To All:
Here are some excerpts from an article in MMSOnline.
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Article From: MMSOnline.com, Derek Korn , Senior Editor
Does your machine control specify radial feed rate from the edge of a tool or its center? Not knowing can cause much longer cycle times or greatly reduced tool life during thread milling operations.
This is because some machine controls specify feed rate at the center of a tool, while others use the feed rate at a tool?s outer edge. (In a circular movement, the feed at the center of the tool is slower than the feed at the cutting edge.) Inexperienced operators might not know whether the ?F? command, which defines the radial tool feed rate in a thread milling program, refers to the feed at the tool?s center or its edge.
For a 4.8-mm thread mill used to create an M6 x 1 thread, the feed rate at the edge of the tool is 238 mm/min. Conversely, the feed rate at the center of that tool is only 47 mm/min. Moving the tool too slowly leads to extended machining time (five times longer in this example). On the other hand, a tool that moves too fast can experience high cutting loads that significantly reduce tool life.
Vargus USA offers free software that can ensure operators use the correct radial feed rate during thread milling operations. ========================================================