Using the right speed are genuinely important during working with spade bits. Right speeds help to avoid overheating and dulling of the bit. Also they help to create neat hole in the material.
Big holes require cutting forces that grow quickly. The machine that does not have too much power will tax you more than loaded big spade drill during making a big hole.
Set Speed and Feed for Spade Bits
Are clear ways to find the right speeds and feeds out. Speed rule is 80 surface feet per minute in materials with 100 Brinell hardness. Reduce this speed in 10 feet for every extra 50 points of Brinell hardness.
Feed matches 0.001 per revolution for every 1/16 inches of drill diameter plus or minus 0.001 inches total. Reduce feed and speed to 45-50% for holes deeper than 4 drill diameters. For deep holes stay to well use low speed.
Calculations help to find those numbers. Rotary Speed comes from dividing the Surface Speed by pi times the drill diameter. Feed Rate is rotary speed times the feed.
Other way for surface feet per minute is 0.2618 times drill diameter times R.P.M. For inches per minute use feed per revolution times R.P.M.
Diversity in setups can alter the work. For instance use manual feed so you can estimate itself. Initial feed for boring is 0.003 until 0.005 per revolution.
Some use formula for mills 152 divided by diameter gives R.P.M. Later R.P.M. Times 0.003 give feed.
G-Wizard Speeds and Feed Calculator computes right values for spade drills in many materials. 2 page Speed/Feed Cheat Sheet helps to quickly cite tools. Always count using the actual diameter of the used drill.
