Driving 10-head hex wood screws into the sill, inserting self-tapping concrete screws into pre-drilled holes, setting expansion anchors, tightening metric fasteners up to M27: Where the drill driver gives out, the impact wrench takes over. The SR 800-18 delivers 800 Nm of tightening torque and 1,200 Nm of loosening torque—ideal for wood construction screw connections, steel-to-wood joints, and anything else that would otherwise only be moved with a ratchet and a lot of leverage.
This smart feature is called ASC, the automatic speed control with two functions: When tightening, it shuts off before the screw is overtightened—when loosening, it reduces the speed so the nut or screw doesn’t slip off the square drive. It also features six torque settings on the adjustment wheel, a 1/2" external square drive for impact sockets, and a center of gravity precisely in the middle of the handle—weighing 3.0 kg including the battery. The battery is a CAS model: compatible with Mafell, Metabo, Lamello, and Prebena; not compatible with Festool or Bosch.
It’s not a given that you’ll buy the Mafell tool at RUWI : We’re manufacturers ourselves—tools for woodworking professionals based in Fluorn-Winzeln, 4 kilometers from the Mafell factory in Oberndorf am Neckar. We carry only what we can recommend from our own experience—and we’ll tell you below when your existing drill/driver is more than enough.
Here's how to use it
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Screwing in Wood Construction: Large hex and fully threaded screws without straining your wrist.
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Fastening into concrete: self-tapping concrete screws and expansion anchors—pre-drill, then drive them in.
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Tighten without over-tightening: ASC disengages before the thread is damaged—and holds the nut by its square drive when loosening.
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Working with impact sockets: 1/2" external square drive—the socket set available at the store fits perfectly.
Does this fit in your workshop?
Let’s be honest: For Spax screws, hardware, and everyday cabinetry work, any good 18-V drill/driver will do—you don’t have to buy it from us—and an impact driver is the wrong tool for the job because it’s too heavy-duty. The SR 800-18 is worth it for jobs that regularly involve heavy-duty fastening: deck and carport construction, substructures, machine assembly, and steel-wood applications. It’s only available as the PURE model without a battery or charger—if you’re already part of the CAS lineup, you can jump right in; newcomers should add a Power Set to their order. And here, too, the statement from the user manual applies: It is not approved for continuous industrial use.
You can read about why your vacuum cleaner should be rated M in the knowledge article on wood dust extraction —and the machine advisor will guide you to the right machine in just two or three questions.
All the details
Function and Application
Design: Cordless impact driver, heavy-duty screwdriving applications in wood and concrete, center of gravity in the middle of the handle
Application: Screws up to M27, automatic speed adjustment for material-friendly operation
Battery system
Drive: 18 V, brushless
System: CAS (Cordless Alliance System), batteries compatible with Metabo, Lamello, and Prebena
PURE version: without batteries and charger
Performance and Screwdriving Specifications
Max. tightening torque: 800 Nm
Max. loosening torque: 1,200 Nm
Max. metric screw size: M27
Torque settings: 6 plus automatic speed control (ASC)
Speed: 0 to 2,575 min⁻¹
Max. impact rate: 3,300 min⁻¹
Tool holder: 1/2-inch square drive
Dimensions and weight
Dimensions: 178 × 80 × 221 mm
Weight: 3 kg including battery
Safety and Quality
Country of Origin: China (country of origin according to Mafell product database)
Warranty: MAFELL-Complete, 36 months after registration
Spare Parts: 10 years from end of production (Mafell commitment)
