| Back Draft | (english) Reverse taper which would prevent removal of a pattern from a mold or a core from a corebox. |
| Back End | (english) 1) Usually refers to the entry end of process lines. 2) The outside lap 2) of the produced coil, or the inside lap of the consumed coil. |
| Back Gears | (english) Gears fitted to a machine to increase the number of spindle speeds obtainable with a cone or step pulley belt drive. |
| BACK PRESSURE | (english) The level of pressure on the return or downstream side of a device or system. |
| Back Rake | (english) The angular surface ground back from the cutting edge of cutting tools. On lathe cutting tools. The rake is positive if the face slopws down from the cutting edge toward the shank, and negative if the face sloopes upward toward the shank. |
| Back-up Balance | (english) Cylinders that supply the force used to hold the back-up rolls up in place. |
| BACK-UP RING | (english) A fabric or plastic device that is used with an o-ring or other gasket to prevent extrusion of the o-ring or gasket into an adjacent space or crevice |
| Back-up Roll | (english) 1) Roll used as a support roll mainly for plater rolls. 2) Two rolls, one on top and one on bottom of the two work rolls which apply pressure and reduce the flexing of the work rolls. |
| Backer (back-up plate) | (english) A “tool” or reinforcing part, which presses against the outer surface of an extrusion die, supporting it against the pressure of the extruding metal. The backer has an opening larger than the die aperture, allowing the extruded product to emerge without marring its soft surface. |
| Backing Board (Backing Plate) | (english) A second bottom board on which molds are opened. |