On 14/08/2020 21:07, Jeff Layman wrote:
On 14/08/2020 15:43, John Rumm wrote:
On 14/08/2020 13:36, Jeff Layman wrote:
On 14/08/2020 12:22, williamwright wrote:
On 13/08/2020 20:17, Dave Liquorice wrote:

The OP says he changed drilling machine but not if he used and
kanckered an 6 mm SDS bit or used the same Bosch drill in an ordinary
chuck fitted to the SDS machine. Not that you are suposed to use SDS
in hammer mode with such a chuck fitted.


The mass of the chuck inhibits the percussive action. The bit slips. It
just doesn't work.

Not sure about that.

As far as I could see, the chuck was rotating and I could hear and feel
the hammer action. Out of interest, I weighed the chuck - it was 390g.
Add around 30g for the 6mm bit and it comes to 420g. The biggest SDS bit
I have is 22mm in diameter (200 - 250mm long?); it weighs 340g. I can't
see that the 90g would make enough difference to affect the
percussive/rotating action. Bigger SDS bits (25/30mm x 450mm) would
weigh far in excess of the chuck weight, but they would work.

If its like the add on chuck I have, then the pattern of slots on the
shank stop it seating far enough back in the SDS mechanism for the
hammer to hit it. So in hammer mode, you would still feel the vibration
from the anvil flipping back and fourth in the drill, but it would not
be striking the chuck. (and the sound is different, since there is no
metallic "clack" as the shank is struck).

I'll check tomorrow and compare shank patterns.

Having said that, if yours works different to mine and does hammer with
the chuck in, you may have a second problem, since a normal drill bit is
not designed for = 2 Joules of hammer energy per blow - so you might
just shatter the carbide off the end anyway!

I hadn't considered that. Is the tip of an SDS drill bit of
different/heavier construction than an ordinary masonry bit?

Yup, and the fluting on the shank different at well to clear waste
faster. Some bits are two flute, and some are four. In some respects,
SDS bits are more akin to a rawl tool style design - designed such that
the masonry is pulverised by the high impact energy, and the rotation is
basically there to clear the waste, and move to the next are to be hit.
Its all about the hammer rather than the drilling.


--
Cheers,

John.

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