The Hole Truth - Time Lost Could Easily Pay For A New Tool
The right tool and the right technique can help you make holes in concrete efficiently.
Making holes in concrete doesn’t have to be hard work. But many contractors make it difficult by trying to make do with the tools they have. When you look at the time lost to using the wrong tool, the cost of that time could easily pay for the new tool or bits needed to speed the process.
That’s the consensus of power tool manufacturers who deal with contractors’ hole-making questions. Here’s how they suggest you get to . . . the hole truth.
Do you have the right tool?
We often see contractors trying to use a hammer drill to do a job that should be done by a rotary hammer,” says Spencer Maid, DeWalt commercial rotary and demolition hammer manager.
Hammer drills are intended for making holes up to 1" in concrete block, brick, or small (up to 5/8") holes in poured foundations, says Maid. “Use them for small fasteners that need holes between 5/32" and 5/8" in diameter. If you are drilling many holes over 3/8", use a rotary hammer,” he says.
“We see contractors burning up hammer drills and bits all of the time because they are using the wrong tool for the job,” says John Olson, Panasonic central regional manager. “When it comes to poured concrete, your best bet is a rotary hammer. A hammer drill is too light of a tool for making any holes in poured concrete.”
Gary Compton, Milwaukee rotary hammer manager, agrees. “Hammer drills have a difficult time making holes in concrete because the hammer drill relies on high rotational speed and a lighter impact to chip away material. A rotary hammer uses pounding force to fracture the concrete. The rotation of the bit changes the orientation of the edges of the bit’s carbide tips in the hole and augers dust out of the hole.
“The difference between a hammer drill and a rotary hammer can be compared with drumming your fingers on a table vs. pounding your fist on a table. The hammer drill impacts the work with fast, lighter blows; while the rotary hammer used powerful, slower blows,” he explains. Given that analogy, it’s easy to understand why a rotary hammer is more effective.
Size up
While it’s tempting to use a smaller tool for a slightly bigger concrete hole-making job, the tool experts recommend against it. Instead, select your tool so the job falls within the operating capacity of the tool, not near or just past the tool’s maximum operating range.
“Look at the optimum range a drill can operate, not the maximum hole it can drill, especially if you are drilling many holes,” says Maid. “Also, consider concrete hardness. If the concrete has a high compressive strength, is older concrete, or has very hard aggregate, consider using a larger tool to make the hole,” he says.
A bit about bits
Concrete bits do not drill the way a wood bit goes through wood or a jobber bit drills steel. Instead, it works by pulverizing the concrete to dust, then evacuates the dust away from the tip and out of the hole. “Drilling in concrete is, in reality, a continuous sequence of actions to pulverize the concrete and to remove the dust,” says Compton.
If you get lost in the bit aisle at your distributor, you’ll find several types of bit shanks for drilling holes in concrete. The different shank designs result from different manufacturers developing novel ways to hold and drive the bit effectively yet be able to withstand the heavy pounding and high-torque rotational forces of the tool. For most people, it’s just a matter or selecting the bit that matches the tool’s bit holder.
“You’ll find SDS or SDS+ bits made for smaller hammer drills which use the SDS Drive system. They are smaller in diameter and the most common bit in use,” says Compton.
For larger holes, you’ll find rotary hammers equipped with either a spline or SDS Max bit holder. Just order the right bit shank to match your tool. Both perform equally well, says Maid.
The cutting edges of a concrete bit are made of steel or carbide. The steel used in bits is a high-grade alloy of chromium, nickel and molybdenum and machined to size under very tight tolerances. Carbide tips are sintered micro-grain carbide and cobalt, molded into a precise tip size and shape. This combination is brazed to the flute, resulting in a very hard, durable tip.
“You can find bits in all price ranges. A good rule of thumb: You should be able to get about 100 holes per bit unless you are operating in very demanding conditions,” says Maid.
Concrete drilling tips
Milwaukee Electric Tool offers the following tips to help you make the fastest and cleanest holes in concrete:
1. Always drill dry. Never add water to the hole. The mud it makes will minimize the hammer blow and can even cause the bit to bind in the hole.
