A mag drill is a portable drill press that clamps itself to steel with an electromagnet, so it can cut a clean 1 in hole through a beam where a hand drill would wander and bind. Hire is about $50 to $90 a day. The magnet needs flat solid steel under its whole base, roughly 3/8 in thick or more, and the cutters are bought rather than hired.
The magnet is the fixture, so the steel is the specification
Holding force depends on thin air gaps and on how much metal is beneath the base to complete the magnetic circuit. Paint, mill scale, rust and a bowed flange all reduce it. Thin plate, checker plate and anything non ferrous give you nothing at all, which is why a vacuum base or a bolt down adaptor is the alternative the counter will offer.
Annular cutters, not twist bits
The tool cuts a ring and drops a slug, which is why it goes through structural steel so quickly. Cutters come in individual diameters and depths, are consumable, and are sold rather than rented at nearly every counter. Buy one or two spares of the size you need, because a chipped cutter on site stops the whole operation.
Overhead and vertical work needs the chain
A mag drill hung under a beam or clamped to a column is held only by current. Lose power and the tool falls, so a safety chain or strap around the beam is standard practice and comes in the case. Cutting fluid also stops behaving sensibly upside down, which is what the paste sticks are for.
Power, and what trips a site circuit
Most rental units are single phase and draw a substantial current at start up, so a long thin extension cord will nuisance trip a breaker or starve the motor. Take a heavy gauge cord of the shortest length that reaches. Federal rules on portable powered tools require guarding and a proper ground path, which a damaged cord defeats.
Questions people ask about mag drill rental
Do the cutters come with the mag drill?
The arbor and pilot pin normally do, the annular cutters normally do not. Counters sell them individually, so take the hole sizes you need from the drawing before you go. Bring the pilot pin back with the machine, since it is small, easy to lose and chargeable.
Can a mag drill be used on stainless or aluminium?
It can cut both, but it cannot hold to either, because neither is magnetic. That work needs a vacuum base attachment or a mechanical clamp, and the cutter and speed change as well. Tell the counter the material rather than only the hole size.
How thick does the steel need to be?
As a working rule the magnet wants around 3/8 in of solid flat steel underneath. Thinner material can be drilled by clamping a sacrificial plate beneath it to give the magnet something to grip, which is a workshop trick more than a site one.