What is a 'PK" screw?

[mhorowit]

I see mention of "PK" screws. Can someone point me to an illustration?

At http://www.aircraftspruce.com/menus/ha/sheetmetalscrews.html is a
Truss Head Type 'A' sheet metal screw, which is what I'm visualizing;
is that it? - MIke

[Stealth Pilot]

On 26 Dec 2006 04:05:13 -0800, "mhorowit" > wrote:

>I see mention of "PK" screws. Can someone point me to an illustration?
>
>At http://www.aircraftspruce.com/menus/ha/sheetmetalscrews.html is a
>Truss Head Type 'A' sheet metal screw, which is what I'm visualizing;
>is that it? - MIke

without checking the ref it sounds correct.
pk refers to the original makers brand. ie Parker Kalon.
they are a standard aviation sheet metal screw used with tinnerman
(another brand) sheet metal fasteners.

[[email protected]]

mhorowit wrote:
> I see mention of "PK" screws. Can someone point me to an illustration?
>
------------------------------------------------------------------------

Dear Mike,

The correct answer (and illustration) depends upon the application.
That's because 'PK' has both generic and specific meanings.

In the generic sense 'PK' means any sheet-metal screw, the 'PK'
reflecting 'Parker-Kalon,' the company that first made them. (But
didn't invent them.)

In aviation a 'PK' was not only a sheet-metal screw it was a temporary
fastener, the precursor of the cleco. Key differences was a fiber
washer affixed to the underside of the head so as not to mar the
aluminum, and a hex head, to allow it to be driven with less chance of
slipping (and marring the aluminum). Otherwise, it was your basic
coarse-pitch, blunt-tip (Type B ?) sheet metal screw, which was often
pressed into service when you ran out of 'real' PK's (and is still
commonly used as a sheet-fastener for repair work).

The funny bit here is seeing kit-builder's wings a'bristle with a
forest of clecos at two-bits a pop... when a real tin-bender would use
half a dozen clecos... and several hundred PK's at perhaps a penny each
:-)

I'm pretty sure I mentioned PK's in my 3-part epistle 'Riveting 101,'
which I've uploaded to my blog ( bobhooversblog.blogspot.com )

-R.S.Hoover

[mhorowit]

wrote:
>
> I'm pretty sure I mentioned PK's in my 3-part epistle 'Riveting 101,'
> which I've uploaded to my blog ( bobhooversblog.blogspot.com )
>
> -R.S.Hoover

A 'riveting' discussion, I'm sure :) - Mike (off to the blog)

PS - An A&P gave me a sample of a #4 sheetmetal screw which met the
Type 'A' description I initially described, but called it a "PK" screw.
I guess it's a case where a trademark name has overrun any subtilities.

[John Kunkel]

"mhorowit" > wrote in message
oups.com...
>I see mention of "PK" screws. Can someone point me to an illustration?
>
> At http://www.aircraftspruce.com/menus/ha/sheetmetalscrews.html is a
> Truss Head Type 'A' sheet metal screw, which is what I'm visualizing;
> is that it? - MIke
>

By strict definition only the pointed sheet metal screw is a PK, the blunt
end (type B) screws have a slightly different thread pitch.

[RST Engineering]

John ...

I've been wrong before and I'll be wrong again, but as I learned it the
blunt head "B" screw is properly called a PK.

And yes, you can ruin a tinnerman quite easily substituting one for the
other.

Jim




"John Kunkel" > wrote in message
. ..
>
> "mhorowit" > wrote in message
> oups.com...
>>I see mention of "PK" screws. Can someone point me to an illustration?
>>
>> At http://www.aircraftspruce.com/menus/ha/sheetmetalscrews.html is a
>> Truss Head Type 'A' sheet metal screw, which is what I'm visualizing;
>> is that it? - MIke
>>
>
> By strict definition only the pointed sheet metal screw is a PK, the blunt
> end (type B) screws have a slightly different thread pitch.
>

[[email protected]]

RST Engineering wrote:
>
> I've been wrong before and I'll be wrong again, but as I learned it the
> blunt head "B" screw is properly called a PK.
>
---------------------------------------------------------------------------------------

Dear Jim,

If you're referring to PK's as temporary sheetmetal fasteners (as I
was), that is also my understanding. It is based on something my dad
said more than fifty years ago when I was sent to fetch a handful of
PK's and returned with regular sheetmetal screws. He said you never
used the pointed type on rivet holes because you were liable to scratch
the metal, "You never want to make a scratch any where near a rivet
hole." Or words to that effect.

But the definition was even easier to remember when he pointed out that
the PK's he needed were black and had fiber washers.

I was even allowed to insert a few dozens of them :-) "Just snug will
do it; just snug is fine."

Odd, the things we remember...

-R.S.Hoover

[Scott[_1_]]

One more question. It was said that PK screws were used on my old
Aeronca to hold the fabric to the ribs. Looking at the bumps from the
screw heads, it seemed they were quite dome shaped, more so than the
common A or B type sheet metal screws I think you guys are talking
about. Is there possibly a separate type of PK for fabric work?

Scott
Corben Junior Ace (no PKs holding the wing fabric on!)



wrote:
> RST Engineering wrote:
>
>>I've been wrong before and I'll be wrong again, but as I learned it the
>>blunt head "B" screw is properly called a PK.
>>
>
> ---------------------------------------------------------------------------------------
>
> Dear Jim,
>
> If you're referring to PK's as temporary sheetmetal fasteners (as I
> was), that is also my understanding. It is based on something my dad
> said more than fifty years ago when I was sent to fetch a handful of
> PK's and returned with regular sheetmetal screws. He said you never
> used the pointed type on rivet holes because you were liable to scratch
> the metal, "You never want to make a scratch any where near a rivet
> hole." Or words to that effect.
>
> But the definition was even easier to remember when he pointed out that
> the PK's he needed were black and had fiber washers.
>
> I was even allowed to insert a few dozens of them :-) "Just snug will
> do it; just snug is fine."
>
> Odd, the things we remember...
>
> -R.S.Hoover
>

[Denny]

An old mechanic might use penny apice PK in place of CLeco, but since
my time is worth something to me I am using Clecos for building... I
can place, remove, and replace a half doezen cleco whilst the old
mechanics are still trying to get the bottom sheet of metal to pull up
against the top sheet with one PK...
denny

[RPE]

I once heard the term "PK" screw used to reference the little spiral
shank, oval head blind hole metal "nails" used to attach data plates and
such to machines, engines etc. Until I googled "PK screw" I had never
seen the reference otherwise so just had this wrong impression all my
life. Well now must go install the bonnet on the tractor.


"mhorowit" > wrote in message
oups.com...
>I see mention of "PK" screws. Can someone point me to an illustration?
>
> At http://www.aircraftspruce.com/menus/ha/sheetmetalscrews.html is a
> Truss Head Type 'A' sheet metal screw, which is what I'm visualizing;
> is that it? - MIke
>