SDS core drill arbor - taper fit guide drill

[David]

I bought a set from ToolSatan, all from the same manufacturer to hopefully get compatibility.

Mexco DCX90 cor drill and Mexco 250mm SDS adaptor pack.

The guide drill in the pack is a taper fit. 10mm drill.

I don't get this taper fit thing unless there is something wrong with the one I got.

By hand, I can push it in until it grips and needs the release rod thingie to make it pop out again. However although the taper is engaged through all the hole (because the bottom is just about sticking through to the release hole) it doesn't seem to grip enough to drill effectively.

When I use the core bit, then pull back, the drill bit is left in the hole.

I suspect from the markings on the shaft that it is not turning much if at all. I would expect that if it was properly engaged then I would have to use the drift to get it out.

No biggie at the moment because I am drilling a guide hole with an SDS drill bit before using the arbor and that seems to be working.

Just wondering what would happen if I didn't use an SDS bit to make a guide hole first.

Instructions just say "Insert A-taper bit into adapter". Nothing about a sharp rap on the top to get it seated or anything.

It is so long since I did any core drilling that I can't remember the fine detail from last time.

Cheers

Dave R

[Tricky Dicky]

The taper drill is only really required to start the hole, without it the c ore drill would wander about the surface. Once the pilot drill has guided the core drill and the hole is started the taper drill can be removed and t he hole completed with just the core drill. Not using the pilot drill all t he way through usually produces a neater hole on the backside with less bre akout. Having said that, I once hired a core drill to drill a large diamete r hole for a flue and the recommendation was to pre-drill a pilot hole all the way through then to use a plain guide bar supplied to guide the core al ong the pre-drilled pilot hole

Richard

[John Rumm]

The simplest solution is to pre-drill a 10mm pilot hole in the wall, then use the centre drill to get started. Once your core is a few mm into the wall you no longer need the centre drill anyway.

Yup, I often drill a 10mm pilot right through the wall just to confirm I am in the right position on both entry and exit, bit in reality you don't need it for guidance of the core.

You would drill (slowly) with the pilot, and it would stay better engaged. However still remove it once started.

[alan_m]

I once found it easier to core drill to a depth of around an inch and then remove the partially cut core and debris with a cold chisel before repeating a few more times. The pilot drill in the pilot hole was used to align the new start.