Concrete Drilling in concrete using a core drill bit with no pilot drill.
Over the years this question comes around – How do I start concrete drilling without a pilot drill?
Now most of you guys know the answer, however it is a very reasonable question as all timber hole saws have a pilot drill, the dry core drills have the option for a pilot drill, so why not a wet core drill?
Firstly, most wet drills are around 400mm long and upwards so to have a pilot drill that size would be expensive and would be something that could break being that long. Now when using a rig mounted concrete core drill it is very easy to get started – just be patient when starting and go very slowly. The machine is held down either by a vacuum pump or bolted down so this will eliminate the core drill bit from trying to ‘skate’ away.
Using a hand held core drilling machine is a different story though. Basically, you need a template. Now the template will help you to get the drilling process started, then can be removed once sufficient depth of the core drill bit has been achieved to stop the barrel from ‘skating’ away from you. Approximately 5 to 10mm deep is usually sufficient.
A template could be as simple as a piece of 10mm plywood drilled to the required diameter of the core barrel being used. The template can be stood on and the drilling process started. A tip when doing this is to start on a slight angle then bring up to plumb. It is easier drilling on an edge to get started than with the whole diameter flush on the surface. Another option is to have a right angle made from timber, this will also allow the core bit to rest on the edge in the corner and on a slight angle to get started.
See pictures below of different templates.