Defining Drilling Speed

 

Approximate starting advice is to set the spindle speed between above 2000 for aluminum, 700-1000 rpms for steel, and slow down if you get heavy drill bit wear.

 In most cases drill presses are too weak to follow the below recommendations. Going slower usually doesn’t hurt, and will prolong tool life. It allows to effectively use low price drilling bits. Most speed recommendations are geared towards manufacturing environments where machining time is very expensive. For the hobbyists shop longer tool life is usually more important, and reasonable advice might be to start off at about 75% of the recommended drilling speeds.

A slower spindle speed won’t hurt anything except in the case of extremely small drill bits (smaller than 1/16″). With small bits, it’s hard to feel resistance from the metal, and therefore, very easy to push down faster than they can remove metal. Using recommended RPMs (spindle rotation speed) mitigates this risk.

Feed Rate:This is how fast the drill bit is pushed down. This isn’t very useful if you’re lowering the drill bit by hand. In general, push hard enough to create a continuous chip (some materials like cast iron just won’t form one), but not so hard that the chips are turning brown. Using high-quality drill bits reduces the risk of it’s damage.

There are machining tables that list maximum speeds and feeds of drills in various materials. The key here is “maximum”. There’s nothing wrong with drilling a hole at less than the maximum speed, in fact in many cases it’s easier to control the drill at lower speeds especially as the point breaks through at the end of the hole.

 

 Drilling Speed (HSS, for carbide up the speeds by 2 to 3 times)

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Material Speed
Range (Surface Feet per Minute)		 1/8 (.125″); 1/4 (.25″) 5/16 (.3125″) 3/8 (.375″) 7/16 (.4375″) 1/2 (.5″)
wood 300-400 9167 4584 3667 3056 2619 2292
high carbon / alloy
steel, up to 275
Brinnel hardness		 55-85 1528 764 611 509 437 382
low carbon steel, up
to 275 Brinnel hardness		 60-100 3056 1528 1222 1019 873 764
cast Iron 50-125 2139 1070 856 713 611 535
tool steel 45-60 1528 764 611 509 437 382
brass / bronze
high strength bronze may
require 70 or less		 150-300 6112 3056 2445 2037 1746 1528
aluminum and alloys 200-300 7639 3820 3056 2546 2183 1910

 

Drilling feed (Inches Per Revolution)

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MATERIAL Dril DIAMETER
2 1 1/2 1 3/4
Aluminum .030 .025 .020 .016
Aluminum Bronze .020 .015 .012 .010
Balkelite .015 .015 .012 .010
Brass .022 .020 .018 .012
Bronze, Common .022 .020 .018 .012
Bronze Phos.; 1/2 Hard .020 .015 .012 .010
Bronze Phos.; Soft .022 .020 .018 .012
Celluloid .010 .008 .008 .006
Copper .020 .015 .012 .010
Copper Mang.; 30% Mn .016 .014 .012 .009
Duralumin .025 .020 .018 .015
Iron, Cast; Med Soft .015 .014 .012 .010
Iron, Cast; Hard .012 .012 .009 .007
Iron, Cast; Chilled .011 .011 .009 .007
Iron, Malleable .018 .015 .012 .010
Monel .015 .012 .010 .008
Nickel, Pure .020 .018 .015 .008
Nickel, Steel; 3 1/2% .015 .012 .010 .008
Rubber, Hard .030 .025 .020 .018
Screw Stock, C.R. .018 .015 .012 .010
Stl, Carbon .018 .015 .012 .010
Stl, Drop Forged .018 .015 .012 .010
Stl, Machinery .022 .018 .013 .012
Stl, Magnet; Soft .011 .010 .009 .008
Stl, Magnet; Hard .004 .003 .003 .002
Stl, Mang.; 7-13% .004 .003 .003 .002
Stl, Mild; .20-.30C .025 .020 .018 .015
Stl, Molybdenum .018 .015 .012 .010
Stl, Spring .010 .010 .009 .007
Stl, Stainless .016 .013 .011 .008
Stl, Stainless .004 .003 .003 .002
Stl, .40-.50C .018 .015 .012 .010
Stl, Struct; A-36 .025 .020 .018 .015
Stl, Tool; SAE, Forged .016 .014 .011 .009
Stl, Tool; SAE, Forged .004 .003 .003 .002
Zinc, Alloy .025 .020 .018 .016