How to differentiate PK (self-tapping) screws and chipboard screws?

[tinnews]

I have lots of both PK (self-tapping screws for sheet metal) and chipboard screws but I don't always know which are which. Is there any easy way to tell them apart?

I guess anything with a pan-head or a cheese-head is fairly likely to be a PK screw but countersunk heads present more of a problem.

I suppose I can try actually screwing them into a sheet of aluminium but before I do that I thought there might be an easier way.

[Bob Minchin]

A crude differentiator would be short ones PK and long ones chipboard although there will always be some to break this 'rule'.

PK will always be hardened but only some chipboard ones will be hard so before using in metal, a brush with an old file will test for hard ones

Chipboard screws will always be pointed but PK not always so.

I've not heard these called PK screws for years (mainly from my Dad) Out of interest, do you know the origin of the term PK?

hth

Bob

[Bob Mannix]

The original manufacturer (since 1913) - Parker Kalon

[tinnews]

No I don't know the origin, I too 'inherited' the name from my father though. He owned/ran a small engineering business in the 1960s and

1970s which manufactured and installed commercial and industrial heating and ventilating systems. The PK screws were used widely on the ducting they manufactured. Much of my stock of PK screws dates from that era! :-)

A google search turns up some people selling PK screws so one can call them that still.

[Bob Minchin]

Thanks Bob