Planing

Planing is a manufacturing process of material removal in which the workpiece

reciprocates against a stationary cutting tool producing a plane or sculpted surface.

Planing is analogous to shaping. The main difference between these two processes is

that in shaping the tool reciprocates across the stationary workpiece. Planing motion

is the opposite of shaping. Both planing and shaping are rapidly being replaced by

milling.

Process Characteristics :

• Uses single-point cutting tool.

• Involves a reciprocating motion between the tool and workpiece.

• Produces plane or sculpted surfaces.

• Leaves parallel feed marks.

Working principle of a planing machine

• The machine used for this process is known as

a planer. The size of the planer is determined by

the largest workpiece that can be machined on it.

The principle involved in machining of a job in

planer is a reverse case of shaper. The work is

rigidly held on the work table or platen of the

machine. The tool is held vertically in the tool

head mounted on the cross-rail. The work table

together with job is made to reciprocate past the

vertically held tool. The indexed feed,after each

cut, is given to the tool during the idle stroke of

the table.

Main parts of a planner• Bed.

• Table or platen.

• Housing or column. Cross-rail.

• Tool-heads.

• Controls.

Types of planer• Standard or double housing planer.

• Openside planer.

• Planer miller.

• Plate planer.

• Pit planer.

• Divided table planer.

Working of a butler planing machine

Driving mechanism

Four different methods are as follows:

• Crank drive.

• Belt drive.

• Direct reversible drive.

• Hydraulic drive.

Feeding mechanism

The horizontal feed is given by moving the tool-head along the cross-rail and vertical

feed,to vary the depth of cut, is imparted by moving the vertical slide of the tool-head

By means of the down feed screw.

• Ratchet and pawl feed mechanism.

• Friction disc feed mechanism.

• Electrical feed mechanism.

Work holding devices

Most of the jobs can be directly held on the machine table with the help of some

general types of fixtures such as:

• Vices.

• T bolts.

• Clamps.

• Stops.

• Angle plates and irons.

• Braces.

• Stop blocks.

• V blocks.

• Planer jacks.

• V blocks.

Planing operations

The only difference with the shaper is that a shaper can machine only small work,

whereas a planer is specially designed for large work. The common type of work

machined in planer are: the bases ans tables of all kinds of machine tools, large

structures,frames of different engines and identical pieces of work which may be small

in size but large in number.The common operations are:

• Planing flat horizontal surface.

• Planing vertical surfaces.

• Planing at an angle and machining dovetails.

• Planing curved surfaces.

• Planing slots and grooves.

Cutting speed, feed and depth of cut

• Cutting speed- the cutting speed of a planer is the rate at which the metal is

removed during the forward cutting stroke. Commonly used planers usually employ

a cutting speed of 6-15 metres per minute and a return speed of about 30metres per

minute.

• Feed- the feed in planing machine is the distance the tool head travels at the

beginning of each cutting stroke expressed in mm per double stroke.

• Depth of cut- it is the thickness of metal removed in one cut and is measured by the

perpendicular distance between the machined and nonmachined surface expressed

in mm.

Precautions

• We should protect machine table from burrs and irregularities of the workpieces.

• Use of crane in fixing the workpiece should be done carefully.

• For the surfacing work the tool head is set vertically.

• Safety clutch must be provided for feed and

power rapid traverse.

• Use of vertical power rapid traverse for feeding the table should never be allowed.