Hello Friends,
I have to punch a couple of 4-inch diameter holes through a 24-inch thick limestone foundation and I’m looking for a tool recommendation. I own a Kango 950 rotary hammer, but can’t find a coring bit that makes sense to use in this application. All the ones I can find are just 3 or 4 inches long.
Does anyone know of a source for longer coring bits (say 12-inches long) to fit this machine? Do I need to rent something else? What’s the best tool to use?
Thanks for your help!
Steve
Replies
short answer is that I don't know, but it strikes me that this is a lot of thickness to go through with a 4" diameter hole. You may consider the option of hiring a concrete cutting specialist to do this job.
Check with your local tool rental stores. The ones around here have 2' long diamond core bits in 4". You pay for the time held and the amount of diamond worn off the bits. Being limestone I would think that these bits would wear slowly and work quickly.
The alternative is use the 4" long bits and break off the core regularly. After a while you would need to attach an extension to meet the bottom. It is more trouble but with only a few holes to bore it might be the way to go. You might core drill and them pulverize the center with a digging bar or such once the hole gets too deep to effectively break it off. The bits and dust can be removed with a wet/dry vac so you don't have to work through them.
To 4lorn1 and Steve. I've used the diamond hole saws. They cut though like a hot knife through butter. Although they are expensive compared to the conventional bits, the time saved more than makes up for it.
While on vacation this past summer, I ended up having to rent a 12" long 4" diameter coring bit. Worked like a champ...though the rental for the bit itself was $80 for the day.
It sounds like the right tool for this job.
I gotta ask - What kind of vacation does one take where he needs to rent a 12" long 4"" dia. coring bit?
Funny...my wife and kids were asking me the same thing.<g>
When I moved to CT, I held on to my lake house back in Wisco. We were there this past summer when the retired neighbor's well went out. The well cap was 8" thick cast concrete, and cast right around the black pipe and conduit for electrical.
He had bids in the range of something like $4800 and up to r&r the cap and replace everything hung inside the well.
I took a day and did it for parts for a little under $800.
Sadly, he's getting priced off the waterfront due to escalating property taxes. He's making me think hard about buying his property.
Another approach, if the 4" holes don't have to be perfectly round, is to draw a ~4" circle on each side of the wall. Using a 12" [or longer] long 1/4" drill a series of closely spaced holes around this circumference. Then procede to enlarge these holes to 3/8" and then to 1/2". By this point, you should have little web left and you can bust the core out with appropriate means - such as a .50 caliber machine gun.
-Peter
What is faster than light? Gravity. Think about it.
Once again , the right tool for the job is explosives. Drill a small hole, pack in the appropriate amount and type of ka-boom, light the fuse and come back when the dust clears.
all of you who replied with experience - is it with a stone wall or with concrete?
there is no comparison at all, none of your concrete experience will prepare you for the trials of making a small hole in a two foot thick stone wall.
yes you can cut stone, but it is so much harder than concrete that most of the time you'll be MUCH more productive by cutting out the stones by removing the mortar with an air hammer/chisel to create one big hole for all the conduits to run thru, then replace the stones with new mortar when you're done. A hole around 1 ~ 2 feet across will likely be the smallest hole you'll be able to make.
It is not clean, or pretty, and will never be anything like cutting a circular hole thru a concrete wall, but then that's what rustic charm is all about!
Just curious - is limestone really harder than concrete?
Pete
in my experience, real stone is super, super hard.
concrete is a very versatile material, but not as hard.
Take a hammer and a chisel and chip out a small hole in some concrete somewhere, then try to do the same thing to one of your stones and see how much slower it goes, with most types of stone.
Now, limestone comes in many flavors, but the ones they used to make a foundation are (hopefully) one of the harder, longer wearing ones.
Granite, that's even harder. It is AMAZING how hard that stuff is to chip away with ordinary concrete working tools.
Remember that stones are made deep in the earth, under untold tons of pressure and heat and all the time in the world. Concrete, on the other hand, is just as strong and fast to cure as needed, with just the right amount of margin for safety. Part of what makes concrete such a great building material is how (comparitively) easy it is to cut and shape after curing.
The easiest way thru a stone wall is to chip away the soft morter (which is softer than concrete, by the way) and remove the stones.
I'm curious as too why you would need 2-4" holes. Sounds to me like a high efficient furnace install, and they need a intake and exhaust...at which point I would buy the concentric kit, and do both through the same hole.
And I have a BS in Geology too, so yes Limestone can be very hard, and very soft, and anywhere in between. But a daimond bit will knock the pee out of it no matter what hardness it is.
In the quarry they use air powered rock drills to drill the holes for dynamite charges. Go to any construction equipment rental store and rent a 195 cfm air compressor and a rock drill. It will take two people to hold it until you get the hole started. If you can tie it off over head you will be much better off. They have replaceable bits that are fairly inexpensive. Buy 6 and take back what you don't use. rock drills are in the same section with jack hammers and rent for the same amount. You probably need a two inch ball to pull the air compressor. A rock drill makes a rounded entry hole and typically fractures the back of the wall upon exit taking out a huge chunk when it comes through. If this were in concrete with rebar you wouldn't have to be necessarily concerned about the bars. The drill will punch through them but it does dull the bits a bit quicker. If you are drilling horizontally it is a dusty, heavy job exactly like using a jack hammer sideways. If appearance or precise alignment is important this not what you want, but if a couple of holes is what you are after, this will do it. Close your eyes and think about what a miners life is like.