MTFCA Forum

What is the thread size for the 3 screws that fasten the magneto post to the top of the 1925 and older hog’s head?

Thanks kindly, Tom in Taylor Mill, KY 41015

Magneto contact fiber screw, Part # 3266:

10-32 x 1/2" or 5/8" length. Steel, pan head single slot.

I have alot of nos screws for sale if anyone needs them, Bob

BTW, the early mag posts have a higher head. Is it a truss head?

I got ahead of myself! The early mag post screws are a fillister head! I was having a senior moment above!

I believe a filister head is referred to as cheese head here, I presume due to its appearance like cheese before cutting. Makes sense, sorta!

Allan from down under.

The original screws were in fact cheese head but in modern times those generally (maybe incorrectly) mean that the head is thick, slotted and FLAT across the top surface while a Fillister head screw is thick, slotted but CURVED across the top a bit. The screws were indeed 10-32 but were rather short for the job and what makes matters worse is that pretty much ALL modern screws are now supplied on the short side of the length spec so 1/2" modern machine screws will generally be slightly shorter than 1/2" and coupling that with the standard cork gasket that Ford supplied and you barely have enough thread into the hogshead. It is rather common to find the top threads in those 3 hogshead holes (aluminum hogshead) stripped out. Look down into the hole and measure things up and take a longer screw for sure and maybe even longer yet and shorten it just enough so it doesn't stick out too far below the bottom of the hole and short into the magneto winding. I deliberately supplied 1/8" longer screws with the mag posts I made to hopefully prevent stripping out the remaining threads in those early aluminum hogsheads. Those are not long enough to short into anything but they "could" stand to be even longer. The spec sheet that came with the mag post called out the length that Ford supplied but what I supplied were just a wee bit longer and mine were stainless steel since there was no evidence that Ford did anything to prevent HIS from rusting.

The threads in the hogshead in my '14 weren't exactly stripped but were worn oversize to the point that they wouldn't hold the screws tightly enough to suit me, so what I did was to make a set of 12-32 screws with heads the size of 10-32s. I then drilled out the holes in the post flange and tapped the holes in the hogshead to match and was in business. It was a lot easier than using a Helicoil or equivalent and it worked just as well.