairly certain that 1 1/4 is actually 1.25. It looks like the 1/16ths got dropped from the left side after 7/8.

Isn't metric a lot easier to deal with?


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Rats! :stupid: You are of course correct. I missed 15/16, and then, in fact, I missed that I had switched to every 1/8 after 1 inch and was still only adding 1/16! (I don't think you'll see 1/16 increments after 1 inch anyway). So, I think I have the table right this time. Unfortunately, I can't figure out how to make a good table right now. I tried saving some HTML code to make the table, but it made the post too long. Oh well, probably not that important.

Thanks for catching my mistake!

Oh, and metric is MUCH better than SAE/imperial, but I'm a US-educated engineer, so I was brought up with both.

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I've gone back to look at the bolt on the hose which screws onto the slave cylinder and a 17mm spanner seems a little bit too loose and a 15mm is not big enough.. Is there such thing as a 16mm spanner?? My tool set goes from 15mm to 17mm and I am wondering why???

I suppose I can always try an Imperial 5/8, glad i can use your table Mark!:)

By the way, the bolts and hoses on my car are all original.. so its strange that I'm having this much trouble to find the correct spanner!

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I just went out and crawled under my car to see what the slave cylinder connection size is. You're right - 17mm seems a little loose. However, I have a 16mm wrench (spanner), and it is too small! I tried 5/8 inch too, and it is too small. So, best guess is that it is a 17mm fitting, but since it is thin, it feels loose in a regular wrench. Usually, it's a good idea to use flare wrenches on this type of fitting, but mine only go to 14mm. I have to take it off soon anyway (I'm going to lift the engine/tranny within the month), so it's good to know :classic: .

Anyway, that's my 2 cents. My car is an 11/69 240Z, but I know the tranny isn't original.

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thanks so much for all the effort you've put in trying to help me out! And also confirming that I am not going mad! LOL

I bought a 17mm flared spanner today and thats too loose too!!So i stopped turning.LOL LOL

I think I will end up going all the way with the flared 17mm one but i have a horrible feeling its going to ruin the thread on that bolt as it is pretty tight. Then I'll be in trouble :stupid:

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You may find a whitworth spanner will fit. Don't think Nissan would have ever used whitworth though.

You could go and buy a crappy (but not too crappy) 16 mm spanner and carefully grind it until it's the right size.

PS. whitworth is a wacky old british spanner sizing system that refers to the thread size rather than the bolt head size. It seems to be dead standard everywhere but the Australian building industry.

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