Posted by Dan Mc on September 24, 2009 at 13:35:49:
In Reply to: barber colman #12 gear hobber questions posted by Jim Pollock on September 14, 2009 at 22:35:31:
Jim- what are you using for cutting oil? 8620 can be kind of gummy and tear when cutting. You need a good cutting oil with some sulfur additives in it- not soluble oil. Don't run water based coolant in that machine- they have no seals on the bearings and were not designed to run water based coolant. Also, is your hob reasonably sharp? Slow your feed per rev down to .030"/.035". This should work ok for roughing and finishing- you can take a deeper cut for roughing-.250 should work fine.
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