机电一体化专业英语黄星夏玉波Unit3课件教学.pptVIP

In the down position, the half-nut lever engages two halves of a split nut around the lead-screw. Make sure the half-nut lever is in the disengaged (up) position. Turn the motor on. The lead-screw should now be rotating counterclockwise. When the lead-screw is engaged the gear train makes kind of an annoying noise, but youll get used to it. Lubricating the gear train with white lithium grease will cut down some on the noise. Just as in facing, you normally will make one or more relatively deep (.010-.030) roughing cuts followed by one or more shallow (.001-.002) finishing cuts. Of course you have to plan these cuts so that the final finishing cut brings the work-piece to exactly the desired diameter. When cutting under power, you must be very careful not to run the tool into the chuck. Measuring the Diameter It is important to recognize that, in a turning operation, each cutting pass removes twice the amount of metal indicated by the cross slide feed divisions. Therefore, when advancing the cross slide by .010, the diameter is reduced by .020. The diameter of the work-piece is determined by a caliper or micrometer. Micrometers are more accurate, but less versatile. You will need a machinists caliper capable of measuring down to .001. Vernier calipers do not have a dial and require you to interpolate on an engraved scale. Turning a Shoulder A shoulder is a point at which the diameter of the work-piece changes with no taper from one diameter to the other. We will make a shoulder on our work-piece by reducing the diameter of the end of the work-piece for a distance of about 1/2. Advance the cross slide about .020 and use power feed to turn down about a 1/2 length on the end of the work-piece. Repeat this a few more times until you have reduced the diameter of the end section to about 1/2. Since the tip of the tool is rounded, the inner edge of the shoulder takes on a rounded profile. Now we will use this pointed tool to