Steel Bit - (4mm) pcs

A 4mm twist drill bit for steel and other metals. Four millimetres is where small fixing work happens: clearance for M4 screws and bolts, holes for pop rivets, mounting light brackets and cleats, drilling cable trunking and enclosures, and opening out a 3mm pilot to take a fixing. It is the smallest size that will take a bit of pressure without snapping the way the finer bits do, which is why it tends to be the one that survives longest in a drill index. Hammer action off, moderate speed, punch mark first. On anything thicker than sheet a drop of cutting oil makes a real difference to how long the edge stays sharp and how clean the hole comes out.