Some FAQ on Rotary Hammer

Q: What do "SDS, SDS-MAX and Spline Shank" stand for?
A: SDS stands for Schnell Drilling System or Slotted Drive System. All modern rotary hammers use one of three types of bit: SDS, SDS-MAX, and SPLINE SHANK.
SDS is also and confusingly called "SDS-Plus" and often written "SDS+". They are all the same SDS shanks are slotted and have curved recesses all of which lock nicely into the chucks of "SDS rotary hammers." They are the smallest of the three shank types, so the biggest diameter SDS bits you'll find are about 1-1/8 inch.

SDS-MAX is the "super colossal" version of SDS-Plus. SDS rotary hammers drill and pound bigger holes (up to 2") with longer bits (up to 28" or so). SDS-MAX hammers have lots of power, so not only is the hammer drilling faster, the chipping function is extremely useful. Most of these large rotary hammers, however, cannot be used as plain drills like their smaller (SDS+) cousins. They have just two "modes": "hammering with rotation" or "hammer only," and the same is true of almost all Spline Shank hammers.

Spline Shank is a bit more confusing because the drill bits for this system have a different-looking shank than the chisels. The drill bits have fins (or "splines") at the end of the shank while the chisels and other hammer tools have a hex shank with a deep indent on one side for the lock. But if the bit says "spline," it is, and it'll fit these tools.

Q: Can I fit a larger size chuck to my drill?
A: No. The design and specification of a drill motor is such that it is directly related to the maximum size of hole you can drill. Fitting a larger chuck would overload the motor and cause damage that would not be covered by any warranty.

Q: Can I fit a standard drill bit into my rotary hammer chuck?
A: Yes, but you have to use an auxiliary 3 jaw chuck adapter and you do it.

Q: Should I buy a hammer drill or a rotary hammer?
A: It depends on your job requirements. Although both tools are designed for drilling in masonry, they accomplish this in different ways. Most hammer-drills utilize a spring-loaded mechanism that requires the operator to place pressure on the bit. These bits have cutting edges that cut with light, breaking blows while they rotate. Hammer-drills are designed for small holes or medium-sized holes in soft aggregate concrete.

Rotary hammers deliver constant, heavy mechanical blows regardless of operator pressure supplied. They use a piston mechanism instead of a special clutch. And what they deliver isn't a "jab" any more -- it's a real punch. You can drill much bigger holes, much faster. Rotary hammers have such force, in fact, that the usual masonry bits are no longer adequate. Their smooth shanks would be pounded loose from the tool's chuck in a few seconds. They need special bits which can lock into the rotary hammer, and keep on spinning while smashing away.The operator simply has to provide enough force to hold the tool in place. Rotary hammers use bits that drill all masonry products and even hard aggregate concrete, granite or quartz. Also they can be outfitted with chisels for chipping masonry.

Now you see what you should buy for your job.

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Q: What is a depth rod?

A: It is a Rod mounted to the drill and lets you know when the bit reaches the desired depth.

Q: Some rotary hammers has the capability of variable speed. What is the advantage of having it?

A: Variable speed selection allows you to adjust the drill for specific jobs. Use high speed for small holes and low speed for large holes.