The engraving represents the best possible form of tool for roughing out wrought-iron, or for removing a large mass of that metal in the lathe or planing-iuachine. When used on large work, it should be tempered to a light straw-color, which will leave it strong enough to stand without breaking the heavy strain due to the cut. It must be held very firmly, and with the cutting edge as close to the tool-post as it can well be.

Roughing Tool, For Wrought Iron

Roughing Tool, For Wrought Iron

The following are its rates of cutting speed and feed, the speed meaning the length of shaving it cuts off, and the feed implying the number of revolutions of the lathe necessary to feed the tool an inch along its cut:

Size of work, inches diameter.

Cutting speed, feet per minute.

Feed.

1 and less

35

25

lto 2

25

20

2 " 5

20

20

5 " 12

18

15

12 " 20

16

12

20 and over

15

12

For work of five inches diameter, and for all sizes below that, the tool should be hardened right out; that is, made as hard as fire and water will make it, and not tempered at all. For work of a larger size, it should be tempered to a light straw-color. This tool, with the top face ground less keen, that is, more nearly horizontal, is an excellent one for steel, and the harder the metal to be cut, the more nearly horizontal the top face must be. It should be placed, for lathe-work, so that the cutting edge stands a little above the horizontal centre-line of the work.