MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - carb to manifold bolts 1500

I am 100 percent sure this has been asked very recently but I'll be damned if I can find it in the archive!

So, what thread are the bolts that hold the carbs onto the 1500 manifold? And why aren't they UNF thread like the rest of the car!?

Cheers all,
Malcolm
Malcolm Le Chevalier

yes it has

I can't remember

think it's mentioned on a John Twist video too
N Atkins

ah ha, found the answer, gotta love rimmerbros for putting all the bolt dimensions on their site. excellent.

http://www.rimmerbros.co.uk/Item--i-GRID005596

5/16ths UNC. Still doesn't explain why its not UNF but hey ho!

Malcolm
Malcolm Le Chevalier

probably purchasing ordered a million of the wrong bolt and they had to be used to cover the mistake :)
N Atkins

The inlet manifold is alloy hence unc. They use a coarse thread in softer metal.

Bit of googleing and....

Coarse Thread Series, UNC/UNRC: The coarse thread series UNC/UNRC is the most commonly used thread system used in the majority of screws, bolts, and nuts. It is used for producing threads in low strength materials such as cast iron, mild steel, and softer copper alloys, aluminum etc. The coarse thread is also used for rapid assembly or disassembly.

Fine Thread Series, UNF/UNRF: This is used for applications that require a higher tensile strength than the coarse thread series and where a thin wall is required.

Hope that helps.
J White

no

what's UNRC and UNRF please
N Atkins

aaaaah. very interesting thanks J, surprised I have not heard/read that before.

Malcolm
Malcolm Le Chevalier

If you ever work on a Mini/Metro you will find a number of UNC threads on ally parts.
Robert (Bob) Midget Turbo

Threads into alloy are usually a coarse thread. If you had ever owned a 1960's British motorbike you would know that!
Guy

Hi Nigel,

The R stands for round.... Unified Round Course or Fine. Basically this means the thread is not a sharp V but has a radius at the trough and peak... commonly occurs when you roll a thread rather than cut it. So really all the nuts and bolts you buy should be specified as UNRC/F but it makes no difference... it will still fit!

The most interesting thing about UNF or UNC is they have exactly the same thread specification as Modern British Metric... only all dimensions including pitch are in inches not mm.

I however am a cheap tight yorkshire man and as such was given a hole load of job lot BSF and BSW nuts and bolts by my college when they were "upgrading"... so when I need a new nut and bolt on my car... it could be anything! (obviously not in this application)

C
C L Carter

right, thank you

that's clear now, I think
N Atkins

This thread was discussed between 15/11/2011 and 17/11/2011

MG Midget and Sprite Technical index

This thread is from the archives. Join the live MG Midget and Sprite Technical BBS now