Mag Drills

In high-volume fabrication shops, the debate often splits between Hougen and Fein. Hougen is widely considered the "American Standard"; their tools are legendary for being easily rebuildable, with parts available at almost every industrial supply house. They are the workhorses of structural steel. Fein (Slugger), on the other hand, is the choice for precision. Their machines often feature superior electronics and "Auto-Feed" capabilities that ensure the perfect chip load every time, which can significantly extend the life of expensive carbide cutters. Milwaukee and DeWalt have carved out the "mobile contractor" niche. Milwaukee’s M18 FUEL Mag Drill is the current king of the cordless world, offering a permanent magnet base that doesn't rely on battery power to stay attached. DeWalt’s DWE1622 is a favorite entry-level professional corded unit because it is lightweight and includes a quick-change chuck system that doesn't require hex keys for every bit swap, making it faster for tasks involving multiple hole sizes.

Most corded mag drills from Hougen, CS Unitec, and Fein use an electromagnet. This requires a constant electrical current to create a magnetic field. If the power goes out or a generator stalls, the magnet fails instantly, which is why a safety chain is a non-negotiable requirement. If you are working on a bridge or a skyscraper, a power blip with a corded drill can lead to a catastrophic drop. The Milwaukee M18 FUEL (2787-20) or DeWalt 20V (DCD1624) uses a permanent magnet base; this makes the most sense for cordless tools. The switch on the tool physically moves internal magnets to engage the pull. This means even if the battery dies or is removed, the drill stays stuck to the steel. This "Dead-Man" safety feature is the primary reason many safety officers are now mandating cordless Milwaukee units for vertical and overhead work where traditional corded units were previously the norm. There are now corded units with permanent magnet bases as well, but these often increase cost 30-40% inline with cordless options so they are far less common.

"Gib adjustment" is the most common maintenance task for most mag drill owners. The "gibs" are the internal rails that the motor slides up and down on. If you notice your drill bit vibrating or your holes coming out slightly oval, it’s because these rails have worn down or vibrated loose. If there is any side-to-side play in the motor housing, your accuracy will suffer, and you’ll likely snap bits. To fix this in the HMD904 specifically, look for the three or four small hex screws on the side of the slide housing. You want to tighten these in small, equal increments until the motor moves smoothly with no lateral movement. Hougen recommends checking these every week if the tool is in daily use. A well-adjusted slide makes the tool feel brand new and prevents the "chatter" that often destroys expensive annular cutters. This is not limited to the HMD904 or Hougen units; other makes and models should have similar adjustments for the rails.

Fein machines are famous for their "Surface Sensor" safety logic. If the magnet doesn't detect a strong enough pull—due to rust, heavy paint, or the material being too thin—the tool will not allow the motor to spin. This is a safety feature to prevent the drill from "lifting" during a cut. If your light is blinking red or the motor just clicks, the sensor is telling you the connection isn't safe. The solution is usually to take a flap-disc or wire brush to the steel to clear a "clean" spot for the magnet. Also, check the bottom of the magnetic base for any nicks or metal shavings. Even a single shard of metal caught on the magnet can create a microscopic "air gap" that the Fein sensor will detect as a failure. Keep a flat file in your kit to occasionally "hone" the bottom of the magnetic base to keep it perfectly flat.

This is a frequent point of frustration for Milwaukee fans. The battery cradle on the M18 FUEL Mag Drill is physically restricted by the frame. The massive High Output 12.0Ah battery is too thick to slide into the slot. This was likely an engineering trade-off to keep the tool as compact as possible for tight-access work on I-beams. For maximum runtime, you should use the High Output 8.0Ah or the newer FORGE 6.0Ah or 8.0Ah batteries. The FORGE batteries are particularly well-suited for this tool because they handle the heat of a high-torque motor better than standard cells. If you find yourself running out of juice too quickly, the community recommendation is to swap to the 8.0Ah rather than trying to "force" a larger pack into the housing.

This often comes down to RPM management. The DeWalt has a two-speed gearbox, but its "Low" speed is still relatively fast (300 RPM) compared to some industrial Hougen models that can go as low as 250 RPM. When using Carbide-Tipped (TCT) cutters, speed is the enemy of longevity. If you run a TCT bit too fast, the heat causes the carbide to become brittle and shatter the moment it hits a hard spot in the steel. Hougen’s gearbox is often tuned for higher torque at lower speeds, which is ideal for HSS (High-Speed Steel) cutters. If you are using a DeWalt, you must be extremely diligent with your coolant flow. If the bit starts to "smoke," you are likely spinning too fast for the material thickness. Many pros suggest using a "cutting paste" rather than a liquid coolant when using the DeWalt on vertical surfaces to ensure the lubrication stays on the teeth.

