Things to Know Before Buying a Cordless Drill
If you want to begin your foray into DIY but know not where to start then by far and away the most obvious place is with a cordless power drill. This super versatile tool solves a myriad of household DIY problems literally at the flick of a switch.
When cordless tools hit the DIY market some 40 years ago, they were considered a luxury item – not anymore – the days of the corded drill are numbered!
Nowadays the power and performance of the traditional corded drill can be matched by its cordless counterpart. Beyond doubt the overriding benefit of a cordless drill is its convenience and versatility. You no longer have to find a mains socket for your corded drill and drag a cable or extension lead around.
There is also little difference in price between corded and cordless version of the same power drill. Only the cost of the battery may make a difference if you are purchasing the drill as a ‘bare’ model.
If you are an occasional user or are happy to take time out while your battery is charging, one battery is absolutely fine. Most power tool batteries can be recharged hundreds of times before they show signs of degradation, and need to be replaced.
If however you are a serious power tool user or want to work for long periods, you’ll need to purchase a second battery and carry a charger. Recharging will mean access to a mains supply too.
Comparing Drill Drivers and Combi Drills – the Essentials
As far as cordless drills go the two most popular cordless drill options are the drill driver and combi drill.
Of the two the combi drill is more powerful but it is also heavier and more expensive.
Which one should you choose? Let’s take a look….
The Drill Driver was invented by Black and Decker in 1961 and is one of the most popular power tools on the market today. Essentially it is a basic cordless rotary drill with an added function for (screw) driving. It allows you to combine speed (used for drilling holes) and torque (twisting force required for turning) using the settings on its torque control ring, to give you the power and accuracy you need when driving screws.
The combi drill however is a drill driver with an additional hammer (percussion) function that for drilling into masonry or concrete. It is therefore more versatile than a drill driver, but also heavier and more expensive.
The combi drill offers the same convenience and functionality of a drill driver, but with an additional ‘hammer’ function and an extra setting on the control ring to adjust the bpm (beats per minute) delivered when hammering.
Combi drills are therefore more of a hybrid solution for everyday drilling, driving and hammering tasks.
Drill Drivers and Combi Drills – Their Uses
Drill drivers are best suited for drilling into softer material such as wood, plastic, veneer and metal, where it uses its ‘rotary’ mode, and putting screws into soft materials, where it uses its ‘driving’ mode. This is all controlled by how tightly you pull the trigger and what torque setting you use.
So if you’re putting up shelves, hanging pictures, assembling cabinets, cupboards or flat-pack, drilling holes in MDF, particleboard or aluminium, go for a drill driver.
You can also extend the drill driver’s use because as well as accepting standard drill and driver bits, it’s chuck accepts a wide range of other accessories such as woodworking gadgets, sanders and hole saws, so there are really endless projects you can get stuck into.
Whereas the drill driver is fine for drilling into softer materials, you are going to need something more robust to drill into denser materials such as brick, masonry, concrete, rock or stone. This is where the combi drill comes in. It combines the dill driver’s ‘driving’ action with a percussion feature for this more heavy duty drilling work.
When a Drill Driver or Combi Drill Should not be Used
Drill drivers and combi drills can handle many day-to-day tasks but are not designed and built for serious heavy duty work, such as heavy masonry drilling or driving large bolts, even if you do have more specialist bits at your disposal for those tasks. There are other tools that can perform that kind of specialist work much more effectively, notably the SDS rotary drill or impact driver (for driving large bolts). These last two tools are designed to absorb impact much more efficiently, but are rather more expensive.
Choosing Between a Drill Driver and Combi Drill
The best cordless drills balance power and weight to give you a tool that’s light enough for anyone to hold on to but has enough grunt to drive screws or drill holes into hard materials. If light weight is top of your list, go for a 12V drill driver – it sacrifices some torque and rpm to give you a tool that weighs less than 1 kg. But, if you’re more concerned with high torque and weight isn’t an issue, an 18V combi drill is your friend.
