Posted by BillS on April 04, 2013 at 10:32:24:
In Reply to: Re: Hobbing Prime Spurs using differential posted by gearhead1 on April 04, 2013 at 09:34:21:
I just corrected both FAQ topics and expanded the detail to explain the
Pickup Constant method for Helicals
Prime Cutting with Pickup Constant and Differential as much as I could:
Be sure to use the method step by step:
Find a C value based on gear specs and desired table feed. Then round C to an integer and use the formula for index gears. Factor numerator and denominator. If you can't get factors that represent change gears, change C and try again.
After finding a useable set of index gears, find the true table feed from the formula using NDP, C and Helix angle. Using this accurate table feed, find an accurate decimal Feed Gear Ratio based on your machine's feed constant. Then find a closely matching set of feed change gears.
Machines don't usually come with a wide range of change gears. So, If you send me your index, feed and differential constants, plus your inventories of change gears, I'll use CPC-HOB to see if there is possibly an accurate setup. The more missing change gears, the more trial and error.
You can send me your gear specs, machine constants, and gear inventory by email; or
you can use the corrected and improved FAQ topic to find the setup yourself.
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