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

Bob Minchin[_2_]

Bob Mannix wrote:
"Bob Minchin" wrote in message
...
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?

The original manufacturer (since 1913) - Parker Kalon

Thanks Bob