This is known as "breakthrough surge." As the bit finishes cutting through the bottom of the plate, the resistance drops to zero. If you are leaning too hard on the handle, the drill will lurch forward, which can cause the magnet to shift or the bit to bind on the ragged edge of the exit hole. Milwaukee’s AUTOSTOP is designed specifically to catch this and shut the motor down before it can cause injury. To prevent this on manual machines like Hougen or DeWalt, you should "lighten up" on the pressure right as you see the coolant start to pour through the bottom of the hole. This indicates you are about 90% through. By easing off, you allow the bit to "clean" the exit hole at a steady pace, which results in a burr-free finish and prevents the tool from jumping.

A flat magnetic base will only have about 10-20% contact on a round pipe, which is extremely dangerous. For pipe work, you must use a Pipe Attachment (like the Hougen 05000). This is a V-shaped chain-mount system that creates a flat platform for your mag drill to sit on. Without this, the magnet will likely slide the moment the bit starts to bite into the curved surface.

The Fein or Hougen features a motor that controls the downward pressure for you. It senses the load on the bit and adjusts the feed rate in real-time. Contractors almost universally agree that if you are drilling hundreds of holes a day, the Auto-Feed is worth the premium. It eliminates operator fatigue and, more importantly, prevents the "uneven" pressure that is the #1 cause of broken annular cutters.

Milwaukee uses a 3/4" Weldon Shank with a quick-release collar. Over time, metal dust and dried coolant can get into the ball-detent mechanism. If the collar won't move, don't use a pipe wrench. Instead, spray some penetrating oil (like WD-40 Specialist) into the arbor and let it sit. In the future, a light coat of machine oil on the shank of every bit before you insert it will prevent this "cold welding" from happening.

Overhead drilling is high-risk. Gravity works against your coolant system and your safety. First, you must use the safety strap; if the power blinks, that drill is a 30lb anvil falling on your head. Second, you cannot use a gravity-fed coolant bottle. You must use Cutting Paste or a pressurized spray. Hougen and Fein both sell "Slick-Stik" or similar wax-based lubricants that you apply directly to the bit to keep it cool without dripping liquid into the motor.

If your motor starts sparking excessively through the vents or if it sounds like it’s "stuttering" or losing power under light load, your brushes are likely worn down. Hougen makes these very easy to replace; there are usually two plastic caps on the sides of the motor. You simply unscrew them, pull out the old spring-loaded brushes, and pop in new ones. If you ignore this, the brushes can eventually damage the motor's commutator, turning a $20 fix into a $400+ motor replacement.

Mag drills are optimized for Annular Cutters, which only cut the "ring" of the hole. A twist bit has to turn the entire center of the hole into chips, which requires much more torque and downward force. This extra force puts stress on the slide and motor mount, leading to vibration. If you must use twist bits frequently, ensure you are using a high-quality Chuck Adapter and keep your bits sharp; a dull twist bit will cause even the best machine to chatter.

The steel itself isn't harder, but the Zinc Coating is the problem. Zinc has a lower melting point and can "clog" the teeth of an annular cutter, leading to friction and heat. When drilling galvanized steel with your drill, use extra coolant to "flush" the zinc chips away. Also, be aware that the zinc fumes can be toxic; always work in a ventilated area or wear a respirator when drilling through heavy galvanization.

Drilling two plates "sandwiched" together is tricky because a burr can form between the plates, causing the bit to bind. Hougen and Fein both offer "Stack Cutters" with a specific tooth geometry designed (special order) to handle the transition between plates. If you are using standard bits, you should pause after the first plate, clear the chips, and then proceed slowly through the second to ensure the slug from the first plate doesn't jam the bit.

Most modern mag drills (especially Fein and Milwaukee) have an internal level or motion sensor. If you are working on a vibrating surface (like a bridge with traffic or near a large generator), the sensor might think the drill is lifting and shut it down. If this happens, try to dampen the vibration or ensure your magnet is on the thickest possible section of the steel to maximize its "holding" signature.

Tapping requires Forward/Reverse and very low RPMs. Only specific models (like some of the CS Unitec or the Fein JME Magshift) have the gearing and electronics for tapping. If you try to tap with a single-speed Hougen, you will almost certainly snap the tap because you can't reverse the motor to clear the chips. Always verify the tool is "Tapping Capable" before buying a tap adapter.

"Too good to be true" deals on Amazon or eBay often feature counterfeit cutters made of soft steel. Real Hougen, Fein, and Milwaukee bits will have laser-etched branding and "Made in USA" or "Made in Germany" markings. If the etching is blurry or the bit feels unusually light, it’s likely a fake. These bits will dull after two holes and can even damage your drill's arbor if the Weldon shank isn't machined to the correct tolerances.