Major Overhauling of Machine Tools

Major Overhauling of Machine Tools

Major Overhauling of Machine Tools - During the life of a machine one or more major overhauls are necessary unless, for a considerable portion of its existence, the machine is to become second rate and incapable of any but inferior jobs. A major overhaul will involve complete stripping of the machine and a through examination of all its elements and parts.

Worn slides will be refaced or rescraped to restore flatness and correct loss of alignment which may have occurred. The working surfaces of tables, etc., will require some renovation and, as far as possible, the making good of broken portions of tee slots, etc.

Repair to a Broken out Tee Slot

A - Plate fitted and Screwed into end milled recess

Replacements will be necessary for the important shafts unless the existing ones are in sufficiently good general condition to serve for a further period after their bearing diameters have been reground to a slightly smaller diameter or made good by some other method (see later). Whatever is done to provide a serviceable shaft, it will be necessary to renew the bearing liner bushes.

The chief issue on the leadscrews will be the condition of the thread. These may be renovated by matching up the thickness of the thread over the whole length, as previously explained, or, if too far gone, a new screw will be necessary. In any case replacements for the nuts will have to be made.

The remaining important items are gears, and unless these have been operating in an oil bath, on exceptionally light or on occasional leads, their replacement will be almost a necessity. A common tendency with gears is to allow them to remain in service provided they possess a full set of teeth, and if the tooth shape of some gears in use were projected and compared with unworn teeth of the same pitch the result would be amazing.

Worn gear teeth promote chatter and vibration which are detrimental to the finish and accuracy of the machined surfaces produced on the machine tool.

The remainder of the overhaul will consist of replacing such standard details as are unfit for further use (e.g. screws, nuts, taper pins, etc.), the removal of bruises and mutilations from the exposed portions of the machine and a final painting to reendow it with some measure of its youthful appearance.

No doubt when labour and material were in plentiful supply many engineers would dispose of a machine and purchase a new one, rather than undertake a major overhaul. Times and conditions are now such that the recommissioning of an old machine is a proposition not to be dismissed without serious consideration.