What is a scrub plane?
What it's used for
Reducing the size of wood
The scrub plane is used to remove large amounts from the surface of a piece of wood.
This might be when eliminating distortion or warping in the first stages of preparing rough stock, or when simply reducing the thickness or width of a piece.
Because it cuts quite deeply and leaves distinct gouges in the surface of the workpiece – which are then usually removed with a jack plane – the scrub plane is often described as an “aggressive” tool.
However, apart from quickly reducing the size of a piece of wood, it can be used for more aesthetic purposes.
These include helping to shape irregular objects and deliberately leaving a gouged surface – perhaps with the gouges criss-crossing the wood to give it a kind of cheese grater or latticed effect for an aged look.
When planing the face of a board, the scrub plane is generally used in diagonal strokes, at between 30 and 45 degress, rather than parallel to the length of the board (along the grain).
That way, excess wood is simultaneously removed along the length as well as the width of the stock.
If planing an edge, the plane is moved in the direction of the grain (with or along the grain).
How it got its name
The origins of the name are unclear, but it's generally assumed it comes from the "scrubbing" action of the plane when making quick, diagonal strokes across the surface of the wood. It's also known a the scud plane, scurfing plane, hunter plane and cow plane (a “cow cut” is an old country term for a radical haircut).
Short, narrow and strong
There are metal scrub planes and wooden scrub planes.
They generally have short soles and relatively narrow but thick blades.
The narrowness makes it easier to take deep cuts out of the wood and the thickness gives the blade extra strength so it doesn't flex under stress.
A metal scrub plane is typically between 230mm (9") and 267mm (10½") long, and narrower than most other planes at around 38mm (1½") wide. Wooden scrub planes tend to be a little larger – around 280mm (11") to 305mm (12") long and up to 50mm (2") wide, although lengths in particular do vary.
Curved iron for gouging
The scrub plane has a wide mouth and a deeply curved cutting edge on the iron to make a deep, gouging cut.
The curve on the cutting edge has a radius of about about 75mm (3"). That is, if the curve formed a complete circle, it would be 75mm (3") from the middle to the edge, or 150mm (6") right across (the diameter).
The scrub plane in both its metal and wooden forms is a "single iron" tool – that is, it has no chip breaker on top of the of iron, just the iron itself held in place by a wedge (wooden plane). . . .
. . . or a lever cap (metal plane).
A chip breaker is unnecessary as the scrub plane is for very rough planing – the wood is tidied up with jack and other planes later – so a moderate amount of tear-out due to the absence of the chip breaker is not normally a problem at this stage.
The scrub plane’s iron is usually bedded at 45 degress, with the iron's bevel (the angle on the cutting edge) facing down.
Metal versions of the scrub plane made by Stanley were allocated Stanley model numbers which are still often used today when cataloguing, advertising and ordering planes.
Scrub planes are listed as the No. 40 (pictured), which is 241mm ( 9½") long and 31.75mm (1¼ ") wide, and the No. 40½, which is a bit bigger at 267mm (10½") long and 38mm (1½) inches wide.
What other planes are used?
Where the scrub leads, others follow . . .
In the process of preparing rough stock – reducing wood to the desired size along its length and straightening and smoothing its faces and edges – the scrub plane is often followed by the jack plane, fore plane, jointer plane, then the smoothing plane, although not all are necessarily used in the process.
Because of the scrub plane’s length (relatively short compared with jack, fore and jointer planes) it is not suited to straightening up wood, as its short sole is likely to follow any undulations along the edges or faces of a workpiece.
The scrub plane has been largely replaced by large power tools such as the jointer and thickness planer.
However, scrub planes are still regularly used for the initial planing of boards too wide to fit through a thickness planer or jointer.
Most jointers can take wood 152mm or 203mm (6" or 8") wide, so the scrub plane these days is sometimes used to reduce larger pieces of wood so that they fit into the machine.
And for some woodworkers, it is still the tool of choice for thicknessing and the initial clean-up of wood.