On Tue, 27 Jun 2017 17:12:10 -0400, "Jim Wilkins"
wrote:

"whit3rd" wrote in message
...
On Monday, June 26, 2017 at 6:40:30 PM UTC-7, bob prohaska wrote:
How were crankshafts made before the development of specialized
machine tools?

I did find http://modelengines.info/goldeng/const/crankshaft.html
but I can't figure out how the author located the offset center
holes in the blank.

That model was turned on centers, with two center-drilled pivot
positions at each end. Then, the ends were cut off so the finished
item doesn't show where the centers were.

Probably forged or cast rough items were similarly turned on
centers.
After you finish the ends, the evidence is gone.

https://books.google.com/books?id=Kc...xtures&f=false



This is the kind of fixture they used in the early days of car and
aircraft manufacturing. Start at about 3:30 and you'll see what it's
about in a few seconds.

https://www.youtube.com/watch?v=WnP_STFjtK4

You see the fixture are work again starting at 4:11; this time, for
grinding.

This not for models; I think Bob's original question was about real
crankshafts.

--
Ed Huntress