HSS Straight Shank Twist Drill (19.0mmx1pc)

Breakthrough is when a bit finishes the hole and exits the far side. For most of the drilling the bit is surrounded by material and everything is steady. Then the metal ahead of it thins to a web, that web can no longer resist, and the bit's own cutting edges pull it forward and bite hard. The drill lurches, the torque spikes, and one of several things happens: the workpiece spins, the bit jams and the machine twists in your hands, or in thin sheet the bit grabs a triangular flap of metal and tears it round with it.

The consequences at 19mm are not trivial. A hand held drill of any power that jams at this diameter will turn a wrist, and hand and wrist injuries from exactly this are common.

Three things prevent it. Ease off the feed pressure as you feel the bit approaching the far face, so the last part is cut gently rather than driven through. Back the work with a piece of scrap timber where you can, so the bit has something to break into rather than fresh air. And hold the machine so that if it does snatch, your wrist can give rather than being forced against its own joint, with the side handle fitted and both hands on the tool.

In thin sheet, a step drill is a better choice than a twist drill at this size for precisely this reason, and we sell those.

Nineteen millimetre holes in steel serve large bolt clearance, structural fixings, plant repair and heavy fabrication.

M35 cobalt high speed steel; the carbide and percussion lines in the catalogue spec belong to a masonry bit and are not applicable.

Buyers are fabricators, structural steel shops, engineering and machine shops, plant and heavy vehicle workshops.

Tell us the material thickness on 94 77 111 8880 and we will say whether a twist drill or a step drill suits it better. Island-wide delivery.