FLEX 24V Cordless 1-Inch SDS-Plus Rotary Hammer FX1551A-Z

FLEX 24V Cordless 1-Inch SDS-Plus Rotary Hammer FX1551A-Z

Flex Continues to Add Heavy Hitters to Their 24V Cordless Lineup

Shifting our coverage over to masonry, the Flex 24V Cordless 1-Inch SDS-Plus Rotary Hammer is making a variety of tasks more convenient with the addition of an interchangeable 1/2-inch keyless chuck standard in the box. More is possible with fewer tools in the bag, ultimately cutting out a few of those trips back to the toolbox.

FLEX 24V Cordless 1-Inch SDS-Plus Rotary Hammer Performance

Flex offers two cordless rotary hammers and this model is the more powerful of the two. If you’re looking for something a little lighter, check out their 7/8-inch rotary hammer here.

As for this model, you’re looking at a rotary hammer with a sensor-free brushless motor that delivers up to 980 RPM with 4350 BPM and 1.9 ft-lbs of impact energy (2.6 Joules). With that performance level, you can expect to drill up to 1 inch in concrete, 1/2 an inch in steel, and 1 3/16 inches in wood.

FLEX 24V Cordless 1-Inch SDS-Plus Rotary Hammer FX1551A-Z

FLEX 24V Cordless 1-Inch SDS-Plus Rotary Hammer Design Notes

3 + 1 Mode Selection

An adjustable knob on the side lets you quickly switch between the three drive settings: Rotary Drilling Mode, Hammer Drilling Mode, and Hammer Mode. In addition to the drive settings, there’s also a position to adjust your chisel angle located between Hammer Drilling Mode and Hammer Mode.

Mode Selection

Interchangeable Chuck

Another notable feature is the interchangeable chucks. Quickly and easily change from SDS-Plus to a keyless 1/2-inch full metal chuck to make the tool more versatile. This is a really handy addition because you can quickly switch between tool applications and materials. An electrician can drill a 1-inch hole in a cinder block wall, transition to the 1/2-inch keyless chuck, and rough-in through 2×4 studs on the interior all with one tool!

Flex isn’t the only brand to have an interchangeable chuck, but they make it easy for you to take full advantage by including both chucks in the box.


My attention immediately gravitates to the overall ergonomics with the tool in hand. The main handle is a bit on the large side but fits well in my medium hands.

The adjustable forward grip aids in keeping the rotary hammer stable while in use. Like other rotary hammers, you can rotate the handle 360°. However, the housing does limit the handle position when you’re using the depth rod and want to rotate the handle around to your right hand.

The combination of the two handles made it easy to control while drilling a few holes in some 4000 PSI concrete we use for testing.

Flex added an isolated handle design to damper the vibration that reaches your trigger hand. Finally, they use a two-finger trigger to reduce some of the finger fatigue that can set in over a long day.

In terms of weight, the tool weighs 7.1 pounds with the side handle and depth rod, and 9.3 pounds with a 5.0Ah battery. You can shave some weight and use the 2.5Ah battery on smaller jobs or jump up to the 8.0Ah pack if you need more runtime. However, we like the weight/performance combination with the 5.0Ah.

FLEX 24V Cordless 1-Inch SDS-Plus Rotary Hammer FX1551A-Z

Additional Features

  • Variable Speed Trigger Switch
  • Integrated LED Light
  • Compatible with all Flex 24V batteries

One feature we would like to see is some kind of anti-kickback mechanism. The risk of a bit binding up is an ever-present concern with any drill and maybe something for Flex to consider in future models.

FLEX 24V Cordless 1-Inch SDS-Plus Rotary Hammer Price And Warranty

The bare tool is available at Lowe’s for $299. At the time we’re writing this, this tool is not available as a kit or part of a combo. Flex offers you a 5-Year standard warranty and if you register your new tool within 30 days of purchase through December 31, 2021, they’ll make it a lifetime warranty.

The Bottom Line

Flex’ cordless 1-inch rotary hammer hits concrete with performance that fits right in with what we expect from professional-level models. While there’s a little room for improvement, there’s no reason to shy away from this model if you’re committed (or thinking about committing) to Flex’ 24V system.

FLEX 24V Cordless 1-Inch SDS-Plus Rotary Hammer Specifications

  • Model: Flex FX1551A-Z
  • No-Load Speed: 0-980 RPM
  • Blows/Min: 0-4,350 BPM
  • Max. Drilling Diameter: 1 Inch, 26 mm (Concrete); 1/2 Inch, 1 mm (Steel); 1-3/16 Inch, 26 mm (Wood)
  • Max. Impact Energy: 1.9 ft-lbs, 2.6 joules
  • Tool Weight (without battery): 7 lbs, 3.2 kg
  • Bare-Tool Price: $299

Rotary Hammer Vs. Hammer Drill…What Do You Really Need?

If you want more information on the differences between a rotary hammer and a hammer drill, we have you covered. Check out the link below where we take a detailed look at the differences and applications for each of these tools.


For more information on the Flex 24V line up, click here

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