How to use an SDS rotary hammer
Updated: 22 October 2026
The first minute with a new SDS rotary hammer is where plugs, tiles and hidden cables meet a piston that does not behave like a combi. Fit the bit with the motor off, pick a mode the model actually has, and stop when the tool or the wall tells you to. This is not a ranking. If you are still choosing, the table is the [Bosch cordless rotary hammer comparison](/hub/drilling-and-accessories/bosch-cordless-rotary-hammer). There was no lab test. Links to amazon.co.uk may earn a commission at no extra cost to you.
The first minute with a new SDS rotary hammer is where plugs, tiles and hidden cables meet a piston that does not behave like a combi.
The first minute with a new SDS rotary hammer is where plugs, tiles and hidden cables meet a piston that does not behave like a combi. Fit the bit with the motor off, pick a mode the model actually has, and stop when the tool or the wall tells you to. This is not a ranking. If you are still choosing, the table is the Bosch cordless rotary hammer comparison. There was no lab test. Links to amazon.co.uk may earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Chisel mode | Holder | Side handle | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Bosch UniversalHammer 18V body | Yes, Vario-Lock | SDS plus | Auxiliary handle in carton | 8.3 | about £97.92 | View offer |
 Bosch GBH 18V-22 with L-BOXX | Yes, vibration published | SDS plus | In the L-BOXX scope | 8.5 | about £180.99 | View offer | |
| Alternative |  Bosch GBH 18V-18 body | No chisel function | SDS plus | Depth gauge and handle | 7.5 | about £122.95 | View offer |
On this page
Before the hole
Look for cables and pipes before the mode switch. Electrical Safety First tells DIY users to use a cable detector, to expect cables to run straight from accessories, and to treat the zone within about 15 cm of the top of a wall or a corner as a place a cable may sit. Switch the circuit off at the consumer unit near a socket or a switch. A beep you cannot explain is a stop. Drilling concrete produces respirable crystalline silica. HSE sheet CN3 says to use extraction where you can, and respiratory protection at APF 20 when drilling is the main task and extraction is missing. None of these boxes includes a GDE dust attachment. Wear eye protection, and hearing protection in a hard room. Hold the tool with both hands, and use the side handle if the carton actually included one.
Bit and mode with the motor off
Change the mode only when the tool is switched off. The UniversalHammer manual says so. An SDS plus bit pushes in and clicks, and it should not fall out when you tug it. ONECHUCK, on the 18 X and the 22 X, also takes cylindrical and hex shanks. The 22 X manual notes about 6–10 mm, which is a small bit, not a masonry diameter. Hammer drilling is rotation plus the piston, for brick, block and concrete. Rotation only is for the odd hole in timber or metal. A few seconds of weak hammering at the start, in green-tool reviews, is the blow building pressure. If it never builds, check the mode and the bit. Let the piston work, and set the depth stop before the row.
Chisel and Vario-Lock
Chisel only on a hammer that has a chisel mode. The UniversalHammer manual has Vario-Lock: it does not click, the chisel locks in 42 positions, and chiselling rotation is clockwise. Set the edge while the tool is stopped, then select chisel mode, then start. The GBH 18V-22 X manual notes 36 positions. The compact GBH 18V-18 has no chisel function on Bosch’s account of that model. Do not turn a selector until your own manual prints a chisel symbol. Published chiselling vibration on the GBH 18V-22 family compares tools. It is not your daily exposure. The action value is 2.5 m/s² A(8) under the Control of Vibration at Work Regulations 2005. If KickBack Control trips, find out why the bit bound before you squeeze again.
When it misbehaves
A green UniversalHammer review describes the tool going dead when a battery thermal cut-out trips, with no warning light. Let the pack cool. Do not read a silent stop as a dead motor. Smoke while chiselling plaster is a stop: take the pack off and use the warranty route. On the GBH 18V-18 X, a UK review says a bit seized after one use. Do not strike it, and do not keep the motor running. Release the collar with the battery off. Get a competent person if a detector is unclear, if you hit a service, if asbestos is plausible, or if the tool smokes. Whether the combi should have stayed in the cupboard is on SDS drill vs combi drill.
Common questions
Which mode is hammer drilling, and which is chiselling?
Hammer drilling is rotation plus the piston, for brick, block and concrete. Chiselling is the piston without that spin, and only on a model whose manual has the mode. The UniversalHammer has it. The compact GBH 18V-18 does not, on Bosch’s account of that model.
Why must the tool be stopped before I turn the selector?
The UniversalHammer manual says to change mode only when the tool is switched off. A selector turned while the motor runs is how a collar gets damaged, and how a chisel starts before you have aimed it.
How do I aim a flat chisel?
Stop the tool, seat the SDS chisel until it locks, then turn Vario-Lock and set the edge. The green manual gives 42 positions and says the lock does not click. The 22 X manual notes 36. Then select chisel mode. Clockwise is the rotation the green manual names.
What do I check before the first hole in a wall?
Scan for cables and pipes, and treat about 15 cm of the top or a corner as a likely cable route. Switch the circuit off near a socket or a switch. Fit the side handle if you have one, and decide whether the hole needs extraction.
Do I need ear defenders and a dust mask?
Wear hearing protection in a hard room. The 97 dB(A) line belongs to the GBH 18V-18 X manual only. For concrete dust, HSE CN3 points to extraction, and to RPE at APF 20 when drilling is the main task and extraction is missing.
The bit will not come out. What do I not do?
Do not hit it with another hammer, and do not keep the motor running. Take the battery off and use the release in the manual. A UK review of the GBH 18V-18 X describes a bit seized after one use. The green keyed adapter jams in the same way.
Related pages
Sources
Maker pages, UK regulations and the amazon.co.uk listings stored for this comparison, read on 19 October 2026. Shelf prices, stars and review counts are those saved listings. A live view of one ASIN the same day had already moved.
- Bosch Professional GB, GBH 18V-22 (retrieved 19 October 2026)
- Bosch Professional GB, GBH 18V-18 (retrieved 19 October 2026)
- Bosch Professional GB, GBH 18V-18 X (retrieved 19 October 2026)
- Bosch Professional GB, GBH 18V-22 X (retrieved 19 October 2026)
- Bosch DIY GB, UniversalHammer 18V (retrieved 19 October 2026)
- Control of Vibration at Work Regulations 2005, regulation 4 (retrieved 19 October 2026)
- HSE, Construction dust: silica (CN3) (retrieved 19 October 2026)
- Bosch Professional GB, AMPShare (retrieved 19 October 2026)