Roughness Comparison Specimens

The measurement of surface roughness is not as straightforward as most other engineering measurements, such as length or 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.

These problems are solved by our range of Roughness Comparison Specimens. They are simple to use, inexpensive, and hence widely used in many different applications.

Samples from our range of comparison specimens

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, eg.
• checking the seriousness of damage to parts caused by nicks, dents and scratches
• checking reconditioned ship propeller blades

Type 130: Composite Set of Roughness Specimens

Our most popular specimen.

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 values of each specimen in both metric and imperial units. (Rz-value label available on request).

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(Type 130 detail)

The 100-series of comparators

The 100 series comparators are a range of heavy-duty sets of roughness specimens for workshop use, covering every common machining process. Click here for full details of our 100 series range.

(Type 119 detail)

The Microsurf 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. Click here for full details of our range.

(Type 321 detail)

Shot and grit-blasting comparators

These two comparators (item 017 for shotblasting, 018 for gritblasting) are specially designed to check the roughness of steel surfaces which have been blast cleaned to cleanliness grades SA 2.5 and SA 3 before painting. They conform to ISO 8503.

Item 013: EDM finish scale to VDI 3400

This comparator scale has 12 specimens of spark-eroded (EDM) surfaces, with VDI Nos. 12 - 45 inclusive. A label on the rear face gives the Ra roughness value for each patch.

Item 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. The accompanying instruction book gives full details in 3 languages.

Items 015 and 016: Ship propeller roughness scales

These comparators were designed together with Esso Corp. and Stone Manganese Marine Ltd., and have 6 specimens of ship propeller blade surfaces in various conditions. No. 015 is the Superintendent's version for office use, no. 016 is the Diver's version for underwater use.