Milwaukee M12 FUEL 1/4-in. Extended Die Grinder (3487-20)

The Milwaukee M12 FUEL 1/4″ Extended Die Grinder, model 3487-20, is a cordless extended straight die grinder built for professional service technicians and tradespeople who need reach, control, and mobility in one compact tool. This is a die grinder designed for grinding, sanding, and cutting in tight spaces. If your work normally puts you inside engine bays, around welds, inside fabricated assemblies, or in spots where a standard body grinder is just too stubby, this tool makes a lot of sense.

Milwaukee built this model around a POWERSTATE brushless motor that produces 0.5 horsepower output and spins up to 20,000 RPM. That gives the Milwaukee M12 FUEL 1/4″ Extended Die Grinder enough speed for common die grinder work while still letting you back things down when you need more control. The four-mode speed control and variable-speed paddle are not fluff features here. They let you match tool speed to the accessory and the material, which is a big deal when you are switching between 2 inch cutting wheels and 3 inch sanding accessories.

The biggest difference on this model is the 4 inch extension. That added reach helps you get into recessed areas without forcing your hand and battery pack right up against the work. In real use, that means easier access inside tight housings, around brackets, and in awkward repair areas where air grinders usually win on shape. Milwaukee is clearly targeting the technician who wants air tool style access without the hose, compressor noise, or setup hassle.

The barrel grip and improved ergonomic handle are there for a reason. Extended die grinder work is usually detailed work, and detailed work gets sloppy fast if the tool feels bulky or twitchy. Milwaukee pairs the slim handle shape with a responsive paddle switch so the grinder feels more controllable during edge blending, surface prep, and controlled cutoff work. The push-button spindle lock also keeps accessory swaps simple with a one-wrench change, which saves time when you are bouncing between sanding and cutting.

Jobsite and shop practicality are also well thought out. The shadowless LED work light helps when you are working under vehicles, inside cabinets, or in any dim spot where the tool itself can block your overhead light. Overload protection adds another layer of durability when the tool is pushed hard. This model is also part of the Milwaukee M12 battery system, so if you are already running M12 tools, it drops right into that platform instead of making you start over on batteries and chargers.

Accessory fit is straightforward: it accepts 1/4 inch shank accessories. Milwaukee calls out it as being designed to perform with 2 inch cutting wheels and 3 inch sanding accessories, which gives buyers a clear idea of where this tool lives. It is not trying to be a giant heavy-removal grinder. It is a compact, precise cordless die grinder for detailed fabrication, service work, metal cleanup, and tight-access grinding where handling matters as much as raw power.

Who should buy it? Automotive technicians, diesel techs, fabricators, maintenance pros, and metalworking users are the obvious fit. Serious DIY users who already own M12 batteries will also get a lot out of it, especially for restoration, fabrication, and repair work. If you need maximum reach and cordless convenience in a compact grinder, this is a smart buy. If most of your work is broad heavy grinding on open surfaces, you may want a larger grinder instead. For tight-access precision work, though, this one is right in its lane.

Milwaukee M12 FUEL 1/4″ Extended Die Grinder Gets Where Bulkier Grinders Cannot

This is the kind of cordless die grinder that makes a strong case for leaving the air hose behind when access and control matter more than brute size.

• Who it’s for: Techs, fabricators, and repair pros who do precise grinding, sanding, and cutoff work in cramped spaces.
• Why it stands out: The 4 inch extension, 4-mode speed control, 20,000 RPM top speed, and M12 cordless format make it far more practical than a stubby grinder for detailed service work.
• Worth knowing: This is a bare tool, so batteries and charger are not included. Also, it is happiest with the accessory sizes Milwaukee calls out, not oversized grinding jobs.

• Is this a cordless or pneumatic die grinder? It is a cordless die grinder that runs on the Milwaukee M12 battery system.
• What accessory shank size does it use? It fits 1/4 inch shank accessories.
• What speed range does it offer? It has a variable speed range from 3,000 to 20,000 RPM with 4 speed modes.
• Does it have a brushless motor? Yes. It uses a POWERSTATE brushless motor.
• Is there a work light built in? Yes. Milwaukee includes a shadowless LED work light for better visibility in tight or dim work areas.