Hard concrete/SDS U/s

[Sidney Endon-Lee]

Just to resurrect an old thread (sorry about the new posting), but the drill that was 'full of sound and fury, signifying nothing' now drills holes in concrete nicely.

The solution turned out to be an idiosyncratic chuck mechanism - an ignorant user rather than a definite bad tool.

In all the other SDS drills I've used, you simply insert the bit as far as it will go, then twist until it 'clicks', and you are good to go.

In this drill, if you do this, it won't work properly.

What you actually have to do is insert bit as far as it will go. Pull on bottom of rubberised chuck, which splits circumferentially, allowing the bit to be inserted further, let go of chuck, which springs back and locks onto bit, which now cannot be pulled out - to release, you have to pull on the bottom of the chuck again.

The above was a mechanism I'd never come across before.

Regards,

Sid

[Andrew Gabriel]

On my metabo, you just push the bit in. You have to turn the nose of the chuck 1/4 turn against a spring to unlock and remove it.

What would have been nice when I first bought it is if the alternate conventional chuck could have used hammer mode too so I could still use my older hammer bits, but it explicity doesn't engage with the drill's hammer output.

[Toby]

I think that is so you dont destroy the weaker bits, as the SDS will probide proper hammer action, rather than just vibrate the bit, like a traditional "hammer drill" does!

[Dave Plowman (News)]

If that worked, there'd have been no need to invent the SDS system?

[Dave Plowman (News)]

That's the same as all the SDS drills I've used. Only SDS mechanism I have which involves rotating anything is my Bosch SDS jigsaw.

[The Natural Philosopher]

Arguably, there never was..

[Dave Plowman (News)]

Isn't it essential to the operation of an 'SDS' drill? No slip as with a friction chuck.

[The Medway Handyman]

Makita & Green Bosch you push & turn to insert, pull back collar to remove. On a Wickes/Kress you had to pull back the collar to insert & remove.

Would the hammer action not knock seven bells out of a normal chuck?

[The Medway Handyman]

No slip plus free forward & back motion.

[Sidney Endon-Lee]

=A0 London SW

We've used different manufacturer's drills then. I've used multiple DeWalt models and several other other brands which I don't remember used by a geological survey company for taking rock samples, which seemed big enough to bore new tube tunnels (and had the battery packs to match, as they were battery powered for use in the field).

I wonder why there's apparently no standard way of fixing SDS bits to SDS drills?

Regards,

Sid

[Sidney Endon-Lee]

=A0 =A0 London SW

Hmmm. The SDS system was invented by the Robert Bosch company, and SDS originally stood for "Steck-Dreh-Sitz", which rendered in English is "Insert-Twist-'Set Fast'" Possibly Bosch has/had a patent on the original SDS chuck design, forcing other manufacturers to do things in a different way?

There is an American patent , but the date on it is nine years after the invention of the SDS system, so it may not be relevant.

Regards,

Sid.

[The Natural Philosopher]

no. I have a perfectly reasonable non SDS hammer dill.

[Dave Plowman (News)]

No such thing - unless you've either got very soft stone or haven't tried an SDS.

[The Natural Philosopher]

believe what you like. SDS is merely a method to hold the drill bit in.

It has no implications beyond convention of being associated with a hammer action.

[Dave Plowman (News)]

So you haven't tried an SDS?

[The Medway Handyman]

The hammer action on an SDS is of an entirely different magnitude. Also, how would the bit achieve the required in & out motion?

[The Medway Handyman]

In common parlance SDS holds the bit firmly against rotational force & also allows a large degree of in/out movement. With what is commonly known as a 'hammer drill' the chuck itself moves back & forth by a very small amount driven by a very small force.

[John Rumm]

Yup, the removal of the requirement for the chuck to move allows massively more impact energy to be transmitted to the bit, as well as not incurring a large increase in vibration of the machine.

[John Rumm]

Not quite sure if you are being obtuse, in the sense that technically "SDS" is used to describe a number of twist and lock mechanisms (for example the blade retention on some jigsaws is also described as SDS), or whether you have never actually used what is colloquially known as a "SDS drill". The latter would simply not function as well with a chuck.

[John Rumm]

well me to, but it does not do what the SDS does by any stretch of the imagination.

Might be fun to work out the difference....

Lets say the conventional hammer drill weighs 2kg, and one is leaning on it with 10kg of push (i.e. 100N). The notched cam arrangement of most hammer drills allows no more than say 1mm of travel per blow, and might have say 20 notches per rotation. Rotation speed lets say is 2400 RPM.

So the hammer effect comes from the users push accelerating the body of the drill forward after the peak of the cam has extended the drill to the maximum length.

f = ma, so a = f/m

a = 100/2 = 50 m/s^2

So over the hammer travel depth, that should accelerate the drill body to a terminal velocity of:

v^2 = u^2 + 2as

v^2 = 0 + 2 x 50 x 0.001 = 0.1

v = sqrt(0.1) = 0.32 m/s

impact energy available from 2kg moving at 0.32 m/s

= 0.5 m v^2

= 0.5 x 2 x 0.32^2 = 0.1 J

Total energy delivered per minute = 2400 x 20 x 0.1 = 4.8 kJ/min

Now try a SDS with 2.7J per blow and 4500 blows per min, you get a total energy delivery of 12.1 kJ/min

So not quite an order of magnitude, but certainly two to three times the impact energy delivery based on those numbers.

(real life experience would suggest a bigger difference - so perhaps there is a error in the assumptions or numbers, or perhaps the SDS drill bit gives a more effective drilling performance?)