What are PK screws
Charles K. Scott
to sheet metal screws. Can someone offer an explanation as to what
they are and what the part numbers are for the various sizes?
Thanks, Corky Scott
Craig C.
From what I can remember Corky, they are like either a truss or
fillister head sheet metal screw. I've got some that we use for
replacing trailing edge stock on the L-5 controls, but they aren't in
a handy location to grab for a part number right now....
Craig
hamst...@my-deja.com
> I've seen references to PK screws and have heard that they are similar
> to sheet metal screws. Can someone offer an explanation as to what
> they are and what the part numbers are for the various sizes?
"P-K screws" is a generic term for aircraft-grade self-tapping
sheetmetal screws that I suspect started on the bomber production lines
of WWII. The "P-K" stands for Parker-Kalon, a large manufacturer of
sheetmetal screws at the time. They're still in business, but their
current claim to fame is a line of self-drilling screws popular among
those who put up prefabricated metal buildings. See:
http://www.emhart.com/products/pk.html
I won't be using too many of those in my airplane.
Judging by the Aircraft Spruce & Specialty catalog, flat head PKs are
AN531, and the round heads are AN530, but there doesn't seem to be an AN
class for the truss-head screws that work so well for attaching minor
fairings and such. For that ACS has their own part numbering scheme that
just concatenates the size, length, point style, head style, and drive
style.
For example, the #4, 1/4"-long, truss-headed, sharp-pointed, phillips,
PK screws I used to secure the .016" leading edge skin onto the ribs for
my Aeronca 65C ailerons are ACS&S part number 4X1/4-A-TR-PH. Actually,
they're 4X1/4-A-TR-PH-SS because I chose the stainless-steel ones. And,
yes, they are virtually identical with the original screws used in that
location when the ailerons were manufactured in 1939.
Hope that helps just a little
Hammy
Sent via Deja.com http://www.deja.com/
Before you buy.
O-ring Seals
(Charles K. Scott) wrote:
>I've seen references to PK screws and have heard that they are similar
>to sheet metal screws. Can someone offer an explanation as to what
>they are and what the part numbers are for the various sizes?
>
>Thanks, Corky Scott
PK has become kind of generic for sheet metal screws. Originally, it
referred to screws manufactured by the Parker-Kalon company.
O-ring Seals
highflyer
>
> I've seen references to PK screws and have heard that they are similar
> to sheet metal screws. Can someone offer an explanation as to what
> they are and what the part numbers are for the various sizes?
>
> Thanks, Corky Scott
You know Corky, I have been calling "sheet metal" screws "PK" screws
for fifty years. I think it is similiar to calling acetylsalicylic acid
"aspirin."
--
HighFlyer
Highflight Aviation Services
John Kunkel
>
> I've seen references to PK screws and have heard that they are similar
> to sheet metal screws. Can someone offer an explanation as to what
> they are and what the part numbers are for the various sizes?
Sheet metal screws, other than head style, come in two basic types. One
type has a pointed tip and the other a blunt tip. I have always called
the blunt tip screws PK and the pointed tip just plain old "sheet metal
screws". I could be wrong on that.
The two styles also differ in the angle of spiral of the threads (or the
threads per inch to some). This is of little consequence on a new
installation but I've found that, when threaded into hardened Tinnerman
nuts, changing from one style to another will often cause one tang of
the Tinnerman to break.
John
Bruce A. Frank
>
> I've seen references to PK screws and have heard that they are similar
> to sheet metal screws. Can someone offer an explanation as to what
> they are and what the part numbers are for the various sizes?
>
PK has become a generic name for the small sheetmetal screws used to do
things like attach ribs and leading edges to the spars. They are also
clearly designed to corrode after a decade or so and stick so firmly
that the driver slot strips no mater how carefully you attempt removal.
The typical screw used on the ribs and other wing parts is a 4-40. To
avoid such irritation I bought hardened STAINLESS. To avoid stripping
the slot or shearing the screw in half on insertion(in thicker areas
like spar webs and caps), even though the screw is technically a
"sheetmetal thread forming " screw, I tap the holes before using them.
If I hadn't bought several thousand from McMaster-Carr a few years back,
I would switch to a larger size.
--
Bruce A. Frank, Editor "Ford 3.8/4.2L Engine and V-6 STOL
BAFRANK(at)worldnet.att.net Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|
*------------------------------**----*
\(-o-)/ AIRCRAFT PROJECTS CO.
\___/ Manufacturing parts & pieces
/ \ for homebuilt aircraft,
0 0 TIG welding
While trying to find the time to finish mine.
John H Ousterhout
- John (wrong again) Ousterhout -
On Fri, 28 Jan 2000 10:09:46 -0600, highflyer <high...@alt.net>
wrote:
>"Charles K. Scott" wrote:
>>
>> I've seen references to PK screws and have heard that they are similar
>> to sheet metal screws. Can someone offer an explanation as to what
>> they are and what the part numbers are for the various sizes?
>>
>> Thanks, Corky Scott
>
JDupre5762
>> to sheet metal screws. Can someone offer an explanation as to what
>> they are and what the part numbers are for the various sizes?
