What Drill Size Should I Use For Self Tappers?

What is a Self Tapper?

Self tapping screws, usually referred to as self tappers, are screws for use when fastening to metal or plastic.

All that is required to insert a self tapper is a pilot hole to introduce the screw. They then form their own thread as the screw is driven into position. Once inserted, self tapping screws may be removed and re-used.

SELF TAPPER SCREW

Selecting the correct drill size

When using self-tapping screws, the chart below shows the suggested drill size that you should use to drill the pilot hole.

As you can see, it is not an exact science, there is a range for each screw size. Broadly speaking, the thicker the material that you are drilling, the more you should move towards the top end of the range when selecting the drill size.

SIZE OF SELF TAPPER	SUGGESTED PILOT DRILL SIZE
Number 2 (2.2mm)	1.6mm - 1.9mm
Number 4 (2.8mm)	2.2mm - 2.6mm
Number 6 (3.6mm)	2.6mm - 3.2mm
Number 8 (4.2mm)	3.1mm - 3.8mm
Number 10 (4.8mm)	3.6mm - 4.5mm
Number 12 (5.5mm)	4.2mm - 5.1mm
Number 14 (6.3mm)	4.9mm - 6.0mm

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