The International Cessna^® 170 Association

Hi All,

Searching for the modern equivalent of this screw from the 170B Illustrated Parts Catalogue:

-15 PK76XZ-8-8
Thanks for any help,

Bob

What that part number indicates is a size/number 8 PK screw, 1/2” long.

“PK” is a reference to the initials of an old mfr’r of sheet metal screws, “Parker Kalon”.

Aircraft Spruce and other aircraft hardware suppliers sell them.

The Spruce PN is 8X1/2-A-TR-PH and they cost about 3-cents each: https://www.aircraftspruce.com/catalog/ ... /zthab.php

Many owners purchase a “screw kit” that has many/most of the exterior screws you will need for fairings and other non-structural fasteners. The 172 kit is appropriate for 170s. https://www.aircraftspruce.com/catalog/ ... -01100.php

The kits consist of stainless steel fasteners and are more attractive and less prone to rust…. however many A&Ps do not like them because they are slightly easier to damage the screwdriver slots as they are slightly softer than plain, cad-plated screws. There are so many extra screws in the kits, and they are so much more attractive than paint-scarred plain cad-plated screws….that we don’t care…we prefer the stainless. (Hint: buy the kit I linked above and you’ll be happy.)

Hi George,

Thank you, this is exactly what I was looking for.

3 cents apiece, I need 2 of them so I will start saving up

The exterior screw kit looks like a good bet.

Thanks,

Bob

Bob, while the IPC calls for a size 8, over time these screws wallow out the sheet or a Tinnerman is forced oversize. Not uncommon. I wouldn't be surprised at all that you will actually need a 10x8.

I've never bought a "screw kit". When I have needed a screw I'd buy 10 of what was suppose to be there, 10 of the next size, and for good measure a few shorter and a little longer. I've got a pretty good collection by now.

Bruce,
You big spender

I try to at least order enough so that UPS doesn't make more $$ than Spruce. Share the rest.

Bruce Fenstermacher wrote:Bob, while the IPC calls for a size 8, over time these screws wallow out the sheet or a Tinnerman is forced oversize. Not uncommon. I wouldn't be surprised at all that you will actually need a 10x8.

I've never bought a "screw kit". When I have needed a screw I'd buy 10 of what was suppose to be there, 10 of the next size, and for good measure a few shorter and a little longer. I've got a pretty good collection by now.

Thanks Bruce,

The other screw holding this fairing, which I pulled out for comparison, does not look like a sheet metal screw as it has a flat end and finer thread like a machine screw; the one in question has been replaced with a "button snap" type of fitting similar to the picture below, probably for a cover or something? Both types of screw seem to thread in properly.

Thanks,

Bob

Bob, PK type screws have different tips/threads depending upon the intended service. Type “A” is a sharp point… Type “B” is a blunt point…. either will work in most fairings and inspection covers but Type A is usually intended for fastening sheet metal parts that have not previously been served…the point helping to “start” the threading. Aircraft hardware is an intense subject all of its’ own and many volumes have been issued discussing it. You might benefit from contacting someone such as Genuine Aircraft Hardware and asking for their free catalog which illustrates and explains the useage of specialized fasteners… or download their catalog: https://www.gen-aircraft-hardware.com/i ... o_Kits.pdf

The screw you depicted above is a common marine snap-fitting for boat covers and upholstery and not ordinarily used for aircraft.

Hi George,

Thank you, I knew the snap fitting had to have been from someone getting creative, I just wanted to return it to "original" but that is never as straightforward as it seems. Plus the reduced drag should make a big difference

Thank you for the Genuine Aircraft Hardware reference, I will look into it.

Thanks,

Bob

Hi Bob, I have that snap fitting in several locations and they are required to keep my windshield cover on. I would send a picture but I am not near my hangar. cheers Bill

cfzxo wrote:Hi Bob, I have that snap fitting in several locations and they are required to keep my windshield cover on. I would send a picture but I am not near my hangar. cheers Bill

Thanks Bill!

Whatever they went to is long gone so time to clean her up.

Bob