Collets provide a quick, easy method of mounting cylindrical parts or bar stock in the lathe with a great deal of centering accuracy. Each collet is actually a small, precision 3-jaw chuck that fits into a special tapered adapter in the headstock. A drawbar that passes through the headstock and threads into the back side of the collet is used to draw the collet up into the tapered adapter. The adapter causes the jaws of the collet to close down, gripping the part to be machined. Typically, collets provide a very accurate part mounting system, but each size collet can accommodate only a small range of diameters of approximately ±.001″ (.02mm).
WW collets differ from milling collets in that they have a hole all the way through the collet and drawbar. The maximum diameter stock that can pass entirely through the collet is 3/16″ or 4.5mm, although collets are available up to 5/16 and 8.0 mm. The WW collets that are larger than the through-hole diameter are sometimes referred to as “pot” chucks.
Sherline collets are numbered logically:
- Inch collets all begin with part number 1160 followed by two digits which indicate the size in 64ths of an inch. For example, a 13/64″ collet would be P/N 116013 and a 1/4″ collet (16/64″) would be P/N 116016.
- Metric collets all begin with part number 1178 followed by two digits indicating the size in 0.1 mm increments. For example, P/N 117813 is 1.3 mm.
These collets are not hardened. They are manufactured by Sherline and are built to standard WW specifications; however, we have come across collets that are called “WW” but will not fit our drawbar and adapter. Sherline collets have a shank diameter of .312-.313 and a .275-40 thread. Be sure to check WW collets made by other manufacturers to be sure they fit our adapter before you purchase them. Sherline manufactures a slightly larger .315″ adapter and drawbar set (P/N 1163) that will accommodate some of these other brands of 8 mm collets.
Sherline WW collets are available in inch sizes by 64ths of an inch from 1/64″ to 5/16″. Metric sizes go from .3 mm to 8.0 mm by .1 mm increments. See the drop-down menu above for sizes and part numbers. Special sizes up to .320″ can be special ordered with approximately a 3-week wait (please call or email for more information). Larger collet “pot” chucks are also available.