| 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. |
| Backing Sand | (english) The bulk of the sand in the flask. The sand compacted on top of the facing sand that covers the pattern. |
| Backoff | Removal of part of coil from entry end of unit; may be necessitated by a defect in coil or by a wreck in the mill, etc. Backoff weight is the part of the coil that is removed and not finished/produced. |
| BACKUP BOTTLE | (english) A vessel, normally cylindrical, which is used to store gas for future release of the energy in the compressed gas to an accumulator. |