Things to Look For When Choosing a Cordless Drill
Understanding Power and Performance
The handheld drill is one of the most used power tools in any DIYers arsenal. Whether you’re hanging a picture or building a house, you’ll be reaching for the best cordless drill you can get your hands on. But you can’t do anything without enough power to safely drill holes or drive screws.
Power is supplied to the tool’s motor as an electrical current, via (in the case of cordless power tools) a rechargeable battery. The motor converts this electrical energy into mechanical energy, which is composed of both speed and torque.
Speed is applied in the same direction as the drill is being directed (often called ‘linear’). It is measured in rpm (revolutions per minute). Manufacturer’s specifications refer to a tool’s maximum speed as ‘no-load’. This is the maximum speed that can be attained by the tool without encountering any resistance (or ‘load’).
Torque on the other hand is applied from a sideways direction – at 90 degrees to the speed. Torque is the turning or twisting force that the tool can produce. It is measured in Newton Metres (Nm) or Inch Pounds. (1 Nm = 8.85 Inch Pounds).
So in the case of a cordless drill power is a combination of speed and torque. It is fed to one or more gears that rotate a chuck and the bit that sits in it.
The Difference Between Speed and Torque
It is important to note that the relationship between speed and torque is inversely proportional.
More speed means less torque, and vice versa.
Higher speed is better for drilling holes into softer material or driving small screws.
Slower speed (greater torque) is better when you encounter tougher materials that require more turning / twisting force to drill or when you are driving larger screws or fasteners.
More heat is generated when greater torque is applied.
Why Gears Make a Difference
Most cordless drills come with two speed gearboxes so you can take on a wider range of projects.
Gears harness the power delivered from the battery and enable it to be delivered across different ranges of speed and torque.
Each gear has a maximum rotation speed and torque. For example, drill drivers with one gear may have a maximum no-load speed of maybe 650 rpm and combi drills with two gears a maximum no-load speed of 2,000 rpm.
Two speed combi drills with their hammer action can typically generate up to 10,000 bpm (beats per minute) in the lower gear and 20-30,000 bpm in the upper gear.
The best drill drivers can deliver between 30-40 Nm of torque and the best combi drills over 70 Nm.
So for light screw driving or drilling one gear is perfectly acceptable, but two gears provide more versatility in the number of applications that can be handled.
How to Use Torque Control
Once you have used the gear selector switch to choose the appropriate gear how do you control the power so as not to overtighten or strip a screw, damage a work surface, or even worse injure yourself?
The answer is to set the correct level of torque on the torque ring. Selectable torque settings (anything from 10 to 24) are normally found as a twist-collar on the body of the drill behind the chuck.
Finding the correct resistance level will depend on the gear setting you have chosen (assuming there is more than one gear), the torque level selected, the screw or bit you are using and the toughness of the material you are negotiating. This is initially down to trial and error but you can always experiment with the torque settings in scrap material first.
But the important thing is that when the selected torque level is reached the motor’s clutch will kick in and disengage the gear to stop the action (not dissimilar to depressing the clutch on your car when the engine is in gear). Often you will hear a click when this happens.
So with a bit of trial and error you should have no problem drilling holes cleanly or driving screws accurately.
More expensive versions come with ‘autostop’ clutches that automatically calculate the correct torque and therefore prevent over tightening and potentially damaging the screw, work surface or both, without you having to experiment with the torque settings.
Why Your Power Tool Battery is so Important
Battery setup is another very important factor to consider when you choose your cordless drill.
Some cordless drills have batteries that slot/slide into the unit itself and others have batteries that clip into its base. Slide battery varieties are more common on drill drivers and have a more natural feel because the handle does not have to incorporate the battery housing. Most combi drills tend to have batteries that attach to the base. Either way manufacturers design their tools for optimum balance.
