Battery terminal posts.

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jakeroyd

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My marine battery has connections where a conventional tapered post is fitted along with a threaded post where you connect your auxiliaries etc.
I bought some M8 nuts last year for mine which did not fit.
After some Googling I established that the posts are in fact 5/16" 18 UNC.

Damm Murricans.

Just so you know.

My battery is not this one but the posts are similar
http://www.batterymegastore.co.uk/product/XV31/?ref=bmuk&gclid=CMus1dia88MCFYSWtAodi30Apw
 
Interesting pvb.
An M8 thread and a 5/16" UNC thread are very similar in terms of od , pitch and angle , so for me an M8 almost fits but not quite.
 
jakeroyd said:
Interesting pvb.
An M8 thread and a 5/16" UNC thread are very similar in terms of od , pitch and angle , so for me an M8 almost fits but not quite.
Click to expand...

Well you've said yours aren't M8, which is fine. But the specs for many batteries actually say "M8".
 
jakeroyd said:
My battery is not this one but the posts are similar
http://www.batterymegastore.co.uk/product/XV31/?ref=bmuk&gclid=CMus1dia88MCFYSWtAodi30Apw
Click to expand...

Interesting. I have a pair of alphalines (from batterymegastore) in the garage ready to fit. Although I don't use them, the screw terminals are not M8.

The post terminals are ALSO not the 'usual' UK size ...... I had to open up brand-new clamps significantly to get them to fit.

A real pain all round. I wonder what market these batteries were originally destined for?
 
pvb said:
Well you've said yours aren't M8, which is fine. But the specs for many batteries actually say "M8".
Click to expand...

+1

Lots of M8 studs in my new electrical system.

The batteries though actually had M8 female threads, which you screw a bolt down into. Not come across this before, but I like it. Along with heatshrink-covered crimped lugs on the cables, it gives a really nice neat connection compared to the bulky old post terminals.

Pete
 
prv said:
+1

Lots of M8 studs in my new electrical system.

The batteries though actually had M8 female threads, which you screw a bolt down into. Not come across this before, but I like it. Along with heatshrink-covered crimped lugs on the cables, it gives a really nice neat connection compared to the bulky old post terminals.

Pete
Click to expand...

Those M8 female threads do indeed seem a neat way of attaching a cable, but are they M8 female threads directly into lead posts, or are there some sort of inserts in there ? I'd have thought a thread into a (very ductile) lead or lead alloy post would be extremely susceptible to overtightening / stripping.
 
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Holy thread revival.

Thought I would ask this in the same place to keep the information together. I have posts that "look" very close to 10mm. For car work I have a box of M10 Metric Fine nuts which do not fit. The posts could be M10 standard but they do look quite coarse. Any ideas what the could be?
 
3/8 unf?
'M10 fine' comes in two flavours, 1.25 and 1mm pitch.

Personally, when something like this excedes my patience, I will run a tap or die over it and then it will be something sensible.
Get a thread pitch gauge, for a few quid, it's a worthwhile tool for avoiding these issues.
 
mlines said:
Holy thread revival.

Thought I would ask this in the same place to keep the information together. I have posts that "look" very close to 10mm. For car work I have a box of M10 Metric Fine nuts which do not fit. The posts could be M10 standard but they do look quite coarse. Any ideas what the could be?
Click to expand...

M10 coarse has pitch of 1.5 mm
M10 fine has a pitch of 1.25 mm
the M10 sparkplug thread has a pitch of 1.0 mm

3/8" UNC is a little smaller in diameter and has a pitch of 16 tpi ( approx 1.59mm)

3/8" UNF has a pitch of 24 tpi ( approx 1.06 mm)
 
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As these are battery posts I'm sure that the battery will be less than 20 years old so I would have thought that imperial is an unlikely prospect so they will be 10mm coarse. However do check both as my posts are 10mm coarse +ve and 8mm coarse -ve.

Richard
 
RichardS said:
As these are battery posts I'm sure that the battery will be less than 20 years old so I would have thought that imperial is an unlikely prospect so they will be 10mm coarse. However do check both as my posts are 10mm coarse +ve and 8mm coarse -ve.

Richard
Click to expand...

Imperial is actually pretty common on battery posts Richard, particularly the ones that are similar to M8. Either on the batteries themselves, or on the clamp on terminals.
 
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