2. Clean the flutes of the bit if they become clogged. Make sure they can evacuate dust from the hole.
3. Keep the shank end of the bit free of dust or debris. Lubricate the bit shank and the bit holder to get the longest life from the tool.
4. Use the shortest bit possible for the hole being drilled. It helps maximize the amount of force transmitted from the hammer to the tip. Because the bit’s tip and flutes wear with each hole drilled, using a longer bit for shorter holes could cause the flutes farther up the shank to bind inside the hole when it is used to drill deeper holes.
5. Drill deep holes in stages. Use a shorter bit to drill the first part of the hole, then finish up with a longer bit. This can help you drill a hole faster and the hole will be straighter and more accurate. Also, it helps long, more expensive bits last longer, saving you money.
6. When drilling deep holes, back the bit out periodically to help clean dust out of the hole.
7. Do not apply excessive force while drilling. Constant, moderate pressure helps you keep the bit going straight and true.
8. If you hit rebar, STOP drilling and move the location of the hole. Or . . . verify with the building inspector or engineer that the rebar may be cut, or that it is okay if the rebar gets loosened from the hammering process.
Smaller rebar and mesh can be drilled through with a four-cutter head or a specially designed bit.
On larger rebar, use special cutter bits. Once you hit rebar, pull out the bit, then use the special cutter bit with a standard drill until you cut through the rebar. Then finish making the hole with the concrete bit.
If you must attempt to drill through rebar with the concrete bit, run the bit very slowly and with very little pressure. This allows the bit to slowly gnaw through the steel. Be aware there is a good chance the bit will suffer damage or break.
Maintain your tools
Next to using an undersized drill for a drilling job, poor maintenance practices are a leading killer of rotary hammers, says Maid.
Rotary hammers create impact through electro-mechanical or electro-pneumatic systems inside the tool. These systems transfer intense forces into concrete in a highly abrasive environment. The components that create this energy must be maintained.
“It’s important to pay attention to the maintenance intervals on these tools,” Maid says. “Too many people run them to failure when timely lubrication and cleaning would have greatly extended the life of the tool.”
The tool’s operator manual outlines appropriate maintenance intervals. He suggests you only use the type of grease recommended by the manufacturer. “Distributors often have rotary hammer tune-up specials. These are good opportunities to have the tools looked over and lubricated. When a tool is run to failure, it’s likely the rings are shot and the cylinder is damaged. At that point, the tool is ruined,” he says.
Cordless possibilities
Today’s cordless tool lines include rotary hammer units capable of making holes in concrete quickly and easily.
“Cordless tools run about twice the cost of a similar corded tool,” says Panasonic’s Olson. “They are especially handy if you are working on a lift because you don’t have to worry about extension cords. We have also found that many maintenance people like the tools because in some plants, they can’t run a power cord without having to apply for a power permit.
“Today’s cordless tools have enough power to sink Tap-Con or Wedge-Bolt fasteners. With these types of fasteners, the time savings a cordless tool can offer can easily recoup the higher initial cost,” he says.
Cordless rotary hammers come in 18-volt, 24-volt, and even 36-volt models. While they may have power that ranks with a corded tool, the weight of the battery and the tool takes some strength and definitely both hands, especially with the higher-voltage tools. “Some of the largest cordless models weigh as much as a circular saw. I don’t know too many people who enjoy holding that kind of weight over their head to do a job,” Olson says. So consider the tool’s weight against the job you will be completing.
Safety tips while making holes in concrete:
• Always wear eye protection.
• Wear hearing protection when using the tool for long periods.
• Bits get hot while operating. You may need gloves or other protection if you will handle or change bits.
• Use two hands. Although these tools are often equipped with clutch mechanisms in case the bit binds in the hole, a firm grip on the tool will help assure it does not bind and begin to spin the tool, which can cause injuries
(Source: Milwaukee Electric Tool, DeWalt)
Published in the May/June 2001 issue of Contractor Tools and Supplies.