The Difference Between Battery Power and Capacity
A battery’s ability to deliver power is denominated in Volts. Higher battery voltage equates to greater power. As you might expect light duty tasks can be accomplished with lower powered batteries whilst heavy duty tasks require more voltage. For example cordless screwdrivers are commonly quoted with 3.6 or 4 Volt batteries, drill drivers with 12 Volts and combi drills, impact drivers and SDS hammer drills with 18 Volts. Batteries with higher voltage ratings weigh more.
A battery’s capacity on the other hand is a measure of how much current can be stored. Capacity or run-time is described in Ampere/Hours (Ah). This commonly ranges between 1.3 Ah to 5.0 Ah. Batteries with larger capacity ratings weigh more.
If you’re a professional-level user you’ll need a big 5.0 Ah battery to drill hundreds of holes per day, but for most DIYers this is excessive. Keep costs down with a 1.5 or 2.0 Ah battery that will last long enough for most tasks, or even better, go for a kit like the Bosch PSB1800 and get two batteries for your combi drill. Just remember to always keep one on charge while you’re working.
The Importance of Battery Size and Weight
The size and weight of a battery contribute significantly to the tool’s footprint, balance, ergonomic profile and how it handles.
Most cordless drills these days come with Lithium-Ion batteries – they’re lightweight, powerful and can hold a charge for months and months without a significant loss of power.
- Batteries with greater power will be larger and heavier than lighter powered ones
- Batteries with greater capacity will be larger and heavier than those with less capacity
In other words for the same weight you can choose between
- higher voltage / lower capacity and
- lower voltage / higher capacity
Your choice will end up being influenced by the tasks you want to perform. Heavy duty tasks will require higher voltage in the first place.
Features of the Battery Charger to Look for
It goes without saying that a battery charger is a must and battery charging time is a significant factor for many, particularly if there is only one battery available. Anything with a ‘fast’, ‘quick’ or ‘rapid’ charge option is good, meaning that 70-80% of the charge should be restored in under an hour.
Charging time relates to how long it takes to ‘refuel’ the battery’s capacity (it has nothing to do with the battery’s power or voltage).
The greater the capacity and the more depleted the charge, the longer it will take to replenish.
Charging times are quoted assuming the battery is fully discharged. Chargers themselves can also supply the current at a fast or slow rate.
Batteries are susceptible to heat and temperature extremes. When in use heat builds up within them and once used they should be allowed to cool before being charged.
The charging process itself also generates heat within the battery.
These days most chargers are sensitive to this danger and stop the charging process if the battery shows any signs of overheating. Also electronic cell protection ensures the battery itself is protected, not just from overheating but also voltage spikes and current overload, especially when being charged. Some chargers are now fan-cooled.
Getting Technical with Battery Chemistry – Cycles, Self-Discharge, Memory Effect
The first rechargeable batteries were created in the 1950’s and composed of Nickel Cadmium or NiCad.
The next generation, introduced in the late 1980’s, were made from Nickel Metal Hydride (NiMH).
The latest generation, Lithium Ion (Li-Ion), were introduced into cordless tools around 15 years ago. But only in the last few years did their prices reduce enough for them to become a realistic alternative to NiCad and NiMH batteries in the power tool market. Nowadays of course Li-Ion batteries are the norm and only the most basic ranges come with NiCad or occasionally NiMH batteries.
To understand the advantages Li-Ion batteries have over their predecessors we need to consider their chemical makeup.
The 3 types of battery – NiCad, NiMH and Li-Ion – are made up of different chemical elements and each provide the battery with different characteristics.
- the number of times they can effectively be recharged (cycles)
- the length of time they can hold the charge whilst left idle (the loss of charge is called ‘self-discharge’) and
- their ability to consume the same amount of charge when continuously recycled. ‘Memory effect’ is the term used to describe any resultant degradation and it comes into play if you do not charge /discharge the battery in the appropriate way.
NiCad batteries can be recharged over 1,000 times and last many years. However they are susceptible to self-discharge (about 20% per month), and high memory effect – they need to be fully discharged once a month to prevent it.
