# Can someone help with the correct method to cut a boulder in half? **URL:** \ **Category:** Factual Questions\ **Created:** [April 30, 2003, 5:45pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198 "2003-04-30T17:45:48Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [April 30, 2003, 5:45pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/1 "2003-04-30T17:45:48Z")
Ok, well they’re not exactly boulders just large rocks maybe 1 to 2 feet in diameter. I am constructing a rock wall this summer with my wife and I need to know what tools to buy to be able to split and shape large stones for making a rock wall, and stone feature in my back yard. I am using the stones that are riddled around my property. I need to be able to cut and shape them. I already have: A John Deer Bckhoe 400D. 20 Pound Sledge. Plenty of chisels And a tool shed full of “normal tool shed tools” Any masons out there? ---
**Author:** ![Kalhoun](https://avatars.discourse-cdn.com/v4/letter/k/3bc359/32.png) [@Kalhoun](https://boards.straightdope.com/u/Kalhoun)\ **Post date:** [April 30, 2003, 6:33pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/2 "2003-04-30T18:33:15Z")
I wonder if some sort of super drill bit would be helpful. I have a stone wall and stone fireplace made from rocks on our property, but we didn’t make it ourselves. It’s the coolest part of our house. You will definitely love it when you’re done. ---
**Author:** ![Slithy\_Tove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slithy_tove/32/18248_2.png) [@Slithy\_Tove](https://boards.straightdope.com/u/Slithy_Tove)\ **Post date:** [April 30, 2003, 6:44pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/3 "2003-04-30T18:44:50Z")
An ancient quarrying technique was to drill a line of holes where you wanted the break, then insert porous wooden doweling. These were kept wet until they expanded and split the rock. Of course, this was used for sheer slabs, not boulders, so your results would be less predictable. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [April 30, 2003, 7:18pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/4 "2003-04-30T19:18:43Z")
Feathers & Wedges Feathers are “L” shaped pieces of metal and wedges are… well, wedges. A line of holes are drilled along the desired split line. The feathers are dropped in perpendicular to the split line. The wedges are then inserted and tapped into place. After all are in place, start at one end and tap each a little further in. Keep going back and forth on the line until the rock splits. Here’s a source [http://www.granitecitytool.com/showitem.cfm?itemnum=48&catnum=0](http://www.granitecitytool.com/showitem.cfm?itemnum=48&catnum=0) Learned this from watching “This Old House”. ---
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [April 30, 2003, 7:40pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/5 "2003-04-30T19:40:09Z")
Thanks **Gary** I’ll go down to Home Depot when my wife gets home and maybe we can pick some of those up. Living in Connecticut lends us the lucky task of finding and excavating all the Rocks in a certain area of our property. My house is a modern Log home, so it’s not really a log home, but kinds looks like one. It has a half A-Frame in the front with two side sections off it. The main living area has a large fire place. And like **Kalhoun** it looks really neat. I am building a rock wall off my porch and then I am putting in a Chat pit with a fire place. **Chat Pit** - is a circular stone structure sunken in the ground four layers. So you walk down four large steps to a sitting area, with a circular fireplace in the middle. Very fun for outdoor summer parties, the bugs hat it when a fire is roaring because everything is warm… So that is my task. My wife and I are psyched, I borrowed my father-in-law’s backhoe for the summer. That will allow us to have a small crane type thing for the larger rocks and allow us to really dig in for those hard to reach stones. I’ll post pics when I’m done. So anyone else know other methods asides from the one **Gary** said? ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [April 30, 2003, 8:09pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/6 "2003-04-30T20:09:16Z")
I’d be suprised if Home Depot had the tools. And you’ll also need a Rotary Hammer to drill the holes. I’m a Bosch fan myself. I have a Bosch 7/8" SDS Rotary Hammer, not a hammer drill, and it really drills concrete and rock. I have one like this [http://www.boschtools.com/Tools+and+Accessories/Tools/prod\_detail.htm?item\_no=11224VSR](http://www.boschtools.com/Tools+and+Accessories/Tools/prod_detail.htm?item_no=11224VSR) You want to just keep tapping the wedges in a little at a time. On This Old House, they were splitting steps off of a slab that was about 3 ft. long and about 10" thick. IIRC they used about 6 or 7 sets of feathers and wedges. ---
**Author:** ![T.Slothrop](https://avatars.discourse-cdn.com/v4/letter/t/3e96dc/32.png) [@T.Slothrop](https://boards.straightdope.com/u/T.Slothrop)\ **Post date:** [April 30, 2003, 8:17pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/7 "2003-04-30T20:17:30Z")
> [@](#): > > Feathers are “L” shaped pieces of metal and wedges are… well, wedges. > A line of holes are drilled along the desired split line. The feathers are dropped in perpendicular to the split line. The wedges are then inserted and tapped into place. After all are in place, start at one end and tap each a little further in. Keep going back and forth on the line until the rock splits. I spent a summer doing this to blue basalt that was hard as, well, rock. We called it “planting the iron flower.” I recommend pulling the drill bit out of the hole frequently so it doesn’t get stuck. ---
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [April 30, 2003, 8:30pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/8 "2003-04-30T20:30:43Z")
Oh Geez, I completely forgot about the drill. :smack: **Gary** - Can I rent a drill similar to yours? If not, I am wondering if it wouldn’t be a good asset to my power-tools? I bet it would. If not home depot where should I get them? we are not starting the project until we get the stones closer to our target location. This weekend I 'm going to show Mrs.Phlosphr how to operate the backhoe and then we should get a lot done. **T. Slothrop** thanks for the Tip. I hope you got paid well that summer. ---
