Sounds like you've experienced splitting! I'm still a rookie but may be able to offer a little encouragement. Walking up to an arbritrary roller (rolled in front of the glacier) is the most difficult split. The people who work with granite for a living work in a quarry, not in people's back yards when they fill a order. Most quarries have seams in the rock either cracked by forces in the earth or when the rock flowed in molten form. At least it has broken in one known direction before! This provided one maybe two flat surfaces to work with. (Which is one or two more than a roller has) From here, its all skill and luck. Finish wedges work for a couple of feet, the longer I think 1 1/2 dia are frequently seen to break the 6-8 ft 45,000 lb blocks heading to the cutting sheds and the 2 in hole is basically used to pour in black powder to start some cracks without wedges. This larger hole is also used with hydraulic wedges often for disposal splitting on construction sites. Back to your situation, roll the rock around to have a look, pick the most likely path for a split, don't try to do all the work with one wedge, sometimes it takes another hole or two when the rip starts going the wrong way. Every quarry I've seen has a huge pile of tailings! SteveV /w3tcompact/icons/smile.gif
Granite Splitting (New Hampshire)
- Thread starter DaveNH
- Start date
- Views: 2205
Crack propagation is a funny thing. What you have to think about when trying to split a rock with no definite grain is how the crack tip 'sees' the rock as it travels through it. The crack that finally splits the rock will be started where you drive the wedges in - what you want it to do is follow and open-up along the right line of least resistance all the way around the rock as it travels.
There's a few ways to do this. One is to drill holes about 3/4 of the way around it (you can never get underneath the rock) - and to chisel between the holes before you start pounding the wedges in. The chiseling doesn't have to be a major effort, you're really just scoring the surface of the rock, creating micro-fractures that the main crack tip can follow and open up. Also - you may want to experiment with the distance between the holes that you drill. I've heard that 12" is a good start - work down from there.
Another way is to use a diamond blade and grind a 3" deep groove around the rock. It doesn't have to be continuous - again around every 12" should do as a start - don't forget to chisel between them - or cut a shallower groove between. One challenge with this approach is to find slim wedges to fit the groove. I've heard of old leaf springs being cut up into 6" long pieces and sharpened for use as wedges.
A few other points to note ...
Be careful - half of one of these rocks rolling against you is enough to ruin your day. Splitting rocks this way is dangerous - make sure someone knows where you're working in case you get pinned.
Even though granite is an igneous rock it still has planes of weakness that it can split along. There's not much you can do about this - you'll only discover them when you try to split it. These planes are created during the formation of the rock for a variety of reasons as the rock cools from molten to solid.
Also, I have heard that the erratic splits are usually the result of forcing the fracture. A method you may want to try is to pound your wedges in tight (you can tell when they're tight from the 'ring') and leave the rock overnight. You may well come back to a split rock in the morning. If not, tighten them up again and give it another few hours.
I can't claim credit for these ideas by the way - I just happened to be talking to my brother who is a civil engineer and has worked on some fairly demanding tunnel projects through granite.
Patrick
P.S. A link you might find interesting is here ... <A target="_blank" HREF=http://www.dakgran.com/web/Part1.asp>Dakota Granite</A>
There's a few ways to do this. One is to drill holes about 3/4 of the way around it (you can never get underneath the rock) - and to chisel between the holes before you start pounding the wedges in. The chiseling doesn't have to be a major effort, you're really just scoring the surface of the rock, creating micro-fractures that the main crack tip can follow and open up. Also - you may want to experiment with the distance between the holes that you drill. I've heard that 12" is a good start - work down from there.
Another way is to use a diamond blade and grind a 3" deep groove around the rock. It doesn't have to be continuous - again around every 12" should do as a start - don't forget to chisel between them - or cut a shallower groove between. One challenge with this approach is to find slim wedges to fit the groove. I've heard of old leaf springs being cut up into 6" long pieces and sharpened for use as wedges.
A few other points to note ...
Be careful - half of one of these rocks rolling against you is enough to ruin your day. Splitting rocks this way is dangerous - make sure someone knows where you're working in case you get pinned.
Even though granite is an igneous rock it still has planes of weakness that it can split along. There's not much you can do about this - you'll only discover them when you try to split it. These planes are created during the formation of the rock for a variety of reasons as the rock cools from molten to solid.
Also, I have heard that the erratic splits are usually the result of forcing the fracture. A method you may want to try is to pound your wedges in tight (you can tell when they're tight from the 'ring') and leave the rock overnight. You may well come back to a split rock in the morning. If not, tighten them up again and give it another few hours.
I can't claim credit for these ideas by the way - I just happened to be talking to my brother who is a civil engineer and has worked on some fairly demanding tunnel projects through granite.
Patrick
P.S. A link you might find interesting is here ... <A target="_blank" HREF=http://www.dakgran.com/web/Part1.asp>Dakota Granite</A>
Well the saga will have to continue next year.
I went out today and proceeded to get 10 wedges firmly stuck in a rock. I thought a had found a minute crack and started to drill holes. About a half hour later I had my ten holes all 6-7" deep even spaced across a 4 footer. Scored a line between holes. Started tapping, one at a time and never got to the "Thunk"./w3tcompact/icons/frown.gif
I've got the wedges right up to the feathers!
