My real point is that 'SDS' is simply a name, and has no actual relationship to drill *quality* other than it specifies a certain form of chuck/drill interface.
Which is why I am unhappy that everyone says 'get an SDS' rather than 'get a Makita XYZ 5000'
It guarantees easy drilling of hard concrete, though, even with the cheapest drill. The reliability of that cheap drill isn't at issue - anymore than the reliability of a cheap hammer drill.
Hence my question, have you ever seen a drill that has an SDS "chuck", but an ordinary cam actuated hammer action? I have not personally.
Hence why I was quering the pedantry of highlighting that "SDS" really only applies to the bit holding design and not the hammer action. You and I know this, but the vast majority of people associate "a SDS drill" with the high performance hammer action, based on the fact that the only SDS drills they ever see have said hammer action. So when someone says "you need a SDS drill" it is pretty obvious what they mean.
My mate has a Kango rotary hammer (about the size of todays 6kg SDS drills) with a pneumatic hammer action. The drill does not have a chuck at all and instead takes morse taper masonry bits.
Sorry to rain on your parade - but my SDS drill (a Bosch GBH 2-24 DFR,
1999 vintage) has a purely mechanical hammer action - and it really has some clout.
(I know this for certain, as after 7 or so years usage the hammer action switch became faulty and I had to dismantle and fix the thing last week, see:
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I believe the key difference between the effectiveness of SDS over non-SDS is that the hammer acts directly on the back of the drill bit and not via the chuck, eliminating extra mass and the small shock absorbing action of conventional chuck jaws.
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But in the case when I last said it, I actually meant "get an SDS drill" 'cos as far as I'm aware all currently available SDS drills are of the pneumatic impact sort - which is the feature I was pushing for that particular problem.
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That and you can hit it a hell of a lot harder. I've used many rotary impact drills over the years and none of them have come close to the effectiveness of even a lowly SDS (pneumatic for the pedants) drill.
IIUC the hammer action in the GBH 2-34 is much the same as that in my Makita HR2450 i.e. it does have an enhanced hammer action... (i.e. the hammer is not achived by a large washer with a sawtooth profile on it mounted behind the chuck).
Some SDS drills get their powerful hammer from a small air driven piston, and some (like ours) use an oscilating weight to thump the end of the bit.
That does make a big difference certainly, hoewever it is not only that. The fact that there actually *is* a real hammer action makes most of the difference. In a standard percussion drill, the hammer action comes from your own "push" being temporarily interrupted by the interaction of the teeth on the fixed rotating cam washers stepping over each other. This why it is difficult to do roto stop on a conventional hammer, since the hammer requires the rotation of the chuck to work.
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The SDS drill I have uses a crank driven piston to push a second free-flying piston into the back of the drill bit. That's pneumatic by most people's standards, I think.
There's a piston that moves back and forth, and air couples this to a moving bit of metal that gives the hammering action. ISTR Hilti had the patent, which expired a while ago; hence the fall in price in hammer drills. Used to be "Hilti" was what SDS is now.
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