Fleet Maintenance Supply Experts

How To Choose The Right Drill Bit For Any Job In The Shop.

How to choose drill bits

The drill has got to be one of the most useful tools ever created. Every fleet garage and heavy-duty repair shop needs holes…just not bad holes, misplaced holes or any of the accidents or injuries that can come from drilling holes. 

Many of the mishaps related to drilling are the result of the wrong choice of drill bit. They are not all the same. Far from it. Knowing the differences and intricacies of their design can help lead you down the straight and narrow path of success in drilling holes in any material. 

Choosing the right drill bits supports precise and productive work. It also helps protect the value of the parts and materials you work on—which can help keep your operation out of the hole, financially speaking. 

It pays to choose the right drill bit for your project. Picking the right one is all a matter of knowing the basic drill bit features, the types of drill bits out there and the metals and finishes that make a difference. That and a few tricks of the trade and you can make perfect holes anywhere and every time. 

Here’s the drill down on bits from Imperial Supplies’ own experts.

First off, what is the difference between metal and wood drill bits—or plastic, glass or ceramic tile for that matter? There are many ways to answer that question—from the bit design and tip angle to the length and flute design. Let’s start with the most fundamental aspect of drill bits: the metal compositions and finishes, since that has a huge role in what materials a bit can handle, how hot it can get and how it will perform overall.  

Know the six Main Hex Bolt Compositions and Finishes

  • Steel bits are either low carbon steel or high carbon steel. They’re what most budget bits are made of and typically used with wood. They get worn and dull quickly, especially when they get hot. 
  • High-Speed Steel (HSS) bits have a composition that withstands the high temperatures from high speeds that cause dulling. A shop standard that tends to be a good value, HSS bits can be used to drill wood, fiberglass, soft metals and plastic.
  • Black Oxide-Coated HSS Bits retain lubricants well for smooth drilling and heat control. They are a durable option for metals, wood, PVC and fiberglass. 
  • Cobalt Bits are durable, dispel heat efficiently and retain their sharpness well. They drill strong metals like stainless steel but can also be brittle and break. 
  • Titanium-Coated Bits are natural friction reducers and their ability to retain sharpness makes them a fine choice for metal, wood, fiberglass and PVC.
  • Carbide-tipped bits are often used for tile and masonry as well as metal. They can be costly, but their ability to drill hard materials and retain sharpness makes them a top performer.

Some Pointers about Drill Bit Tips

One of the main questions people ask is “what is the difference between 118- and 135-degree drill bits?” There are three main variations of drill bit tips. A 118-degree point is primarily for wood or plastic where entry is easier. A 135-degree point is used for drilling holes in metal and harder surfaces to eliminate the bit from sliding or skating. The third is a split point. Are split-point drill bits better? Split point bits have small cuts on either side of the cutting flutes on the tip to bite in faster and prevent skating.

Drill Bit Lengths Make a Difference

  • Jobber Length – this is the most common bit length used in general purpose drill bits.  
  • Taper Length – this length is intended for making pilot holes for the shanks of wood screws.
  • Extra Length – like the name says, they’re longer. Some refer to these sizes as “aircraft-length.” 
  • Mechanics Length – the shorter flute length and overall length makes them less prone to breaking and better for harder drilling than jobber length bits.
  • Screw Machine Length – with the lowest length-to-diameter ratio, these are the shortest of the bits.

Know Your Flutes and Shanks

Flutes are the spiral grooves cut into the drill bit. A fast spiral has more twists per inch and facilitates large amounts of swarf (shavings) at low drill speeds. A low spiral has less twists per inch and is used in high-speed drilling where swarf is expelled quickly. Standard twist drills tend to have two flutes with low spirals. The part of the bit where the flute ends and transitions into the part inserted into the drill is called the shank. The shank can be cylindrical, or for a tighter grip and more torque, it can be hex or slotted drive system (SDS). 