NiMH batteries can also be recharged about 1,000 times. They suffer less memory effect than NiCad batteries but still need a full discharge every 3 months to prevent it and also have a high self-discharge rate (30%).
The lifetime of Li-Ion batteries is less than that of NiCad or NiMH batteries – maybe 500 charge cycles – but Li-Ion batteries have no memory loss and minimal self-discharge – maybe 5-10%.
In line with the above there are techniques to consider when charging the battery in order to maximise its lifetime. NiCad batteries should never be allowed to discharge below 70%, NiMH below 30% and Li-Ion batteries below 20%.
When not in use batteries should be stored in a cool place and out of the sunlight.
The Drill Chuck – Keyed or Keyless
The chuck is an important power drill feature. Drill drivers and combi drills come with a 10 mm (⅜”) or 13 mm (½”) 3-jawed chuck. A 10 mm chuck is perfectly acceptable for most projects, whilst more powerful cordless drills tend to have 13 mm chucks. For drilling holes wider than the diameter of the chuck you can always purchase tapered bits. The 3 jaws accommodate both drill bits with their round shanks and hexagonal bits (used for screw driving).
Chucks are either keyed or keyless.
Keyed chucks require the chuck jaws to be tightened or loosened using a separate T-shaped toothed key whose nozzle is inserted into a hole in the collar and whose teeth engage with the collar’s teeth.
Keyless chucks are tightened or loosened by turning the collar directly by hand without the use of a key. Keyless chucks can have one or two collars or sleeves.
Single-sleeved chucks are more convenient and can be adjusted with one hand. This makes it very easy to swap between bits and accessories.
Two collared types require you to hold the lower collar with one hand whilst turning the upper collar with the other.
Some keyless chucks can also be ratcheting i.e. tightened to a maximum torque level and then no further – you’ll hear a click when this level is reached.
The main benefit of keyless chucks is that you never have to worry about misplacing the key but the downside is they cannot be tightened as much as a keyed chuck. This can become a problem if you are using a keyless combi drill in hammer mode as the continuous impacts into masonry will eventually cause the bit to loosen and sometimes get stuck in the hole.
A Handy LED Work Light
An LED work light is useful when you need to drill inside a cupboard, but it’s even handier when it stays on for a while after you let go of the trigger. I also prefer it when the work light is up above the trigger rather than on the battery pack so you can light up the precise area if you need to poke the drill in a tight spot.
‘Nice to Have’ Features of Cordless Drills
A Brushless Motor for Efficiency and Longevity
A brushless motor contributes significantly to a cordless drill’s longevity. With a brushless motor you get increased efficiency due to the motor’s modified components. A small electronic sensor/controller in the motor eliminates friction and delivers more power.
The amount of power that is delivered is also controlled by the amount of resistance the drill encounters.
The brushless motor only generates as much power as it needs, whilst traditional brushed motors will always deliver the maximum power they can, when fed the same amount of current.
Also a brushless tool can never deliver ‘more’ power than a brushed tool running from the equivalent voltage battery.
By eliminating friction a brushless motor runs cooler, more efficiently and quietly and with less vibration than a brushed motor.
The brushless motor also sees greater longevity because its mechanical components are less likely to fail.
These benefits do come at a cost though – approximately 30% more than the equivalent tool running with a brushed motor, although having said that prices of brushless tools have decreased significantly in recent years.
In general you need to be quite a serious DIY enthusiast or professional to justify a brushless version, unless of course cost is less of an issue and you just want the luxury of having the best tool for the job!
All-metal transmission – a Sign of High Quality
An all-metal transmission is a sign of a high-quality cordless tool that is built to last. With the all- metal transmission you are getting higher quality components that wear less.
An Electric Brake – a Great Safety Feature
An electric brake is an extremely useful safety feature that stops the drill rotating as soon as you release the trigger.
The Handy Battery Fuel Gauge
On the battery a fuel gauge tells you how much charge is remaining, very useful if you only have one battery and a limited amount of time to complete the job.
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