Flex Cordless 5" Angle Grinder Offers Great Design and High Performance
We've gotten our hands on the Flex cordless tools as a new product launch, and have been impressed with what we've seen so far. One of the questions we always try to answer in every review is "Where does the Flex fit?" We take this very seriously when we take a closer look at the Flex 24V Brushless Cordless 5" Angle Grinder.
advantage
- Electronic speed regulation (four gears)
- Anti-recoil sensor
- Slender handle design
- Simple one-step guard adjustment
- excellent kit value
- Lifetime Warranty on Tool, Battery and Charger if you register on 12/31/22, 5 Year Warranty Standard
shortcoming
- no electronic brake
Flex designed their first cordless grinder with an impressive top speed of 10,000 RPM. That's pretty high, and they designed four electronic speed settings to help you control the speed in case you need to slow down.

Still, the speed is only impressive if the tool can handle the load. We tried various cuts, sanders, and polishes to see how it compared to other 5-inch cordless sanders we've used.
Impressive power levels for this class. We were able to bog down the wheel on the run, but it holds up just as well as any other model we've used in the 5-inch class. When we turned our attention from cutting the 1/4" angle iron to grinding away some of the top layer, we were impressed with how quickly it removed material. Switching to the flip pan, it left us with a nice, polished sheen.

We did most of our testing with the 5.0Ah battery in the kit, and we recommend you stick with that. Once we're done with it, we put it on the charger and it doesn't need any cooling time before it starts charging. We switched to a 2.5Ah battery and it was noticeably easier to bog down the wheels. You can enjoy the lower weight for the lightest of tasks, but stick with the 5.0Ah battery pack for those medium and heavy duty tasks.
Flex 24V Brushless Cordless 5" Angle Grinder Design Instructions
ergonomics
The Flex is designed with a slimmer handle than many smaller angle grinders, a move we like. Combined with overmolding in all the right places, it provides a secure grip as you sand and cut at various angles.
One of the advantages of a small angle grinder is that it is lighter than a larger one. This model weighs 4.3 pounds without the battery and side handle, and 6.4 pounds with the 5.0Ah battery.
switch option
The Flex comes in two grinder styles. They're pretty much identical except for how you use the power. The model we're reviewing has a paddle switch. The other uses an on/off slide switch.
on alert
The Flex Cordless Sander makes guard adjustments a snap. Just turn it counterclockwise (if you're looking down from the top) until it's where you're looking for. To remove it, rotate it so the guard is pointing straight out from the tool, you will feel it loosen enough to be replaced.
Shockshield side handle
In the Flex world, Shockshield is the term they use for dampening vibrations. In this case, it's on the side handle. There's a breakout near where it attaches to the tool, allowing some vibration to be dampened before it reaches your hand.
Handles mount on the left or right, but there is no center top mounting point.

Kickback Protection
The Flex includes a kickback sensor on the tool. The motor will automatically stop if you wind up the wheel or the wheel strikes back at you. Despite that control, there's no snappy electronic braking when you let off the switch. A 27 wheel takes about 2.5 seconds to stop, so it's not as slow as some wheels.
Flex 24V Brushless Cordless 5 Inch Angle Grinder Price
No matter which style you want to use, the kit comes with a 5.0Ah battery, fast charger, and tool bag for $249. If you're already using the platform, the bare tools are available for $179. Compared to other high-end brands in the same performance range, this is a very solid value.
Remember, if you register before 12/31/22, your Flex tool, battery and charger will also be covered by a lifetime warranty.
the bottom line
We set out to determine the applicability of this model in the world of cordless grinders. The Flex 24V Brushless Cordless 5 Inch Angle Grinder competes very hard against premium professional models in the small angle grinder category. It's not on the same level as a cordless 6-inch grinder, but that's not what it's designed to compete with. We prefer its slimmer handle design, and it's nice to have some speed control. Where it really sets itself apart, though, is the kit value. Compared to the bare metal, the Flex only charges an extra $70 for the battery and charger, making this kit significantly less than its competitors.
Flex 24V Brushless Cordless 5" Angle Grinder Specifications
- Model: Flex FX3171A-1C (Toggle Switch Kit)
- Motor: Brushless
- Speed: 3500/5000/7000/10000 RPM
- Wheel Diameter: 5 inches
- Arbor Diameter: 5/8"
- Electronic Speed Control: Yes
- Overload Protection: Yes
- Variable speed: yes
- Side handle: yes
- Spindle lock: yes
- Length: 12.48 inches
- Width: 5.43 inches
- Weight: 4.28 lbs.
- Warranty: 5 years (Lifetime if registered before December 31, 2022)
- Kit Price: $249