The metal scrub plane’s design is more basic than that of most other types of metal plane. For instance, there is no blade adjustment mechanism and no chip breaker, or cap iron, between the iron and the lever cap.
The ductile cast iron body holds all the other parts. Ductile means the iron is less brittle than other types, making it more resistant to impact and fatigue.
As the body of the metal scrub plane is usually relatively narrow, the sole is narrow, too. It is usually around 38mm (about 1½ inches) but can be up to 50mm (2″).
The iron, or blade, is narrow compared with those of most other planes, usually 25mm (1”), 31.75mm (1¼”) or 38mm (1½”) wide, and relatively thick at around 4mm (5/32″).
It has a very distinctive rounded, or “cambered”, cutting edge, so that the blade acts as a gouge to remove lots of excess wood.
Support for blade
The iron is supported underneath by two cross-members of the body which are angled so that the blade beds onto them at around 45 degrees.
Lever cap, clamp bar, lever knob and stops
On some scrub planes, the lever cap fits behind a clamp bar – a metal rod, the ends of which fit into holes in the cheeks of the plane’s body.
A pair of stops – known as lever cap stops – hold the lever cap in the correct position when it is placed behind the clamp bar and over the blade.
The lever cap knob has a short bolt that threads through the lever cap and tightens against the blade. The end of the threaded bolt advancing against the blade levers the cap against the clamp bar, holding the iron firmly in place.
On other scrub planes, there is no clamp bar, the lever cap being secured by a screw which goes through a keyhole slot in the cap and into a threaded hole in the body of the plane. Tightening the lever cap knob levers the the cap against the screw, holding the blade firmly.
On some scrub planes, the blade is adjusted laterally – to make it parallel with the sole across its width – by turning the “set screws” with a screwdriver. There is a set screw in each side of the plane’s body. On planes without set screws, the lateral adjustment is done by hand after the lever cap knob has been loosened.
The mouth is the opening, or slit, in the sole of the plane through which the cutting edge of the iron projects to cut the wood. Because the scrub plane is used for the fast removal of excess wood, the mouth needs to be wide to allow relatively thick shavings through.
Tote and front knob
The tote, or rear handle, is usually the pistol grip type – shaped rather like the handle of a handgun, or pistol – and is positioned on the heel of the plane.
The front knob, which the woodworker presses down on when planing to ensure the plane cuts into the wood, is rounded for a comfortable grip, and is fastened to the toe.
Both tote and knob are held in place by bolts that go from top to bottom of the handle and into the body of the plane.