Adjustable Work Parallels in Shop Work

Posted By Richard Barker on 09 May 2014

Posted in The Vintage Machinery Almanac

This article first appeared in Practical Engineering 1940 Vol1 No21. The information that is contained within this article is therefore valid as of 1940. The article outlines methods of efficiencies within Manufacturing at the time.

If a very useful form of adjustable work parallels is employed when setting-up work on the sensitive drilling machine it will be found that the operation is facilitated. Especially will the device be found valuable when a number of holes have to be drilled through plate.

Ordinarily when handling such work the plate is rested upon a machine table. Each time the drill breaks through, a burr is raised on the underside surrounding the edge of each hole. This burr must be filed off at each stage if the plate is to sit down flatly upon the table, and in order to maintain accuracy of drilled holes. As will be appreciated, also, this type of adjustable parallel is greatly superior to the use of strips of material or other packing pieces which are commonly resorted to when having to set up plates in the manner described.

Stepped Edges

The device ordinarily comprises two identically shaped side pieces. These are made exactly the same size, and are provided with one edge stepped in the form of a right angle. The depth and width of this step in each case should be -1/2in., this dimension resulting in a very convenient size of step likely to prove suitable for most ordinary shop work.

The lower edge of each plate is bevelled away at 45 deg. Both ends of each plate are slotted so as to receive the links. It will be seen that the link is secured to the slot in the second plate by means of a cheese-head screw, whilst the first plate is free to slide on the aforementioned links, the slots at each end of the first plate being made slightly wider to permit such sliding action.

The links are also provided with an elongated slot extending for a considerable portion of the total length. The set screw passing through the slot and screwing down into a tapped hole provided at each end of the first plate enables the link to be clamped up with the first plate in any lateral position relative to the second plate. Thus, by simply releasing two screws, the parallel may be adjusted to suit differing widths of work.

It is advisable to use a good quality steel for both the bars, and to harden and finally surface grind them all over, as in this manner much longer life will be secured. If soft plates are used burrs will inevitably arise due to handling and storage, which, if not frequently removed, may cause serious error in machining of holes.


Take the example of flat work plate in position on the stepped portions. The first plate is simply adjusted as explained until the gap between the steps is wide enough to permit the admission of the work-plate. Screws are then locked, and drilling may commence. Thus set, all holes may be drilled, tapped, reamered, faced, etc., as desired, without removing the plate from the parallels for the removal of burrs, because the lower surface of the work-plate is not in contact with any surface, as is the case when the plate is rested directly upon a machine table.

In the case of cylindrical work pieces, the parallels will prove equally adaptable and useful. In this case, instead of   employing the parallels with the stepped edges uppermost, the device should be inverted. Adjustment of the first plate by means of screw permits the sides of parallel to be set so as to suit the diameter of bar being handled. Care should be taken to ensure that the gap between the two adjacent faces of both plates is wider than the diameter of the hole to be drilled. If this is not done the drill will foul the sides of the plates on breaking through.

Technical Education

Mr. B. Mouat Jones, Vice-Chancellor of the University of Leeds, opening a discussion on "The Future of Technical Education," at the eleventh annual convention of the Yorkshire Council for Further Education, said: "We cannot help feeling that all this mechanisation of the armed Forces will bring to the public consciousness the vital importance of everything mechanical, technical and technological; and that awakening will result in a much greater public interest both in technology and technical education. I believe there will be a corresponding difference in the attitude of the general public to engineers and physicists particularly, and a considerable enhancement of the social prestige of the technologists and technicians."