Elements of General Drafting for Mechanical Engineers

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 edition. Excerpt: ...in the ruling pen or to negligence in repairing it. The ruling pen should have its blades made of the best tempered steel. It can be tested for the softness or hardness of the material by drawing a Swiss file lightly across its nibs. The insides of the blades of the ruling pen should be as little concave as possible. One blade should be arranged with a properly designed hinge or a device for opening the blade quickly and widely. Many draftsmen oppose the hinged ruling pen on the ground that the joint for the hinge impairs a certain rigidity which is essential when the pen is in use. It is undeniably true that a blade is more rigid when not jointed, but hinged ruling pens have been designed, and there are some few on the market, which meet all the essential requirements of rigidity. It is vitally necessary that the hinged ruling pen be designed with an effective device for taking up the wear at the joint. 102. A pen must be kept thoroughly clean, and a pen is not necessarily thoroughly cleaned by drawing a rag through it when the nibs are close together, but, if it is necessary, each nib should be rubbed off and smoothly polished. Hence, the convenience gained from a common sense wide-opening pen. 103. The handle should be made of a material that is not easily broken. Bone or ivory handles are undesirable because they are easily broken, but an aluminum or ebony handle is very satisfactory, particularly the former. 104. The ends of the nibs must be kept in prime condition. Such a condition obtains when the ends of the nibs are perfect arcs whose radii are not over one thirty-second of an inch; are sharp as a pocket penknife; and both touch the paper when the pen is placed with its axis in a plane perpendicular to the plane of the paper....