What size wrench or socket for a 5mm X 0.8 nut?

[Lucid Moments]

Never run across one of these before but there is one on my BMW starter. One of the studs for a wire. My 8mm is too small and my 9mm is too big. I am making due with a 5/16" socket but I am afraid of a matter - anti-matter explosion by mixing standard tools and metric fasteners.

 

[Wrench97]

5/16" is 7.95mm so actually smaller then 8mm I think you're playing with tolerances of the socket size or worn socket?
Is there corrosion on the nut?

 

[Lucid Moments]

5/16" is 7.95mm so actually smaller then 8mm I think you're playing with tolerances of the socket size or worn socket?
Is there corrosion on the nut?

The nut is actually new. And I don't use either the 8mm or 9mm enough for them to be worn at all. So you think it is just likely I got a freak undersized 8mm?

 

[Wrench97]

The nut is actually new. And I don't use either the 8mm or 9mm enough for them to be worn at all.

I was thinking the 5/16 socket was worn, though if a new rebuild it could very well be a SAE nut I've seen it before.

 

[M6erfan]

8mm. 8mm. 8mm.

Try another socket, or 8mm wrench, on it.

 

[Wamsutta]

8mm. 8mm. 8mm.

Try another socket, or 8mm wrench, on it.

That makes sense because 6mm usually takes a 10mm socket.

 

[M6erfan]

That makes sense because 6mm usually takes a 10mm socket.

It also makes sense because 8mm wrench size conforms to DIN, ISO, ANSI, JIS 5mm thread standards.

 

[ricleh]

I have 5/16-18 nuts on my 2001 530i. They hold on the child restraint latches. It took me a while to figure out they weren't metric. They came that way from the factory.

 

[M6erfan]

I have 5/16-18 nuts on my 2001 530i. They hold on the child restraint latches. It took me a while to figure out they weren't metric. They came that way from the factory.

Huh. I had a 2001 530i Sport, one of my favorite cars ever! I never came across those bolts. That's a very odd size for the germans to use. Must be a reason behind it.

 

[NFH2740]

I have come across M5 fasteners that had 7mm heads.

 

[RTM]

I have 5/16-18 nuts on my 2001 530i. They hold on the child restraint latches. It took me a while to figure out they weren't metric. They came that way from the factory.

I had a 2001 530i Sport, one of my favorite cars ever! I never came across those bolts. That's a very odd size for the germans to use. Must be a reason behind it.

Maybe a US made car, with a US required feature, that the Germans didn’t engineer in, so a US based engineer did the design work?

Or a port added option?

 

[4xdog]

My vintage Diamond 4-inch adjustable wrench gets used once in a while for things like this. It's not a toy, although it looks like one.

 

[Stubby1743]

Under all three standards, an M5 nut/bolt head should be 8mm.

See this chart:-

Bolt Depot - Metric Bolt Head/Wrench Size

www.boltdepot.com

 

[goldtang]

May be 11/32 odd ball yes but who knows with car manufacturers

 

[2ndGearRubber]

Maybe a US made car, with a US required feature, that the Germans didn’t engineer in, so a US based engineer did the design work?

Or a port added option?

There is weird stuff that pops up.

I have seen many late model vehicles with SAE hose sizes for brake booster lines printed right on the side of the rubber.

My assumption is someone in the design team dropped the ball to make the hard formed plastic abomination brake booster line, so the executive decision was made to buy a warehouse full of hose to get the project out the door. Thus at some point this hose all needs used up, so the tell the engineering dept "hey if you can make something use 3/8 ID rubber hose easily, do it so we can get rid of this ********". It's not like the booster lines fit multiple cars with the addition of the 3/8 line to make the manifold connection more adaptable, so IMO its not plausible as an actual design choice.

 

[ricleh]

Maybe a US made car, with a US required feature, that the Germans didn’t engineer in, so a US based engineer did the design work?

Or a port added option?

Very possible.

 

[decableguy2000]

May be 11/32 odd ball yes but who knows with car manufacturers

I was going to mention this, used to common on electrical connections.

 

[goldtang]

Was my thoughts, I do have a 1/4 drive socket in that size and a couple more sockets of strange sizes I have not used often but have been good to have

 

[Luciferi]

Huh. I had a 2001 530i Sport, one of my favorite cars ever! I never came across those bolts. That's a very odd size for the germans to use. Must be a reason behind it.

Seat belts at one time had a specific bolt requirement that was sae. I don't know if this is still true or not. I can imagine child safety latches falling in the same restraints category.

All my old Honda service manuals list the bolt sizes in diagrams and seat belts we’re always in sae.

 

[Lucid Moments]

In this case I know it was a 5mm nut. It goes on the top stud on the starter solenoid for my '87 BMW 325is. I lost the original nut off it so took the starter to the hardware store and found the 5mm nut to fit on it. I only had one 8mm socket and threw it across the shop in irritation and it is a crappy location to put a wrench on. I finished the job with the 5/16 socket I was using. I am not far from spending a day cleaning out the shop and I hope to find the socket then.

 

[MBfreak]

99,9 % of what I have worked on was 8,0 mm hex.
For some reason some old NAF ( swedish maker of pneumatic PI controllers ) used 11/32, ie appr 9,7 mm .
Swedish made.
But that was 55 years ago

Ola