Keyed shafts - when did they first appear historically?

If, by key, you mean an axial square pin that fits in a square hole formed in the shaft and wheel, I'd say it's a fairly late invention. It takes a relatively complex and precise operation to mill the shaft and broach the wheel.

More likely would be a radial pin through the shaft and wheel. It would only take a crude drill and pin to make it work.

I've seen the pin arrangement in lots of early stuff.

Way before that. I recall soapstone bracelets made on a simple wooden lathe with a square hole chipped through the stone to make an arbor for a drive shaft with a square section. IIRC, this was ~500AD in the UK.

Actually, it takes a grooving chisel and a hammer!

Mark Rand

I don't know about lathes, but all the old grind stones I've seen were wedged to the shaft. The shaft has a square-ish crossection, and the stone a fairly oversize hole with noncritical shape. They're locked in place and roughly adjusted square and true by hammering wooden wedges into the hole; final trueing is done by dressing the stone while it is in place on the shaft.

However, that may well be just a local way of doing things.

-- Aamund Breivik

snipped-for-privacy@ifas.ufl.edu

It's always hard to posit "the first" whatever.

Identifying the first reference to "keyed" shafting, let alone before 1500, is probably impossible.

I'm ignorant as to the really old archaeological evidence.

There's some picture evidence of squared shafting generally, and for lathe flywheels, in Robert S. Woodbury's "History of the Lathe to 1850." Woodbury shows a cranked wheel-and-cord drive (French) from the second half of the fifteenth century--so pre-dates your requirement. But it only shows a square shaft through the wheel, no other detail as to how the shaft and wheel are kept together. Probably wedges. Is a wedge a key? Or it may be a force fit. Could be a shoulder with a pin set in radially or similar, but there's no telling from the print.

I would think axial square-pinned mounting of a wheel or handle on a circular iron shaft easily pre-dates 1800. As pointed out by another, it doesn't take sophisticated machinery, just hand tools, to make a keyway. One quick older way was to drill for a straight (circular, of course) pin, half in the shaft, half in the wheel (if the wheel is at the end of the shaft).

Frank Morrison

I can't find it right now but I've seen descriptions of the Roman water powered flour mills, like those at Barbegal that described square shafts passing through a square hole in the waterwheels & gears. I'm pretty sure the article cited earlier Greek evidence of similar technology. So the keyed shaft in that form appears to be known to well into antiquity.

On Thu, 08 Jul 2004 23:52:58 -0500, Jim Levie wrote: (along with others) [snip] --

Thanks all -- I'll pass on the square shaft/square hole and the round shaft/wedge concepts -- that might be the easiest way to accomplish what he want to do.

Steve

Soil & Water Science, UF

Mill machinery was mostly wood prior to the industrial revolution, the bits I've seen used square timbers and square holes. It's relatively easy to split out a mostly square timber from a log and dress it down with an adze and you can make a squarish hole in a grindstone a lot easier than a perfectly round one with hand tools. Wedges would be used to retain things.

Most of the drawings I've seen for medieval wood lathes were the pole or bow type, no flywheel. I've seen one drawing of a treadle lathe with a crank and a flywheel, like a lot of these period drawings, they were long on style and short on substance, this supposedly was first seen in the 1500s(hardly medieval). I've no idea whether the flywheel was wood, stone or iron. Wood could be built up like a wagon wheel right off a wooden hub, stone or cast iron could be centered on a square with wedges. Getting such a thing balanced must have been interesting, probably why pole lathes were popular.

Stan

Prior to the industrial revolution, iron was very expensive. The only technology for forming iron parts was blacksmithing. So it's very unlikely that an iron flywheel would be used. Enough energy for the purpose could readily be stored in a wooden wheel (eg a cast-off wagon wheel).

snipped-for-privacy@prolynx.com (Stan Schaefer) wrote:

: snipped-for-privacy@ifas.ufl.edu wrote in message news:... :> Greetings all -- :> :> A friend is designing a 'medieval' wood lathe and is casting about :> for an authentic method to lock the flywheel to the shaft. Does :> anyone out there know of a reference to a keyed shaft before 1500? :> Conversely, how where grind stones locked to grist mill shafts? :> :> Steve (Ironflower.com) :> Soil & Water Science, UF : :Mill machinery was mostly wood prior to the industrial revolution, the :bits I've seen used square timbers and square holes. It's relatively :easy to split out a mostly square timber from a log and dress it down :with an adze and you can make a squarish hole in a grindstone a lot :easier than a perfectly round one with hand tools. Wedges would be :used to retain things. : :Most of the drawings I've seen for medieval wood lathes were the pole :or bow type, no flywheel. I've seen one drawing of a treadle lathe :with a crank and a flywheel, like a lot of these period drawings, they :were long on style and short on substance, this supposedly was first :seen in the 1500s(hardly medieval). I've no idea whether the flywheel :was wood, stone or iron. Wood could be built up like a wagon wheel :right off a wooden hub, stone or cast iron could be centered on a :square with wedges. Getting such a thing balanced must have been :interesting, probably why pole lathes were popular. : : :Stan

the square keys locking a shaft to a wheel for example were only developed when it became possible to turn shafts true in a lathe and similarly turn the wheel bore accurately to match the shaft. Ive no date for this development Prior to the advent of an accurate metal turning lathe most shaft to wheel fixings were done by having the shaft square with a square bore in the wheel. the key was developed from the wedge, which was used from medeaval times to assemble the first clocks and similar multipart machines. these metal wedges were similarly developed from wooden wedges used in early building and furniture constructiopn.

?mund Breivik wrote: