Reviewing these mechanical conditions, we may at once see sufficient reasons for the platen movement of planing machines; and that it would be objectionable, if not impossible, to add a traversing or cutting action to tools already supported through the medium of eight joints. To traverse for cutting would require a moving gib joint in place of the bolted one, between the standards and main frame, leading to a complication of joints and movements quite impracticable.
When we pass from Plutarch to Maximus Tyrius and Apuleius, the darkness grows perceptibly thicker, and is no longer broken by the lucida tela diei with which the Theban thinker had combated at least one class of mistaken beliefs. These writers are so occupied with developing the positive aspects of supernaturalismdaemonology, divination, and thaumaturgythat they can find no place for a protest against its extravagances and perversions; nor is their mysticism balanced by those extensive applications of philosophy to255 real life, whether under the form of biography or of discourses on practical morality, which enabled Plutarchs mind to preserve an attitude of comparative sobriety and calmness. Hence while Maximus is absolutely forgotten, and Apuleius remembered only as an amusing story-teller, Plutarch has been perhaps the most successful interpreter between Greek humanity and modern thought. His popularity is now rapidly declining, but the influence exercised by his writings on characters differing so much from one another and from his own as those of Montaigne, Rousseau, and Wordsworth, suffices to prove, if any proof be needed, how deep and wide were the sympathies which they once evoked.CHAPTER XIII
ONE:Bruce turned them over one by one. There was no mistake about the matter at all. They were the same numbers as those given in the handwriting of the dead man. The whole thing seemed impossible, but there it was.Screw-cutting machines may be divided into modifications as follows:(1) Machines with running dies mounted in what is called the head; (2) Machines with fixed dies, in which motion is given to the rod or blank to be threaded; (3) Machines with expanding dies which open and release the screws when finished without running back; (4) Machines with solid dies, in which the screws have to be withdrawn by changing the motion of the driving gearing; making in all four different types.
(1.) Into what classes can gearing be divided?(2.) What determines the wearing capacity of gearing?(3.) What is the advantage gained by employing wooden cogs for gear wheels?(4.) Why are tangent or worm wheels not durable?"And what do you want to write about?"A planing machine with a running platen occupies nearly twice as much floor space, and requires a frame at least one-third longer than if the platen were fixed and the tools performed the cutting movement. The weight which has to be traversed, including the carriage, will in nearly all cases exceed what it would be with a tool movement; so that there must exist some very strong reasons in favour of a moving platen, which I will now attempt to explain, or at least point out some of the more prominent causes which have led to the common arrangement of planing machines.
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