units
mil = 0.001"
micron = 0.001mm
25.4 microns = 1 mil
tolerance
dimensional variation
measuring tools
caliper
dial indicator
6Dof
six degrees of freedom
structural loop
rotary to linear motion
mechanical advantage
MA = output force/input force
MA = D applied force/D load moved
screws
v-thread
leadscrew
acme
square
ball
Leadscrew nut
wear-compensating
back lash
rotary bearings
L/D > 3
runout
linear bearing
L/D > 1
flexure bearing
snap-lock
thrust bearing
plane bearing
accuracy
repeatability/precision
resolution
Abbe's Principal
angular error amplified by distance
rigid couplings
set-screw
clamp
flexible couplings
helical
jaw coupling (spider)