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I've seen two drills - one 600W the other 700W. Both 0-3000 rpm. But for 600W some guy said it can't make it with concrete, while for 700W reviews say that it does it. Both are hammer drills. I'm not mentioning models as the site isn't about product recommendation and anyway I want to learn how to choose them.

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    This is generally not a site for product recommendations. But if you provide the two model #s then someone might be able to explain the differences between them. Commented Dec 1, 2019 at 16:57
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    @manassehkatz-Reinstate Monica but I said "I'm not mentioning models as the site isn't about product recommendation".
    – R S
    Commented Dec 1, 2019 at 17:02
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    I know what you said. I am just saying that if you provide 2 specific examples then we can look at them and say "Oh yeah, the 700W has 'xyz feature' that the 500W doesn't, that's what you need to look for" or "No real difference except power, the salesman was just trying to upsell" or possibly something else. Without that, someone (not me - I don't know enough about hammer drills) can give you some general guidelines which may or may not explain why someone said the 500W wasn't a good choice. Commented Dec 1, 2019 at 17:06
  • Check SiHa's answer below, it may have a better detailed answer than mine.... I believe answered votes can be changed.
    – Jack
    Commented Dec 2, 2019 at 5:24
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    I'll add that so much of this sort of decision depends on how much drilling you plan to do. If you have just one hole to drill, then even a low-end homeowner-type drill will eventually drill it. If you have a lot to drill or plan on doing this regularly, get a higher-end or even professional level tool. You might also consider renting if you just have a project to complete.
    – jwh20
    Commented Dec 2, 2019 at 14:51

2 Answers 2

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More important than the power rating is the type of hammer drill. This is a very useful link which explains the full difference between a 'Hammer Drill' and a 'Rotary Hammer'.

The former achieves the hammer action by spinning a bumpy disk against the end of the driveshaft of the chuck, which makes is vibrate a bit. These are OK for soft brick, but not much else. If you hit a piece of flint in some concrete, it will just stop, or cause the drill to wander into a softer area.

If you're going to be drilling concrete, you'd be much better off with the latter type. This uses a piston which hammers directly onto the rear of the drill bit, which slides in the chuck (this is also commonly referred to as 'SDS', for the type of chuck).

When comparing this type of drill you will usually find that, as well as power rating, they have the impact energy in kJ (kiloJoules) quoted. Obviously bigger is better. Most can also have the chuck locked so that it can also be used for chiselling, tile removing etc.

IMO - if you are going to be drilling concrete, you would be well advised to pick an SDS drill. You won't regret it.

P.S. As noted in the comments: Both are routinely described as "Hammer Drills". The distinguishing feature of the better type is the SDS chuck.

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    I always thought the terms were interchangeable and some were made better than the others, not realizing there a substantial difference in how they are made. (I should have known better, but I never researched it.) I just went with name brands that always performed, after I used other "rotary hammer drills" that did not do what I needed.
    – Jack
    Commented Dec 1, 2019 at 22:17
  • Note that there are as well hammer drills with SDS.
    – glglgl
    Commented Dec 2, 2019 at 9:50
  • @glglgl - they are the same thing though, I think. The important feature of the SDS chuck is the fact that the bit slides, and it is hit from the rear, rather than thew whole chuck moving with each impact.
    – SiHa
    Commented Dec 2, 2019 at 10:43
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The only way I would go by sorting this out nowadays if I was new to this sort of stuff, is reading reviews.

With my experience I have owned a number of hammer drills which should go through concrete but didn't. I find that these types of tools are investments and quality is key.

To try to answer in my non technical fashion, more wattage, more power to transfer rotational force into impact force. If the impact isn't strong enough, the drill will not go through the toughest concrete, as I have experienced.

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