The following points highlight the various operations performed on shaper in industries. The operations are: 1. Operations Involved in Shaping a Rectangular Job on Shaper 2. Machining a Thin Job on Shaper 3. Cutting an Angle on a Large Job 4. Cutting a Dovetail Bearing on a Shaper 5. Shaping a V or Key Way Centrally in a Block 6. Shaping Regularly Angled Component and Few Others.
Operation # 1. Operations Involved in Shaping a Rectangular Job on Shaper:
First of all the vise should be set on the table with the jaws parallel with the stroke of the ram. Then the material may be placed in the vise and shaped to the required thickness. Next, the material must be turned so that this finished surface is against the solid jaw of the vise and then the metal shaped to the required width.
Vise must then be turned by 90° so that the jaws are perpendicular to the stroke of the ram; and job placed in one end of the vise so that the surface to be machined is close to the top surface of the vise jaws. The other end of the vise should be blocked with a piece of material of the same thickness, to keep the jaws parallel.
The solid jaw of the vise will keep the work square in the plane parallel to the jaws. A solid square must be used to set the work square in the plane perpendicular to the jaws before the jaws of the vise are tightened. The end may then be machined to the required length. In taking a finishing cut, the speed should be increased.
Operation # 2. Machining a Thin Job on Shaper:
In machining a thin job on shaper, the important point to be borne in mind is that it should be prevented from warping. For this purpose, first a light cut should be taken off each side to relieve the internal strain of the metal. Then more light cuts should be taken off each side, alternately, until the correct thickness is obtained.
Operation # 3. Cutting an Angle on a Large Job:
When cutting an angle on a large job, using a shaper having a universal table, the universal table should be tilted (tool-head should not be swung to the required angle), because this makes it possible to use the automatic table feed. If the tool head is set at the required angle and there is an automatic down feed, then it will be necessary to use the hand down feed.
In a more frequently used method, the work-piece is held in a shaper vise and the shaper head set over to the required angle. The clapper box should be tilted with the top slanting away from the surface being cut so that the cutting tool can clear the workpiece on the return stroke.
The shaper head slide is used to feed the cutting tool in cutting the angular surface. When shaping angular surfaces with the shaper head set at an angle, the ram must not be run back into the column, otherwise the shaper head slide will strike the column.
Operation # 4. Cutting a Dovetail Bearing on a Shaper:
First the tool head of the shaper should be set at the same angle as that of the dovetail to be cut. The work, once set, should not be disturbed in shaping the angular and flat surfaces of the dovetail. The clapper box is tilted at an angle to allow the tool to clear the work on the return stroke.
The horizontal surfaces should be machined before completing the angular surfaces. A right-hand tool and a left hand tool are used to machine the angular sides, one at a time, as shown in Fig. 14.25. Both roughening and finishing tools should be used if considerable stock is to be removed.
In using two tools and moving the tool-head from one side of the centre line to the other, great care must be exercised, because, if there is any variation in the angular setting of the head, a variation in the angular sides of the dovetail will result.
Another way of cutting a dovetail, when the sides of the work are parallel and the solid jaw of the vise is parallel with the stroke of the ram, requires only one tool. First, the sides of the dovetail may be rough cut to within 0.4 to 0.8 mm of the finished size.
Next, a light cut may be taken on one side, and then the work be reversed in the vise without disturbing the setting of the table, and a light cut taken off the other sides. Size should be checked and the process repeated until the finished size is obtained. Using this method, the dovetail will be held central with the work and the angles will be the same.
In shaping dovetail bearings, it is very important to incline the clapper box in the proper direction so that the tool will swing away from the work on the return stroke of the ram. It is important to note that the clapper box must be set in a direction away from the surface being machined (or in other words, the clapper box should be turned away from the surface to be cut).
Operation # 5. Shaping a V or Key Way Centrally in a Block:
One method is to lay out the job and shape to scribed layout lines. A more accurate method of shaping a Vis to set the vise jaws parallel to the stroke, set the tool-head at the required angle, and rough cut the layout lines. Next, take a cut from side of the V, then reverse the job in the vise.
With the table set in the same position, lake a cut off the opposite side. Continue this until both sides of the V are cleaned up and the proper depth has been obtained. The V will then be in the centre of the block. The same procedure may be used in shaping a keyway.
Operation # 6. Shaping Regularly Angled Component:
Parts like hexagonal nut are shaped by holding them in an indexing fixture or dividing head. A headstock and tailstock each have a central parallel tongue on their machined base, thus allowing them to be lined up by means of one of the table grooves.
The spindle in the headstock can be rotated with the help of dividing plate and locked in a desired position. Catch plate, or chucks can be mounted on the end of the spindle on headstock. Dividing plate is a circular steel disc having a series of circular holes equally spaced on different circles and is a light press fit on the spindle.
The accuracy of the work is dependent on the accuracy of the pitching of the holes in the dividing plate, and the absence of ‘play’ in the spindle, the plate, and the plunger.
Operation # 7. Shaping an Irregularly Curved Surface:
The required shape is scribed on the surface of the material. After the work has been secured in position on the machine, the operator, by skilful manipulation of the vertical and horizontal feeds, guides the cutting tool so that it will follow the layout lines. This method is also known as contour shaping.
Operation # 8. Cutting a Keyway on a Shaper when the Key Way does not Extend the Entire Length of the Shaft:
For this purpose, first drill a hole slightly larger and deeper than the width and depth of the keyways at the place where the keyway ends. Set the position of the shaper stroke so that the tool will stop in the centre of the drilled hole at the end of the forward stroke. Then the keyway may be cut in the usual manner.
In this operation, the clapper box must not be tilted or else the cutting tools may bind on the side of the groove. Further, the shaper should be equipped with an automatic tool-lifter which lifts the tool clear of the work piece on the return stroke. If the shaper is not equipped with an automatic tool-lifter, the tool should be lifted clear of the groove manually on the return stroke.
Operation # 9. Machining Angular Surfaces on Shapers:
The angular surfaces may be machined on a shaper by:
(i) Setting the workpiece at the desired angle.
(ii) Swivelling the vise to the required angle.
(iii) Setting the tool head to an angle.
Operation # 10. Sequence of Machining Sides of a Rectangular Piece Square and Parallel:
Fig. 14.26 shows the correct sequence for machining the four sides of a block to ensure that its sides are square and parallel. Of course, it must be ensured that dirt and burrs are removed from the work, vise, and parallels to avoid any inaccuracy.
Determine the cutting speed and material removal rate for shaper operating at 2 cutting strokes/sec to machine a workpiece of 300 mm length at a feed of 0.4 mm/ stroke and 6 mm depth of cut. Determine the time to machine the component with width of 150 mm. Also determine the chip cross sectional area and power required if cutting edge angle is 90°, and specific cutting energy is 1500 N/mm2.
N = 1.5 strokes/sec, (= 90 strokes/min),
l = 300 mm, f= 0.4 mm per stroke
Assume 25 mm extra stroke on either side effective length of stroke L = 300 + 2 x 25 = 350 mm
If ratio of working to return stroke is 2, then cutting speed: