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Repair Center  Finding the Correct Masonry Drill Bit: SDS, SDS-Plus, SDS Max, and Spline Drive

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Finish Nailer Repair - Replacing the Driver Guide (Ridgid Part # 79004001022)

Finding the Correct Masonry Drill Bit: SDS, SDS-Plus, SDS Max, and Spline Drive

Finish Nailer Repair - Replacing the Driver Guide (Ridgid Part # 79004001022)

"What type of drill bit fits my hammer drill?" This is one of the most common questions we get from hammer drill and rotary hammer owners here at eReplacementParts.com. The confusion is very understandable, considering that there are several drill bit systems and terms out there that sometimes overlap in definition and compatibility. We're happy to take this opportunity to sort through the jumble, break the information down, and make the task of finding the right bit easy, like it should be.

Masonry Drill Bit The most important factor in matching a bit to its hammer drill is knowing the chuck system of the tool, and choosing bits designed to correspond to that system. For hammer drills and rotary hammers, there are three major chuck/bit design systems available:

1. SDS/SDS-Plus (in terms of compatibility, "SDS" and "SDS-Plus" are completely interchangeable.)

2. SDS Max, and

3. Spline Drive
This article explains the design differences between these systems, and it explains why knowing a power hammer's chuck system design is the key to getting a compatible bit for that hammer.
  Match the Bit Type to the Chuck System To find a compatible bit for your hammer drill or rotary hammer, you only need to know one thing: the chuck system (SDS/SDS-Plus, SDS Max, or Spline). It's that simple. Although there are other bit type considerations when making a purchase, as far as making sure that the bit shank will fit the hammer chuck, matching it to the chuck system is the one and only step. This is because the type of chuck system completely determines two things:

1. The diameter of the bit shank (the end of the drill bit that fits into the chuck), and

2. The number and type of grooves/keyways on the bit shank that fit into the innards of the chuck.   So, for example, any of the SDS-Plus bits pictured below (despite their differing bit diameter, length, and other features) will fit perfectly into any SDS/SDS-Plus chuck system, because their shank diameters are the same, and the number/placement of their grooves are the same. Comparably, any SDS MAX or Spline bit will also fit perfectly into any tool with a matching chuck system. (SDS and SDS-Plus are the only cross-compatible bit systems, making the terms interchangeable.)

Power Hammer Drill Bits Here's the catch:

Hammer drill and rotary hammer owners must know which chuck system their tool uses. The type of chuck system cannot be determined by simply looking at the chuck, probing its opening with a finger, or by any other means. Tools that use these systems will almost always be advertised with the name of the chuck system as part of the tool's advertised name. However, because a tool model number always corresponds to only one kind of chuck system, model numbers are used to pinpoint the exact tool (chuck system included) after sale. Also, the name of the chuck system may be written on the tool somewhere and can always be found in the user manual. The point is that if the chuck system isn't already known, then the tool's model number must be known in most cases to find out which system it uses.
Example: The Bosch 11224VSR Hammer Drill uses an SDS-Plus system, and probably included that information in its advertised name. But, like its title on our parts page for this tool, chuck system details are usually omitted from a tool's title after sale, since the model number is included in the title and is the surest way of leading to accurate information concerning the tool.   If you have the model number of your tool but aren't sure about which chuck design it uses, try the following:

  • Look up what the chuck system is in the user manual (often available online at manufacturer websites), or look for it written on the tool somewhere.
  • If a manual isn't available, use the model number of the tool in a broad internet search to find out the tool's specifics.
  • Look closely at an old bit. The chuck system to which it corresponds is almost always engraved somewhere on the hardware.
  • If the above resources are not available or don't produce the needed information, simply try fitting the different types of bits into the chuck (SDS/SDS-plus, SDS Max, and Spline). The tool might need to be taken somewhere where hammer bits are sold for this test, if the variety of needed bits is not available otherwise. The correct bit is the only one that will fit into the chuck.
After matching the right bit design to its mirror chuck system, other factors that determine bit type can be explored from there (bits for chiseling, cutting, digging, chipping, etc.) to match user preference and application. Below is a detailed description for each of the three chuck systems. [Back to top]   SDS/SDS-Plus, SDS Max, and Spline Chuck Systems Explained "Since they can be tough to keep separate, why the different chuck systems?" That's a fair question. Bosch developed the first SDS system back in 1975. In English-speaking markets, SDS stands for "Special Direct System." SDS chuck systems are specially adapted for concrete and other masonry hammering. In hammers that use traditional chucks, the striking piston uses part of its energy to move the heavy chuck piece back and forth, as well as the drill bit. In an SDS system, the flat end of the drill bit is the only thing that the piston hits and has to move. This makes its energy usage more direct, efficient, and effective. Also, the grooves in an SDS bit shank allow the bit to slide back and forth when it is hit by the piston, providing even more potential for the bit to be accelerated efficiently by the energy of the piston. The snappiest feature of the SDS systems is probably their one-hand bit changing. Inside each SDS chuck there are spring-loaded balls designed to fit into the grooves of SDS bit shanks. After being inserted into the chuck, an SDS bit just needs a little twist for those balls to snap into place and hold the drill bit. In German markets, SDS stands for "Steck, Dreh, Sitz" (Insert, Twist, Stay). Cool, huh? And those are the major benefits of SDS systems. Spline drive bits and chucks are an older system that, like the SDS Max system, is designed with the above features in mind, but for the most heavy-duty masonry drilling; although, SDS Max systems include some advantages over Spline systems.  

