
Milwaukee has announced two new M18 Fuel cordless die grinders.
The two new die grinders will be replacing the Milwaukee 2784 M18 Fuel die grinder, which first launched nearly 6 years ago.
Milwaukee says that their new brushless die grinders deliver the next advancement in power, performance, and versatility, and feature enhanced safety, precision, and control.
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Both tools are said to provide 11A corded performance and are designed to help cut the cord of AC and pneumatic die grinding.
The new die grinders feature a RapidStop brake, which is advertised as stopping most accessories in less than two seconds.
Milwaukee M18 Fuel Die Grinder with Slide Switch (2939)

There will be two new models. Shown just above is the 2939 braking die grinder, with slide switch.
The slide switch die grinder is said to be able to remove up to 12″ of weld bead (1/4″ x 1/2″) per charge with an M18 XC 5Ah battery and carbide burr.
Key Features & Specs
- 1/4″ collet
- 27,000 RPM max
- 2″ max sanding accessory
- 2″ max cutting wheel accessory
- Spindle lock
- 15.5″ long x 3.11″ wide x 3.3″ tall (tool-only)
- Weighs 2.9 lbs (tool-only)
Price: $249 for tool-only (2939-20)
ETA: January 2023
Milwaukee M18 Fuel Die Grinder with Paddle Switch (2984)

Shown here is the 2984 braking die grinder with paddle switch and One-Key connectivity for tracking and tool management.
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Milwaukee says that the die grinder can deburr up to 35 pipes (4″ black iron) per charge with an XC 5Ah battery and 3″ flap wheel.
Key Features & Specs
- 1/4″ collet
- 20,000 RPM max
- Variable speed: 8K, 11K, 14K, 17K, 20K RPM
- 3″ max sanding accessory
- 2″ max cutting wheel accessory
- One-Key
- LED light
- Spindle lock
- 16.2″ long x 2.99″ width x 3.3″ tall (tool-only)
- Weighs 3.1 lbs (tool-only)
Price: $299 for tool-only (2984)
ETA: January 2023
Discussion
What’s interesting here is that these two tools are more different than I would have expected. The slide-switch model has a single speed and operates at a faster max RPM; the slide switch model operates at 27K RPM while the paddle switch tool has a variable speed dial with 20K RPM max.

In retail product images, the slide switch model is described as being suited for heavy material removable use, while the paddle switch model is described as being for precision and control work.
The different specs limit the maximum accessory size of the tools, with the slide switch model (27K RPM) being compatible with 2″ sanding and cutting accessories, and the paddle switch model (20K RPM) being compatible with 3″ sanding and 2″ cutting accessories.
Additionally, the paddle switch model alone is One-Key-compatible, for inventory management and tracking purposes.
All of these differences result in the slide switch model being $50 less expensive (tool-only).
To sum it up:
Milwaukee 2984 – Variable speed braking die grinder with paddle switch and One-Key.
Milwaukee 2939 – braking die grinder with slide switch.
We can typically expect for slide switch and paddle switch grinders to be very similar, aside for the power switch. Here, it seems that the two tools were designed with greater focus on tailoring the tools for different users or applications.

I suspect that the differentiation stems from feedback and user requests Milwaukee received since launching their first-generation tool. That first M18 Fuel die grinder (2784) came out nearly 6 years ago, in early 2017, and it featured a 20K RPM speed and slide switch.
At the time of this posting, the new and older slide switch models are both priced at $249 for the tool-only purchasing option.
Milwaukee promises “improved performance” with the new grinders. It’s reasonable to expect motor performance and maybe efficiency advancements over the span of 6 years.
When I first posted about the first-gen model, several readers declared the lack of variable speed or a paddle switch to be a deal-breaker.
I suppose that there is still strong enough interest in a single speed slide switch model.
Jared
That’s a pretty nice addition to the lineup. Wildly expensive for my use compared to pneumatic-power, but it doesn’t mean I’m not attracted to it.
fred
I was thinking that they are both very modestly priced compared to the Dotco’s that we used. While I don’t expect that they will replace pneumatics for near-continuous duty use – I can see the appeal of losing the hose for many smaller jobs – particularly those away from the shop.
MM
The price of pneumatic die grinders is all over the place. It’s been many years since I bought one, but at the time a basic model Ingersoll-Rand was about $50, the nicer ones with the composite body were 2 or 3 times that price, and it only went up from there as you got into more and more powerful models.
I think you’re right, there’s no way these cordless models are going to replace a commercial-duty pneumatic like a Dotco or a big flex-shaft tool in a factory application. But for misc. work they are excellent.
Jared
Ha. I think we have a different caliber of die grinder in mind for comparison.
I’m not saying this Milwaukee tool is a bad deal, just that it must be targeted at someone with greater need for it than I have, even though I would like to have one.
Joe
I’d like a .5 HP M18 version of the M12 stuff. The M12 is good for about 70% of the work I do, but their stall/shutoff points are set pretty low, and don’t work well with 3″ discs, the extra power from their 18 volt line up would help.
STEVEN WOBIG
I have the Milwaukee Rotary Tool and I’m curious if a Die Grinder would be a better tool to use. When I do use the Rotary Tool, I do tend to lean on it pretty hard – I’ve broken a couple of bits, but never stalled the tool. I’m thinking both tools are about the same size, but the Die Grinder is maybe more powerful? Wondering other people’s experience. I like the paddle switch on the one, but wonder if it is worth bothering with as it is not a high use tool for me. Thanks!
Stuart
Rotary tools and die grinders are absolutely NOT the same size. Rotary tool and M12 Fuel die grinder? Maybe.
With rotary tools and die grinders, you need to let the tool do the work. If you’re breaking bits, that can happen, but if it’s happening a lot you might be using too much lateral pressure.
Rotary tool vs. die grinder depends on the size and scope of work being done. Die grinders are also sized for 1/4″ accessories while rotary tools are sized for 1/8″ and smaller.
Not knowing how you’re using your rotary tool, I would suggest maybe the M12 Fuel die grinders as a step-up. Going from a 12V-class rotary tool to an 18V-class brushless die grinder is more of a huge leap.
Big Richard
Odd that the paddle switch model is “detuned” compared to the slide switch. But at least the paddle switch is variable speed, for my uses I’d take the control of the variable speed over the power advantage of the slide switch. Now maybe if they put a variable speed dial on the slide switch model…
XRH07
not putting variable on the slide switch was very bone-headed of them. Die grinders often get used in awkward positions so having to rely on the paddle for variable speed kind of sucks. They make the 4.5-5″ angle grinders with paddle/slide. And both have variable speed options.
Big Richard
My thoughts exactly.
SamR
I have the Gen-1, and it is ridiculously powerful! It will require you a ton of attention during operation.
When pushing the Gen-1 die grinder hard against the workpiece. The tool will walk you everywhere! Left and right!
This happened when I was grinding a weld. I ended up using the M12 grinder 2486-20, which is less violent!
Honestly, using the M18 Gen-1 is scary! I am happy to see the Gen-2 with the paddle switch option.
Pat
For those of us without an air compressor big enough to run a pneumatic die grinder for any length of time, these are very interesting. For a shop with a big compressor, maybe, it depends on the usage.
But for home use, very interesting.