15 Drill Bit Types you Need to Know

Now that you know the basic attributes of drill bits, it’s time to go deep on the right design for the substrate, or material, you’re working with. In the heavy-duty world, technicians need to drill holes in a wide range of substrates from hard and soft metals to glass, plastic, wood—and maybe even tile or concrete when odd repairs and improvements come up. Having the right drill bit, sharp and ready, can make the difference between a ruined part or a speedy repair. Use this helpful list to make the right choice. 

1. Twist drill bits are the classic drill bit for everyday use. Depending on their composition and coating, twist drill bits are the go-to for most metal-, wood- and plastic-drilling jobs. A comprehensive set of twist drill bits is a must for any garage.

2. Step drill bits are good for drilling metal up to ¼” thick as well as wood. The beauty of these cone-shaped bits is they enable you to use one bit to drill holes with different diameters. They are useful in enlarging holes in sheet metal. 

3. Hole saws aren’t technically drill bits, but they cut big holes using a drill—and they’re very useful in the garage for making holes for hoses and wires. They have a toothed blade in the shape of a circle. Bi-metal hole saws can cut metal. Ones made of carbide can cut ceramic tile or masonry—and with a diamond edge, you can do it even quicker.

4. Countersink drill bits are used to create a conical surface hole with a smaller hole in the center to allow a screw to sit flush with a metal or wood surface.

5. Counterbore drill bits create flat bottomed larger holes on top of smaller holes so that the screw can be hidden lower than the surface. They are good for wood or metal substrates.

6. Installer drill bits are a special type of twist bit used for wire installation. They can be long and they can drill through a variety of materials. Once through the surface, you can put a wire into a small hole in the bit and use the bit to draw it back through the hole. Then you can attach the wire to an additional wire and pull it through the hole.

7. Spade drill bits are typically used to drill large holes in wood—up to 1-1/2”. The flat blade has a sharp point at the lead to position and guide the bit.

8. Brad-point drill bits are for wood. The brad-point in the middle of the bit is there to aid precise positioning and ensure a clean exit hole. Wide flutes evacuate large amounts of swarf.

9. Auger drill bits are wood-borers with screw tips that start holes easily and pull bits through the material quickly. They come in long sizes and have big flutes to aid in sawdust removal.

10. Self-feed drill bits are also wood-borers but they’re smaller and don’t have large flutes to evacuate swarf. The screw tip design helps position the bit and draw it down easily. 

11. Forstner drill bits are good for drilling flat-bottomed holes in wood that can hold dowels. The bit has a point for precise positioning. Best used with drill presses that allow force and control.

12. Plug cutters bore holes into wood, creating leftover plugs that can be replaced over the tops of screws to conceal them.

13. Glass drill bits have carbide tips shaped like arrowheads. Successively larger bits are often used to increase hole sizes. 

14. Masonry drill bits are made with formidable carbide tips to put holes in brick, concrete and other tough substrates. Some work with standard drills; others are designed to be used with rotary hammer or hammer drills. 

15. Tile drill bits typically have a hard and sharp carbide tip that can drill holes in tile without causing chips and cracks. 

Final Thoughts on Drill Bit Care

Is it worth it to sharpen bits? When bits are dull, they often break because people tend to apply too much pressure on them—not safe and not cost effective. Keep your bits sharp by using a sharpening tool or the fine grit wheel of a bench grinder. When drilling metal, drill bits can also snag when emerging through the bottom side. So ease off the pressure at the end and try putting a block of wood underneath to prevent the metal from pushing out, snagging your bit and breaking it. Also prevent your bits from becoming chip magnets. Use a demagnetizing tool to prevent metal swarf from sticking to the bit, creating friction, clogging flutes and pitting your cutting edge.

With the right drill bit, the most indispensable tool in the shop, can be made even more useful. Imperial Supplies is here to help you make every hole a success by building an arsenal of bits that arms you for any task. Let us know how we can help! 

Follow Us