21.0 mm Drill Bits | McMaster-Carr

Black Oxide—The dark finish increases wear resistance and reduces friction to improve chip flow, so these bits can last 50% longer than uncoated bits.

					Shank
	Drill Bit Size, mm	Decimal Size Equiv.	Overall Lg., mm	Max. Drilling Dp., mm	Type	Size	Drill Bit Point Type		Each
Jobbers' Length





				Black Oxide
				21.0	0.8268"	243	102.9	Morse Taper	Morse 2	Standard	3070A326	0000000

Reduced-Shank High-Speed Steel Drill Bits

Jobbers' Length


Standard	Split

Cut large holes with drill presses and portable drills that have a standard-size chuck. The shank on these bits has a smaller diameter than the cutting tip. High-speed steel is good for general purpose drilling in most metals. Also known as Silver and Deming bits.

Jobbers' Length—These bits have the balance of rigidity and length needed for most applications.

Black Oxide—The dark finish increases wear resistance and reduces friction to improve chip flow, so these bits can last 50% longer than uncoated bits.

Gold Oxide—Like black oxide, this finish adds wear resistance and reduces friction for improved chip flow. Because it’s less prone to flaking off, it offers better rust protection when bits aren't in use.

					Shank
	Drill Bit Size, mm	Decimal Size Equiv.	Overall Lg., mm	Max. Drilling Dp., mm	Type	Size	Drill Bit Point Type		Each
Jobbers' Length





				Black Oxide
				21.0	0.8268"	152	53.3	Reduced Round	1/2"	Standard	3091A46	000000



						Gold Oxide
						21.0	0.8268"	152	63.5	Reduced Round/3-Flat	1/2"	Split	6154N27	00000

Reduced-Shank Cobalt Steel Drill Bits

Jobbers' Length

Split

More wear resistant than high-speed steel, these bits cut large holes with tools that have a standard-size chuck. The shank has a smaller diameter than the cutting tip and fits drill presses and portable drills. Cobalt steel bits last at least twice as long as high-speed steel. They can also run up to 25% faster at higher temperatures without being damaged on hard materials such as nickel. Also known as Silver and Deming bits.

Jobbers' Length—These bits have the balance of rigidity and length needed for most applications.

Uncoated—Polished to eject chips, these are also known as bright finish bits.

					Shank
	Drill Bit Size, mm	Decimal Size Equiv.	Overall Lg., mm	Max. Drilling Dp., mm	Type	Size	Drill Bit Point Type		Each
Jobbers' Length





				Uncoated
				21.0	0.8268"	152	58	Reduced Round	1/2"	Split	8939A617	000000

High-Speed Steel Step Drill Bits

Standard

Drill multiple hole sizes using only one bit. These have steps with progressively larger diameters—the deeper they drill, the bigger the hole. Count the steps as you drill to achieve the proper size. These bits also deburr as they cut, so they're good for thin materials like sheet metal and plastic panels. Wear and heat resistant, high-speed steel is versatile for use on a range of materials.

Titanium Nitride (TiN) Coated—Drill at higher speeds and last longer than uncoated and oxide-coated bits, especially on tough materials like hardened steel and nickel.

Uncoated—The most economical option, uncoated bits perform best when used on low-carbon steel and aluminum. Polished to reduce friction, they're also known as bright finish bits.

			Shank
Drill Bit Size, mm	Decimal Size Equiv.	Overall Lg., mm	Type	Size	Drill Bit Point Type		Each





			Titanium Nitride (TiN) Coated
			5.0, 7.5, 10.0, 13.0, 16.0, 19.0, 21.0, 23.0, 26.0, 29.0, 31.0, 33.0, 35.0	0.1968", 0.2953", 0.3937", 0.5118", 0.6299", 0.748", 0.8268", 0.9055", 1.0236", 1.1417", 1.2205", 1.2992", 1.378"	79	Hex	11.1 mm	Standard	89275A35	0000000



					Uncoated
					5.0, 7.5, 10.0, 13.0, 16.0, 19.0, 21.0, 23.0, 26.0, 29.0, 31.0, 33.0, 35.0	0.1968", 0.2953", 0.3937", 0.5118", 0.6299", 0.748", 0.8268", 0.9055", 1.0236", 1.1417", 1.2205", 1.2992", 1.378"	79	Hex	11.1 mm	Standard	89275A15	00000