14 replies to this topic

[Spannerhead]

It's been over 20 years since I've messed about with a car that wasn't all metric. So now I'm putting the engine back in the MPi mini and the mixture of different threads is driving me a bit nuts. Lots of the bolts that came off when is dismantled the engine bay are pretty knackered, so I want to replace them with new shiny ones.

So the very basic question from a man who should know better, is what are the standard types of thread I'll be encountering? I have an excellent Nut and Bolt store down the road from me who do mixed bags, both UNF and UNC, do I need both, or just one type?

[Guess-Works.com]

With an MPi, really depends on which bits you're talking about...

Anything related to the engine will be imperial, something which are related to the modern MPi bits and bobs are more likely to be metric...

[Spannerhead]

My point exactly!!! It's mostly the bolts that attach all the brackets for the alternator etc, clutch slave cylinder, manifold studs, etc, etc ....

[Ethel]

You'll develop an eye to judge by the coarseness of the pitch.

UNF for fine UNC for coarse, Metric falls somewhere between the 2 (closer to UNC). Look at the bolt head too, metric often has an M on it and has the strength grade in numbers, e.g. 8.8
Imperial stuff has lines (3 or 6 of 'em), a bit like spokes, to show the grade. UNC is typically used for threads in low strength components - castings etc.

Bolt Depot - Bolt Grade Markings and Strength Chart

[Spannerhead]

Thanks guys, I'll buy a bag of both then!

[Spannerhead]

ARGHHHHHHHHHHHHHHHHHHH

See this is exactly what I mean. I now have a mix bag of each of UNC and UNF from my local Nut and Bolt shop. NEITHER are the same as the bolts holding on the alternator bracket, the thread pitch is different. WHY???????????? What other threads are there?????????

This is why I hate British engineering, make things as crap as possible from as many odd mix of parts as possible ..... makes me want o go back to Jap/European cars ......

[Guess-Works.com]

Ah, that's because on the MPi, the alternator bracket is bolted to the head which is unique to the MPi, so is therefore probably Metric...

[Spannerhead]

But the bracket I'm bolting is to the block, is that metric to?

[minidaves]

hate mpis they use all 3 thread types metric for the modern part and unf in some of it and unc into other bits, oh the joy

dave

[SolarB]

ARGHHHHHHHHHHHHHHHHHHH

See this is exactly what I mean. I now have a mix bag of each of UNC and UNF from my local Nut and Bolt shop. NEITHER are the same as the bolts holding on the alternator bracket, the thread pitch is different. WHY???????????? What other threads are there?????????

This is why I hate British engineering, make things as crap as possible from as many odd mix of parts as possible ..... makes me want o go back to Jap/European cars ......

But if all the threads were one type where would the fun be?

[MRA]

hate mpis they use all 3 thread types metric for the modern part and unf in some of it and unc into other bits, oh the joy

dave

Dave, you forgot to mention Whitworth

[SolarB]

Dave, you forgot to mention Whitworth

Is that the flywheel bolt?

[Ethel]

There is the Moss Catalogue there's a list of fastener part numbers by thread type near the back.

You can always console yourself with the fact that the two UN threads are superior to one universal metric type and that there is some intelligence behind Rover keeping compatibility between new revisions and the models they replace.

[Spannerhead]

Cheers guys, input always appreciated.

'You can always console yourself with the fact that the two UN threads are superior to one universal metric type' - funny how it seems to be ok for the rest of the world though! (I do of course exclude the US in that statement, who's car making is on a par with us Brits...)

So am I right in saying if I have a bag each of metric, UNC and UNF one of the buggers will fit everything on a Mini except the odd special bolt like the Flywheel one .... ?

[Ethel]

Well the Yanks invented 'em and we standardised them first, so if anyone is to blame it's the rest of the world. I find it's often better to buy the specific bolts, or studs, when you need them to get the right lengths & shanks. A few 1/4, 5/16 & 3/8unf nuts are handy though and you could keep a few short screws for through bolts.