My first experience with one of these has not turned out well. Granted
it was a cheap one from Toolstation, but the core itself is not
concentric with the Guide drill, nor with the arbour. So I can't get
it stated.

Is this usual for these things?

It appears to be a fault to me, and I'm waiting to see what Toolstation
say, but it's wise to be prepared. Trouble is I bought it two months
ago, before I got the flu, and have only just got round to using it.

R.

TheOldFellow brought next idea :
My first experience with one of these has not turned out well. Granted
it was a cheap one from Toolstation, but the core itself is not
concentric with the Guide drill, nor with the arbour. So I can't get
it stated.

Is this usual for these things?

Yes, probably a manufacturing defect - if you are certain it is
correctly assembled?

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Blue Spot from Amazon UK are fine.

The core itself should be cylindrical with the threaded boss in the
centre - if not it has been damaged (oval) most likely by dropping.
The arbor likewise should be concentric with the drill shaft & core.
Otherwise the core will turn in a precession making cutting much
slower and getting started even with a guide drill very difficult
indeed :-)

If your drill is a chuck (vs SDS), remove it from the drill and turn
it 120-degrees, check again, then repeat if necessary. Sometimes the
chuck does not take to the arbor "hex" and if pushed too far into the
drill the chuck will not self-centre.

Also verify the guide-drill which is often a "spike fit" is in fact
central, they can become canted in the arbor requiring a few whacks on
the drift to get it out and relocated. You must use a guide drill if
the drill is of any size.


A new sintered diamond core can be glazed, which makes starting the
first time doubly difficult. This can be solved by turning it manually
with the guide-drill in place or running on an old paving slab slowly.
The variation in cheap diamond core drills is usually the amount of
diamond and its even distribution (or lack of) through the sintered
tabs. That said, cheap bits work fine - it is only the really tough
materials that need "proper bits" otherwise you will see nothing but
sparks and take many hours.

On Wed, 18 Nov 2009 10:12:26 -0800 (PST)
"js.b1" wrote:

Blue Spot from Amazon UK are fine.

The core itself should be cylindrical with the threaded boss in the
centre - if not it has been damaged (oval) most likely by dropping.
The arbor likewise should be concentric with the drill shaft & core.
Otherwise the core will turn in a precession making cutting much
slower and getting started even with a guide drill very difficult
indeed :-)

Rolling the SDS+ arbour with the spike fit guide drill in it on the
bench shows them to be concentric when assembled, but add the core drill
and that is clearly not so. There isn't really any other way to assemble
them.

Toolstation have agreed to refund or replace - we are now discussing
which, since I need a core drill - but since my delivery they dropped
this (Silverline) one, so it will have to be one of their others. Their
Customer Service is very good.

R.

On Nov 18, 7:12*pm, TheOldFellow wrote:
add the core drill and that is clearly not so.

Unfortunate.

Toolstation have agreed to refund or replace - we are now discussing
which, since I need a core drill - but since my delivery they dropped
this (Silverline) one, so it will have to be one of their others. *Their
Customer Service is very good.

Indeed - better store than Screwfix.