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Carbide Bits for Concrete Drilling Applications

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When using carbide bits and hammer drills for anchoring to concrete it is important that the hole size meets the anchor size requirements. In order for anchors to work successfully, hole size is critical.

It is also very important to use bits that meet ANSI standards. ANSI stands for American National Standards Institute. The ANSI was founded in 1919 as a non-profit, private organization that acts primarily as a standards coordinator and approval body. Many years ago, different manufacturers of anchors would manufacture anchors and bits to their own tolerances. This meant that carbide bits had to be manufactured and sold by a specific company. Confusion among customers resulted since different anchors were being used with different bits. It was decided that a standard for the industry should be created and adhered to by all anchor and bit manufacturers. The ANSI standard that pertains to concrete bits is B212.15 and gives a range that finished diameters for rotary and concrete drill bits must meet. Included below is a chart showing the minimum and maximum tolerance ranges for each size of concrete anchor.

Diameter of Drill Bit Minimum Diameter Maximum Diameter
1/8” .134” .140”
5/32” .165” .171”
3/16” .198” .206”
7/32” .229” .237”
1/4” .260” .268”
5/16” .327” .335”
3/8” .390” .398”
7/16” .458” .468”
1/2” .520” .530”
9/16” .582” .592”
5/8” .650” .660”
11/16” .713” .723”
3/4” .775” .787”
13/16” .837” .849”
27/32” .869” .881”
7/8” .905” .917”
15/16” .968” .980”
1” 1.030” 1.042”
1-1/8” 1.160” 1.175”
1-3/16” 1.223” 1.238”
1-1/4” 1.285” 1.300”
1-5/16” 1.352” 1.367”
1-3/8” 1.410” 1.425”
1-7/16” 1.472” 1.487”
1-1/2” 1.535” 1.550”
1-9/16” 1.588” 1.608”
1-5/8” 1.655” 1.675”
1-3/4” 1.772” 1.792”
2” 2.008” 2.028”

Carbide bits that are designed for drilling holes for concrete anchors come in four styles that reflect the hammer drill that they if into.

Straight Shank: The straight shank bit shank (the part that fits into the drill) is smooth and can be round or hex. They fit into Jacob's style chuck that requires a chuck key. Hammer drills that have Jacob's style chucks are referred to as a mechanical type hammer drill. This means that the striker does the hammering and the drill actually hits the end of the bit- metal against metal. This type of hammer drill hammers up to 48,000 blows per minute and rotates 900 rpm to 2,500 rpm.

SDS or SDS Plus (SDS+): SDS stands for Slotted Drive System, Spline Drive System or Schnell Drilling System bits. They are all the same shank which is slotted and have curved recesses that fit into keyless chucks. This allows the bit to move within the chuck, creating a much harder impact than a standard Jacob's style chuck hammer drill. The types of hammer drills that have keyless chucks are referred to as rotary hammer drills. They are electro-pneumatic - which means the striker ensures that the hammer bit doesn't hit the end of the bit. This mechanism results in a quieter, more efficient design for drilling concrete. The typical SDS rotary hammer drill hammers at 4,100 blows per minute and rotates at 750 rpm and can be switched from rotation only to rotation & hammering. The largest diameter drill bit for the SDS rotary hammer drill is 1-1/8".

SDS Max: The SDS Max carbide bit is a larger diameter shank than the regular SDS bits. To compare the two- the SDS diameter of the shank is about the size of your small finger while the SDS Max diameter is about the size of your thumb. These types of hammer drills are referred to as "combi hammers" because they have 2 settings- hammer & rotation as well as hammer only. In other words, they are designed to either drill holes in concrete using carbide bits or chisel concrete using special chisels. These types of drills also utilize the electro-pneumatic system for hammering but these hit much harder than the smaller SDS style hammer drills. The typical performance of a combi hammer bit it 2,800 blows per minute and a rotation of 360 rpm. These drills typically take up to a 2" bit.

Spline: Spline carbide bits are of an older style that fit into many different hammer drills. These bits are designed for the spline chuck hammer drill. The bits have fins (or "splines") that fit into the chuck and create a very positive connection and are locked in with a key. The typical hammer drill's performance that utilizes these spline bits is 1,300 to 2,700 blows per minute. The rotation speed is 140 to 300 rpm.

Below is a list of manufacturers that make the different types of drills used with each style of carbide bit:

Straight Shank Bits

AEG, Black & Decker, Bosch, DeWalt, Hitachi, Hilti, Kango, Makita, Metabo, Milwaukee, Porter Cable, Ramset, Red Head, Ryobi, Skill


AEG, Black & Decker, Bosch, DeWalt, Hitachi, Hilti, Kango, Makita, Metabo, Milwaukee, Porter Cable, Ramset, Red Head, Ryobi, Skill


Black & Decker, Bosch, DeWalt, Hitachi, Hilti, Kango, Makita, Metabo, Milwaukee


AEG, Black & Decker, Bosch, DeWalt, Hitachi, Kango, Makita, Metabo, Milwaukee, Ramset, Red Head, Ryobi

Below are links to each of the hammer drill manufacturers listed above. You can find a wealth of more information about each unique manufacturer by visiting the links below:

All of the carbide bits explained above as well as the drills from these manufacturers work together to ensure that a hole is drilled into concrete properly and safely. Choosing the correct bit and drill for your application will help your project be a success!

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May 28th 2009 Mike Pistorino

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