Page:Practical Treatise on Milling and Milling Machines.djvu/48

42 A good quality of lubricant that is free from tendency to gum should be used, and a generous quantity applied daily.

The tension of the chain is usually regulated by the adjusting screws in motor bracket. It should run at a tension tha tmight be termed just a little too slack for a leather belt; that is, a slightly greater sag should be allowed.

Adjustments. As bearing surfaces and parts wear, it becomes necessary from time to time to make adjustments, and at all important points convenient means are provided for doing this. Flat bearings are provided with tapered gibs that are easily adjusted, and cylindrical bearings, like those of the spindle, have ready means of taking up wear. It is essential that any adjustment required be promtly

Fig. 3

made, for otherwise the accuracy of the machine is impaired. Furthermore, parts wear much more rapidly as the lost motion becomes greater. By a little examination and adjustment every now and then, the efficiency of a machine can be maintained and its life indefinitely prolonged.

Before proceeding to adjust or take anything apart, it is a good plan to carefully study the principle of construction. Many times this simple precaution will obviate considerable trouble.

The prevailing practice in designing spindle bearings is to have the front bearing on the spindle tapered and the rear bearing straight. On our machines the front bearing is adjusted by loosening check screw N and tightening nut F, Fig. 3. This draws the spindle back into the box, and as the bearing is tapered, the lost motion is taken up.