david lang wrote:
Having problems with putting screws into the edge of 18mm MDF.

I've tried correct size pilot holes and special MDF screws from SPAX but I
still get splitting and a slight bulge where the screw is.

Either don't, find another way to do it, or use a
tap (which you could make out of a screw), with
clamping as suggested by "ben". I guess
drill'n'fill'n'screw would be fiddly.