GB1202292A - Method and apparatus for internally truing small diameter tubes - Google Patents

Abstract

1,202,292. Grinding. COMPAGNIE FRANCAISE THOMSON HOUSTON-HOTCHKISS BRANDT, and DIAMANT BOART FRANCE. 3 April, 1968 [3 April, 1967], No. 16040/68. Heading B3D. A method of internally trueing or finishing a tube 13 with a diameter which is small with respect to its length, such as a capillary tube of glass or quartz for use in a laser, comprises causing progressive penetration into the tube of a succession of wires 2 under mechanical tension and covered with respectively progressively finer abrasive concretions, the diameter of the wires being respectively progressively larger until the desired nominal diameter for the inside of the tube is obtained and at the same time effecting relative rotation between the tube and wire. In apparatus for carrying out the method, the wire is held between a tension-adjusting device and a stress-limiting device mounted in respective arms of a U-shaped frame 1. The stress-limiting device consists of a clamp 11 for gripping the wire and a ring 10 which abuts a series of resilient discs 9, the wire passing through a grommet 12. The tension-adjusting device comprises a hollow shaft 3 having a split grommet 4 which is closed on to the wire by a ring 5 screw-threaded on to the shaft and engaging a split conical termination 32. Tension is applied to the wire by rotation of a screwthreaded ring 6 abutting the frame 1. The wire is in three parts, the first 21 being of smaller diameter than the tube before machining, the second 22 having a slightly larger diameter than the first part and covered with abrasive, and the third part 23 being of the same size as the second part but not covered with abrasive so as to act as a guide for the finished sections of the tube. Either the tube or the wire is held fixed while the other is moved longitudinally and rotated and the movements may be effected manually or automatically. The abrasive covered section is formed with grooves, channels or a helical groove for enabling the material ground away to be removed. The same operation is repeated with progressively larger wires having progressively finer abrasive until the tube has reached the desired final size.