Brass tubes are prepared for polishing by being floated with a file, the teeth of which act as cutters and take off the top skin of the metal. Instead of floating, the tubes maybe polished by grinding with an emery wheel of about 150 fineness. This wheel, 12 in. in diameter, is fixed on the end of the polishing spindle by means of a false nose, the wheel being held in place by a nut screwed tight on the end of the thread of the upindle. On the bench is fixed a large compound slide-rest with an arrangement to carry the tube; a table is placed both in front and at back of the slide-rest to prevent the tube bobbing about. The advantage of the slide-rest is that any size of tube from 5/8 in. to 2in. may be ground by simply raising or lowering the tool-holder and the tube carrier. The tube is placed on the carrier and adjusted till there is the slightest pressure or allowance for grinding by the wheel. The side of the wheel, not the edge, is used to grind with, and the tube is passed between the rest and the wheel, which takes off from the tube, with a circular motion, the thinnest possible amount of brass.

Each side is served in this manner.

Tubes are ground much more quickly by this method than by hand floating. After grinding, the tubes are treated with ordinary polishing sand and finally finished off with the ordinary cotton mop and compo. The mops should be closely sewn together, the rows of stitching being about 3/8in. apart. They are further strengthened by bolting together with four ordinary snap-head, square-shank 1/4-in. diameter iron pins with nuts.