RS PRO Surface Gauge Set

RS Pro adjustable parallel set, used for checking, marking or positioning work. Consist of two precision ground pieces which slide smoothly on each other.

Parallels consist of 2 piece dove tailed together
Locked in place by set screws
Can be set to a micro meter for size

Set of 6 Parallels 3/8"-2 1/4" (9.5 - 57.2 mm)

Vinyl pouch

Parallels, Surface Finish & Hardness

Surface Finish

Any machined component has a surface geometry which consists of three basic elements:

Form or Curvature - Whether the surface has irregular bumps or dimensional changes
Waviness - Whether the surface has regular repetitive ripples or patterns (e.g. milling patterns)
Roughness - The shapes or irregularities that are smaller than, and form part of the waviness pattern (e.g. material micro-structure)

Waviness and roughness are traditionally the most difficult elements to measure when comparing surface finish, however, they have a radical effect on the performance of the finished component. Variations will cause aesthetic appearance changes, component wear variations, oil retention variation etc. Many manufacturers therefore specify a range of roughness values which their components should be manufactured to, often expressed as: Ra, Rq (RMS), RzDIN, Ry, Sm,mm.