Groove or step turned or ground into a part before coating, so the sprayed layer reaches the finished dimension with the required thickness and its edges sit protected inside shoulders. The shoulders are chamfered, usually around 30 to 45 degrees, rather than square, to avoid edge chipping. Undercut depth equals the finished coating thickness plus any allowance for repair of worn metal.
Undercut the journal 0.015 per side with 45 degree shoulders, we'll put 0.025 on and grind back.
To a welder, undercut is a defect along the toe of a weld; in a spray shop it is a machining instruction, so check who wrote the note.
Also heard as
- undercutting
- recess
Related terms
Grind stock
Extra coating thickness sprayed beyond the final size so it can be ground or machined to finish.
Dimensional restoration
Rebuilding worn or mis-machined surfaces to original size with thermal spray, then machining to finish.
Bridging
Coating that forms a continuous skin across the edge of a mask, so it tears or lifts when the mask comes off.
Same word, different worlds
A notch the arc melts into the base metal beside the weld toe that the weld metal never fills back in.
Gear EngineeringA notch cut into the base of small-pinion teeth when the generating tool removes part of the working involute.
GeosyntheticsDigging out soft or unsuitable subgrade below grade and replacing it with better fill.