Oil grooves for sliding surfaces on Machine Tools / Ölschmiernuten für Gleitführungen an Werkzeugmaschienen

My ongoing quest to restore the Deckel FP2, Chipmaster and Eagle surface grinder, makes you deep dive into Machine tool design frequently.

Once the castings where back with shiny new precision ground sliding ways, the question comes do I improve on some of the shortcomings, like no oil grooves? Or leave it factory standard? Well this is probably one of the main reasons why I decided invested in old machine tools, the new machines from china also require a fair amount of work to perform consistently and last for some time.... Might as well spend the time on an old machine tool and in the process learn the trade.

Well back  to the topic at hand, how to cut the oil grooves inside dovetails? There are various tidbits on the web giving advice, but nothing seemed elegant and time efficient. As example one could spend a lot of time with a precision setup on the manual milling machine to engrave oil grooves. Or a setup on a CNC. Or use a hand held dremel like tool, or use a custom ground scraping tool.

When you consider the options, it becomes apparent why a lot of old machines, have very simple oil grooves like elongated Z's,  straight connected 0's, long straight slots with perpendicular grooves similar to I. A few examples shown below.

But we know better, there is a great book by M Weck ( Werkzeugmaschinen 2 - Konstruktion und Berechnung ) Pg 245 it shows some examples and the form which shows best performance, a trapezoidal zig zag form (figure 1 below) When you think about what happens to the viscus fluid while the slides are sliding across one another back and forth, this almost acts as a staged pump.  The pumping action helping the spread of oil, since it can not run back along the inclined grooves. The one thing my research did not find is the best angle for the inclined grooves. The angle needs to satisfy two opposing requirements, retain as much oil to evenly spread on the opposing slide, 2. feed oil to the next stage. My starting point is 25͒͒͒͒͒͒°, lets see how this goes.

Now once the form is selected, the down side is this form probably is the most complex to produce. This made me go in search of methods we used before machine tools, and the result is a simple tongue and grove planer with a special ground tip.  Below take one on such a tool, for 60° dovetails. The angle might vary on your specific requirement, but I can see a use in inverted V slides used on the lathe and in square columns used in the Deckel.