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Application Calibration

Our goal is have your machine operating at optimum efficiency and effectiveness. To do so, our bits should be tested in your shop so that we can help you determine the best operating parameters.

Whenever trying out one of our bits, we suggest you use the samples just like you would the bits that you are currently using. As you become comfortable with the performance of each tool, crank up the feed rate and see if the edge quality is affected. If you have been using bits designed for metal cutting in the past, you will probably find that you will get a much better cut at a higher feed rate with PreciseBits tools. As a bonus, you will find that the cutting edge will last longer if a proper chip load is maintained.

Calibration Process

A good way to find the "best" cutting speed for the combination of spindle RPM, cutting diameter and material is to:

start cutting a piece of the wood that you are testing with a feed rate about ½ of the feeds shown below. Cut full plunge (just a bit of the flutes showing above the top surface of the wood) for 1 in.
increase the feed rate by 10% and cut full plunge for another 1 in.
keep increasing the feed rate in this manner until the bit breaks.
reduce the final feed rate by 25% and record your results. The number you will have derived represents the best production feed rate for this combination of tool diameter, depth of cut, and material,. As you will discover, the best cutting rate is closer to the point at which the bit breaks than it is to a feed rate that is so slow that the bits burns against the wood like a tire spinning on pavement. The 25% de-rating will act as a margin to prevent breakage as the bit wears.

Suggested Speeds and Feeds (cutting hard maple)

RPM	Feed rates for selected tools
RPM	0.0250" dia.	Plunge (depth of cut)	0.0313" dia.	Plunge (depth of cut)	0.0625" dia.	Plunge (depth of cut)	0.1250" dia.	Plunge (depth of cut)
20,000	9 in./min	0.100"	20 in./min	0.125"	25 in./min	0.313"	40 in./min	0.500"
30,000	13 in./min	0.100"	30 in./min	0.125"	37 in./min	0.313"	60 in./min	0.500"
40,000	18 in./min	0.100"	40 in./min	0.125"	50 in./min	0.313"	80 in./min	0.500"
50,000	22 in./min	0.100"	50 in./min	0.125"	64 in./min	0.313"	100 in./min	0.500"
60,000	27 in./min	0.100"	60 in./min	0.125"	74 in./min	0.313"	120 in./min	0.500"

Providing Feedback

Please complete the following chart and let us know your results. Our support team can be reached at fax 719 481-0464, telephone 719 488-9640 or email at support@PreciseBits.com. With these numbers, we can help you improve your cutting performance and bit life.

Bit Diameter	# of Flutes	Depth of Cut	Material Cut	Spindle RPM	Feed Rate that Broke Bit


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Copyright 2002-2008 Think & Tinker / PreciseBits Updated March, 2008