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How radius effects speeds and feeds in relation to chip breaking

Bob Gray

Plastic
Joined
Nov 13, 2007
Location
Redwood City
I mostly do mill work but am starting to get more into mill turn.

My question is as radius of the tool increases so if I go from say a .008" radius to a .016 radius how does that effect the the calculation for chip break.
I was running 6061 aluminum with Iscar VCGT1604 IC20 inserts and during the finish opp I just could not break the chip. I tried a higher SFM a increased feed.

On a hunch I switched over to Kyocera VCGT160404R A3 which is directional and noticed and improvement in chip break but every now and then during the finish operation I still get some stringing. Which I would like to eliminate.

I'm leaving .012" X&Z for clean up. Using 1000 SFM with a feed of .006 with speed limited to 1600 RPM

I've look at several insert manufacture web sites, they have the formulas. But no good guides of what to do or simple rules to follow. So If I could get a good resource I can read through or watch that would be great.

Thanks
 
tip radius is basically the min thickness you should cut with said insert. too low and it just is rubbing instead of cutting which wears it out more.
chip breaker is seperate depending on design.

long strings are ususally due to not enough feed to make a thick enough chip that breaks its self.
aluminum is common to be stringy depending on material cutting.

and only 0.006" per rev? that is super low.
 
It’s a complex subject I found out!, we had a good rep from sandvick, he started showing me how the calculations worked! I was in over my head, even tiny amounts in chemistry change the character of the chip, amazing there are folk doing PhD s in cutting tool geometry but the best thing is get the catalog, there’s a wealth of information like radius tool life and all sorts in there, and a call to the rep will usually result in sound help, they were brilliant, even when we used someone else’s tools!, worth getting to know your rep( plus the odd free sample!) the calendars are now scenic as opposed to perelli im afraid, I preferred the 80s ones!
I found the bigger the radius the more power needed on Ali the surface had a sweet spot, lots of trial and error im afraid
Mark
 
A LOT will depnd on the quality and origin of the 6061, some of which is like cooked mozzarella and will not break a chip as long as you have a certain fundamental orifice
 








 
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