Fleet Maintenance Supply Experts

Know your Drill Bits

choose the right drill bits

Let our Drill Bit User Guide point you in the right direction!

How many times have you grabbed the closest drill bit to get a drilling job done, without really knowing if it’s the right one? Once? Twice?

If you’re like a lot of us, you’ve probably done it more times than you’d care to admit. But we all know the bit you choose can make all the difference. Which is why picking the right one from the start is so important.

We’ve put together the Drill Bit User Guide below to give you a general idea of the most commonly used drill bit types and their uses. Our hope is that, after reading through the Guide, you’ll have a better idea of which bit to choose BEFORE you start the job.

Primary Design Features

●     Bit Lengths

●     Jobber
These drill bits lengths are the most common because they can be used for many “run-of-the-mill” jobs encountered on most projects. Jobber bits have fairly long flutes, generally 9 to 14 times their diameter, allowing them to drill holes deep enough, again, for most common needs. Great for processes which require higher speeds, deeper holes, longer life, greater precision and maximum durability.

●     Screw Machine
Shorter flutes provide increased toughness and precision required for use in screw machines and other automatic drilling equipment. Shorter overall and flute length, allows them to be used in tight spaces and for portable drilling applications that require rigidity. The trade-off is that screw machine bits can drill holes only as deep as their flutes.

●     Taper Length
Taper length bits have longer flutes and generally can drill deeper holes than jobber bits. In fact, their flute lengths are the same as comparable-sized taper shank bits, and they can be used with standard chucks and collets, making them low-cost substitutes in some applications.

●     Mechanics Length
A mechanics length bit is simply a bit with a shorter flute length and shorter overall length than a standard jobber bit. This shortening of the bit makes it considerably stronger and less prone to breakage and shearing, making it suitable for harder drilling.

Generally speaking, the shorter the drill bit, the better the outcome. Screw machine drill bits will deliver more precision and better value because they will remain more rigid and straighter than their larger counterparts. On the other hand, shops that perform various standard drilling processes may prefer the versatility and cost savings that come from using jobber drills. Jobs which require the drilling of deep holes may require taper length drills. For harder materials and hard metal drilling, a mechanics length drill bit is recommended as they are a stronger bit. 

●       Drill Point Angle

●       Standard 180 degrees angle which can be found on most common types of drills. Typically, these drill bits have two cutting lips.

●       Self-centering 135 degrees angle for faster drilling. This type of drill bit is perfect for drilling into stainless steel materials because they have four cutting lips with a sharp center. 

Flute Design

●       Standard design is most common, with flutes set at 30 degree angles.

●       Parabolic design features an open design that helps remove chips from the drilled hole. very efficient for drilling soft materials like plastics and other similar materials.

