Buying Planers and Jointers

The term "planer" may refer to several types of woodworking machines or metalworking machine tools:

Planer (or Thicknesser or Thickness Planer), a machine that creates boards of an even thickness throughout their length.

Jointer, a machine that produces flat surfaces and straight edges on boards.

Hand planer, a small hand-held power tool used much as a hand plane, which functions like a small Jointer.

Metalworking planer, a type of metalworking machine tool.

Planers

A planer (aka a thickness planer or thicknesser) is a woodworking machine which is used to create boards that are of an even thickness throughout their length.

Design

Portable planers like the Delta TP305 to the right consist of three elements: a cutter head which contains the cutting knives; a set of infeed and Outfeed rollers which draw the board through the machine; and a table which is adjustable relative to the cutter head to control the resultant thickness of the board. Some portable planers differ slightly in that the table is fixed and it is the cutter head/feed roller assembly which is adjusted.
Industrial planers are capable of accepting very wide boards and removing large amounts of material in a single pass. These machines are driven by powerful induction motors and are of very heavy-duty construction. The Powermatic 1791262 above is a great example of the higher-end industrial planers.

In recent times, a range of light-weight portable planers have become available which use universal motors and are much cheaper than the industrial versions.

Operation

In operation, the table is set to the desired height and the machine is switched on. The board is fed into the machine until it makes contact with the infeed roller, which grips the board and draws it into the machine and past the rotating cutter head. The knives remove an amount of material on the way through and the outfeed roller pulls the board through and ejects it from the machine at the end of the pass.

In order to achieve a board that is flat and of uniform thickness along its length, it is necessary to start with a board that has at least one perfectly flat reference face. The board is fed with this reference face flat on the table and the cutter head removes an amount of material from the opposite face so that it is made parallel to the reference face. The reference face is often created by first passing the board over a jointer (see below).

One problem often encountered when using a planer is sniping. This manifests as a deeper cut on a short section of the board at either end and is caused by incorrect feeding or misalignment.

Jointers

A jointer (also known as a surface planer, buzzer, or flat top) is a machine used in woodworking to produce a flat surface on a board.

The jointer derives its name from its primary function of producing flat edges on boards prior to joining them edge-to-edge to produce wider boards. The use of this term probably arises from the name of a type of hand plane, the jointer plane, which is also used primarily for this purpose. To the left is an example of a jointer, the Delta 37-800 Industrial 8" Jointer.

Design

Fundamentally, a jointer consists of two parallel tables - the infeed and outfeed tables - a moveable Fence which is normally kept perpendicular to the tables, and a cutter head which is driven by some form of mechanical motorisation, commonly today an electric induction motor.

The cutter head contains 2 or more knives which are sharpened to a fine cutting edge. The knives are arranged radially in the cylindrical cutter head such that their cutting edges protrude from the cutter head so that they will come into contact with the board being cut as the cutter head spins. The cutter head's axis of rotation is set parallel to the table surfaces and perpendicular to the feed direction. The knives cut into the board in the direction opposite to the feed.

The infeed and outfeed tables are capable of being raised or lowered independently of each other and in relation to the cutter head. The outfeed table is set so that it is Level with the knives when at the top dead centre of the rotation of the cutter head. The infeed table is adjusted so that it is lower than the outfeed table and this gives the depth of cut.

Jointers for home workshops usually have a 4-6 inch (100-150mm) width of cut. Larger machines, often 8-16 inches (200-400mm), are used in industrial settings.

Operation

In operation, the board to be jointed is held with its face against the fence and the edge to be jointed resting on the infeed table. The board is fed across the cutter head and onto the outfeed table. The knives in the revolving cutter head remove an amount of material and the relationship of the two tables and the fence keeps the board oriented in such a way that the result is an edge which is flat along its length and perpendicular to the board's face.

A jointer may also be used to flatten the face of a board, in which case the sole focus is to produce a flat surface on the face of the board and the fence is not used. This procedure is often performed prior to edge jointing so that the board has a flat reference face for subsequent operations, such as when using a planer.

To straighten a piece of bent timber, the guard is temporarily swung out of the way. The machine is switched on and the timber is slowly lowered to the blade, with the hollow side down. A few cuts are made out of the hollow side. The timber is turned end for end and the same procedure is done to the other side. This is repeated as required with the operator sighting along the length of the timber from time to time to check on straightness of the timber. The operator must be very careful not to apply pressure in the middle of the work, and force it into a false straightness. When the timber is almost straight, the guard is replaced and the last cut is made in the normal way.

Twisted material is treated in a similar way.The operator lays the timber on the bed of the machine and rocks it slowly from side to side to estimate the amount of twist. If there is say 20mm of twist in the board, he holds the board level and takes 10mm off one end, then repeats it for the other end.

Jointers are also used for making rebates in finished timber. The fence is set to the width of the rebate and the infeed table is set to the depth. A jointer that is used for rebating has the outside ends of it's blades also sharpened and set with a small clearance from the cutter head.

A jointer cannot be used to create a board of even thickness along its length. For this task, after jointing one face, a planer should be used.

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