Published circlip thrust ratings assume a perfectly sharp groove corner. Whatever radius your cutting tool leaves comes straight off the load-bearing face — subtract it from the groove depth before you believe the number.
The groove wall carries thrust over a flat ring of metal one groove-depth high, so capacity is proportional to that depth. A tool nose radius replaces the bottom of that face with a curve that carries almost nothing. The groove still gauges to full depth, which is why no inspection catches it: a 0.2 mm radius costs about 39% of a 20 mm shaft’s rating and 11% of a 100 mm one, because depth grows with diameter and the tool radius does not.
On small shafts it is not a derating but a wipeout. A 10 mm groove is 0.2 mm deep, so a 0.2 mm nose radius removes the bearing face entirely and there is no percentage left to quote. It also flatters the real situation whenever the retained part has a chamfer of its own — that tips the ring and lets it roll out of the groove, a larger loss than the corner radius and one no published dimension lets you compute.
Estimate with the rule, then check it against the calculator that models it properly.
Open Circlip Calculator →Published circlip thrust ratings assume a perfectly sharp groove corner. Whatever radius your cutting tool leaves comes straight off the load-bearing face — subtract it from the groove depth before you believe the number. The groove wall carries thrust over a flat ring of metal one groove-depth high, so capacity is proportional to that depth.