Hole Saws

Hole Saws

A hole saw cuts a large clean hole that a drill bit cannot, and diameter is chosen to match what passes through it rather than by preference. Common jobs set the common sizes: 20mm to 25mm for cables and small pipe, 38mm to 52mm for waste and soil connections, and larger diameters for downlights and ducting. Buy the exact size the fitting needs, because a hole cut oversize cannot be corrected. Material and tooth pattern decide what the saw will survive. M42 bi-metal construction welds a hardened high speed steel edge to a flexible backing, so the teeth stay sharp in metal while the body flexes instead of shattering, which is why bi-metal is the standard choice for anything beyond softwood and can handle stainless steel, mild steel, plastic and timber. Constant pitch spaces the teeth evenly and cuts predictably in consistent material. Variable pitch alters the spacing so the teeth do not all bite in rhythm, which reduces the vibration and juddering you get in thin sheet or tube. Two things matter more than the saw. Run the drill slowly with firm steady pressure, since speed generates heat and heat destroys the teeth. And back the saw out regularly to clear the slug and let it cool. Quick change arbors let you swap diameters without unscrewing the pilot each time, which is what makes a set faster than buying singles.

Addax is the widest range, with M42 bi-metal constant pitch hole saws at 20mm, 25mm and 70mm and a 38mm bi-metal variable pitch saw, alongside a 60mm M42 bi-metal saw. Dargan supplies a 9 piece hole saw set covering the common diameters in one purchase, and Faithfull a quick change hole saw set. For twist and masonry bits see Drill Bits, and for the wider tool range Hand Tools.