For those who like machines and mechanisms (and I’ll assume that is most of you as it is me), there is a world of interest in learning how things “used to be.” How were chronometers made accurate enough for sailing ship navigation well before we could look up the time on our iPhones? One of my favorite topics is all the tooling manual machinists need that CNC doesn’t. The electronics and computer software make it superfluous. A rotary table, for example, is unnecessary to the CNC’er (unless you want to turn it into a 4th axis), but quite useful for manul machining. Yet, there are many fascinating ideas one can derive from the old ways of doing things. Ideas that are often useful despite the electronics of today. The old machining books are priceless (though fortunately, often very cheap in used book stores–keep an eye out!). I learn so much from them, and periodically we see something dredged from the past reinvented and made useful to as in the present. The odd conversion of shaper tool to lathe finishing tool (a skivving tool or “shear” bit) is one such example, and there are many more.

HSM has a fascinating thread going about how machinists got by without DRO’s back in the day. I plucked two pictures that tell of one machine’s abilities in this respect:

The venerable Kearney and Trecker 2D was a very sophisticated mill in its day…

Note the dial indicator with grooved trough. One inserted either precision rods or gage blocks into the trough. The table then “bumped into” that stack which would register very accurately on the indicator.

While we’re on the subject of how old machines worked, how about Constant Surface Speed? As you go to smaller and smaller diameters while facing (or turning) on a lathe, you need to speed up the spindle to maintain a constant SFM. This results in a nicer finish. The feature is common on CNC’s. Monarch had a version of the 10EE that could do it (Monarch’s motor drive electronics were one of its most innovative features, and most difficult now that the world has moved on to VFD’s and such). But how about a much older lathe?

This is how Cunliffe & Croom did it in 1914:

The clockwork mechanism apparently adjusted a potentiometer that varied the speed of the DC motor…


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