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MG MGB Technical - Windscreen fixing screws

Hi Guys,
I want to replace the 4 short screws CMZ 305 & 4 long screws CMZ 308 that fix the top rail to the bracket & pillar with stainless steel equivalents as the current original (zinc?) are a rusty mess. I believe they should be posi countersunk. Can anyone confirm the thread (UNF?),diameter & screw length?
Cheers, Charles
Charles9

According to Mo$$, they are cross-slot UNC, which seems a bit odd. I don't fancy taking one out to check it, in case it snaps off.


Dave O'Neill 2

Odd indeed, they screw into a steel bracket not alloy.

B&G describes CMZ306 and 308 as Pozi countersunk UNF, otherwise sizes as on that chart. Confirmed (mine have been out at least twice) against a No.10 UNF tap.
paulh4

Hi Guys,
Thanks for your comments. I have assumed up to now that the screws would be UNF as the only screws that were UNC when i did my under bonnet refurb 18 were the bolts that hold the air filter pots onto the HIF carbs.
Cheers, Charles
Charles9

UNC is generally only used when the screw goes into aluminium alloy or cast iron. Metals like those need a coarser thread than UNF.
Mike Howlett

This thread was discussed on 23/08/2019

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