International Correspondence Schools · Scranton, Pa. : The Colliery engineer co. · leaf 342
nted on columns, similar to that shown in Fig.418. The column yJ is set in an upright position near theface of the heading, the top B of the column being forcedagainst the roof of the tunnel by the capstan screws Cwhich rest in special castings D on the floor of the heading.It is a common practice… … Fig. 417. 932 RAILROAD CONSTRUCTION. working of the drills. The arm E at right angles to thecolumn slides up or down the column by means of the collar F, and may be clampedin any position by the clamp G.The drill is carried on this armand revolves about it as an axis,thus giving a wide range…
Railroad engineering
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