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Making An Impact

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The regular drill can’t always cut it, so to speak, hence we have impact drills and rotary hammers.

One of the most innovative tools to come out of post-war Germany was the impact drill. Its technology allowed it to add a ‘striking’ mechanism to the normal drill operation, widening the drill’s usage from timber and metal to materials originally requiring time consuming and expensive specialised equipment. However, impact drivers are often a misunderstood tool.

One of the most innovative tools to come out of post-war Germany was the impact drill.

For example, a colleague who has been a long-member of the power tool industry – formerly a sales rep, and now a tool shop owner – was recently asked about his thoughts on the future of impact drills. His answer was succinct and telling: “Impact drills are being used by tradesmen as an all-purpose drill, and are rarely used in brick and concrete. They have all the ‘bells and whistles’ such as variable speed, two-speed gearboxes, and the impact function. They will run spade and auger bits, sink bugle screws for decking, and drill the odd brick or two if and when required. They still have a place. But have largely been replaced by 2kg rotary hammers.”

‘Rotary hammers’ and ‘impact drills’ are names often used interchangeably, but it is a great mistake to do so.

They are separate tools, totally different in design and function.

Impact Function

I once saw a cartoon that aptly illustrated the difference between an impact drill and a rotary hammer. It depicted Superman, red faced and teeth gritted, pressing with all his might to drill a hole in a stone wall, an impact drill in his clenched fist. Below him stood a little boy reading, his book in one hand and a rotary hammer in the other. He smiled while effortlessly drilling deep into the same wall. The cartoon’s caption was “Push it, mate!”

The impact drill requires the operator to apply external energy to make it work. It delivers a high rate of blows per minute (BPM) – over 10,000, commonly – and low impact energy. Impact drills are best suited for drill bits up to 10mm in size. Some can go up to 13mm but by that stage we’re entering rotary hammer territory.

The round shank drill bit is fitted into the chuck and the chuck and drill bit move forward and backward as the drill spins on its axis.

How Does It Work?

Simply put, two notched plates are pushed together when pressure is applied to the drill – for example, when the operator pushes the drill bit against a wall. The rotation of the drill causes the plates to jump, or ‘skip’ over one another rapidly, causing a pulsing action. This assists in the drilling of masonry. Lighter drilling of small holes is a breeze with the impact drill.


Electricians, plumbers, and builders are the most common users of the impact drill, which is really two tools in one!

In one mode, it can be used as an ordinary drill, ideal for working with wood and soft materials.

Then, with a flip of a switch, it can be put into impact mode for fixing anchors into masonry or concrete, installing conduit straps, and – as is the case with electricians – drilling small diameter holes.

Whole Kit And Caboodle

In the 1970s it was so often the case that a tradie’s power tool kit would feature a 9¼ inch circular saw, a 7¼ inch saw and a decent impact drill. This was the extent of many a tradie’s tools. Rotary hammers were too pricey and if there was work enough for them on a big job, they were hired for the duration.

Today, with lower prices and a plethora of brands, it is common to see younger cashed-up tradies buying both an impact drill and a rotary hammer.

With the advent of the SDS bit, patented by Bosch in 1975, improved electronics and cordless tools powered by lithium-ion batteries, impact drills should be part of every tradie’s kit.

Most companies offer kits, many of which include an impact drill, a rotary hammer, batteries and chargers in a contractor bag, all for the price that, even 10 years ago, you would have paid for an impact drill alone.

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