The Boston Machinist; Being a Complete School for the Apprentice as Well as the Advanced Machinist. Showing How to Make and Use Every Tool in Every Branch of the Business. with a Treatise on Screw and Gear Cutting (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: deep. After doing this countersink them with a three-square countersink, made for the purpose. 5. Lesson Fifth. You will now learn other modes of drilling, the first being to drill holes through pieces of iron. In doing this they are first laid out a certain distance from the edges with a pair of dividers. Then make a punch-mark the distance from the edge or position where you wish to drill the hole. After marking this punch-mark set your dividers the size you want to drill the hole, and strike a circle around the mark made by the punch. Having done this, proceed to drill the hole, taking great care to drill within the circle, and if your drill runs to one side chip a piece out of the opposite side with a half-round chisel; this will bring the drill back to the centre of the circle. Continue this practice till the hole is perfectly true, and if you are careful at the first you will find no difficulty in drilling holes, and drilling them properly. 6. To Drill a Large Hole in the End of a Shaft. This is only done when you have no chuck that will hold the shaft. To do it properly drill a small hole the depth required with a straight spiral drill, or if you have none use a flat drill that is straight chapter{Section 4on the sides; then follow with one or two more larger sizes, as may be required. The object of using a small drill first is because, there being less pressure endwise on the drill, it will not run out side- wise, as it would if the small holes were not drilled first. In drilling with small drills, such as centre- drills, always speed up your drill as fast as it will run. This prevents breaking the drills, and. there is no danger of burning the points thereof, as some suppose, except the steel be very hard. 7. To Straighten Shafting. This should be don...