Bit Types

  1. HSS (High-Speed Steel)
    HSS bits are the most popular drill material for maintenance drilling applications. They specialize in drilling through steel, deriving their strength from a mixture of vanadium and tungsten. HSS drill bits are commonly referred to as twist bits because of their cylindrical shank and are the go-to drill bit for general use. They come in sizes ranging from 0.8 mm to 12 mm, and also drill through wood and plastic.
  2. Brad Point
    Ranging in sizes from 3 mm to 10 mm, the brad point drill bit, or spur point, has the same shape as the twist bit, but the tip is shaped like a “W.” That allows the outer points on the edge to start cutting the hole before the center point makes contact with the material. Brad point drill bits are ideal for drilling wood and plastic, as well as specific jobs like doweling. These drill bits often have a depth stop to allow you to choose the required depth of the hole you drill.
  3. Masonry
    Masonry drill bits are perfect for drilling into concrete, stone, and brick when the drill is set to hammer. They have a tungsten carbide tip for added durability and come with a cylindrical shank or a hexagonal shank to stop them from slipping in the chuck when the drill is under pressure. The maximum reach of a masonry drill bit is 400 mm, and they range in size from 4 to 16 mm. The strain on masonry bits is immense, causing them to heat rapidly. This melts the tungsten coating and causes the drill bit to heat up. Either keep some cold water nearby to dip the bit, or make sure you remove debris from the drill bit as you work.
  4. Multi-Purpose
    These drill bits are good all-rounders. They can be used in hammer or rotary mode and have a diamond ground tungsten tip. It can drill through metal, wood,  plastic, ceramic tiles, and masonry.  When drilling masonry, use the rotary mode because the prolonged use of the hammer setting may damage the coated tip. For extensive masonry drilling, the recommendation is to use a dedicated masonry drill bit.
  5. Titanium Nitride HSS
    The titanium coating on the drill bit helps to reduce overheating. It’s the reason that this bit has a lifespan up to six times longer than other comparable drills. Like the high-speed steel drill bit, this one can drill through wood, metal, and plastics. This drill bit requires less maintenance and is a great general purpose tool.
  6. Cobalt HSS
    Cobalt HSS bits are made from precision ground, alloyed high-speed steel, and solid cobalt. They are incredibly hard-wearing as well as resistant to high temperatures and abrasion. Cobalt drill bits can tackle steel, cast steel, stainless steel, cast iron, bronze, and other high tensile steels. This is one tough cookie!
  7. Reduced Shank HSS
    These drill bits have a wider diameter and a reduced shank to fit your drill chuck. The purpose is to drill holes larger than the width capacity of your chuck. As an example, you might have a 13 mm width capacity on your chuck, but the reduced shank bit has a maximum diameter of 16 mm. When drilling pilot holes, don’t exceed 25 percent of the reduced shank’s diameter. This drill bit is great for drilling wood, metal, and plastics.
  8. HSS Rivet
    These drill bits are designed for drilling tiny holes to insert rivets. They have fluted sides to increase the longevity of the bit. It means more holes for your money. The depth of the hole must not exceed one and a quarter times the diameter of the hole. Also, the drilled hole has to be larger than the rivet to allow for expansion and reduce fatigue.
  9. Spade
    When you want to drill a large hole through wood, this spade bit is the one for the job. They have a ¼-inch hex shank for better grip in the chuck, and a long spike with two spurs on either side. This brad point drill bit has a long reach, but it can reach further with a shank extension attachment. Spade bits typically range in diameter from 6 to 38 mm.
  10. Auger
    Auger drill bits are capable of drilling larger holes in dry, thick and hard lumber. They’re distinctive by their size. The shank is hexagonal for extra purchase in the drill chuck, and the screw-thread tip draws the drill into the material with minimum effort. Auger drill bits have large flutes for removing the wood, while the single-spur cutting edge cuts a neat and wide hole circumference.
  11. Forstner
    Commonly used for drilling holes for concealed hinges like the sort found on kitchen cabinets, Forstner bits range in size from 26 mm to 35 mm and are capable of drilling large diameter holes in wood. Saw-tooth Forstner bits leave a larger and rougher hole. These are better for drilling end grain. Continuous rim Forstner bits leave a smaller, neater hole size.
  12. Countersink
    Countersink bits create beveled openings at the top edge of a pilot hole. Typically, they come in 13 mm, 16 mm, and 19 mm, and there are different varieties for drilling metal and wood. They’re used in conjunction with countersink screws and rivets that sit flush with the surface of the material.
  13. Drill/Countersink
    This countersink bit is an amalgamation of the HSS drill bit and the countersink drill bit. It sits in the chuck via a small grub screw, which is adjusted using an Allen key to get the desired length. Drill/countersink bits are useful for drilling pilot holes for countersunk screws and come in two varieties — fluted or cross-hole. They are identified by the gauge of screw they correspond to, such as 6G, 8G, and so on.
  14. Self-Centering
    Self-centering bits drill accurately centered holes for hinges in wood and other material. The drill bit has a tip that sits in the countersunk hole, aligning itself with the center. When pressure is applied, the bit get released from the spring-loaded sleeve and works into the material. Like the drill/countersink bit, the HSS bit in the sleeve is removable, by turning a grub bolt with an Allen key. Self-centering drill bits are also associated with the size of screws they are designed to pre-drill.
  15. Spear Point (Glass and Tile)
    The name describes the design of this bit. They’re tungsten-tipped drill bits that specialize in drilling through glass and ceramic tiles. Spear points will drill through porcelain, but toughened glass is beyond their capabilities. You can also use this drill bit to drill stone, marble, and granite.
  16. Diamond Tile
    This drill bit is better suited to hard surfaces like masonry and tiles, including porcelain. Start by rotating the drill bit at a 45 degree angle, then as it starts to bite, ease the drill upwards until it is straight. Like the spear point drill bit, set the speed on your drill to slow. You also need to have a supply of water to help keep it and the material cool and to increase the abrasion.
  17. Special Direct (SDS) System
    SDS drill bits are for drilling into dense material like masonry, concrete, and stone. They are incredibly robust and work with your drill in rotary hammer mode. The shank has unique slots to allow for speedier bit changes. There are two types of SDS drill bits — SDS-Plus and SDS-Max. These variants last longer, making them a good choice for extensive heavy drilling.
  18. Step Drill
    Step drill bits have a conical body with stepped sides. This is your go-to drill bit for making multiple hole sizes. They make holes in thin material, enlarge existing holes, and lightly burr. Step drill bits have a titanium-nitride coating to minimize heat build-up and increase lubrication. Conical versions are available without the stepped pattern.
  19. Plug Cutting
    Plug cutters are excellent for hiding screw heads. One part of the drill bit cuts a hole with a countersunk base, while the other cuts a plug to the exact dimensions of the hole. This conceals the screw. They are a favorite of cabinet makers and craftspeople who build high-end wooden products. To cut accurately, use a center press as these drill bits have no central point to steady them as you make your cut.
  20. Saw Bit
    Saw bits have a standard HSS drill bit tip, but the shaft of the drill bit changes to a cutting edge after the first 15 mm or so. As the drill bit bites into the material, the abrasive teeth give you the ability to cut laterally. Drill bits work best with a downward force toward the tip, so working the drill bit sideways across the surface of your project can be difficult to control. This creates inaccurate holes.

Let’s Get Drilling

For more information on the right drill lengths, materials, flute configurations, shank style and other specifications that are best for your shop’s needs, get in touch with us today. Imperial Supplies is ready with more than 1,800 drill bits and extensions, power drills, pneumatic drills and more. Plus, all the drilling equipment expertise you’ll need to keep your shop outfitted, efficient and ready.

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