The spring-pole lathe is an odd chook. As a reciprocating, foot-powered lathe, it has two disadvantages: Not solely do you must elevate your coronary heart price to make use of it (God forbid), nevertheless it actually doesn’t work half the time—for each slicing stroke, there’s a return stroke because the work spins again. Due to this, when the spring-pole lathe comes up in dialogue, I typically see people questioning, “Why not simply construct a flywheel treadle lathe? In the event you’re going to make use of a foot-powered lathe, at the least let its movement be steady.” I perceive this impulse. To the informal observer, the treadle lathe doesn’t appear that totally different from the spring-pole lathe, and certainly it have to be at the least twice as environment friendly with out a return stroke. Is that true, although? I’m not significantly satisfied.
I consider that this mind-set partially comes from a view of the spring-pole lathe as a strictly worse model of the treadle lathe, the previous being made out of date by the latter. This, nonetheless, is demonstrably unfaithful. Although the spring-pole lathe is first attested within the 1200s, it’s unclear when the primary treadle lathes have been produced. Da Vinci sketched one within the 1400s, although trendy lathes constructed from that sketch have confirmed to be extraordinarily ineffectual. By the 1600s, we see a treadle lathe pictured in Joseph Moxon’s Mechanick Workout routines, although Moxon devotes way more dialogue to the pole lathe than the treadle lathe.
A century later in France, Andre Roubo described a spring-pole lathe in use by knowledgeable cabinetmaker working with dried wooden. It’s not till the nineteenth century that we see the decline of the spring-pole lathe, however even then it stayed in skilled use as a staple of the Excessive Wycombe chairmaking business, driving the manufacturing of roughly 4,700 chairs a day on the business’s peak. It finally fell out {of professional} use within the Nineteen Fifties.
So what’s occurring right here? How may the spring-pole lathe compete with continuous-motion lathes? Although there are definitely a lot of elements at play, I feel the obvious is construct complexity. A spring-pole lathe could be constructed with easy instruments in a day or two. Probably the most mechanically rigorous issue is in making a flat mattress and parallel facilities. The treadle could be so simple as a free plank. Whereas an appropriately sized spring pole (round 12 ft. lengthy) could be tough to supply within the trendy period, many turners (myself included) use a bungee wire as a substitute—low-cost, efficient, and compact.
Evaluate this to a treadle lathe, by which the treadle connects to an arm that turns the flywheel, which is linked to a pulley that’s match into the headstock and drives a spindle, which drives the workpiece. The variety of transferring components is multiplied; there’s now metalwork that must be outsourced, and making and balancing a flywheel isn’t any imply feat. That’s much more upfront price in time and components for each the trendy hobbyist and the historic skilled, in addition to extra transferring components to put on and restore sooner or later. Absolutely, although, that upfront price pays for itself through the rise in effectivity. The treadle lathe cuts twice as a lot because the pole lathe; it have to be twice as environment friendly, proper?
Not fairly. All these further transferring components don’t simply complicate the construct course of—in addition they add friction into the system, leading to a lack of power between the leg and the workpiece. Although I sadly don’t have a treadle lathe to do my very own experiments on, from what I can discover, trendy treadle lathe house owners usually report between 700 and 1,000 revolutions per minute (RPM) on their lathes. Evaluate this to my spring-pole lathe—I’m averaging 1,200 to 1,800 RPM throughout the slicing stroke for basic spindle turning. Half that quantity to take the return stroke into consideration and we nonetheless find yourself within the territory of 600 to 900 lively RPM—not a lot slower than the treadle lathe in any respect. Granted, these numbers take extra power from the operator to realize on the pole lathe than on the treadle lathe, however let’s be trustworthy right here—you most likely want the cardio. I do know I do.
Taking all of this into consideration, I feel we will see why the spring-pole lathe was and nonetheless is a formidable machine. Lots of the benefits that it had for preindustrial craftspeople translate properly into the trendy hobbyist’s store. So subsequent time you see a spring-pole lathe, somewhat than questioning why somebody would construct such an antiquated machine, take a second to think about the great thing about its effectivity by means of simplicity. In spite of everything, what number of different medieval machines survived the commercial revolution?
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