Weird threads used by Volvo in 1950/60’s

[Salop Farmer]

I was wondering if anyone knows if the Philips head screws used to hold the door catch mechanism into the door are available anywhere? The car is a 1960 Volvo PV 544. The screws in question measure 2.4mm dia x 1mm pitch x 12 mm long.
I can find no information on this size.

[Salop Farmer]

Correction sorry : 5.4mm dia x 1mm pitch x 12 mm long

[grumpydad]

Hi
I think you will find the thread form is unc
having a amazon 144 and 240 and 940
it looks like the change over was on the 240 look at the PCD on the wheels
140 inch 240 metric
hopes that helps

[john.wigley]

Not only Volvo, 'Salop Farmer'. Like us, Sweden used a mix of systems until quite recently. In fact, it is still possible to buy a pound of 4" nails from many a lanthandel (country general store) in the remoter parts of the country!

Regards, John.

[eternal optimist]

I wonder if it might be a BA thread?

[142 Guy]

First off, a Volvo of that vintage would not be Metric so best to provide dimensions in decimal inches. A 5.5 mm major diameter is 0.2126 inches which is just short of the diameter of an #12 screw (0.216"). A 1 mm pitch is 25.4 threads per in; but, I bet it might be 24 TPI which would make it a #12 UNF screw. At 24 TPI you really need a pitch gauge to get an accurate measurement.

There is a British Standard Whitworth thread that is 7/32" (0.219") with 24 TPI that is very close. The 1800 used a BSW fitting on the oil line for the oil pressure gauge; but, that is the only BSW thread that I am aware of on Volvos.

[Salop Farmer]

Thanks 142 guy and everyone who contributed. I have imperial and metric thread gauges so will recheck sizes tomorrow. My car definitely uses a combination of metric,UNF and whatever this latest screw size turns out to be!!

[Salop Farmer]

I have remeasured the thread in imperial 7/32(0.218) inches diameter x 24 TPI x1/2” long. Does anyone know if I will be able to buy screws of this size ?

[Burdekin]

Originally Posted by 142 Guy

First off, a Volvo of that vintage would not be Metric so best to provide dimensions in decimal inches. A 5.5 mm major diameter is 0.2126 inches which is just short of the diameter of an #12 screw (0.216"). A 1 mm pitch is 25.4 threads per in; but, I bet it might be 24 TPI which would make it a #12 UNF screw. At 24 TPI you really need a pitch gauge to get an accurate measurement.

There is a British Standard Whitworth thread that is 7/32" (0.219") with 24 TPI that is very close. The 1800 used a BSW fitting on the oil line for the oil pressure gauge; but, that is the only BSW thread that I am aware of on Volvos.

PVs were metric, Amazons imperial.

[Salop Farmer]

Sorted Screws ..... They are 12 - 24 UNC which I must admit I have never come across before! You learn something every day! 🤨 Thank the Lord for the internet!