Drilling Made Easy

Drilling into concrete is simple but at times can be very frustrating and costly. Stick a carbide bit into a rotary hammer and off you go — you’re drilling holes. If you are drilling a lot of holes the next question on the owner’s mind is, "How do I maximize my investment in the rotary hammer and the carbide drill bits?" Here are some principles about drilling into concrete.

To drill into concrete you need to have two things happen: you need to chip or break up the concrete in a very specific area and you need to remove the concrete chips from the hole. Although these may seem like two simple tasks, they’re not.

What is the best way to chip the concrete and remove the dust? There are several bit and rotary hammer drill manufacturers who have their own opinion and design. Regardless of what company you talk to, some simple facts remain. You need a bit that drills a round hole, has carbide that is durable enough to take the punishment of drilling and has an effective means to get the dust (concrete chips) out of the hole. How all of this is most effectively done is why different manufacturers have different patents on their products.

Most masonry drill bits use a plate of carbide that is brazed into the drill bit blank. The carbide plate’s point has a special bevel, similar to a cold chisel, molded in it for use in rotary hammer drills. This beveled edge is what is used to chip or break the concrete while the hammering mechanism of the rotary hammer drill is hitting the other end of the drill bit. The spiral incorporated into the drill bit is called the fluting. The fluting transports the dust out of the hole as the rotary hammer turns the bit. As a general rule, the faster you get the dust out of the hole, the faster you drill the hole.

STAYING POWER. With the basics aside, how do you keep your rotary hammer drill (a drill that uses the slotted drive system connection end) and bits drilling faster and longer?

1. Before inserting the connection end of the drill bit into the rotary hammer, clean it. Dirt and grit accumulates on the connection end and when it is stuck into the drill chuck, the dirt and grit get inside the chuck and the hammering mechanism of the tool. The grit inside the chuck will cause premature chuck failure and excessive drill bit wear.

2. Once the connection end is clean, lubricate it with a small amount of grease or oil. Greasing the connection end will reduce the friction that is generated in the chuck, thus limiting heat build-up and excessive chuck wear.

3. Since 99 percent of rotary hammer tools have an electro-pneumatic hammer mechanism, it is important to let the tool do the drilling. Apply only enough pressure on the tool to keep the drill’s hammering mechanism engaged. Some people feel they can get the tool t0 drill faster by pushing harder on the tool. You may be able to get it to drill faster for a couple of holes with a new drill bit, but it is not sustainable. Let the tool do the work and your arms will thank you.

4. When drilling horizontally (into a wall), support the weight of the rotary hammer. Allowing the drill bit to carry a portion of the weight will cause side pressure on the drill bit. This pressure puts undue stress on the fluting and on the side of the carbide plate. The bit will break when the pressure is too great or because the bit has been exposed to this stress for a period of time.

5. Don’t drill a hole so deep as to go beyond the fluting. This impedes dust removal and generates heat. The heat build-up can be so intense that it melts the brazing material at the tip and allows the carbide plate to move and fracture.

6. When through drilling a slab on grade, clean the fluting of your drill bit regularly. It’s common for mud to accumulate on the drill bit every time the bit goes through the slab and the tip goes into the sub-grade. When the mud fills the fluting, you once again caused a blockage of dust and the same thing will happen as described in point number 5 previously.

LONGER-LASTING DRILLS. How do you make your bits and tools last longer? Quite simply, by heeding the words your father used to tell you, "If it won’t go, don’t force it."

The biggest effect of prolonging the life of both your bits and your rotary hammers is not to press too hard on the tool when you are drilling — it is easier on the operator as well. Having said that here are a few tips to make your bits and tools last longer.

1. Inspect your tool and bits before use. It’s best to use a new bit when drilling. If you don’t have a new bit, look to make sure the bit you are about to use is in good condition. Make sure the carbide head is still in good shape; check to see that the fluting is not worn down so much that it will not remove the concrete dust from the hole (the No. 1 reason why bits stick in holes); and, inspect the connection end to make sure there is no excessive wear (the No. 1 reason why bits get stuck in the chuck).

2. Make sure you lubricate the connection end of the bit. To reduce chuck repairs and bit breakage, apply a small amount of grease (no more than a
¼-inch dollop) in the grooves of the clean connection end.

3. Pay attention when drilling. If your drilling rate decreases rapidly, you may have broken your bit or hit rebar. When drilling holes greater in diameter than ½ inch, your bit has a good chance of surviving its encounter if you back off quickly. Advances in head geometry design of masonry bits have produced bits that drill rounder holes and are more resistant to rebar. Bits that tout a "cross" head design, an "X" head or a multi-cutter will usually drill more round holes than a drill bit with a single plate of carbide. This rounder hole is produced because the drill bit is more stable in the hole during drilling. This stability causes the bit to be more resistant to rebar hits.