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mk1 centre speedo housing
https://www.ausmini.com/forums/viewtopic.php?f=2&t=101360		 Page 1 of 1
Author:  MINIRO [ Thu May 26, 2022 3:48 pm ]
Post subject:  mk1 centre speedo housing
The 4x holes/threads on the firewall where the centre speedo mounts to are pretty butchered.

Just checking that they were originally 3/16 UNF thread.

Thank you
Author:  ozmini [ Thu May 26, 2022 4:08 pm ]
Post subject:  Re: mk1 centre speedo housing
No, 10-32 thread.
Author:  Bill B [ Thu May 26, 2022 6:32 pm ]
Post subject:  Re: mk1 centre speedo housing
ozmini wrote:
No, 10-32 thread.


"Ozmini" is right: The screws are properly 10gauge UNF X 32 threads per inch.
But the size is commonly referred to as 3/16inch diameter because it is almost the same.

For some reason, Unified National Fine (UNF) and Coarse (UNC) threads under 1/4inch diameter are sized by machine screw gauge sizes (0 to 12).

3/16inch is 0.1875inch but is not a UNF/UNC size; but 10gauge UNF/UNC is just larger at 0.1900inch.

Sorry to go into details. Hope it helps - it has taken me a long time to get my head around all the different threads used on minis.
Author:  eightfifty [ Thu May 26, 2022 7:42 pm ]
Post subject:  Re: mk1 centre speedo housing
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Author:  Bill B [ Thu May 26, 2022 10:16 pm ]
Post subject:  Re: mk1 centre speedo housing
And while "eightfifty" is on the line about fasteners, a question I'd like explained relates to the use of Pozidrive and Phillips drive screws.
All the BMC Standards specifications in your books mention Phillips drive but from experience I have found that almost all the machine and self-tapper screws on Australian minis are actually Pozidrive headed. And my main source for new Pozidrive screws is from Mini Spares UK- so they were used in UK assembly too.
Are they both considered to be interchangeable?
Author:  eightfifty [ Thu May 26, 2022 10:29 pm ]
Post subject:  Re: mk1 centre speedo housing
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Author:  DavidE [ Fri May 27, 2022 8:05 am ]
Post subject:  Re: mk1 centre speedo housing
Bill B wrote:
And while "eightfifty" is on the line about fasteners, a question I'd like explained relates to the use of Pozidrive and Phillips drive screws.
All the BMC Standards specifications in your books mention Phillips drive but from experience I have found that almost all the machine and self-tapper screws on Australian minis are actually Pozidrive headed. And my main source for new Pozidrive screws is from Mini Spares UK- so they were used in UK assembly too.
Are they both considered to be interchangeable?


From Wikipedia:

The Pozidriv, sometimes incorrectly spelled "Pozidrive", is an improved version of the Phillips screw drive. It is designated "Type IA" by ANSI standards.[20] and "Type Z" in ISO documents. The Pozidriv was patented by GKN Screws and Fasteners in 1962.[21][22] It was designed to allow more torque to be applied and greater engagement than Phillips drives. As a result, the Pozidriv is less likely to cam out.[10][23][24] It is similar to, and compatible with, the Supadriv screw drive.[25]

Pozidriv screwdrivers are often designated using the letters "PZ" followed by a size code of 0, 1, 2, 3, 4 or 5 (in order of increasing size).[10] The numbers do not correspond to nominal screw size numbers. PZ1 is normally used on screw diameters from 2-3mm, PZ2 from 3.5-5mm and PZ3 from 5.5mm to 8mm. These sizes roughly correspond to the Phillips head numbers.

Pozidriv screws have a set of radial indentations (tick marks) set at 45° from the main cross recess on the head of the screw, which makes them visually distinct from Phillips screws.[10]

While a Phillips screwdriver has slightly tapered flanks, a pointed tip, and rounded corners, a Pozidriv screwdriver has parallel flanks, a blunt tip, and additional smaller ribs at 45° to the main slots. The manufacturing process for Pozidriv screwdriver bits requires a slightly more complex cutter than that for Phillips, however both can be manufactured in four cuts from a tapered blank.

Pozidriv and Phillips appear broadly interchangeable, but may cause damage if incorrectly used. Pozidriv screwdrivers will jam fit into Phillips screws, but when tightened they may slip or tear out the Phillips screw head. Conversely, while Phillips screwdrivers will loosely fit and turn Pozidriv screws, they will cam out if enough torque is applied, potentially damaging the screw head or screwdriver.[10][23]
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