Core drilling--anybody do that?

dodge man · Nov 21, 2017

I also don’t get it. I’ve done some of it through work. We take cores to determine pavement thickness. Asphalt is easy, concrete takes some work. We usually take 4 inch cores. You need an electric source and a water source.

It takes about a 6000 watt generator and we usually get about 300 gallons of water in a tank. We put it all on a trailer of mine. It basically just a high quality drill rig mounted on a stand that is waist high. The water is for cooling the bit and yes the bits are diamond bits that look like a hole saw and are expensive. I think for the bit and the core drill machine are like $150 for a day.

Pilot · Nov 22, 2017

Ok, I certainly need to clarify.
The posts are attached to steel anchors, U shaped except square, not rounded. The anchors apparently have a pin going down into the concrete. I just guessed maybe 18" while sitting at the keyboard--I don't know how deep the longest one goes, but looking at similar anchors at HD, it is much less than 18". I can cut the steel with a die grinder, then the core drill will have to make a hole around the pin so we can pull it and surrounding concrete out to leave a hole. A new steel railing upright would be anchored in the hole that is left. That's the idea, anyway. Will know more when the rail guy comes and takes a look. But somehow, we need a new hole. He may be able to do the hole job.

bcp · Nov 23, 2017

You have something like these to remove?

Bruce

Egon · Nov 23, 2017

Weld onto the existing steel in the concrete.

Leave old steel in and drill new hole alongside it.

dodge man · Nov 23, 2017

Ok I get it, it’s for a deck or patio or something similar. I was thinking posts for a fence line. How thick is the concrete? If you have water nearby, a garden hose works, and a110 volt outlet, not a big deal to do it your self. My guess would be a couple of hours. You could also probably get by with a 2 or 3 inch bit.

IXLR8 · Nov 23, 2017

I just rented a core driller and bits to put some holes in my foundation to run power to my shop. Drill motor was $75/day and bits were $35/day. The motor was 110v, no issue running it on a 100' extension cord. Water was needed to cool the bit and flush out 'slurry' that was generated. The drill motor had a level on it so you stood a shot at making a level/straight hole. It took about 15 minutes to drill thru the 8" of foundation I was working on. One hole did hit a piece of rebar, that hole took about 20 min to get thru. I would call around to your local rental places and see what they have, and for how much, and do it yourself. The rental place I used had bits from 1" to 12". You could use a hand held drill motor up to a 5" bit, after that you needed the motor on a stand. If you just have a 1/2" steel stud you want to core out, I would use a 3" bit and spend 15 min per hole and DIY. I was warned that if you didn't use enough water to flush out the slurry, the core would get stuck inside the bit with little hope of getting it out without damaging the bit.

Oldpath05 · Nov 23, 2017

I looked at a bunch of youtube videos on this core drilling thing, wasn't sure what it was, with very few straight to the point on a low budget option, the nearest straight forward drilling thing looks to be the farthest away, Europe most likely, of coarse US only showed the $$$$$$$$ options. Seems like everything or everytime I look at something on youtube it's over on other side of the planet, for a low budget one man do it yourself thing-a-majig on whatever I'm doing, ok got that of my chest.
Handheld Wet Core Drilling - YouTube

MossRoad · Nov 23, 2017

Pilot said:
Ok, I certainly need to clarify.
The posts are attached to steel anchors, U shaped except square, not rounded. The anchors apparently have a pin going down into the concrete. I just guessed maybe 18" while sitting at the keyboard--I don't know how deep the longest one goes, but looking at similar anchors at HD, it is much less than 18". I can cut the steel with a die grinder, then the core drill will have to make a hole around the pin so we can pull it and surrounding concrete out to leave a hole. A new steel railing upright would be anchored in the hole that is left. That's the idea, anyway. Will know more when the rail guy comes and takes a look. But somehow, we need a new hole. He may be able to do the hole job.

Well, that certainly clears things up. :thumbsup:

KWentling · Nov 23, 2017

Oldpath05 said:
I looked at a bunch of youtube videos on this core drilling thing, wasn't sure what it was, with very few straight to the point on a low budget option, the nearest straight forward drilling thing looks to be the farthest away, Europe most likely, of coarse US only showed the $$$$$$$$ options. Seems like everything or everytime I look at something on youtube it's over on other side of the planet, for a low budget one man do it yourself thing-a-majig on whatever I'm doing, ok got that of my chest.
Handheld Wet Core Drilling - YouTube

That video is pretty good. We installed a large machine tool at work and drilled 56 3" holes 14" deep and then drilled a 12" diameter "counterbore" for the leveling jacks and anchor system. We rented the drill and bought our own bits. The drill was a drillpress, like a mag base drill only with a vacuum base. Due to the big bit we were using we Tapconed the base down. The drill worked great with the 3" bit. Was too fast a speed and underpowered for the 12" bit, but it did do the job. Got another installation coming up where we are going to drill 95 12" diameter holes 5" deep. We have a set up now using a skid steer to run a hydraulic drillpress. We'll see how that works. I can see drilling the 3" with a hand drill without a problem in your case. I would check the rental places.