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"The pursuit of productivity when applying microdrills (tools less than 0.125" diameter) may be as much creative as it is scientific. The characteristics of the drill itself, machining parameters, hole depth, setup integrity and workpiece composition play delicately intertwined roles.
As a drill gets longer, relative to its diameter, its tendency to bend increases. A low length-to-diameter ratio minimizes the deflecting forces that break drills and produce crooked or mis-sized holes. Deeper holes mean higher length-to-diameter ratios. In general, hole depths three or more times drill diameter are considered "deep." But microdrills usually far exceed those ratios."
That is the introduction to a wonderful article we posted earlier this month on our Facebook Page called "The Skinny on Micro Drills" It's very informative on the unique problems found in micro-drilling operations. Take a look at the link if you get some time.
On of the best manufacturer's we found for carbide microdrills is M. A. Ford®. They also manufacturer other precision ground miniature carbide cutting tools including carbide end mills, carbide burs, carbide boring tools and carbide reamers.
Carbide's high wear resistance enables users of microdrills, as a rule, to triple cutting speeds in many materials. Tool life can increase as well. The extra rigidity of carbide helps with hole size and location, too.
Many companies tend to move toward HSS or cobalt tools when drilling, however, because the extra rigidity of carbide makes it likelier to fracture. A lot of what makes a carbide micro drill work comes down to the geometry design that keeps the drill on center and evacuates chips efficiently. We've had some good success using the M. A. Ford series 302 and their new 305 drills in miniature drill applications. Here's some details on the 305 drill:
I'm told that they're also working on some miniature coolant fed drills in the near future so remember to ask us to get a status update on that project the next time you talk to one of our folks. In the meantime, here's a video of the 305 doing some drilling...