BS 817:2008 specifies the construction, and dimensions and tolerances, for rectangular and square surface plates for use as working planes for engineering purposes. It applies to those plates made of cast iron or granite, in two size ranges, from 160 mm × 100 mm to 2 500 mm × 1 600 mm and from 12 in × 12 in to 96 in × 48 in, and in four grades of accuracy.
BS 817 is applicable to new surface plates and to plates that are being resurfaced after they have become worn.
In addition to the definitive requirements, BS 817 also requires the information to be supplied by the purchaser and the items to be agreed between the contracting parties to be documented.
For compliance with this standard, both the definitive requirements and the documented items must be met.
BS 817 has been fully revised to bring it up to date. The tolerances are given in metric units, including those for the inch sizes of surface plate, and the intended use of plates of each of the four grades of accuracy specified is included for information.
BS 817:2008 supersedes BS 817:1988, which is withdrawn.
