I have an injection moulded device .. which is to be fixed by self
The unit has no ?pilot? holes just ?shallow dimples? to allow screws to
The unit has same feel & weight as Polypenco I have used in the past -
but I have no knowledge of its characteristics other than it is
injection moulded, and therefore likely to be thermoplastic
I am fitting the unit through a plywood base which will be reinforcing a
lid to collecting drum ? overall thickness of about 12mm
The screws supplied ? No.7 self tappers are not long enough, so I need
to use longer screws.
I could try and source some longer No. 7 screws, although the No.7 seem
quite small for the task ???. Or take 2 different approaches.
#1 drill out the moulding and tap to M4 ? in which case any tips or
hints for tapping into such a material would be welcome ? and is the
fairly fine thread form of M4 suited to holding in a such a material.
#2 slightly simpler ? I have plenty of No8 stainless self tappers - but
would not like to simply screw these in, in case they crack the
moulding. From what I find in my ref books the hole for a No.8 self
tapping screw is 3.5mm if drilled clean.
Any issues with this approach ? the coarser thread may be of benefit in
holding in the plastic.
For both options is there a recommended drill speed & lubricant for such
5 years ago