Drilling a hole

Drilling is a process for removing material from a workpiece in order to create a hole. Drilling requires a cutting tool called a drill bit. The drill bit is rotated and forced into the surface of the material, removing metal in the form of chips and producing a round cavity in the process.

Drilling is often carried out late in the manufacturing process, after previous operations have already enhanced the initial component’s value. The drilling application, although seemingly simple, is a complex operation that can have significant consequences if the tool malfunctions or is run beyond its capacity.

Drilling is concerned with both the diameter of the hole and the depth of the hole. It can be done on a milling machine, lathe, or machining center, but there are also machines designed specifically for drilling called drill presses. Deep hole drilling requires specialized equipment

Drilling at an angle

Drilling at an angle can seem difficult, but don't worry, there's several methods you can use to create angled holes. You can try some basic tricks if you don't need your angles to be too exact. Otherwise, try building an angled jig with a piece of wood for your hand drill, or creating an angled jig that fits onto the plate of your drill press.

Twist Drill

Twist drills are the most common and easiest way to put a hole in steel, wood or other non-ferrous materials with a drill bit but with so many options to choose from it is important that you use the correct one for your specific application. Twist drills are rotary cutting tools that normally have two cutting edges and two flutes

Spotting drills

This tool pinpoints the exact location of a hole to prevent common deep-hole drilling mishaps such as walking, or straying from a desired path. It can also help to promote accuracy in instances where there is an uneven part surface for first contact

Types of holes

Through hole

Blind hole

Chamfer hole

Step hole

Holes for different purposes

  1. Holes with clearance for bolts
  2. Holes with a screw thread
  3. Countersunk holes
  4. Holes that have a good fit
  5. Holes for tubes (heat exchangers)
  6. Holes that form channels
  7. Holes to remove weight for balancing

Drilling large holes

  • Method #1 Use a trepanning tool
  • Method #2 Enlarge the hole with a boring tool
  • Method #3 Use helical interpolation with milling tools

Drilling micro holes

How to change drill bit

Machines to use for drilling holes

Manual Hand Drill

Portable Electric Drill

Chordless Battery Drill

Masonary Drill

BenchTop Drill Press

CNC Router

Which drill for plastic?

You can use the same bits as for wood. However, drill slowly. If you drill fast, friction can rapidly cause plastic to melt, clogging the tip and flutes of the drill with melted shavings, especially if the bit is blunt. As shavings cool and get stuck in the flutes, or coat the bit, the problem gets worse and the bit can get stuck. It's not such a big deal when drilling through thin plastic, but I've found that when drilling through thicker sheets and specifically acrylic (commonly known by the brand names "Plexiglass" or "Perspex"), this can be a problem

Drilling Large holes using Hole Saw

Hole Saw

Drilling very large holes greater than 1 1/2 inches with a standard bit is impractical as you would need a drill with a huge amount of power and torque to overcome friction in order to drill through timber. Instead, drilling large holes can be accomplished with a hole saw. This has small teeth like a handsaw and the "blade" is in the form of a cylinder.

Some hole saws are only designed for drilling wood or plastic while other versions are made from HSS steel and suitable for drilling iron, steel and other metals in addition to wood.

Drilling into concrete

Hammer Drill

With a good hammer drill and concrete drill bits, making holes in concrete is almost as easy as drilling in wood. The hammering action of the masonry bits pulverizes the masonry in contact with the tip of the bit.

Rotary hammers are more powerful, though, and have a “hammer-only” mode with no rotation. This is also known as ‘rotary stop’ or ‘chisel’ mode. The rotary motion of the drill is switched off and the hammer action only is applied. The piston inside moves back and forth driving the drill bit back and forth, driving it in turn into the material

The pounding power of a hammer drill is measured in BPM (beats/blows per minute)

Masonry bits are available with a round section shank for use in a conventional chuck. However, a better choice is an SDS type bit. The shank on this type of bit doesn't slip in a chuck and can be quickly inserted and extracted from the SDS chuck on the power drill.

Drilling Hole through Rebar

Drilling through concrete is tough to begin with, but when your masonry drill bit encounters a piece of rebar the project comes to a screeching halt. Masonry drill bits are coated with mineral grit; they pound and grind through brick and cement-based materials. Although abrasive bits are capable of grinding through steel rebar, sharp-edged drill bits are faster and more effective

Because builders don't leave any indication of the location of rebar, there's always a chance that your concrete drill bit will encounter metal. When your concrete drill bit (hammer bit) hits rebar, you should stop drilling and replace the concrete bit with a metal bit (rebar bit). Once you clear the metal, you can reattach the concrete bit and continue drilling through the masonry material.

Drilling Tips for Hammer Drills

Tip #1: Clear the debris

The flutes on a drill bit are designed to pull up the debris from the hole as you drill, but the best way to clear the hole is to occasionally pull the bit out of the hole as you’re drilling. Less debris in the hole reduces friction, which means smoother drilling, less chance of binding and longer-lasting drill bits.

Tip #2: Avoid over drilling

Most hammer drills and rotary hammers are sold with a side handle and depth stop. Do yourself a favor and use them. There’s no reason to burn up both time and bits by drilling deeper holes than you need to. And you don’t always want to drill all the way through a concrete block to its hollow core—some plastic anchors need a back to stop them or they will get pushed right through the hole.

Tip #3: Don’t push too hard

There’s a “sweet spot” where the right rpm combined with the right pressure drills fastest. But you won’t find that sweet spot by pushing down as hard as you can. In fact, too much pressure will slow the drilling process and put a whole lot of unnecessary wear and tear on the motor gears. Plus, you’ll break bits

Tip #4: Drill a smaller hole first

If you need to drill a couple holes that are larger than the recommended capacity of your drill, start with a smaller hole first. This will significantly reduce the load on the drill. Also, smaller bits don’t skate around as much as larger bits do, which is helpful when you need a hole in a precise spot.

Drilling into tiles or glass

These are made from tungsten carbide and suitable for drilling glass or tiles. When drilling glass, if possible lay it flat on a soft cloth or newspaper for support. Drill at low to medium speed and either spray the area being drilled with water to cool and lubricate the bit, or make a "dam" of plasticine around the area and fill it with water

Demagnetizing the drill bit

Over time, drill bits can become magnetized so they collect shavings while you're drilling. This can interfere with the drilling process by increasing friction, clogging the flutes and getting in the way of the cutting edge so that it can't shave through a hole properly. A demagnetizing tool is a useful gadget for removing magnetism from drill bits, screwdrivers and other tools. Often these de-magnetizing tools can also be used for magnetizing

Sharpening the drill bit

With some skill, you can learn to sharpen a drill bit on the fine grit wheel of a bench grinder. However the bit needs to be held to the wheel at a relatively precise angle, which takes a bit of practice

An alternative is to use a sharpening tool like this one by Drill Doctor. These machines are basically composed of a motor driving a small grindstone. To sharpen a drill, you insert it in the appropriate sized hole in the top of the sharpening tool and twist it a few times. This product covers all sizes up to 12 mm or 1/2 inches

Drilling holes through a PCB

Hand Drill

A great number of holes with small diameters of about 1 mm or less must be drilled in printed circuit boards (PCBs) used by electronic equipment with through-hole components. Most PCBs are made of highly abrasive fiberglass, which quickly wears steel bits, especially given the hundreds or thousands of holes on most circuit boards. To solve this problem, solid tungsten carbide twist bits, which drill quickly through the board while providing a moderately long life, are almost always used

What drill bit to use?

Old fashioned hand drills for wood working