Pozi-Drive Screws vs Square-Drive Screws

When attaching the outer-skin panels to the fuselage formers in our flight simulator cockpit, we have to use screws and not glue so that at a later stage the cockpit can be dis-assembled. But what type of screw should we use?
The issue is what the screw head actually looks like. Ideally we want it to look like a rivet if possible, since actual aircraft skins are covered in rivets. Essentially there are three types of screw-head:

  • The old fashioned round headed single slot woodscrew,
  • the round headed (“Phillips”) Pozi-Drive combination woodscrew/chip-board cupboard screw and
  • the round headed square-drive combination woodscrew/chip-board cupboard screw.

The single-slot screw is difficult to use with a modern battery-operated  screwdriver drills so let’s just consider the remaining two:

Pic of Cross head Screw and Square head screw
Pozi-Drive Screw (left) and Square-Drive screw (right)
Pic of screws inserted into wood
When the screws are inserted into wood and countersunk, they look like this.

As you can see the “square-drive” screw on the right already looks much more like a rivet than the pozi-drive cross screw. Now if we paint over the recessed screws:

Pic of painted screw heads
Painted over screw heads

The result is now pretty clear – the square-drive head with the recessed square hole now resembles a rivet quite closely once it is painted over.

So, when attaching the outer skin panels or any screw which will be visible, use square-drive screws. For general-purpose fastening, the pozi-drive screws are a bit cheaper, are easier to use and are available in larger ranges.