"Jim Wilkins" wrote in message
...
On Nov 24, 11:00 am, "Ed Huntress" wrote:
"Jim Wilkins" wrote in message
......
'Could be. I haven't read anything about it for decades, and there's been
quite a bit written about Maudslay's screw-cutting lathe. The trouble with
these informal histories is that they tend to use each other as sources,
which perpetuates a lot of wrong ideas.

Ed Huntress

I just checked my two best sources, Holtzapffel #2 and Oscar Perrigo's
1916 "Lathe Design", Both skip quickly over the rationale for the
choice of flat vs vee lathe ways, and suggest that ease of production
was as much or more of a factor as sustained accuracy.

jsw

Well, yeah, we know that's why it was done later, after planers came into
widespread use. It's a lot easier to make three planes work together than
four.

And that may be (and I agree with your conclusion; it probably is) the
reason it was done from the very beginning.

As I think about this, I'm remembering what I thought about it at the time,
30 years ago. I believed then that the issue was the difficulty, without
planers, mills, or big surface grinders, of getting the four planes of a
pair of V-ways coordinated for straight and smooth travel. One way to
interpret this is that you can adjust the single plane of the flat way a lot
easier than the pair of planes you have with a second V. So to say that it
was simpler to correct accuracy with the V-and-flat could just mean that; if
the ways are hand-finished, you're correcting accuracy, and V-and-flat is a
lot easier to correct than two V's.

Maybe. g

--
Ed Huntress