Tips for Drilling Holes in Metal

By placing an order of cobalt drill bits, it’s most likely that you’ll have to drill a hole through a piece of metal.

Here are some tips to make the task fast, easy and safe.

Protect Your Eyes

It only takes one tiny metal fragment to cause a serious eye injury, so proper eye protection when drilling metal is an absolute must. For the best protection, choose safety glasses that wrap around the sides of your face.

Make a Dimple

Generally speaking, drill bits have a tendency to wander when you first start drilling. To prevent this, measure and mark where you want the hole and then use a center punch and hammer to create a small dimple. This gives the tip of your drill bit a place to ride in as you begin to drill.

Although our products are advertised to be self-centering and anti-wandering, it’s still suggested you do the dimple if you use a hand drill.

Lubricated Bits Last Longer

For drilling holes in steel that’s 1/8 inch or thicker, use cutting fluid, multipurpose oil like 3-IN-ONE or cool water. Lubricating the bit reduces friction and heat buildup, which makes drilling easier and your bits last longer. For easier-to-drill metals like aluminum, brass or cast iron, lubrication isn’t usually necessary.

Clamps Prevent Stitches

Never hold a piece of metal in one hand while trying to drill through it with the other. The drill bit for metal could catch, instantly causing the workpiece to spin, strike and slash (sharp metal edges slice to the bone!). Always use a minimum of two clamps to securely hold down your workpiece.

Start with a Small Hole

Need a big hole? Start small! Most twist bits are available in sizes up to 1 in. in diameter, but you’ll get the best results by starting with a 1/4-in. hole and drilling successively larger holes with your drill bit for metal until you reach the size you want.

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Drill at a Slow Speed

The faster a bit spins, the hotter it gets. And heat dulls bits quickly. In general, it’s a good idea to drill through metal using as slow a speed as possible using a drill bit for metal. Hard metals like steel and larger drill bits require even slower speeds. High speed drilling will often just overheat the drill bit and the metal, without actually doing anything. Please refer to the RMP chart for common metals at the end.

High Pressure

Regarding technique, the trick for drilling hard metals is to, beside drill with a slow speed, put high pressure on the drill. The goal is to get the drill to "bite" the metal, cutting of shavings. A drill press will be very useful here (if you can get access to one).

Make a Sandwich

For clean, precise holes in thin sheet metal, make a wood sandwich. Simply sandwich the sheet metal between two pieces of wood and clamp everything down on a table or workbench. The wooden ‘bread’ layers of the sandwich keep the sheet metal flat and prevent the drill bit from wandering as it bores through the sheet metal.

Step Up to a Drill Press

While it’s fairly easy to drill most holes in metal using nothing more than a handheld drill, you’ll almost always get greater accuracy and better results using a drill press. Most drill presses are actually built with metalworking in mind. Pulling down on the handle causes the bit to plunge straight down into a workpiece and make a very precise hole.

Drill presses also come with beefy cast-iron tables with tilt and height adjustments, and allow a variety of clamping options. Speed changes are as easy as opening the lid and moving a rubber belt from one pulley to another. The most expensive drill presses are floor-standing models, but you can buy a decent benchtop unit for about $100.

Disable the percussion function

Percussion is used for masonry work, and will only damage the drill bit and work when drilling metal.

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Drilling Through Metal Problems and Solutions

Below we have listed some very common problems that people discover when they drill through metal. I have provided what the problem is likely to be and how to resolve that.

Problem - The drill bit breaks.

Possible Cause and Solution - This is the most common problem, especially for small bits. M35 cobalt drill bits are composed of 95% high speed steel and 5% cobalt. While the 5% cobalt makes the bits much more durable as well as giving them an abrasive quality that helps it to cut through hard materials repeatedly, it also makes the drill bits more brittle than ordinary HSS drill bits. The cause of breaking could be shaking, tilted bit, and unsteady workpiece.

Please watch out for snapping of the bit on the exit hole, never angle the drill while drilling and use a drill press.

Problem - The drill bit can’t penetrate the workpiece.

Possible Cause and Solution - The material of workpiece could be too hard for the drill bit. M35 cobalt drill bit is suitable for metals less than HRC 38 degree, not suitable for hardened steel, heat treated steel, high carbon steel and steel blended with unknown impurities. You’ll need to use carbide bits to drill these hard metals.