>
Snip
>For example, the #4, 1/4"-long, truss-headed, sharp-pointed, phillips,
>PK screws I used to secure the .016" leading edge skin onto the ribs for
>my Aeronca 65C ailerons are ACS&S part number 4X1/4-A-TR-PH. Actually,
>they're 4X1/4-A-TR-PH-SS because I chose the stainless-steel ones. And,
It is not readily known but there are two thread pitches for the "sheet metal
screw" In the example 4x1/4-A-TR the A stands for one thread pitch that is
primarily for sheet metal attachments without any other fastener. Substitute a
B and you would get a blunt point screw with a different thread pitch that is
designed for use with Tinnerman nuts. Tinnerman nuts being the green sheet
metal nuts used to attach some fairings. Some Tinnermans are "U" shaped and
clip over the edge of a sheet and some are just slightly convex shaped
rectangles of steel. The hole for the screw has two ear like projections for
the screw to engage. Using "B" types really makes for a stronger joint with
Tinnerman nuts.
John Dupre'
Alan Davenport
I'll let you figure out the rest.
John H Ousterhout wrote:
> And all this time I've been calling them "Pinckneyville screws".
>
> - John (wrong again) Ousterhout -
>
> On Fri, 28 Jan 2000 10:09:46 -0600, highflyer <high...@alt.net>
> wrote:
>
> >"Charles K. Scott" wrote:
> >>
Terry Menees
Bruce A. Frank <BAFRANK@**SpamBlock**worldnet.att.net> wrote in message
news:86suh7$rk1$1...@bgtnsc03.worldnet.att.net...
> Charles K. Scott wrote:
> >
> > I've seen references to PK screws and have heard that they are similar
> > to sheet metal screws. Can someone offer an explanation as to what
> > they are and what the part numbers are for the various sizes?
> >
The Schweizer SGS2-8 (TG-2), of WWII fame, utilized Parkor Kalon screws
rather than rivets in most of its aluminum structure. It provided a
quicker, easier method of construction, requiring little skill. It looks
rather odd when you see all those little slot headed drag producers sticking
out on the fuselage and wings, but it worked for what it was intended.
Terry
Charlie
John Kunkel wrote:
> Sheet metal screws, other than head style, come in two basic types. One
> type has a pointed tip and the other a blunt tip. I have always called
> the blunt tip screws PK and the pointed tip just plain old "sheet metal
> screws". I could be wrong on that.
> The two styles also differ in the angle of spiral of the threads (or the
> threads per inch to some). This is of little consequence on a new
> installation but I've found that, when threaded into hardened Tinnerman
> nuts, changing from one style to another will often cause one tang of
> the Tinnerman to break.
> John
The 'pointed tip' are referred to as "Type A" and are for use as self
tapping in sheet metal. The 'blunt tip' are for use with Tinnerman type
fasteners. The Type A (pointed type) should NOT be used with a Tinnerman.
Charlie Walker (A&P)
Lee Phillips
which gives a visual ID for distinguishing them from garden variety
automotive or screen door screws...... Of course, having the truss head
doesn't make them "aviation", but NOT having a truss head generally means
the screw is NOT aviation.
Lee (A&P)
Charlie <cwa...@compu.net> wrote in message
news:389E25E8...@compu.net...
Shotzy
<All you never wanted to know about "P-K" self tapping screws, and knew
better than to ask.
<
<AN504, machine screw;
Round head, slotted or recessed (phillips, reed & prince).
Type a = fluted (pointed end).
Type b = slotted (blunt split end).
Fine pitch thread for fastening into cast and thick sections and tinnerman
type nuts.
Sizes; 4-40, 6-32, 8-32, 10-32, 1/4-28.
Before the first dash number;
"C" = crs steel (stainless).
Between first and second dash numbers;
"R" = recessed head.
"F" = fluted shank.
"S" = slotted shank.
After last dash number;
"C" = chromium plate.
Carbon steel = QQ-S-633.
CRS = QQ-S-763.
Examples;
AN504-4-8 = Rnd hd, 4-40, carbon steel, slotted head, 1/2".
AN530C-10R-8C = Rnd hd CRS, 10-16, recess head, 1/2", chromium plated.
<
<AN530, sheet metal screw;
Same as AN504 above EXCEPT as noted below.
Coarse pitch thread for fastening thin sheet metal.
Sizes; 2-32, 4-24, 6-20, 8-18, 10-16, 1/4-14.
<
<AN531, sheet metal screw;
Same as AN504 above EXCEPT as noted below.
Flat head, 82 degree cntsk.
Carbon steel = MIL-S-6033.
CRS = MIL-S-6033.
Example;
AN531C6RF8 = Flt hd, 82 deg. csk., CRS, 6-20, Recessed hd (Phillips), fluted
Shank (pointed), 1/2"
<
<NAS548, sheet metal screw;
Same as AN504 above EXCEPT as noted below.
No type "A"
Flat head, 100 degree cntsk.
After basic part number;
"F" = frearson recess.
"P" = Phillips recess.
"S" = Slotted recess.
After last dash number;
No letter = cadmium plate.
Steel = MIL-S-18729
Example;
NAS548F8-8C = Flt hd, 100 deg. csk., steel, frearson recess, 6-18, 1/2",
chromium plated.
<
This is all BUNAVAIR data: I have the charts for all the tap drill and body
drill sizes for these screws. I can scan them and E-male if you need them.
JIM Scott
Charles K. Scott wrote in message <86s4cn$aa0$2...@merrimack.Dartmouth.EDU>...
>I've seen references to PK screws and have heard that they are similar
>to sheet metal screws. Can someone offer an explanation as to what
>they are and what the part numbers are for the various sizes?
>
>Thanks, Corky Scott
Shotzy
Addendum;
AN531 and NAS548;
Coarse thread for fastening thin sheet metal
sorry about the omission
Shotzy wrote in message ...