reciprocating cutting action.It generates flat or contoured surfaces in a series of straight cuts.Its efficiency is higher than that of the shaper.
The work on the planer is held on the machine table and moves under the tool which is carried on the rail.The bed must be approximately twice as long as the table to support it at all positions during the stroke.The double-housing on one side only.Open-side planers are designed for work-pieces which are so wide that they can pass between the housings of double-housing planers.The double-housing machine,however,offers greater rigidity.
Some of the work that was formerly done on the planer is now done on the planer-type milling machine since the former is not so efficient as the latter.However,there are still many jobs that can be carried out better and more economically on the planer than on any other machines.For
example,angular surfaces are often easier to machine on a planer.Planning is also most effective in the machining of long and narrow surfaces.In addition,the planer usually takes the important first cut on the rough forging or casting to establish a reference surface for subsequent machining.
Grinding Machines
Grinding,or abrasive machine,is one of the most rapidly growing metal removal processes in manufacturing.Many machining operations,previously done on conventional milling machines,lathes and shapers,are now performed on various types of grinding machines.
There is a great variety of grinding machines.The machines that are generally used are cutter grinder,surface grinder,centerless grinder,external grinder,internal grinder,and tool grinder.
Five types of grinding operations are performed on grinding machines:
（1）Surface grinding.Surface grinding are used to produce flat,angular and irregular surfaces.In the surface grinding process,the grinding wheel revolves on a spindle;and the workpiece,mounted on either a reciprocating or a rotary table,is brought into contact with the grinding wheel.
（2）Cylindrical grinding.Cylindrical grinding is the process of grinding the outside surface of a cylinder.These surfaces may be straight,tapered or contoured.Cylindrical grinding operations resemble lathe turning operations.They replace the lathe when the workpiece is hardened or when extreme accuracy and superior finish are required.As the workpiece revolves,the grinding wheel,rotating much faster in the opposite direction,is brought into contact with the part.The workpiece and table reciprocate while in contact with the grinding wheel to remove material.
（3）Centerless grinding.Centerless grinding machines eliminate the need to have center holes for the work or to use workholding devices.In centerless grinding,the workpiece rests on a workrest blade and is backed up by a second wheel,called the regulating wheel.The rotation of the grinding wheel pushes the workpiece down on the workrest blade and against the regulating wheel.The regulating wheel,usually made of a rubber bonded abrasive,rotates in the same direction as the grinding wheel and controls the longitudinal feed of the work when set at a slight angle.By changing this angle and the speed of the wheel,the workpiece feed rate can be changed.
（4）Internal grinding.Internal grinders are used to accurately finish straight,tapered or formed holes.The most popular internal grinder is similar in operation to a boring operation in a lathe.The work-piece is held by a workholding device,usually a chuck or collet,and revolved by a motorized headstock.A separate motor head in the same direction as the workpiece revolves the grinding wheel.It can be fed in and out of the work and also adjusted for depth of cut.
（5）Special grinding processes.Special types of grinders are grinding machines made for specific types of work and operations.A brief description
of the more commonly used special types follows:
Tool and cutter grinders:There grinding machines are designed to sharpen milling cutters,reamers,taps and other machine tool cutters.
The general purpose cutter grinder is the most popular and versatile tool grinding machine.Various attachments are available for sharpening most types of cutting tools.
Jig grinding machines:Jig grinders were developed to locate and accurately grind tapered or straight holes.Jig grinders are equipped with a high speed vertical spindle for holding and driving the grinding wheel.They utilize the same precision locating system as do jig borers.
Thread grinding machines:These are special grinders that resemble the cylindrical grinder.They must have a precision lead screw to produce the correct pitch,or lead,on a threaded part.Thread grinding machines also have a means of dressing or truing the cutting periphery of the grinding wheel so that it will produce a precise thread form on the part.
Boring Machine
Boring,also called internal turning,is used to increase the inside diameter of a hole.The original hole is made with a drill,or it may be a cored hole in a casting.Boring achieves three things:
Sizing:Boring brings the hole to the proper size and finish. Straightness:Boring will straighten the original drilled or cast hole. Concentricity:Boring will make the hole concentric with the outside diameter within the limits of the accuracy of the chuck or holding device.
The boring operation is generally performed in two steps;namely,rough boring and finish boring.The objective of the rough-boring operation is to remove the excess metal rapidly and efficiently,and the objective of the finish boring operation is to obtain the desired size,surface finish,and location of the hole .The size of the hole is obtained by using the trial-cut procedure.The diameter of the hole can be measured with inside calipers and
outside micrometer calipers.Basic Measuring Instruments,or inside micrometer calipers can be used to measure the diameter directly.
Shoulders,grooves,contours,taper,and threads are also bored inside of holes.Internal grooves are cut using a tool that is similar to an external grooving tool.The procedure for boring internal shoulders is very similar to the procedure for turning shoulders.Large shoulders are faced with the boring tool positioned with the nose leading,and using the cross slide to feed the tool.Internal contours can be machined using a tracing attachment on a lathe.The tracing attachment is mounted on the cross slide and the stylus follows the outline of the master profile plate.This caused the cutting tool to move in a path corresponding to the profile of the master profile plate.Thus,the profile on the master profile plate is reproduced inside the bore.The master profile plate is accurately mounted on a special slide which can be precisely adjusted in two directions,in order to align the cutting tool in the correct relationship to the work.Normal turning cuts are taken with the spindle rotating counterclockwise.The boring cut is taken with the spindle revolving in a clockwise direction,or \
相关推荐：
loading