DIYbanter - View Single Post - How to differentiate PK (self-tapping) screws and chipboard screws?

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Bob Minchin wrote:
wrote:
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.

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?

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.

--
Chris Green