High speed drilling will often overheat both the drill bit and the metal. The overheated workpiece becomes much harder and can’t be drilled by the same bit. The solution is to slow the RPM and try a different drilling spot.

Another possible cause is that the drilling device isn’t powerful enough. Then you need to change the drill.

Problem - The drill bit is making a high pitched squealing noise.

Possible Cause and Solution - Most likely the drill bit is running too fast. You can either slow down the speed, or if you don't have a variable speed, drill in short bursts, leaving time in between each drilling session

Problem - The drill bit becomes very hot or even fries/melts.

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Possible Cause and Solution - This can be caused by one of two things. Like the problem above the drill bit is going too fast. If that is the case, then the same solution as shown above will help solve that problem.

Secondly the drill bit may require some lubrication. You can buy spray tins of drilling and cutting oil to help resolve this problem. You can also use water to help keep the drill bit cool.

Be careful with water though especially if you are using a power drill plugged into an electricity supply.

Problem - Your drill bits get blunt very quickly.

Possible Cause and Solution - The solution to this is that your drill bits are overheating and you should use lubricant as explained above. Just be aware though that if the drill bits have been over heated a lot, they are practically useless and may need replacing.

Most drill bits can be sharpened, but that takes some skill, and it is always better to buy a drill sharpener machine.

Problem - The drill bit is wobbling.

Possible Cause and Solution - The bit may not be centered in the chuck, so always check that first. That is always a big problem when using very small bits, such as when you are drilling a pilot hole. Often the drill bit gets caught in just one jaw of the chuck, and it is off center.

The other problem could be that the drill bit has been damaged, and is bent or even slightly warped. If that is the case, then it will need to be replaced.

Problem - The drill bit slips and skids across the metal surface.

Possible Cause and Solution - No matter what type of metal you are drilling, it’s suggested that there should be a pilot hole drilled first. Usually this is done using a very small drill such as a 3 mm drill bit.

However before that, a center punch should be used to make a dent in the metal, that will accommodate the pilot hole drill bit. Makes sure that you do that, and that it is deep enough to allow the small metal drill bit to grab the metal.

Problem - Drill bit jams in the chuck at the end of the drilling.

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Possible Cause and Solution - This is one of the most common problems when drilling through metal. The honest answer is that this is usually caused by our impatience. It is all too easy when getting near the end of the hole, to force it through.

Too much pressure or weight on the drill bit will cause the drill bit to jam or lock up in the chuck if we try to force it through. Go easy on the pressure and allow the drill bit to cut all the way through the metal.

Drill Bit RPM Guide & Chart for Drilling Speeds

Please note the drill bit size is shown in inches, and the RPM is shown as the maximum RPM the drill bit should be used when drilling.

Drill Size Aluminum Mild Steel Cast Iron Stainless Steel

1/32" 36600 13446 12224 8557

3/64" 24448 8964 8149 5705

1/16" 18336 6723 6112 4278

5/64" 14669 5379 4890 3423

3/32" 12224 4482 4075 2852

7/64" 10478 3842 3493 2445

1/8" 9168 3362 3056 2139

9/64" 8149 2988 2716 1902

5/32" 7334 2689 2445 1711

11/64" 6668 2445 2223 1556 3/16" 6112 2241 2037 1426

13/64" 5642 2069 1881 1316 7/32" 5239 1921 1746 1222

15/64" 4890 1793 1630 1141

1/4" 4584 1681 1528 1070

17/64" 4314 1582 1438 1007

9/32" 4075 1494 1358 951

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Drill Size Aluminum Mild Steel Cast Iron Stainless Steel

19/64" 3860 1415 1287 901

5/16" 3667 1345 1222 856

21/64" 3493 1281 1164 815

11/32" 3334 1222 1111 778

23/64" 3189 1169 1063 744

3/8" 3056 1121 1019 713 25/64" 2934 1076 978 685

13/32" 2821 1034 940 658

27/64" 2716 996 905 634

7/16" 2619 960 873 611

29/64" 2529 927 843 590

15/32" 2445 896 815 570 31/64" 2366 868 789 552

1/2" 2292 840 764 535 Hopefully we have provided you with enough information to allow you to drill metals successfully.

If you follow the tips above but still can’t get a good result, please contact us by sending message through Amazon’s system. Our helpful customer service will respond your email and solve your issue as soon as possible.

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