How To Drill Through Metal

Most of the projects around the home that use a drill are based around drilling through wood, but sometimes you may need to know how to drill through metal as well. Drilling through metal is not difficult as long as you have the necessary tools, which are fairly common and you may already have in your toolbox.

How To Drill Through Metal

The most important thing to know about drilling through metal is that you can use just about any drill. Your drill does not need to have a very high maximum speed since you should turn your bits fairly slowly when drilling into metal. A high torque level can help to get through tougher materials, but the speed itself won’t matter.

More important than the drill itself is the drill bit you will be using. Twist bits used to drill metal have a flatter end, as opposed to jobber drill bits that are normally pointed. Any point at the tip of the drill bit will probably be damaged if you try to use it to drill through metal.

Tools for Drilling Through Metal

• Clamps
• Scrap wood
• Pencil or marker
• Center punch
• Hammer
• Drill
• Drill bit (or bits) designed to drill through metal
• Cutting oil or other lubricant
• A rag

Be sure to wear safety goggles when drilling anything, but especially metal. The material being removed can be very sharp and can cause a lot of damage to unprotected eyes. Heavy work gloves can be a good idea as well.

You can also use a drill press designed for metal to handle the drilling.

Steps for Drilling Through Metal

1. Place the scrap wood down on your workbench.
2. Clamp the metal you will be drilling to the scrap wood and bench. Use two clamps – since the drill will create a rotation point, you do not want your metal to spin.
3. Mark the spot you want to drill with the pencil.
4. Use the hammer and center punch to create a dimple in the metal. This will help prevent the drill bit from traveling.
5. Using a fairly low level of RPMs and light pressure, begin drilling.
6. Add cutting oil to the surface if necessary.
7. For thicker or harder materials such as stucco or metal, stop at regular intervals to cool down the drill bit.
8. Wipe with the rag intermittently.
9. Once the hole is complete, use a twist bit that is slightly bigger than the hole, and twist it by hand on the edges. This will de-burr the edges and clean them up.

If your drill bit isn’t large enough, you’ll want to move to cutting the circle out of the metal with a different tool.

Considerations When Drilling Through Metal

Taking care of basic setup is important when using a drill for any material like brick or hard surfaces like granite, and metal is no exception. Making decisions on what methods to use and making sure you have everything you need before starting the job will help you complete it quickly and safely.

Drill Bits for Metal

There are different levels of drill bits that are suitable for drilling through metal. These fall into four categories: steel, black oxide, cobalt steel, and titanium coated. Each of these different types of drill bits can be used, but to decide which one is best for you, I will look at the facts.

Steel Drill Bits

Steel twist bits, also known as high-speed steel (HSS) bits, are generally the least expensive option for drilling through metal. They are effective will just about all metals that can be drilled, they can be sharpened, and are easy to take care of. The main drawback is that the steel drill bits can dull quickly if used for large jobs where they have to drill more than a few holes.

Black Oxide Drill Bits

Black oxide bits are made when HSS bits are heated and hardened, leaving a strong coating. They should really only be used for drilling metal, but they can also be used for wood in an emergency. The hardness of these bits is much greater than high-speed steel, and they hold up to higher temperatures much better, so they will last longer.

Cobalt Steel Drill Bits

Made out of a stronger base material, cobalt steel bits are usually the most expensive of the different bits listed here. They last for an incredibly long time but in general should just be used in a drill press, not a handheld drill, since they are more brittle than the other bits that have high-speed steel as their core.

Titanium Coated Drill Bits

These bits start out as standard HSS bits but then are coated with titanium for strength and durability. There are a few different types of titanium coating that are used, but each of them has the same end result. While these coated bits can last up to six times longer than a high-speed steel bit, they cannot be sharpened without removing the titanium coating.

Which Drill Bit is Best for Metal?

While all the different drill bit types are useful, consider whether you are going to be using the bits to drill metal consistently, or if they may be used for other projects. If you are not drilling through a lot of metal on a regular basis, standard high-speed steel bits should be fine. If you have a lot of holes to drill, consider using titanium-coated drill bits.

Drilling Large Holes

Metal drill bits go up to about one-inch diameter, but when drilling holes that size I recommend you do not just jump in with the biggest bit you can find. When drilling holes over about a quarter-inch in diameter, start with a smaller drill bit and then change your drill bit and increase the size in multiple steps.

Not only will the cutting process go more smoothly, but also your bits will last longer since they will not heat up as much as if you went straight after it with the large bit. Large drill bits should also be run more slowly than smaller ones – keep them under 1000rpm, and you may even want them down around 400rpm once you get up to one-inch bits.

Step Drill Bits

Another type of bit that you can use to drill larger holes in metal is called a step drill bit. These bits are made in a conical shape so they cover multiple size diameters. With step drill bits, you will not need to swap out bits when sizing up unless you drill a pilot hole first. 

It is very important to measure properly and pay attention to the level of diameter you are at when drilling since it is easy to pass up to the next step.

Hole Saws

Once you get to holes over about one inch in diameter, you will want to drill through your metal with a hole saw. These specialized drill bits still attach to your regular drill but are shaped in such a way that they act as a saw cutting in a circular fashion. If you only have one hole to drill in this size, your local hardware store may rent them.

When using a hole saw it is even more important to use scrap plywood or MDF as a backing. With the unique shape and cutting action, I want to make sure that everything stays in one place and the table underneath is not damaged.

Other Tips for Drilling Through Metal

Heat is the enemy of the drill bit, as well as the metal you are trying to drill through, so I need to do my best to keep the heat down. This will help my drill bit to stay sharp for longer, as well as preventing my drilled material from accumulating any heat-related flaws such as warping or discoloration, or breaking down.

• Drill slowly: While it may seem counterintuitive, it is more efficient to keep your drill at a fairly low RPM setting when drilling through metal. When the material and/or the bit heat up, they have a tendency to smear instead of cut. This in turn increases the amount of heat and reduces the cutting power.
• Lubricate: Reducing heat with lubrication is very effective when drilling metal. Cutting oil has already been mentioned as a lubricant, but you can also use 3-In-One Oil, WD-40, or even standard motor oil that you would use in your car.
• Give the bit a break: Longer time spent drilling means an increase in heat. Break that up if it is taking a while to get through the metal you are drilling, and cool down the drill bit. You may try keeping a cup of cool water next to the work area to dunk it in.
• Pay attention to smells and smoke: While some smells are common in a work area, be attentive to anything that smells like it is burning. Even though metal cannot easily burn, the backing you are using will probably be made of wood. If the metal gets hot enough to make that wood smoke, back off for a bit.

Lining up your material and keeping your drill straight are also important when drilling through metal. There are different ways to achieve ensure that your holes are straight and located in exactly the right place.

• Sandwich your material: Even with a center punch, sometimes a drill bit just does not want to stay in one place when you are trying to drill through hardened metal. In these cases, sandwich the sheet metal between two pieces of plywood and clamp them together on the table. Drilling through the wood first will ensure that the drill bit will stay in one place.
• Use a drill press: If you have the space and the budget, a drill press can make a big difference when you have to drill a lot of holes in a short period of time. Handheld drills will always have their place for portability and usefulness, but a drill press can make quick work out of multiple holes, and you won’t have to worry about angles.

Conclusion

With the right drill bit and a little bit of know-how, you can drill through metal fairly easily. Softer metals like aluminum and brass will be a piece of cake, but even steel can be drilled through with a handheld drill. Follow all safety precautions before drilling and make sure to measure twice.