Torque repeatability via torque-limiting ratchets or sleeves Micrometer

a micrometer reading not accurate if thimble over- or under-torqued. useful feature of many micrometers inclusion of torque-limiting device on thimble—either spring-loaded ratchet or friction sleeve. without device, workers may overtighten micrometer on work, causing mechanical advantage of screw tighten screw threads or squeeze material, giving inaccurate measurement. however, thimble ratchet or friction slip @ torque, micrometer not continue advance once sufficient resistance encountered. results in greater accuracy , repeatability of measurements—most low-skilled or semi-skilled workers, may not have developed light, consistent touch of skilled user.

might seem there no such thing little torque on thimble, because if 0 tightening of threads goal, less torque, better. however, there practical limit on ideal. tiny amount of torque, although slight, involved in normal hand movements of well-practiced micrometer use. light not zero, because 0 impractical skillful feel of how contact being made. , calibration reflects amount, tiny is. if 1 changes afraid touch sort of gingerliness, 1 being inconsistent norm calibration reflects, resulting in reading 1 3 tenths big (on typical metal part).

related torque topic interuser variation in normal. important try not have idiosyncratic touch, because although works intrauser consistency, interferes interuser consistency. people use rather heavy touch matter of habit, , fine in can highly accurate readings long calibrate micrometer accordingly. problem arises when use else s micrometer, or when uses theirs. heavy-touch user gets false-small readings, , normal-touch user gets false-big readings. may not arise in one-person shops, teams of workers sharing company-owned instruments must capable of interpersonal consistency close-tolerance work successfully. there , easy way synchronize on topic: used feel of how torque takes slip typical friction sleeve or click typical ratchet thimble—and incorporate same feel every use of micrometer, have no sleeve or ratchet. proper training machining trade, although not uncommon encounter coworkers not trained on point. in many cases seems in drilling don t overtorque idea trainees heads, opposite extreme mistakenly taught, user thinks goal compete else on can generate lightest touch. individuals naturally differ in touch, such competition not effective @ generating interuser consistency imagining every thimble has sleeve slip.

bench micrometers of super-mic class entirely obviate interuser variation having user dial handwheel until needle reads 0 on gauge, producing same pressure on every reading.