[TR] How do they manufacture gears?

pethier at comcast.net pethier at comcast.net
Wed Feb 11 09:08:54 MST 2009


----- fishplate at charter.net wrote:
 
> An example of cutting a small gear is at 
> 
> <http://www.deansphotographica.com/machining/projects/gearcutting/gearcutting.html> 
> aka  http://tinyurl.com/gear-cutting  
> 
> with some pictures.  This is for a camera gear, but just imagine it a
> bit larger.  

The process shown here is approximate, if I am seeing these pictures correctly, but the error is small and is taken care of in the hand-filing he did after.  The correct process is for the cutting head to advance across the blank, not be plunged towards the center.

> Cutting a helical gear just requires holding the blank at
> the proper angle. 

That would only give an approximation of a helical gear.

The actual process is a bit more complicated.  A large machine which I believe is called a "hobb" is used.  It has a rotary cutting head with cutters shaped like the "grooves" in the gear.  As the cutter head proceeds at angle across the gear blank, the gear blank rotates slightly.  The cutter advances slightly with each cut. The process is called "hobbing a gear".

Phil Ethier


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