Clutch Pedal Box Cover Screws - Thread Size?

[Paddy_SP]

Well, I've finally given up trying to find the missing top cover for my clutch pedal box (item 11 in the attached image) - it's in my garage somewhere, but it's successfully managed to evade me by finding somewhere out of sight to hide... So - I've got to make a new one - I finally found a piece of stainless that's the right size (shame it's a piece of box that I'll have to cut up, rather than a nice easy sheet...), but I'm blowed if I can work out what size the screws (item 17) are meant to be as the holes are all clogged up with paint. Anyway - am I correct in thinking that the originals are self-tappers?

[Ex Member]

#10 - 24 machine screws (3/16" UNC).  They are not self tapping.

Edited April 20, 2017 by Red90

[Paddy_SP]

Thank you - that is most appreciated!

[David Sparkes]

I'm going to disagree with Red90 here.

The part number shown in the list extract shown by the OP is 78227.

That number goes back to Series 2 days (at least).
In a Military Parts Manual of April 1964 the screw is described as SCREW self-tapping. Parker Kalon Type 'A. binding hd. No. 10 x 1/2 in.
There is a military Part Number VAOS/Z2/ZB.12653, LR part 78227.

The thread is actually 10x32, a UNF thread, but the shank is shaped to provide a self cutting action.

'Parker Kalon' turned out to be an American firm, and the 10-32 sizing is also an American way of sizing screws.
From this page we are told "10-32 threads are historically the original rack screw type. The term 10-32 comes from Unified and American Screw Threads for Bolts, Nuts, and Machine Screws standards published by ANSI B1.1-1974. The number “10” is simply a size designator with no numerical meaning. The number “32” refers to 32 threads per inch. You can identify a 10-32 screw by measuring the diameter with a ruler at exactly 3/16? (0.190?).".

On an original screw the tapered end that enables it to be self cutting is clearly visible.

My wild theory was that this is the last remnant of the Willys vehicle that was used as the base for the first Land Rovers.
That is a guess, as I know nothing about the pedal arrangements of those vehicles.
A quick search has found this link which shows that Willys did use PK screws in 1937 and 1945.

Who can say what evaluation led the King brothers to decide this was the best fastener for the job? Could it have been something as mundane as access to a stock of US Military surplus, about to be abandoned in the UK or Europe?

You can almost guarantee the correct part from Land Rover Fasteners, but the responsibility for checking with them is with you. Other suppliers merely list whatever they can get to sell.

Regards

[western]

LRSeries do this alternative which supersede the 78227

http://www.lrseries.com/shop/product/listing/3199/SL510031-SCREW-SMALL.html?search=78227&page=1

[Ex Member]

Can you guys not get #10 screws at a hardware store?  They are common as dirt here.  No need to buy any special screws.

As to the above statement they are fine thread.  All I can say is my 1991 Defender 90 original screws are 10-24.  10-32 is insanely fine.

[Kevm]

I think the moral of this story is - when you take things apart put it back together loosely till you are ready to fix it.