Richard J Kinch wrote:
How does one machine a toothed wheel for a film sprocket such as this:

http://www.lavezzi.com/product272.html

That item is a stack of several cylindrical components, with the toothed
portion apparently a slice out of a long toothed stock piece, somewhat like
the sprocket stock you can get to make gearbelt pulleys. Would this
toothed stock just be cut from round stock using axial cuts from a custom
bit, incremented with a spin indexer?

Production units are probably cut with an internal broach.
To do a one-off or small quantities, you don't need a custom milling
bit--a straight end mill will do it. The tooth sides can be straight,
although curved would be better (circular, no need for involute as on a
geartooth). That's where you'd need a custom cutter, easy enough to make
using a single-bit flycutter.
You just mill the teeth, and the arc between them, in stages on a rotary
indexing table after turning the profile on the lathe.


I also have an interesting specimen, a 4-inch diameter metal sprocket that
appears to be an exquisitely fine cast version. Is that possible?

"exquisitely fine cast" would probably mean investment cast, using a
sacrificial plaster-type mold where the mold cavity is formed with a wax
pattern. Or die-cast, using a metal mold (most likely on a production
item). You can do some pretty exquisite casting with sand, too.

--
Ken Grunke
SW Wisconsin
http://www.token.crwoodturner.com/
Member, Coulee Region Woodturners AAW chapter
http://www.crwoodturner.com/



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