What is a magnetic drill (and when a DIYer needs one)
In this guide
A magnetic drill is a portable drill press with a magnet base that clamps it to steel. You carry it to the work, switch on the magnet, then feed the cutter straight into a beam, plate or pipe. It's also called a mag drill, a mag base drill or a magnetic drill press.
This guide is part of our drilling hub. The magnet only works on ferrous metal, so see our steel page for how steel and stainless behave.
Parts of a magnetic drill
- Magnet base. The flat base that grips the steel. Most corded drills use an electromagnet. Milwaukee's M18 FUEL cordless model uses permanent magnets, so it keeps its grip even if the battery dies.
- Motor and slide. The motor rides on a slide (a dovetail track with adjustable gibs). That keeps the cutter moving in a straight line.
- Feed handles. You turn these to push the cutter into the steel, like on a drill press.
- Arbor. Holds the cutter. Evolution's drills take cutters with a 3/4-inch (19 mm) shank.
- Coolant system. A bottle or tank that feeds cutting fluid down to the cutter.
- Switches. One for the magnet and one for the motor.
- Safety strap or chain. It goes around the beam, so the drill can't fall if the magnet lets go.
How a mag drill works
- Clean the steel and set the drill on it. Paint, rust and chips under the base weaken the grip.
- Switch on the magnet. On Evolution's drills, the magnet runs at 50% until the motor is on too. Then it's at full strength.
- Strap the drill to the work.
- Start the motor and turn the feed handles to drive the cutter in.
The magnet is strong. Evolution rates its S28MAG and EVOMAG42 at 2,860 lbf (1,300 kgf) of adhesion. Milwaukee rates its cordless model at up to 2,000 lb of holding force.
That grip depends on the steel. Evolution's electromagnet works on ferrous surfaces only and needs plate at least 3/8 inch (10 mm) thick. Its manual warns that thinner material cuts the magnet's hold and can become dangerous.
Annular cutters: the "magnetic drill bit"
Most mag drills run annular cutters. These are short, hollow cutters with teeth around the rim. Hougen's patent for the design describes how it works: the cutter cuts only a ring at the edge of the hole and leaves a solid core in the middle.
A spring-loaded pilot pin runs down the center. It helps you line up the hole and pushes the core (the "slug") out when the cut is done. Because the cutter removes only a ring of metal, it needs less power than a twist bit of the same size.
| Annular cutter | Twist drill bit | |
|---|---|---|
| What it cuts | A ring; the center comes out as a slug | The whole hole, as chips |
| Typical use in a mag drill | Large holes | Small holes, up to the drill's twist capacity |
| Pilot hole needed | No; the pilot pin centers it | Often, for bigger sizes |
| Fits | The drill's arbor | A chuck or adapter |
Capacity: two real examples
| Spec | Evolution S28MAG | Evolution EVOMAG42 | Milwaukee 2787-22 (cordless) |
|---|---|---|---|
| Annular cutter capacity | 1-1/8 in (28 mm) | 1-5/8 in (42 mm) | 1-1/2 in |
| Max cutting depth | 2 in (50 mm) | 2 in (50 mm) | Not listed on the page |
| Twist drill capacity | 1/2 in (13 mm) | 1/2 in (13 mm) | 1/2 in |
| Speed | 450 to 480 rpm | 450 rpm | 400 / 690 rpm |
| Magnet | Electromagnet, 3/8 in min plate | Electromagnet, 3/8 in min plate | Permanent magnets |
| Weight | 26 lb (12 kg) | 26 lb (12 kg) | — |
Milwaukee lists the 2787-22 kit as no longer available. It's here as an example of a cordless, permanent-magnet design.
Uses
- Structural steel. Bolt holes in beams, columns and base plates, on site.
- Trailers and equipment. Holes in frames you can't move to a drill press.
- Thick plate. Big, clean, square holes in plate too heavy to lift onto a table.
- Vertical and overhead work. Evolution says its drills can run upright or upside down if the magnet holds. Use cutting paste instead of liquid fluid there, and wear eye and face protection for falling chips.
Magnetic drill vs similar tools
| Tool | Best for | Why not a mag drill |
|---|---|---|
| Drill press | Parts that fit on the table | Work has to come to it |
| Hand drill + twist or step bit | Smaller holes in thinner steel | Hard to keep big holes straight. See step bit vs twist bit |
| Hole saw in a hand drill | Thin sheet | Wanders and binds in thick plate |
| Drill guide with a bushing | Holding a hand drill square | Fine for small bits. See what is a drill bushing |
| Magnetic drill | Big holes in thick or installed steel | Costly; only works on ferrous steel |
Safety
- Never use it on a structure being arc welded. Evolution warns the welder can ground through the drill's cable and damage it.