**Author:** ![NurseCarmen](https://avatars.discourse-cdn.com/v4/letter/n/5daacb/32.png) [@NurseCarmen](https://boards.straightdope.com/u/NurseCarmen)\ **Post date:** [April 30, 2003, 8:37pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/9 "2003-04-30T20:37:05Z")
You should be able to rent a rotary hammer drill just about anywhere that rents equipment. Remember, the drill is only as good as the bit. Depending on the stone, you will be flying through bits. The nice thing about Home Depot, is they don’t mind if you buy too many and return the unused ones. So estimate how many bits you’ll need, double it, and add ten. 🙂 ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [April 30, 2003, 8:39pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/10 "2003-04-30T20:39:04Z")
Maaaauuuuud-dib! ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [April 30, 2003, 8:43pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/11 "2003-04-30T20:43:25Z")
Personally, I’d go with primacord. Hey, can _you_ think of a more fun way to split rocks? ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [April 30, 2003, 8:46pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/12 "2003-04-30T20:46:05Z")
> [@](#): > > \*Originally posted by T. Slothrop \* > \*\*I spent a summer doing this to blue basalt that was hard as, well, rock. We called it “planting the iron flower.” I recommend pulling the drill bit out of the hole frequently so it doesn’t get stuck. \*\* An air compressor, buy one of those too, is handy to blow the chips and dust out of the hole. Be sure to wear goggles and perhaps a dust mask when drilling and clearing the chips. You might have to buy the parts fore the “iron flower” off the web. If your area does a lot of stone work, you might be able to get them locally. Check the yellow pages for stone work or stone cutting. A worker in the area might be able to tell you where to get them. ---
**Author:** ![Sock\_Munkey](https://avatars.discourse-cdn.com/v4/letter/s/aeb1de/32.png) [@Sock\_Munkey](https://boards.straightdope.com/u/Sock_Munkey)\ **Post date:** [April 30, 2003, 8:49pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/13 "2003-04-30T20:49:59Z")
> [@](#): > > \*Originally posted by Padeye \* > \*\*Maaaauuuuud-dib! \*\* Heh, good one. 😃 One thing to keep in mind is that some stones have natural lines of cleavage where they will split easier than if you just pound away at any spot. ---
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [April 30, 2003, 9:02pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/14 "2003-04-30T21:02:30Z")
I’ll be splitt’in mostly igneous glacial granite. So, **NurseCarmen** I’ll be going through quite a few bits. I will of course wear proper eye gear as will Mrs.Phlosphr. I’ll ask the guy at Home Depot about the proper number of bits needed. We are talking about several hundred stones, and a _summer long_ project. We’ll do most of the splitting first. and then we just have to lay the stone. I’m hoping that’ll be the easy part. ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [April 30, 2003, 9:26pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/15 "2003-04-30T21:26:22Z")
I notice from the site posted above that there are hydraulic splitters available. If we’re talking several hundred stones, I’d suggest trying to rent one of those bad boys for a weekend. Because drilling several hundred holes in solid granite sounds like No Fun to me. Big diamond-tipped saw blades might also come in useful. ---
**Author:** ![trabi](https://avatars.discourse-cdn.com/v4/letter/t/ecae2f/32.png) [@trabi](https://boards.straightdope.com/u/trabi)\ **Post date:** [April 30, 2003, 9:38pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/16 "2003-04-30T21:38:14Z")
Why not get a stone mason to do it for you? If he’s the real McCoy he’ll study the stone for a few minutes and then tap it lightly with a hammer in just the right place, and it will miraculously fall into two halves. A joy to watch… ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [April 30, 2003, 9:45pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/17 "2003-04-30T21:45:44Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > \*\*Personally, I’d go with primacord. Hey, can _you_ think of a more fun way to split rocks? \*\* They want to split them. Not pulverize and distribute at the same time. It does sound like fun though. I’ll bet you could charge admission! ---
**Author:** ![herman\_and\_bill](https://avatars.discourse-cdn.com/v4/letter/h/f1d935/32.png) [@herman\_and\_bill](https://boards.straightdope.com/u/herman_and_bill)\ **Post date:** [April 30, 2003, 11:00pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/18 "2003-04-30T23:00:09Z")
Why not just rent a jack-hammer? there are electric powered ones and it would work better than a hammer drill, and you can learn a new trade and loose weight at the same time. If it was just a few rocks I’d try a masonry saw-blade in my hand saw, just saw about a half inch or so deep then use the chisels in the slit. You can use a masonry hammer, just tap out a line with it, pass over it a few times 'till it is scored well, then start hitting a lot harder and it should break close to the line. ---
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [May 1, 2003, 1:06pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/19 "2003-05-01T13:06:29Z")
I don’t want to use a stone mason. _I WANT TO HAVE THE FUN_, and learn a little at the same time. ---
**Author:** ![mallocks](https://avatars.discourse-cdn.com/v4/letter/m/f4b2a3/32.png) [@mallocks](https://boards.straightdope.com/u/mallocks)\ **Post date:** [May 1, 2003, 1:15pm UTC](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198/20 "2003-05-01T13:15:05Z")
ah, but if it’s anything as good as **trabi** says, then you should hire him just to do one rock and watch, sounds like fun 😃 [Next page](https://boards.straightdope.com/t/can-someone-help-with-the-correct-method-to-cut-a-boulder-in-half/172198.md?page=2)