 

SDS-Plus Icon When Bosch introduced the first SDS system, it was simply called SDS. Later, improvements were made that helped the shank design hold more firmly, and the design changes were dubbed "SDS-Plus." However, the improvements did not have any impact on compatibility, so SDS and SDS-Plus are interchangeable in both terminology and function. For new tools, SDS-Plus (sometimes written "SDS+") has simply replaced SDS. SDS-Plus bit shanks have four indentions on them: two that are open-ended, and two that are close-ended (which keep the bit from flying out of the chuck). The SDS-Plus icon above shows a top view of an SDS-Plus shank, and depicts the orientation of its four grooves. Also, see the picture below for side views of SDS-Plus shanks:

SDS-Plus Bit Shanks   SDS-Plus systems are the most common, since they're adapted for relatively less-heavy drilling (in comparison to larger hammer drills), and their shanks have a diameter of 10mm. [Back to top]  

 

SDS Max Icon SDS Max bits are only compatible in SDS Max chuck systems. SDS Max is designed for even heavier-duty work than SDS-Plus, and accordingly, the range of SDS Max bit sizes leans more toward the larger end of masonry drill bits. In many ways, the SDS Max system was designed to improve upon and replace the older Spline drive system. The main improvement of this system is that it allows for more piston travel, so that when the piston hits the bit, it hits harder and the bit cuts more efficiently. Despite the design upgrades, Spline drive systems remain popular with some users and are still manufactured. SDS Max bit shanks have five indentions on them: three that are open-ended, and two that are close-ended (keeping the bit from flying out of the chuck). The SDS Max icon above shows a top view of an SDS Max shank, and displays the situation of its five grooves. Here's a picture with side views of SDS Max bit shanks:

SDS Max Bit Shanks SDS Max systems are the newest, and, overall, best systems for the most heavy masonry drilling out there. Their shanks have a diameter of 18mm. [Back to top]  

 

Spline Drive Icon Spline drive bits are only compatible in spline drive chuck systems. As discussed above, Spline drive systems are for the most burdensome drilling workloads, like SDS Max, but they are an older system. Although the SDS Max system improves upon the Spline drive design, many users still prefer Spline drive and continue to use it out of preference. The icon above shows a top view of a Spline drive shank, and shows its many-grooved design. A Spline bit shank from the side:

Spline Bit Shank Spline drive shanks have a diameter of 19mm. [Back to top]   Chuck Adapters for Hammering Drills
Yes, adapters are available that allow bits from different systems to be used in the same tool. Most opinions on these adapters suggest that it's best to avoid them if possible, since one more part (and a loose one at that) can just mean an opportunity for the part to break or be lost. But chuck adapters are also very handy when they're the only available option. Chuck adapters are available to convert between the following systems:

SDS Max        ---->      Spline Drive

Spline Drive    ---->      SDS Max

SDS Max        ---->      SDS/SDS-Plus

Spline Drive    ---->      SDS/SDS-Plus


The obvious restriction is that chuck adapters don't (and shouldn't) convert from the smaller SDS/SDS-Plus systems to the larger SDS Max and Spline drive systems. If chuck adapters were available for an upgraded conversion, the hammer drills with the original SDS-Plus system probably wouldn't be rated high enough to handle the workload for which SDS Max and Spline bits would be required. [Back to top]   2-Flute and 4-Flute Bits So far, this article has only discussed differences between hammer drill bits that relate to their compatibility in chucks. Of course, after compatibility is resolved, shoppers still have a host of drill bit types to choose from to match bits to a given application. One of the most important and common decisions that bit shoppers have to make when looking for masonry bits is the choice between 2- and 4-flute bits.

2- and 4-Flute Masonry Bits Flutes are the cross section pieces on the tips of masonry bits that give them their shape, as can be seen in the picture above. 2-flute bits are a more traditional design of masonry bits. The more recently-developed, 4-flute bits cut much more efficiently. In general, the 4-flute bits cut faster, with more energy efficiency, less bit wear, and get stuck in their holes less easily than 2-flute masonry bits. This is especially true when the bit makes contact with rebar or other metals in concrete. 2-flute bits easily get caught up on obstructions like rebar, and sometimes get really stuck because of it. The 4-flute design helps the bit just continue to cut right through the material. [Back to top]
Conclusion Those are the major pointers when it comes to finding and selecting a compatible masonry bit for a given power hammer. The chuck system of the tool must be known, and knowing the tool's model number is the surest way to find out which chuck system the tool uses. Visit our Hammer Drill Bits page to begin your search for the masonry bit your power hammer needs. Or, browse our Hammer Drills and Rotary Hammer pages to find your hammer's tool parts page.   [Back to top] What we're about.

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