- The slug is hot and sharp. Evolution says it shoots out at the end of the cut. Keep people clear below you, and handle slugs with gloves.
- Chips are hot and sharp, too. Wear safety glasses and gloves, and clear chips with a brush, not your hand.
- Don't drill thin stock on the magnet alone. Below the rated thickness, clamp the work or use another tool.
How to choose (or rent) one
For a few small holes, you don't need a mag drill. A drill press, or a hand drill with a good bit, will do.
Our guide on how to drill metal covers speeds and oil. For hard steel, see the best drill bit for hardened steel. Drilling into an installed beam? See drilling a steel stud or beam.
A mag drill pays off when you need many holes bigger than a twist bit can drill well, in thick or installed steel. Rent one for a one-off job. If you buy, check:
- Cutter capacity and depth. Match them to your biggest hole and thickest steel.
- Minimum plate thickness. Lower is more flexible, but read the manual.
- Magnet type. Electromagnet (corded) or permanent magnet (cordless). A permanent magnet keeps its grip without power.
- Twist drill capacity. Most take a chuck for bits up to 1/2 inch.
- Weight. These are heavy. Evolution's are 26 lb, and you'll lift it onto the work.
- What's in the box. Safety strap, coolant bottle, guard and chuck adapter.
Need the bar stock for pins and punches after you drill? See what is drill rod. Use our drill bit selector to pick bits for smaller holes. Milwaukee's other tools are on our Milwaukee brand page.
Key takeaways
- A mag drill is a drill press you take to the steel. The magnet base holds it on, and a slide feeds the cutter straight in.
- The magnet only holds on ferrous steel. Evolution's manual says its electromagnet works on ferrous surfaces only and needs plate at least 3/8 inch (10 mm) thick.
- Mag drills usually run annular cutters: hollow cutters that cut a ring and eject a slug. Many also take twist bits up to 1/2 inch.
- Always fit the safety strap. An electromagnet lets go if the power cuts out. Milwaukee's cordless model uses permanent magnets instead.
- For a DIYer, a mag drill pays off for many large holes in thick steel. For a few small holes, a drill press or hand drill is enough.
Questions people ask
What is a mag drill used for?
Drilling large, straight holes in steel that can't go to a drill press: beams, columns, plate, trailer frames and heavy equipment. Fabricators and steel erectors use them for bolt holes.
How does a magnetic drill work?
You set it on the steel and switch on the magnet. An electromagnet, or a permanent magnet on some cordless models, locks the base down. Then you turn on the motor and pull the feed handles to drive the cutter straight into the steel.
Can you use regular drill bits in a mag drill?
Yes, with a chuck or a twist-drill adapter, up to the drill's rated size. Evolution's and Milwaukee's models list 1/2 inch for twist bits. For bigger holes, use annular cutters.
What is a magnetic drill bit?
Usually it means an annular cutter: a short, hollow cutter with teeth around the rim. It cuts only a ring of metal and pushes out the center as a slug, with help from a spring-loaded pilot pin.
Will a mag drill work on aluminum or stainless steel?
Not by its magnet. The magnet holds only on ferrous steel. Aluminum isn't magnetic, and common 304 and 316 stainless barely are. You'd have to clamp the drill or the work another way.
How thick does steel need to be for a mag drill?
Evolution's manual lists 3/8 inch (10 mm) as the minimum and warns that thinner steel cuts magnet hold and can be dangerous. Check your drill's manual, since makers rate this differently.
Magnetic drill vs drill press: which do I need?
If the work fits on the drill press table, use the drill press. It's cheaper and safer. Bring a mag drill to steel that's too big, heavy or already installed.
Sources
- EVOMAG42 and S28MAG instruction manual: specs, ferrous surfaces only, 3/8 in (10 mm) minimum plate, 2,860 lbf adhesion, safety strap, slug and arc welding warnings (Evolution Power Tools)
- M18 FUEL 1-1/2 in magnetic drill kit 2787-22: permanent magnets, up to 2,000 lb hold, 1-1/2 in annular and 1/2 in twist capacity, 400/690 rpm (Milwaukee Tool; discontinued)
- US Patent 4,516,890, Annular cutter: cuts a groove at the periphery and leaves a solid core (Hougen, via Google Patents)
Change log: Nov 6, 2026: Rewritten from the 2023 archive post. Removed the false claims that the magnet holds the bit and that mag drills work on non-ferrous metal; added how the magnet and annular cutter work, specs from Evolution and Milwaukee, and the safety strap rules.
