As a footnote to my earlier reflections on Hand or machine? and Designer-makers: the world we have lost, it has struck me that the nature of accuracy in craft work has completely changed between hand and machine skills.
In hand work accuracy is the exercise of dexterity and poise, arising from judgement in the combination of the perceptions of the senses and the application of the hand. Skill is a constant response to, and if required, correction of what has been done to the artefact before.
Accuracy in machine work is all about consistent referencing to the established datum.
Sophisticated, modern, automated machines can establish a new accurate datum with each process, as programmed in advance. Hand operated machines, with scope for manually introduced error, need to be referenced back, as far as possible, each time to the original. Correction and modification is likely to result in unintended deviation.
