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Just bought this hammer drill to drill in very hard concrete, which it was unable to do. What surprises me is that I feel absolutely no difference (vibration while holding it, sound it makes, drilling efficiency) between when I set the hammer function or the drilling function.

The switch to select between hammer and normal drilling is clumsy though.

Question: is it the case that hammer and drilling function should always feel obviously different when using it?

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My hammer drill sounds and feels exactly like a normal drill except when pressing the end (where the bit goes) into something. Take out the bit, press it into your palm, and pull the trigger. Is it still identical? –  Ghost Nov 5 '13 at 22:45
    
Oh and as far as not being able to drill into the concrete, did you use a masonry bit? –  Ghost Nov 5 '13 at 22:46
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On all the hammer drills I've ever used, the hammer clutch is only engaged while pushing the bit into material. You can definitely feel and hear the hammer action and it is quite different from being set to "drill only". –  gregmac Nov 5 '13 at 22:53
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Some hammer drill are combination hammer and conventional twist. Verify that the switch is set to hammer if it so equipped. –  mikes Nov 6 '13 at 1:34
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@SpectralGhost Your comments are answering the question - you would do well to turn your comments into an actual answer. –  The Evil Greebo Nov 6 '13 at 9:39

2 Answers 2

up vote 2 down vote accepted

Combination Drill Motors

In most combination drill motors, the hammer mechanism works similarly to this.

enter image description here

In this case, the lower jagged bit is fixed, and the upper portion rotates with the shaft. As the shaft rotates, the two plates slide against each other. The jagged edges cause the upper portion to tension a spring, storing potential energy. As they slide further, the energy in the spring is released, and the weighted shaft is driven forward (down in this illustration). This allows the tool to deliver many beats per minute, but reduces the force delivered in each beat.

This system allows the hammer mechanism to take up less space, but the limited hammer travel and weight, reduce the force delivered to the shaft. Which is why a combination drill motor will likely never fully replace hammer drills.

Hammer Drills

In a hammer drill, the hammer mechanism is almost always separate from the rotation mechanism. This allows the weight; or hammer, to be driven independently of the rotating shaft. As the shaft rotates, the weight will be driven into the end of the shaft, producing a linear force along the shaft.

This system will produce less beats per minute than a combination device, but will exert much more force per beat.

Feel the Beat

Because the hammer mechanism in a combination drill motor may have a very high frequency (beats per minute), and lower force per beat, the hammering action may be less noticeable. You'll also find that while the drill is spinning freely (not pressed against a surface), the hammer action is not engaged at all.

So to answer your question directly. Yes, it is possible to not really notice a difference between the hammer and non-hammer settings when using a combination drill motor. However, if you can't feel the hammering, the surface you're drilling probably won't either. Not all hammer mechanisms are created equal. Higher quality tools will almost always, have higher quality hammering mechanisms.

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For drilling over 1/4" dia and deeper than 1/2", you may need to upgrade to a rotary hammer. The SDS and SDS plus grades are much more capable. Some areas can rent them. –  HerrBag Dec 23 '13 at 15:56

My hammer drill sounds and feels exactly like a normal drill except when pressing the end (where the bit goes) into something. Take out the bit, press it into your palm, and pull the trigger. You should be able to notice a difference.

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Thanks so much for this answer! I was just about to return my new cordless hammer drill because it didn't appear to be hammering, but pressing it into my palm indeed made it work. –  glibdud Jun 28 at 16:45

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