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For drilling small holes in metal, the breast drill shown in Fig.

A valve grinding tool patterned largely after a breast drill is shown at Fig.

To break the seal, a hollow reamer or facing tool, fitted into a drill press or breast drill, is slipped over the post.

The placing and working of the former consumes considerable time, and the labor of drilling with the breast drill is excessive and exhausting.

For this the Scotch or ratchet drill, if the job is heavy, is employed, and if light, the breast drill.