The larger the drill bit that needs to be held, the larger the head of the collet will need to be. Collets are measured across the diameter of the head when open.
Collets for pin vices come in four standard sizes which are categorised by the sizes of drill bits they will hold. Each end of a double-ended collet will be a different size, so these collets will essentially have two sizes.
These sizes are:
Collet size:
Drill bit size:
Size 1
0 – 1.2mm (0 – 0.04 inches)
Size 2
1.3 – 2.4mm (0.05- 0.09 inches)
Size 3
0.8 – 2.0mm (0.03 – 0.07 inches)
Size 4
1.8 – 2.9mm (0.07 – 0.11 inches)
Some pin vices can only hold certain sizes of collet. This is normally because the chuck head of the vice is too small to hold the larger collet as it was designed for more precision drilling.
Information regarding which size collets can be used in the vice should be provided with the purchase.
The drill bit size is measured from the diameter of its shaft end, but this information will normally come with or will be etched on the drill bit shaft.
Before using your pin vice, select your drill bit and use a collet that will accommodate its size.