View Full Version : "16ths"

04-17-2003, 08:30 PM
What is the reason that US Mfg use "16ths" in their power shafts on their equipment.
This is very common in rock crushers.
i.e. 1 15/16",2 3/16",2 15/16",etc
Why do they not use 2",2 1/4",3", etc.
Just wondering

04-17-2003, 08:55 PM
I was told by and old guy who was a salesman for Rexnord corp.that this came about during WWII. He said that those sizes were adopted by the NAVY because they are close to metric shaft sizes in that range so that found material could be used(i.e. siezed enemy stores)as 1-15/16"is roughly50mm(49.21mm)2-15/16" is roughly75mm(74.61)3-15/16"is roughly 100mm(100.012mm)and so on so in a pinch they could be used with little effort.This seems plausible but I don't know if it is true.We also early in the late 1800"s used a lot of really odd sizes like 1-1/16" and 1-13/16"reasons why are not to clear.but still some corelation exits as 1-1/16"-27mm(26.987mm)and 1-13/16"-46mm(46.037mm)are very close to common bearing bores in metric diem.It is also possible to argue that it had something to do with european compitition.

Doc Nickel
04-17-2003, 09:09 PM
This is a complete WAG, but I alsways assumed it was due to finishing down raw sizes. Just as a "2x4" is actually 1.5" by 3.5", I simply assumed that when one made a shaft, one bought, say, 1-1/2" bar (a standard size) and then turned it down as a cleanup and truing measure. Without taking too much off, a 1.5" rod would give a decent 1-7/16" finished shaft. Cleanup a hot-rolled bar of one and a quarter and yo get a finished 1-3/16" shaft.

Like I said, that's a wild guess, but at least to me it makes sense.