The Roughness Comparison Specimens are simple to use, inexpensive, and therefore widely used in many different applications. They are great for checking roughness of turned, milled, ground, reamed, polished or lapped parts during machining.
The measurement of surface roughness is not as straight forward as most other engineering measurements, such as length, angle or hardness; and in order to get good accuracy, expensive instruments are needed. These are often unsuitable for workshop use, where roughness of machined surfaces can usually be assessed conveniently and with sufficient reliability using visual and tactile (fingernail) comparison with a standard set of surfaces machined in the same way.
There are types to choose from:
Comparison Standards Type 130
This set consists of 30 comparison specimens, covering six commonly-used machining methods (6 turned, 6 end-milled, 6 horizontally milled, 6 surface-ground, 3 lapped, 3 reamed/drilled. A label gives the Ra and Rz values of each specimen in both metric and imperial units.
Great for checking the roughness of spark-eroded surfaces as described in the VDI 3400 Guideline, the roughness of steel surfaces which have been prepared for painting by blast-cleaning, as outlined in ISO 8503 and estimating the surface roughness prior to accurate measurement by a stylus instrument, as recommended
in BS EN ISO 4288, eg.
They can by used to check the seriousness of damage to parts caused by nicks, dents and scratches and reconditioned ship propeller blades
Made from 100% Nickel
Comparison Standards Type 013
This comparator scale has 12 specimens of spark-eroded (EDM) surfaces, with roughness values corresponding to nos. 12 - 45 inclusive as specified in the internationally-used guideline document VDI 3400.
A label on the rear face gives the Ra and Rz roughness values for each patch.
It is a scale often used by German machine manufacturers
BS EN ISO 4288
13132 - Surface Roughness Standards Composite Set - Includes Surface Roughness Standards and Certificate of Conformance
13133 - Roughness Comparison Set includes EDM Finish Scale, and Type 013