55mm Long 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.

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.

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







				Black Oxide

				4.0	0.1575"	55	13.9	Round	4 mm	Split	00000000	00000


				4.1	0.1614"	55	10.2	Round	4.1 mm	Split	00000000	0000
				4.2	0.1654"	55	13.5	Round	4.2 mm	Split	00000000	0000




						Titanium Nitride (TiN) Coated

						4.1	0.1614"	55	10.2	Round	4.1 mm	Split	0000000	0000

Smooth-Finish Carbide Drill Bits


Jobbers' Length Round Shank	Split

With more cutting edges than other drill bits, these cut continuously and consistently for a smoother finish. They also stay centered to produce holes that are straighter and more accurate. However, since there’s less space between the cutting edges, they don’t clear chips as quickly. Made of carbide, these are the hardest and most wear-resistant drill bits you can buy. They stay sharp at high temperatures and faster speeds for the best performance on hard and difficult-to-machine materials. Carbide can be brittle, however, so these bits require a rigid machine tool holder to prevent breakage and should not be used in hand drilling applications.

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

Uncoated—Excellent for a range of materials but won't last as long as coated 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

				4.0	0.1575"	55	21.9	Round	4 mm	Split	000000	000000


				4.2	0.1654"	55	21.9	Round	4.2 mm	Split	0000000	00000

Diamond-Coated Router Bits for Composites

With a diamond coating, these bits resist wear when used on abrasive materials, making them last about 50 times longer than uncoated bits. Their sharp cutting edges and flute shapes are specifically designed to cut through tough materials such as composites with minimal resistance. This means less strain on your router and more control when cutting, leading to a smooth cut. Bits are made of solid carbide for longer tool life and faster cutting speeds than high-speed steel.

Diamond-Coated Carbide


Drill/Mill Cut Style—Plunge-Cut	Drill/Mill Cut Style—Plunge-Cut, Straight Flutes

Drill/Mill Cut Style—Bits with a drill/mill cut style have a pointed end for easier plunge cuts than square-cut bits.

Plunge Cut—Plunge-cutting bits let you cut directly into the workpiece from above. Other bits are best for operations where the peripheral teeth do most of the work such as trimming, contouring, and finishing.

Straight Flutes—Bits with straight flutes are for general purpose use. They quickly remove material, leaving a rough finish.

	Overall Lg., mm	No. of Flutes	For Tool Type	For Use On		Each
Drill/Mill Cut Style—Plunge-Cut







	Straight Flutes

	4	12	4	55	6	CNC Machine	Fiber-Reinforced Plastic, Composite	0000000	0000000