Making holes in concrete doesn’t have to be hard work. But many contractors make it difficult by trying to make do with the tools they have. When you look at the time lost to using the wrong tool, the cost of that time could easily pay for the new tool or bits needed to speed the process.
That’s the consensus of power tool manufacturers who deal with contractors’ hole-making questions. Here’s how they suggest you get to . . . the hole truth.
Do you have the right tool?
We often see contractors trying to use a hammer drill to do a job that should be done by a rotary hammer,” says Spencer Maid, DeWalt commercial rotary and demolition hammer manager.
Hammer drills are intended for making holes up to 1" in concrete block, brick, or small (up to 5/8") holes in poured foundations, says Maid. “Use them for small fasteners that need holes between 5/32" and 5/8" in diameter. If you are drilling many holes over 3/8", use a rotary hammer,” he says.
“We see contractors burning up hammer drills and bits all of the time because they are using the wrong tool for the job,” says John Olson, Panasonic central regional manager. “When it comes to poured concrete, your best bet is a rotary hammer. A hammer drill is too light of a tool for making any holes in poured concrete.”
Gary Compton, Milwaukee rotary hammer manager, agrees. “Hammer drills have a difficult time making holes in concrete because the hammer drill relies on high rotational speed and a lighter impact to chip away material. A rotary hammer uses pounding force to fracture the concrete. The rotation of the bit changes the orientation of the edges of the bit’s carbide tips in the hole and augers dust out of the hole.
“The difference between a hammer drill and a rotary hammer can be compared with drumming your fingers on a table vs. pounding your fist on a table. The hammer drill impacts the work with fast, lighter blows; while the rotary hammer used powerful, slower blows,” he explains. Given that analogy, it’s easy to understand why a rotary hammer is more effective.
Size up
While it’s tempting to use a smaller tool for a slightly bigger concrete hole-making job, the tool experts recommend against it. Instead, select your tool so the job falls within the operating capacity of the tool, not near or just past the tool’s maximum operating range.
“Look at the optimum range a drill can operate, not the maximum hole it can drill, especially if you are drilling many holes,” says Maid. “Also, consider concrete hardness. If the concrete has a high compressive strength, is older concrete, or has very hard aggregate, consider using a larger tool to make the hole,” he says.
A bit about bits
Concrete bits do not drill the way a wood bit goes through wood or a jobber bit drills steel. Instead, it works by pulverizing the concrete to dust, then evacuates the dust away from the tip and out of the hole. “Drilling in concrete is, in reality, a continuous sequence of actions to pulverize the concrete and to remove the dust,” says Compton.
If you get lost in the bit aisle at your distributor, you’ll find several types of bit shanks for drilling holes in concrete. The different shank designs result from different manufacturers developing novel ways to hold and drive the bit effectively yet be able to withstand the heavy pounding and high-torque rotational forces of the tool. For most people, it’s just a matter or selecting the bit that matches the tool’s bit holder.
“You’ll find SDS or SDS+ bits made for smaller hammer drills which use the SDS Drive system. They are smaller in diameter and the most common bit in use,” says Compton.
For larger holes, you’ll find rotary hammers equipped with either a spline or SDS Max bit holder. Just order the right bit shank to match your tool. Both perform equally well, says Maid.
The cutting edges of a concrete bit are made of steel or carbide. The steel used in bits is a high-grade alloy of chromium, nickel and molybdenum and machined to size under very tight tolerances. Carbide tips are sintered micro-grain carbide and cobalt, molded into a precise tip size and shape. This combination is brazed to the flute, resulting in a very hard, durable tip.
“You can find bits in all price ranges. A good rule of thumb: You should be able to get about 100 holes per bit unless you are operating in very demanding conditions,” says Maid.
Concrete drilling tips
Milwaukee Electric Tool offers the following tips to help you make the fastest and cleanest holes in concrete:
1. Always drill dry. Never add water to the hole. The mud it makes will minimize the hammer blow and can even cause the bit to bind in the hole.
