Parts of Planer
A standard double housing planer has the following main parts.
(ii) Work table
(iii) Column or housing
(iv) Cross rail
(v) Saddle
(vi) Tool head
(vii) Driving and feed mechanism.
Bed :-
The bed of a planer must be a element or casting twice as
long as the table. The bed acts as the foundation of the machine.
The other parts are attached to, or supported by the bed. The bed
has accurately finished ways on which the worktable slides. The
gearing or hydraulic cylinder for driving the table is housed under
the bed.
(ii) Worktable :-
The table is a heavy rectangular casting, which carries the work by a very long hydraulic cylinder or by a pinion gear driving a rack which is fastened under the center of the table.
The motor driving the pinion gear is of reversible type with variable speed. The upper surface of the table has T slots in it to facilitate the clamping of the work or vises and special fixtures with Tools. The top surface of the table also has accurate holes for supporting the stop pins etc.
The side of the table has a groove for clamping planer reversing dogs at different positions. In some planers, hydraulic bumpers are fitted at the end of the bed to avoid the table from overrunning.
(iii) Column or housing :-
The frame of the planer is the same hollowbox type used on large milling machines. The frame is basically two heavy columns fastened together at the top with a large bracing section and fastened at the bottom to the machine bed.
This creates a very strong, rigid structure which will handle heavy loads without deflection. On a double housing planer, two housings or columns rise vertically at the sides of the machine. They support the cross rail and house the elevating screws and controls for the machine.
(iv) Cross rail :-
The cross rail is a heavy box or similar construction. It is mounted in a horizontal position on the vertical ways of the housing. It slides up and down on veer or flat ways, controlled by hand or by power operated screws. These cross rails are so heavy that they are counterweighted, with either cast-iron weights or hydraulic cylinders, in order that they may be moved easily and positioned accurately.
After being positioned, they are clamped in place. The purpose of the cross rail is to carry the vertical tool heads which by means of feed screws may be moved from left to right. It is very essential that the cross rail, when clamped, be parallel to the table for obtaining accurate machined surfaces.
(v) Saddle :-
The saddle is fitted to the ways of the cross rail. On its front surface are ways to which the tool head is fitted, together with a vertical feed screw that provides for a vertical movement of the tool head. There are two saddles one for the left tool head, the other for the right tool head. Each one may be operated independently of the other.
(vi) Tool head :-
The tool head of a planer is similar to that of a shaper both in construction and in operation. The tool head is attached to the saddle which contains the tool post which. in turn, holds the cutting tool. The tool post is hinged to the head so that on the return movement of the table the cutting tool will be raised and ride on the top of the work.
This saves the cutting edge of the tool from being damaged and permits the automatic traverse feed to operate without interference. A feed screw is provided to move the tool head with respect to work. The tool head can be swiveled for taking angular cuts. There are four tool heads, two in vertical position on the cross rail, and the other two known as side tool heads mounted one each on the two columns below the cross rail.
Planer Tools:-
Planers are expensive machine tools. In most cases, they represent high overhead rates and, accordingly, must be operated at the highest possible efficiency and over as continuous a time period as possible. A fundamental requirement for economical planer operation is that all cuts should be as heavy as possible. Planer tools are though similar to shaper tools, but they are much larger and heavier.
Planers are expensive machine tools. In most cases, they represent high overhead rates and, accordingly, must be operated at the highest possible efficiency and over as continuous a time period as possible. A fundamental requirement for economical planer operation is that all cuts should be as heavy as possible. Planer tools are though similar to shaper tools, but they are much larger and heavier.
Planer cutting tools may be of the following types:
(i) Forged solid type
(ii) Tool bits held in holders.
Tool bit is preferred by some because it is more economical than a set of solid tools and often is more convenient.
The straight round nose tool is intended mainly for taking roughing cuts on castings. The broad nose tool is used for taking finishing cuts on cast iron. The round nose left and right hand fools are used for planning vertical surfaces on cast iron or steel work pieces.
For smaller angles, such as often occur in planning work, the facing and cornering tool is used. This tool will allow machining in sharp corners. Knife tools are found useful on some classes of work where sharp comers are required.
Diamond point tool is largely used for horizontal planning on the surface of steel and cast iron for either roughing or finishing cuts. The slotting tool is used for forming grooves and cutting pieces of work into parts. Side recessing and under cutting tool is used for cutting grooves or slots in vertical or angular surfaces. The radius tool is used for finishing radii.
A tool holder of cranked form and cutters of any convenient shape can be held quite firmly in it.
Planer Feed Mechanism:-
As in a shaper, in planer too feed is provided to the cutting tool intermittently and at the end of the return stroke. Cross feed or horizontal feed is given by moving the tool head along the cross rail and it is used for machining horizontal surfaces.
Down feed or vertical feed is given by moving the vertical slide of the tool head with the help of down feed screw of the tool head. For machining work pieces of different heights, sometimes longer vertical movement of the tool is required.
This is achieved by moving the cross rail up or down along the column ways. Down feed is given when machining a vertical or angular surface.
Planer Tool Holder:-
When using tool bits, the common practice is to use a heavy tool shank of plain carbon steel or of high strength treated alloy steel with High speed steel.
Cast alloy or Carbide tip clamped or brazed to the shank.
High speed steel or cast alloy tools are used for heavy roughing cuts. Carbide tools are used for finishing cuts. Caution must be exercised in using carbide tools on machines not equipped with an automatic lifting device for the tool on the return stroke. If the tool is permitted to rub the work, the cutting edge is likely to be chipped.
High speed steel or cast alloy tools are used for heavy roughing cuts. Carbide tools are used for finishing cuts. Caution must be exercised in using carbide tools on machines not equipped with an automatic lifting device for the tool on the return stroke. If the tool is permitted to rub the work, the cutting edge is likely to be chipped.
Cutting tool shapes for common planer operations. The tools are usually tipped with high speed steel, cast alloy or carbide inserts.
Planer Work Holding Devices:-
Since heavy cuts (as much as 25 mm ) are taken at 18 to 30 m/min on a planer, the work piece must be solidly fastened to the table. Since the work piece is unusually heavy and must be reciprocated, it must be fastened \ to not only resist the cutting forces but also the high inertia forces that result from the rapid acceleration changes at the ends of the strokes.
Various devices used for holding work pieces on the planer table are:
(i) Planer vise
(ii) Step block
(iii) Planer screw jack
(iv) V -block
(v) End stops
(vi)Angle plate
(vii) Clamps
(viii) Parallel strips
(ix) Holding down dogs
(x) T -bolts, nuts, washers, packing, wedges etc.
(ii) Step block
(iii) Planer screw jack
(iv) V -block
(v) End stops
(vi)Angle plate
(vii) Clamps
(viii) Parallel strips
(ix) Holding down dogs
(x) T -bolts, nuts, washers, packing, wedges etc.
