Drilling Techniques
If you ever need to drill a technique, this shows you how.
Wood
Many bit types will drill wood successfully.
Standard universal twist drills have poor angles for woodwork, they will cut but make an unnecessarily hard job of it. However they are the most common wood drilling bit, since one low cost bit type will drill many different materials.
Lip & spur bits, aka brad point or dowel bits, perform rather better in wood than standard HSS twist drills. The point stops bit wandering, the cutting angles are faster, and the outer edge angles cause less damage to the remaining wood.
The fastest lowest energy use bits for wood are steep angled twist drills. These are a few times quicker drilling than lip & spur bits.
Masonry bits are useless on wood, as they have no cutting edge.
Augers cut clean holes in wood rapidly and energy efficiently, and are often used for large holes. However they are high torque low rotational speed bits, so lower power drills can struggle with them.
Spade bits aka flat bits are basic low cost low performance bits. They damage the surrounding wood surface, use a lot of electrical energy per hole, and sometimes misbehave. Their main advantage is low cost for large holes.
See Drill Bits for the many other wood cutting bit types.
Mild Steel
Standard HSS bits are used, or titanium coated bits. Harder bits such as cobalt also work, but cost more.
Titanium coated bits have much better life than HSS on steel. They also remain sharp much longer, making the work quicker and easier.
Tables of ideal drilling speeds for steel are available, and the closer to these speeds one uses the less likely problems are to occur.
First use a centre punch to indent where drilling will happen. This stops the bit from wandering.
Drill a small centre hole all the way through first, then enlarge it to full size with a bigger bit. The reason for this is that standard twist drills have a small relatively blunt section in the centre.
Stainless Steel
Stainless steel is harder to drill than mild steel. HSS bits are not very successful. Cobalt steel bits will drill ss, but don't last long.
See Superhard Drills for other bit options.
Aluminium
Aluminium bonds to HSS bits. This problem can be reduced with a lubricant, such as paraffin.
Titanium coated bits perform much better than HSS with aluminium, since they don't bond to the ali.
Its common to see advice not to use titanium on aluminium, as there is a compatibility problem with an aluminium alloy used on aircraft. However most of us are unlikely to encounter such alloys on DIY tasks, so premature bit failures should not occur when drilling aluminium.
Cast Iron
Glass & Tiles
Only use glass & tile drills. These are abrasive bits, so progress is slow compared to cutting bits.
Masonry & Stone
The lower budget option is a TCT masonry bit with a drill set to hammer action.
A much better option is an SDS drill with a standard SDS masonry bit. SDS delivers far better performance than non-SDS hammer drills, resulting in holes produced in a fraction of the time, and with minimal effort. The holes produced are much cleaner too, with much less surrounding breakup than with more basic hammer drills.
The pauper's option is a drill with no hammer facility plus a TCT masonry bit. However failure to use hammer action causes very short bit life, and this approach will only drill some masonry.
Very rarely is it necessary to drill masonry by hand today, but it is possible. See Drill_Bits#Manual_Hammer_Drill
Clearing the hole
Holes in masonry tend to be left with a lot of dust in them after drilling. This blocks some of the hole and reduces the security of wallplug fixings.
Its perfectly possible to fit wallplugs without clearing the hole, but failures to insert and to fix securely will occur.
Debris may be removed by:
- blowing in the hole - eyes shut!
- hoovering the hole
- Put a bendy drinking straw in the hole and blow
- A blower consisting of a rubber bulb with stalk
- bicycle pump with a thin tube
The first 2 will only clear holes of limited depth, the latter 2 are best used for deep holes.
Reinforced Concrete
Masonry bits will not drill through steel reinforcement, and HSS bits that drill steel will not drill concrete. The solution is a bit designed for both, such as Irwin cordless, Bosch multi-construction, etc.
Butter & Soft Cheeses
3 for £1 long drill bits are suited to these materials. Don't be tempted to try them on anything harder.
Plastics
Twist drills all work on plastics. HSS or titanium coated are fine. With softer plastics, beware of the tendency to dig in and jam; use low pressure and pull the bit back frequently.
With very shallow holes, eg 2mm sheet material, the jamming problem can be avoided by moving the drill around while drilling. This is a quicker option.
Removing Bits
In nearly all cases a drill bit should continue to rotate forwards while the drill is pulled out.
Augers must be rotated backwards to remove them.
Never waggle the drill from side to side to aid bit removal. This greatly increases friction, making removal much harder. The bending results in many damaged and some ruined drill bits. Damaged bits put greatly increased forces on drill bearings, causing tool failures. Damaged bits are much more likely to break in use, sometimes causing hand injuries.
Vertical Drilling
Discussion of methods to get holes accurately vertical