possible to core concrete with a two-handed hammer drill instead of a coring rig?
hi folks, i’d like to wet-drill some holes into concrete for drainage and planting. i’ve used a diamond circular saw blade on this concrete, and i’ve used hole saws on wood, but never a diamond coring bit. i want to drill ten or twenty 4-1/2″ holes with accuracy better than 1/4″, and spending $100 on a coring bit sounds more economical than hiring out the job.
i have a two-handed 15A hammer drill which i think could accommodate a core bit adapter (why do those cost $20?!). my question is, with no arbor or center bit, and no specialized coring rig, would i even be able to drop the drill towards the ground and start the bit in the spot i want, or will it wander crazily? in other words, is the coring rig essential for incidental, amateur core drilling?
Replies
I think the main problem you'd encounter is that it will take 5-10 minutes per hole, and your arms will get pretty tired holding the drill perfectly still for that length of time. Plus your hands will not be free to water the bit, brush/wash away dust, etc.
Where do you get a 4-1/2 diamond core bit for $100?
Diamond core bits work by grinding away the concrete, and need a flow of water to cool the bit, and flush away the slurry. Hammer action will destroy the bit. The bit needs to be held steady or it will bind on the core. Hand holding a diamond bit of this size is an invitation to injury.
Rent a proper core rig if you need holes bigger than 4".
4" and small can be done with a SDS-Max rotary hammer and the correct carbide core bit. These usually have a pilot bit, are easy to use, and are used dry.
Bosch has core bits up to 4" or so for a regular SDS rotary hammer. I have never used one at that size, so cannot say how well they work.
Hammer drill will not be effective at those sizes, a rotary hammer is required.
Check out you local rental shop for the proper equipment.
thank you, folks. i will rent the proper rig instead of attempting this by hand.
It would be interesting to have someone (such as yourself) try it, and report on how it went.
4"
I've done 4", but only a half-dozen holes.
Hand held, non-hammer. My "pilot hole" was a piece of 3/4" plywood with a hole the size of the coring bit. Set the ply where I wanted it, stood on it, and the hole in the ply kept the bit from wandering as it started into the concrete. Once the bit had purchase, I'd pull the ply.
Had a garden hose on trickle.
Drill 6 or 8 3/4" holes at
Drill 6 or 8 3/4" holes at about 6 in dia, bust out slug with sledge. (Assumes you already have bulldog or similar and bits and can swing a sledge accurately enough to hit a 6 inch circle !)
Finish edges back down to 4-1/2" with small form and portland cement mortar or pea gravel concrete, use coloring in filler for good effect.
option: 7" HF $15 diamond blade in sidewinder with garden hose watering, cut square holes.