Dowel pins are used to locate machine parts in a fixed position or to maintain alignment between them.They are of three types, viz. Spring dowel sleeves (hollow), Solid Dowel pins (hardened) and Taper Pins.Spring Dowel Sleeve generally conforming to IS 5988-1970 hardened and tempered to 445 to 515 HV - 2 x 16mm to 12 x 100mm.