Abstract: A guideway 10 of a guideway set in a coordinate measuring machine has a scale in the form of a metal strip clamped and bonded to an accessible face 46 of a spar 30, the latter being formed of a thermally stable material and being connected at one end to a reference position defined by a bracket 18 and a mounting plate 16 on the guideway 10. The spar 30 is mounted on the guideway 10 by spaced blocks 34 which are designed to accommodate any longitudinal movement of the guideway 10 due to thermal expansion, so that the spar 30 and the scale are effectively maintained in position. Because relative movement between the spar 30 and the scale is substantially prevented, the position of the scale is substantially fixed, providing improved scale accuracy.

Abstract: In a co-ordinate measuring machine, a linear guideway comprises two tubular guides 14, 16 mounted on a column 10 in a parallel spaced apart relation and extending in a direction parallel to the longitudinal axis of the column 10. The guides 14, 16 are mounted on the column 10 by a plurality of elongate bars 20 formed for example of carbon fibre. The bars 20 are so designed as to allow change in relative length between the guide 14 and the column 10 but to retain the guide 14 in a rigid relation to the column 10 in a direction along the axis of each of the bars 20. The guide 16 is mounted on the column 10 by a plurality of pairs of bars 50 similar to the bars 20. Each of the guides 14, 16 is anchored relative to the column 10 at one respective end. A carriage 12 is slidably mounted on the guides 14, 16 by suitable bearings and requires five degrees of restraint and one degree of freedom in the axial direction of the guides 14, 16.

Abstract: In a co-ordinate measuring machine a guideway base is formed from tubular components 10-14 of a lightweight material. An electrically heated strip 16 is located centrally of the tubular elements and fans 18 are also provided within the base. The strip 16 and the fans 18 can maintain the temperature of the base structure at a constant level at or above the ambient temperature so that changes in the latter do not result in any thermal expansion of the material of the base structure.

Abstract: A vertically-movable carriage 18 has an attached first electric motor 22 which, through rollers 24, provides a friction drive with a traction bar 16. The carriage 18 is connected by a wire rope 26 to a counterbalance weight 32. The weight (32) has an attached second electric motor 36 which, through rollers 38, provides a second friction drive with a guide bar 34. The total mass of the motor arrangement is thereby split, with one motor compensating for the other.

Abstract: In a co-ordinate measuring machine a base structure (10) supports guideways and carriages providing for movement of a probe adapted to contact a workpiece, and a separate structure (20) is provided for supporting the workpiece itself. The structure (20) can be supported directly on a foundation (16) by an arrangement of bars (54) capable of restraining all six degrees of freedom of movement of the structure (20), i.e. straight line movement in each of the X, Y and Z directions and rotation about each of the X, Y and Z axes. Each bar (54) is stiffened in the direction of its own axis but enables compliance in all directions normal to this axis to accommodate small movements of the structure (20) without stress or strain. The base structure (10) is mounted on the workpiece structure (20) by a similar arrangement of the bars (54) which thereby restrain all 6.degree. of freedom of movement of the base structure (10).