A combi drill is the most common type of all-purpose drill. Combi drills can tackle everything from nimble screwdriving to tough hammer drilling. And because they operate deliver both drilling and driving functions, the best drills are designed to offer an optimum level of power & torque vs. weight.
Cordless combi drills range from 10V right up to the 36V. As technology advances, the power-to-weight ratio improves and the use of Lithium-ion batteries ensures that some very powerful combi drills are still light enough to use for long stretches of time.
What’s the difference between a combi drill and a drill driver?
A combi drill is usually bigger and heavier than a drill driver. As such, it is not as nippy at popping screws into wood but is more powerful at drilling larger holes into tougher materials. As with drill drivers, combi drills feature adjustable torque settings for screwdriving and allow you to set the drill to match the type of screw to the material to ensure it goes flush to the surface and no deeper.
What’s the difference between a combi drill and an SDS hammer drill?
Generally speaking, combi drills tend to be lighter than SDS drills, and less effective at drilling larger diameter holes into masonry or concrete. Combi drills are mostly cordless and commonly used for drilling into wood, typically by site joiners, builders or other professionals. However, the new breed of 18V Lithium–ion combi hammer drills are starting to reach similar levels of power to SDS drills and will tackle tough drilling into masonry or brickwork.
It’s important to remember that combi drills and SDS use different drill bits. SDS drills use special fluted SDS drill bits which work with the sliding chuck mechanism, the ‘Special Direct System (SDS)’, that gives SDS drills their hammering power. Combi drills use standard drill bits.
What are the important factors to consider when buying a combi drill?
Drilling capacity
Typically a lighter combi drill 12v or 14.4v, will be sufficient for woodworking jobs. But if you’re going to need for masonry drilling, an 18v combi hammer drill will be more suitable.
To compare combi drills for drilling power, look for the ‘max drilling capacity’ in different materials. Usually this is shown as wood: XXmm, steel: XXmm, and sometime concrete:XXmm. This shows the maximum diameter of hole the combi drill will make.
As a yardstick, the cheaper 14.4V combi drills tend to perform as follows: masonry: 13mm, wood: 25, steel 13mm.
A top quality 18V Bosch or Makita may have have spec in this region: masonry: 16mm, wood: 50, steel 13mm.
It’s worth also considering the impact rate for drilling – a reflection of the drilling speed and an indication of the progress rate for driving screws in metal and wood
Screwdriving capacity – Torque
When using your combi drill for screwdriving, it’s clearly important to apply the appropriate amount of torque. You want to avoid forcing the screw too deep and potentially damaging the head.
The torque for a combi drill is shown in the following terms:
Max torque is shown as Nm (Newton metre)
Max size of wood screw
Max size of machine screw
On combi drills, the torque adjustment ring sets the point at which the clutch in the drill disengages from the motor. Usually you’ll find between 13 – 25 torque settings (plus the drill setting).
It’s important not to confuse torque with speed. High torque comes from lower gearing, so it generally means you compromise on speed of drilling. So if you only occasionally require higher torque (i.e. you mostly work with smaller or medium-sized screws and fastenings) go for a combi drill with greater rpm to allow faster as and more agile working.
As a measure of a combi drill’s torque look for the following values:
Max torque is shown as Nm
Max size of wood screw
Max size of machine screw
Batteries and chargers
It’s probably only a matter of time until all combi drills use Lithium-ion batteries. They’re better in many ways: lighter and more powerful, they ensure a longer run time and go for longer between charging. They’re also faster at recharging and are more environmentally friendly.
Another bonus of Li-ion batteries is that many brands now make all their powertools compatible with the same batteries. The Makita MXT and Ryobi One brands are good examples. So if you have other tools with the same brand, it’s worth thinking about the compatibility of the batteries.
Unsurprisingly, Lithium-ion batteries cost more than the nickel-cadmium (NiCad) and nickel-metal hydride (NiMH) batteries. However, the advantages in performance mean that if you are going to make some serious demands on your drill, it will be worth it in the long run to go for a Li-ion based tool.
IMPORTANT always look for Ah (Amp Hours) on the batteries
Some combi drills can seem excellent value but it’s essential to look closely at the battery spec. This can be anything from 1.3Ah to 3.0Ah and you’ll experience a significant difference in the performance and staying power between the lower and higher range of combi drill batteries. This is due to the difference in energy density between them.
Recharging time
The quality of the batteries can make a big difference to the price of combi drills. If you’re a busy site joiner, for example, you can justify paying for two 3.0 Ah Li-Ion batteries (the best out there). With a good charger, and two high density batteries like these, you should never run out of battery power. However if you’re going to use your combi drill infrequently, less powerful batteries should suffice, particularly if you are drilling into wood, not masonry.
Weight and size
If it’s likely that you’ll be using your combi drill for long periods during the working day, weight is a serious consideration – and a combi drill may not always be the best choice. As drill drivers get more powerful they’re becoming a popular alternative to combi drills. If you’re repeatedly driving lots of screws, especially overhead, using a cordless drill driver can be the logical choice. However if you’re tackling any sort of tough drilling where you’ll need to put a bit of weight behind it, a combi drill will be more appropriate.
Weight guide: highest and lowest
Combi drills tend to fall into the weight ranges below. The arrival of lightweight Lithium-ion drills now means that you can find a poweerful 18V combi hammer drill that’s as powerful as a 12 volt model.
12V: 1.4 – 2.5kgs
14.4V: 1.3 – 2.5kgs
18V: 1.6 – 2.8kgs
Chuck
Most modern combi drills operate with a keyless chuck, which allows you to open and close the chuck with just your hands – and not a chuck key. Combi drill chucks are very often a standard 13mm size and it’s worth looking out for those drills with an all-metal chuck. Bosch have recently introduced an auto lock chuck for enhanced grip and safety.
As with all kinds of drills, It’s important to use your chuck with care and, from time to time, clean the dirt that accumulates as this can avoid your bit jamming. Placing a little bit of grease in your chuck every now and then can really help.
All metal gears and replaceable brushes
One sign of a quality combi drill is the robustness of the components. The best powertool manufacturers will ensure that drills are engineered with precision and include parts like all metal gearing, and metal gear housing that that protects the gearbox and ensures the gear selection remains smooth. Replaceable brushes are also a sign of quality, and will be a real benefit if you look after your drill and get it serviced (a smart alternative to buying a new one at the first sign of trouble).
Sidehandle
Combi drills may be neat and compact but they can pack quite a kick. A sidehandle can be very useful in directing the power accurately.