2. Clean the flutes of the bit if they become clogged. Make sure they can evacuate dust from the hole.
3. Keep the shank end of the bit free of dust or debris. Lubricate the bit shank and the bit holder to get the longest life from the tool.
4. Use the shortest bit possible for the hole being drilled. It helps maximize the amount of force transmitted from the hammer to the tip. Because the bit’s tip and flutes wear with each hole drilled, using a longer bit for shorter holes could cause the flutes farther up the shank to bind inside the hole when it is used to drill deeper holes.
5. Drill deep holes in stages. Use a shorter bit to drill the first part of the hole, then finish up with a longer bit. This can help you drill a hole faster and the hole will be straighter and more accurate. Also, it helps long, more expensive bits last longer, saving you money.
6. When drilling deep holes, back the bit out periodically to help clean dust out of the hole.
7. Do not apply excessive force while drilling. Constant, moderate pressure helps you keep the bit going straight and true.
8. If you hit rebar, STOP drilling and move the location of the hole. Or . . . verify with the building inspector or engineer that the rebar may be cut, or that it is okay if the rebar gets loosened from the hammering process.
Smaller rebar and mesh can be drilled through with a four-cutter head or a specially designed bit.
On larger rebar, use special cutter bits. Once you hit rebar, pull out the bit, then use the special cutter bit with a standard drill until you cut through the rebar. Then finish making the hole with the concrete bit.
If you must attempt to drill through rebar with the concrete bit, run the bit very slowly and with very little pressure. This allows the bit to slowly gnaw through the steel. Be aware there is a good chance the bit will suffer damage or break.
Maintain your tools
Next to using an undersized drill for a drilling job, poor maintenance practices are a leading killer of rotary hammers, says Maid.
Rotary hammers create impact through electro-mechanical or electro-pneumatic systems inside the tool. These systems transfer intense forces into concrete in a highly abrasive environment. The components that create this energy must be maintained.
“It’s important to pay attention to the maintenance intervals on these tools,” Maid says. “Too many people run them to failure when timely lubrication and cleaning would have greatly extended the life of the tool.”
The tool’s operator manual outlines appropriate maintenance intervals. He suggests you only use the type of grease recommended by the manufacturer. “Distributors often have rotary hammer tune-up specials. These are good opportunities to have the tools looked over and lubricated. When a tool is run to failure, it’s likely the rings are shot and the cylinder is damaged. At that point, the tool is ruined,” he says.
Cordless possibilities
Today’s cordless tool lines include rotary hammer units capable of making holes in concrete quickly and easily.
“Cordless tools run about twice the cost of a similar corded tool,” says Panasonic’s Olson. “They are especially handy if you are working on a lift because you don’t have to worry about extension cords. We have also found that many maintenance people like the tools because in some plants, they can’t run a power cord without having to apply for a power permit.
“Today’s cordless tools have enough power to sink Tap-Con or Wedge-Bolt fasteners. With these types of fasteners, the time savings a cordless tool can offer can easily recoup the higher initial cost,” he says.
Cordless rotary hammers come in 18-volt, 24-volt, and even 36-volt models. While they may have power that ranks with a corded tool, the weight of the battery and the tool takes some strength and definitely both hands, especially with the higher-voltage tools. “Some of the largest cordless models weigh as much as a circular saw. I don’t know too many people who enjoy holding that kind of weight over their head to do a job,” Olson says. So consider the tool’s weight against the job you will be completing.
Safety tips while making holes in concrete:
• Always wear eye protection.
• Wear hearing protection when using the tool for long periods.
• Bits get hot while operating. You may need gloves or other protection if you will handle or change bits.
• Use two hands. Although these tools are often equipped with clutch mechanisms in case the bit binds in the hole, a firm grip on the tool will help assure it does not bind and begin to spin the tool, which can cause injuries
(Source: Milwaukee Electric Tool, DeWalt)
Published in the May/June 2001 issue of Contractor Tools and Supplies.
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