A Workshop tip from “The old Yeovilian”

In machining such things as Axles etc, there is often a sharp corner where a diameter is reduced to a smaller diameter. This is bad practice. At the junction, there is a problem with a potential fatigue crack. In engineering parlance, it is always a problem where “Rapid change of area occurs”. Consider the axle for instance at the point where it is subject to bending and shear. At each revolution, the bending is one way and then back. Just like raking a paper clip. At the junction of the small and large diameter a small radius should be machined, say 0.1” for a 1.0” shaft. A corresponding rebate in the wheel or whatever should be used so that it mates with the shaft. Notice that a ball race has a small rebate on the inner and outer diameters. Sharp edges on the outer edges of a machined piece should also be considered as possible points for fatigue cracks. An engineering drawing should always have a notation—”Break sharp edges”.

A Workshop tip from from “Ex-Gunner”.

We all know how difficult it is to obtain a decent finish when using the end face of either a slot drill or an end mill. Conventional “Flycutters” will leave a good finish but are often bulky with out of balance forces or lack rigidity. One solution which gives excellent results is to modify a scrap end mill or slot drill. First grind off all but one tooth near the end face, just enough to clear the machined surface and give access to the remaining tooth. Without touching the outer diameter sharpen the remaining tooth ensuring that you get point contact on the machined surface. Lightly stone a small radius on the corner. Off you go, the cutter has minimal out of balance forces and it can be gripped in the usual collet. It gives a superb finish and as the OD is known, it can be used up to an edge. It is also very cheap and can be re-sharpened. Have a go and see how you get on.