MASTERING THE LATHE 6

We can use drills and reamers to make holes but a boring bar allows us to make a hole any size we want. We are not confined to a standard drill size. The lathe was invented to produce perfectly round objects, and we think in terms of cylindrical objects such as shafts or axles. However, the other side of the coin is making perfectly round holes for the axles to run in. This is where being able to bore holes comes into play.

A boring bar is held in the tool post in a similar way to turning and facing tools. A hole in a cylinder is roughed out first using a drill, leaving enough material under the finished size. This ensures that finishing by using a boring bar will achieve the desired accuracy and surface finish.

Buy?

Several brands of boring bars tipped with tungsten carbide are available, with sizes to suit different diameters and the depths of the hole you need to make. Advanced designs even include built-in damping to minimise ‘chatter’ — the high-pitched noise and the movement that mars the surface finish with tiny corrugations. Replaceable cutting tips for these boring bars have shapes and hardnesses for different materials such as cast iron, high-tensile steels, aluminium, etc.