File:The manual training school, comprising a full statement of its aims, methods, and results, with figured drawings of shop exercises in woods and metals (1906) (14782738012).jpg

Identifier: manualtrainingsc00wood (find matches)
Title: The manual training school, comprising a full statement of its aims, methods, and results, with figured drawings of shop exercises in woods and metals
Year: 1906 (1900s)
Authors: Woodward, Calvin Milton, 1837-1914. (from old catalog)
Subjects: Manual training. (from old catalog)
Publisher: Boston, D. C. Heath & co.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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n of the spindle. The small toolsused in the drill-press are: drills, twist-drills, chucks, boringbars, and cutters. The chief difficulty in using the drill con-sists in properly supporting or clamping the piece to be drilledor bored. A smaller post-drill may be thought sufficient for asmall shop. After general lectures on the planer, shaper, and drill, singlestudents are put at each, and are closely watched and instructedby the teacher personally. As soon as they are familiar withtheir work, they are set to teach what they know .to a new setof boys. Later on these last boys became teachers of a thirdset, and so on till each has become acquainted with the toolsand has executed the specified exercises; the supervision re-quired from the teacher is thus reduced to a minimum. Mean-while the lathes are kept in systematic use. Chap. IV.) THE GOOSE-NECK DRILL. 141 In all machine-work the great practical difficulty lies not inthe proper adjustment of tools and of work for rigid material, but
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Fig. 125. Goose-neck Drill, Putnam Machine Company, Kitchburg, Mass. it arises from the springing of both tool and work when understrain. No tool is so rigid as not to bend, and no piece can be 142 THE THIRD, OR SENIOR YEAR. (Ohap. IT. SO securely clamped or supported as not to yield when subjectedto pressure, and the yielding is greater for points farther fromthe supports. Hence, pieces which should be long cylindersare larger in the middle than at the ends; screws which easilyreceive nuts at their ends, bind persistently farther down ; andso on in various ways. Again, iron and steel are not homoge-neous ; cast-iron in particular is full of inequalities. Hard spotsare found where the tool bends excessively. This may not bevisible to the eye, but it makes itself known in the case of snugfits. The necessity of running the tool over the work a secondtime for the purpose of removing the inequalities due to unequalhardness becomes obvious in actual work. Good judgment indealing with these

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