In cases where surface roughness needs to be measured with great precision, elaborate instruments must be used. These are expensive, and 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.

Our range of Roughness Comparison Specimens can help in such cases. They are simple to use, inexpensive, and hence widely used in many different applications. The golden rule to follow, is to use comparison specimens which have been machined by the same process as the workpiece being checked.

Roughness Comparison Specimens

No. 130: Composite Set of Roughness Specimens

Our most popular set. This set consists of 30 comparison specimens, covering six of the most commonly-used machining methods: 6 cylindrically turned, 6 end-milled, 6 horizontally milled, 6 surface-ground, 3 lapped, 3 reamed/drilled. Type 130: Composite Set of Roughness Specimens Composite set type 130
The label states the Ra values of each specimen in both metric and imperial units. (Rz-value label available on request). Type 130 detail Type 130 detail

100-Series Comparators

The 100-series comparators are sets of roughness specimens in slightly heavier-duty presentation than the Microsurf comparators, and are more suited to workshop use. The 100-series comparators cover the same range of machining processes as the Microsurf series. 100 Series Comparators
Details of our 100 series range. Type 119 detail Type 119 detail

Microsurf range (300-series) of comparators

This is a range of light-weight comparators more suited to office and design shop use.

Each set in the range is presented in a plastic wallet, with an instruction card giving full details on the roughness values of the specimens. Details of our Microsurf range.

Microsurf series of comparators
Type 321 Detail Type 321 detail

Special comparators for particular applications

No. 013: EDM finish scale to VDI 3400

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 back states the Ra roughness value for each patch. Item 013: EDM finish scale to VDI 3400 Item 13

No. 014: Fine-Blanking scale to VDI 3345

This comparator was designed in cooperation with Feintool AG, and provides samples of the edges of fine-blanked parts. Item 014: Fine-blanking scale to VDI 3345 Item 14
The accompanying instruction book gives full details in 3 languages.
Item 014

Nos. 015 and 016: Ship propeller roughness scales

These comparators were designed in co-operation with the Esso Petroleum Company, and marine propeller manufacturers Stone Manganese Marine Ltd., and show 6 specimens of ship propeller blade surfaces in various stages of reconditioning.

No. 015 is the Superintendent’s version for office use.

Item 015 Item 15
No. 016 is the Diver’s version for underwater use. Item 016 Item 16

Nos. 017, 018: Shot and grit-blasting comparators to ISO 8503

No. 017 for Shot blasting
No. 018 Grit-blasting
These two comparators are specially designed to check the roughness of steel surfaces which have been blast cleaned to cleanliness grades SA 2.5 and SA 3 in preparation for painting. They conform to ISO 8503.
Shot and grit-blasting comparators Items nos. 17 and 18 (to ISO 8503) for blast-cleaning

Typical Applications of our comparison specimens:

  • checking roughness of turned, milled, ground, reamed, polished or lapped parts during machining
  • checking the roughness of spark-eroded surfaces as described in the VDI 3400 Guideline
  • checking the roughness of steel surfaces which have been prepared for painting by blast-cleaning, as outlined in ISO 8503
  • estimating surface roughness prior to accurate measurement by a stylus instrument, as recommended in BS EN ISO 4288,
  • checking the seriousness of damage to parts caused by nicks, dents and scratches
  • checking reconditioned ship propeller blades