The rotary hammer is quite the useful tool when you want to drill or punch holes in hard materials such as concrete. For cured concrete that needs to have an anchor installed, a hole must be drilled first so the anchor can be attached. The most used bit for this type of project is the spline shank bit.
| Spline Drill Bits | Core Drill Bits | Spline Chisel Bits |
|---|---|---|
What is a Spline Shank Bit?
The name come from the cross-sectional profile of the spline shank itself. This type of shank has 12 teeth that is designed to fit into the spline drive of the hammer drill.
Spine bits used to be a popular choice for rotary hammers and demolition hammers before the SDS bits became more popular.
Parts of a Spline Bit
The bit is made up of four different sections.
Cutting Tip & Head: Both parts work together to break up the concrete itself. The carbide tip is quite hard and durable, allowing to bust up the concrete with ease.
Flute: This is the depression or trough of the bit that allows the dust from the concrete to be removed while the drilling action is taking place.
Land: This is where the spiral portion of the bit, which resembles the crest of a wave, is raised.
Spline Shank: The 12 teeth are designed to fit perfectly into the drill so that no adjustment needs to be made during the drilling or hammering process.
All four sections work together to drill or punch holes in concrete so that anchors can be attached or to meet the needs of the project that requires holes to be placed in concrete.
Spline vs. SDS
What is the difference between SDS Max and Spline?
The main difference between a spline bit and an SDS bit is in the size and profile of the shank. A spline shank with its 12 sprocket design offers more contact area and hence more efficient. On the other hand, an SDS-max bit is easy to use and keep the bit securely locked inside the tool holder, yet allows it to move up and down during the hammering action.
The spline drill bits and chisel bits have different profiles. The sprocket shank is only available for the drill bits where it is important for the rotational motion. The spline chipping bits have a smooth shank. Conversely in case of SDS-plus or SDS-max, both drill and chisel bits have similar shank design.
Pros & Cons of Spline Bits
Of the advantages that spline bits offers, the most important one is the torque provided by the bit itself when placed in the rotary hammer. Because of its shape and design, it allows for maximum torque to be applied. The result is that holes are drilled easier and with less effort on the person operating the device.
You will need to let the bit do the work and not try to push or force a hole with extra effort. Otherwise, you risk cracking or breaking the concrete depending on its thickness.
There really is no downside to the spline bits, apart from their limited uses as drills beyond their design. Since SDS-max is getting more popular, not all stores are carrying the spline bits.
Pros of SDS Bits
From the pure performance aspect, you will hardly notice any difference between a spline bit and an SDS-max bit. The SDS-plus is smaller and cannot match the performance of the spline.
The SDS-max bits are widely available and in many places they are slightly cheaper when compared to spine bits.
Spline Bit Sizes
The spline bits come in several different sizes that are based on the thickness of the concrete itself and the size and depth of the hole that needs to be created. For the most part, the bit sizes are as follows.
- 3/8” x 10”, 6”, and 12”
- 7/16” x 12” and 14”
- ½” x 12”, 18”, 23.5”, 30”, 36”, and 48”
- 9/16” x 12”, 18”, 23.5”, 24”, 30”, and 42”
- 5/8” x 6”, 12”, 18”, 24”, 30”
- 11/16” x 12” and 23.5”
- 27/32” x 13” and 23.5”
- 7/8” x 12”, 18” 23.5”, and 36”
- 1” x 12”, 18”, and 23.5”
- 1 1/8” x 12”, 18”, 23.5”,
- ¾” x 12”, 18”, and 23.5”
- 1 ¼” x 18” and 23.5”
- 1 3/8” x 18” and 23.5”
- 1 ½” x 18” and 23.5”
Keep in mind that the usable length of the bit is generally 6-inches shorter. This means you will have to account for this difference when using the bits.
Dan Miller is a professional toolmaker with extensive experience in the metalworking and tooling industry.
An avid DIY enthusiast and passionate hobbyist woodworker, Dan shares his expert knowledge here.