MACHINE-SHOP PRACTICE 429 



which pull in and out in a straight line as well as swing in 

 a circle. This straight-line adj ustment allows a number of 

 holes to be drilled in a row without swinging the table. 



495. Shaper. Shapers and planers are used for finishing 

 plane surfaces. The shaper is a small machine on which 

 light work is fastened to the bed or held in a planer chuck. 

 The tool is held in a tool post at the end of a ram which is 

 made to move forward and back, the cut taking place 

 on the forward stroke. There are both geared and crank 

 shapers, the kind used depending on the method of running 

 the ram. With a crank shaper one belt is required to drive 

 the machine, while a geared shaper requires two belts 

 running in opposite directions. This latter type may be 

 operated either by friction between the two pulleys or by 

 shifting the belts alternately onto a tight pulley and thus 

 alternating the direction of the ram. 



496. Planer. A planer works on the same principle as 

 the shaper, the shaft to which the tight pulley is fastened 

 being geared to the platen or table so that the table runs back 

 and forth. The work is fastened to the platen or held in a 

 chuck. The tool is held in a head which may be raised or 

 lowered to suit the work. This head is fed across on a cross- 

 guide by means of a screw actuated by a ratchet-feed. Heads 

 are also placed on the housings so that they may be adjusted 

 to plane on the edges or sides of the work. Considerable 

 skill is required to fasten the work, so that when completed 

 it will not spring out of shape, but will remain true. 



497. The Operations of Planing. The planer is one of 

 the heaviest of machine tools. Planing is rough and heavy 



