Polishing

is the longest, and not the least expensive proce in the needle manufacture. This is done upon bundles containing 500,000 needles; and the same machine under the guidance of one man, polishes from 20 to 30 bundles at a time; either by water or steam power. The needles are rolled up in canvas along with some quartzose sand interstratified between their layers, and the mixture is besmeared with rape-seed oil. Fig. 762. represents one of the rolls or packets of needles 12 inches long, strongly bound with cords. These packets are exposed to the to-and-fro pre ure of wooden tables, by which they are rolled about, with the effect of causing every needle in the bundle to rub against its fellow, and against the siliceous matter, or emery, enclosed in the bag. Fig. 763. represents an improved table for polishing the needles by attrition-bags. The lower table M M is movable, whereas in the old constructions it was fixed; the table C has merely a vertical motion, of pre ure upon the bundles, whereas formerly it had both a vertical and horizontal motion. Several bundles may obviously be polished at once in the present machine. The table M M may be of any length that is required, and from 24 to 27 inches broad; resting upon the wooden rollers B , B , B , placed at suitable distances, it receives a horizontal motion, either by hand or other convenient power; the packets of needles A , A , A , are laid upon it, and over them the tables C , C , C , which are lifted by means of the chains K , K , K , and the levers L , L , L , in order to allow the needles to be introduced or removed. The see-saw motion forces the rouleaux to turn upon their own axes, and thereby creates such attrition among their contents as to polish them. The workman has merely to distribute these rolls upon the table M , in a direction perpendicular to that in which the table moves; and whenever one of them gets displaced, he sets it right, lifting by the help of the chain the loaded table. The table makes about 20 horizontal double vibrations in the minute; whereby each bundle, running over 24 inches each time, pa es through 40 feet per minute, or 800 yards in the hour. IMG:4147767755307473660_illo0884a.png:Scouring cask