This article first appeared in Practical Engineering 1940 Vol1 No23. The information contained within the article is accurate as of 1940. This article articulates methods as applied in Engineering and Workshops at the time.
It is often an advantage to have an adjustable stop for the traverse of the top or cross slide of the compound rest. Here is a device which can easily be made. The principle is applicable to other machine slides. It consists of two strips of flat bar steel having elongated slots by means of which they can be adjustably attached to the sliding member and the member on which it slides, one at each end.
The bar is cut from strip metal, and the slot is formed by drilling along a centre line a series of overlapping holes. The slot is then filed to a width equal to the diameter of the screw, which should have a plain part under the head of a length equal to the thickness of the bar.
On the fixed member is fitted a stop piece consisting of a slotted bar with one end turned up to act as an abutment. It is held to the base of the compound rest by a cheese-headed screw. A guide pin is fitted to keep the slide in alignment.
The Adjusting Screw
A similar slotted bar is fitted on the slide. This also has an upstanding part (set in line with the upturned end of the other bar) which carries a cast-steel adjustable abutment screw with a milled head. Thus, after the bars are adjusted approximately to the position in which their ends will meet a fine adjustment can be obtained. The arrangement allows for an approximate and quick adjustment by means of the cheese-headed screws, and a final exact adjustment by the milled abutment screw. To prevent accidental turning of the adjusting screw a lock nut could be fitted, but this would not give a quick adjustment.
It will be seen that a simple method is needed to ensure against the slackening of the screw. The cast steel bar has its end turned up and over itself as shown, so that the turned-over piece does not quite close down. When the hole is drilled for the thread the two parts are pinched together and the hole drilled and tapped to fit the screw. Then they are opened out, after which the shaped end is made red-hot and quenched ; then drawn down to a light violet colour and again quenched. It will then be hard and springy.
The threads for the screw will then be out of pitch in the two pieces, and to fit the screw they will have to be pressed together so that the thread pitch coincides. On release, there will be spring pressure along the thread and the screw will be locked sufficiently to prevent its working loose due to vibration.