How saw blades are made

Saw blades get dished on purpose and then ground flat, so the internal stress stays and the wobble goes.

stations: 7
things upstream: 41
raw sources: 17
steps from the ground: 6

The short version

A carbide-tipped circular saw blade begins as a laser-cut steel disc. Heat treatment hardens and toughens it, tensioning locks in a stress that fights vibration, and grinding brings it back flat before it is balanced. Carbide tips are then brazed to the rim and sharpened by CNC grinders with diamond wheels. Small plain-steel blades can instead be punched from strip in one press.

Laser out the disc

A high-powered CO2 laser follows a CAD path through sheet steel, usually a high-carbon, high-chrome grade. One Irwin plant cuts alternating areas of the blank so heat cannot build up in any one spot.

Goes in
Sheet steel
Harden and temper

Discs go into the heat at 860 °C to 1100 °C, depending on the steel, then get quenched. Clamped in packs, they warm slowly again to 350 °C to 560 °C, which gives up some hardness for toughness.

860 °C to 1100 °C
Tension the body

Tensioning leaves a slight dish across the diameter and builds in a stress that resists vibration during a cut.
Grind it flat

The dish itself is unwanted, so a surface grinder takes the disc back to flat and to its required thickness. The internal tension survives.
Balance by hand

At the Irwin plant, skilled machinists measure each disc, grind it on a bench grinder and check it again. Typical 10-inch blades are held to within 1 gram across the diameter. Freud does this step with an automated system.

within 1 gram
Braze on carbide tips

Tungsten carbide tips are sorted by machine and brazed to the rim automatically. Freud's brazing alloy puts copper between layers of silver, so the joint can take hard knocks.

Goes in
Tungsten carbide
Sharpen with diamond

Computer-controlled multi-axis grinders with diamond wheels shape every tip. On the Irwin line this happens inside an enclosed cabinet.

End of the lineSaw blade

Worth repeating

Copper pull saws turned up in an Egyptian tomb from Djer's reign, in the 31st century BC.
The Irwin plant visited by Canadian Contractor made hundreds of thousands of blades a year on three shifts of only 10 people each.
One patent describes a press tool that turns out a virtually finished small circular blade with every stroke, leaving only the tooth tops to grind.