Abstract: An inside chuck device for machine tools, adapted to chuck a cylindrical work having an axial bore at the peripheral surface of the bore of the work. The chuck device has a chuck having a guide portion adapted to be received by the axial bore of the work so as to guide and center the latter, and a plurality of radial projections. Each of the projections has such a height that the circle contacting the outer side of the projections has a diameter at least 0.02 mm greater than the inside diameter of the work.

Abstract: A hydraulic pressure producing system including clutch means located between an output shaft of a motor and a rotary pump arranged in a liquid and operated from outside. The rotary pump is driven only when the clutch means is engaged to obtain a discharge pressure.

Abstract: A fluid-operated press comprises a crosshead, a bead, four upstanding posts each extending vertically between each corner portion of the crosshead and each corner portion of the bead, and a slider disposed between the crosshead and the bead and slidably fitted on the posts to be slidable along the latter. An upright wall structure located outside the slider and the posts is clamped between the crosshead and the bead to enhance rigidity of the frame structure of the press. The upright wall structure has a wall portion surrounding at least that portion of the peripheral surface of each post which, as viewed in cross-section of the press through the upright wall structure, is positioned between two lines obtained by extending two adjacent sides of a rectangle which is formed by connecting the center points of the four posts.