From Longman Dictionary of Contemporary Englishwork your fingers to the bonework your fingers to the bone (also work your socks off informal)WORK HARD to work very hard → work
Examples from the Corpus
work your fingers to the bone• In those days we got up at 5 in the morning, and worked our fingers to the bone.• His mother had had a hard life - had worked her fingers to the bone bringing up six children. 