The Cessna 120-140 Association Forum

Hi,

Has anyone mapped the old Cessna parts numbers, e.g. those used in the C120/140 parts manual, to MS or AN numbers?

Example: pk76xz-8-8 used on the aileron bracket inspection panel. This is a machine screw.

I've seen similar part numbers used on the C-170.

Thanks, Chris

Actually, those screws (and most of the other screws in similar "inspection cover" applications) are not machine screws. They are called truss head type B sheet metal screws with a sort of sheet metal thread, but not tapered, and a blunt tip (type "B" as opposed to type "A"). They are intended to screw into Tinnerman nuts and the nut is designed to lock into the minor diameter of the thread. The "8-8" designation indicates it's a #8 screw 8/16 (1/2) inch long. You can order them here. Type "A" screws will not lock properly and tend to fall out.

They are available in steel or stainless. If you use stainless against aluminum you should use a nylon washer under the head to help prevent dissimilar metal corrosion (NAS1515H08L)

Type B PK screws are also used to hold the cowl and wing root fairings on.

They are "non-structural" and, to the best of my knowledge, have never had an AN, NAS or MS spec.

Thank you for the very informative answer. It looks like it goes with a Tinnerman A1348-8Z-1D.

I purchased the stainless Cessna 120 screw "kit" from Spruce. I'll check there first. And, find some nylon washers.

Keep 'em flying, Chris

riedener wrote: ↑Wed Jun 14, 2023 10:15 amIt looks like it goes with a Tinnerman A1348-8Z-1D.

Yes. There are a number of configurations: flat, u-shaped, j-shaped, etc.

Lots of good information here.