So they'll sit there until warmer weather.
Maybe it will split on it's own.
I found this site on the web.
Interesting but I'm not that frustrated yet. /w3tcompact/icons/smile.gif
http://www.cnw.com/~ibis/dave/cave/rock/rock01.htm
Thanks again to everyone!
Dave
I went out today and proceeded to get 10 wedges firmly stuck in a rock. I thought a had found a minute crack and started to drill holes. About a half hour later I had my ten holes all 6-7" deep even spaced across a 4 footer. Scored a line between holes. Started tapping, one at a time and never got to the "Thunk"./w3tcompact/icons/frown.gif
I've got the wedges right up to the feathers!
So they'll sit there until warmer weather.
Maybe it will split on it's own.
I found this site on the web.
Interesting but I'm not that frustrated yet. /w3tcompact/icons/smile.gif
http://www.cnw.com/~ibis/dave/cave/rock/rock01.htm
Thanks again to everyone!
Dave
Egon
Epic Contributor
If it's freezing out fill the holes with water and then wait.
Egon
Egon
After consulting my book of everything Fred Flintstone used to know, I have the following ideas. You like to drill holes, this is good. Ten wedges will blow open any 4 ft rock around here. How long are your feather and wedges? Mine are like 2-3 inches long. The holes are like 3- 31/2 deep for these. If you strike the feathers before the rock opens, you either have mismatched sets or are using the wrong hole size (too big). If everything is working as it should, you should be able to put a wedge in a single hole in the middle of a rock and start a split for a couple of inches on either side of the single wedge. The force these things generate is unbelievable. SteveV/w3tcompact/icons/smile.gif
Steve,
I bought 10 "3/4" feathers and wedges from "The Compleat Sculptor, Inc." (http://www.sculpt.com/)
They are 4" long and I'm drilling .75 holes to a depth of 6-7". When the feathers are against the wedge (as they would be in a hole) I measure .75 at two inches from the bottom, the top of the wedge is about 1.125
I'm getting about two inches of travel on the wedges.
Am I drilling too big of a hole?
I made an assumption that 3/4" wedges were for a 3/4" hole. (Please reserve comments about assumptions)/w3tcompact/icons/smile.gif
Many thanks to all who helped.
Please have a safe and happy New Year!
I bought 10 "3/4" feathers and wedges from "The Compleat Sculptor, Inc." (http://www.sculpt.com/)
They are 4" long and I'm drilling .75 holes to a depth of 6-7". When the feathers are against the wedge (as they would be in a hole) I measure .75 at two inches from the bottom, the top of the wedge is about 1.125
I'm getting about two inches of travel on the wedges.
Am I drilling too big of a hole?
I made an assumption that 3/4" wedges were for a 3/4" hole. (Please reserve comments about assumptions)/w3tcompact/icons/smile.gif
Many thanks to all who helped.
Please have a safe and happy New Year!
I went and found the toolbox and tapemeasure. Here's what I got from my local masonary supply house: overall length 3 in. with the feathers 1/4 to 3/8 in shorter than the wedge. The feathers placed together without the wedge make a 1/2 in diameter circle (split in the middle of course). When expanded with the wedge flush with the bottom of the feathers, the diameter has expanded to 3/4 in./w3tcompact/icons/grin.gif This system is designed for a 5/8 in hole and I drill to like 3 1/2 deep to use them. Occasionally, I bottom one out in the hole,[hmmm] but this is pretty evident when it happens by the change in sound./w3tcompact/icons/smile.gif Attached are my rough split driveway posts being installed. SteveV
Attachments
hayden
Veteran Member
I think his measurements are for 5/8" wedges. If your's are 3/4 then they go in a 3/4 hole.
I've only done a little splitting and it's been with 3/8" wedges, but I think the problem you are having is that you're trying to split too think a rock. Rock's I've seen with 3/4" drill holes remaining are typically 12"-18" thick.
You might try calling Swensens Granite Works. They are in Amherst NH and I think also in Concord. That's where I bought my wedges and they might be able to help you.
Peter
I've only done a little splitting and it's been with 3/8" wedges, but I think the problem you are having is that you're trying to split too think a rock. Rock's I've seen with 3/4" drill holes remaining are typically 12"-18" thick.
You might try calling Swensens Granite Works. They are in Amherst NH and I think also in Concord. That's where I bought my wedges and they might be able to help you.
Peter
Peter,
I was able to get a few of the F+W free from the monster and made measurements like Steve described.
The only difference between his and mine is that mine are four inches long.
I tried an experiment today. I took a slice of rock from a previous attempt and drilled three holes, one 5/8" and the other two 3/4". All three hole where 5 inches deep. The piece was about 18 inches thick, looked like a section from the an orange.
I put a set of F+W in hole #1 (5/8") and the rock cracked after 6 good taps.
I put a set of F+W in hole #2 (3/4") and they stuck.
I put another set in hole #3 (3/4") and added a 1/8" shim between the F and the W and it spit after about 8 or so good taps.
Then I proceeded to smash the dickens out of the remain section trying to recover the F+W and doing so I broke the handle on my little sledge!
I'll look up Swensens Granite Works tomorrow and see what they say.
I'm also going to call the company I bought them from and see what they say.
Thanks
I was able to get a few of the F+W free from the monster and made measurements like Steve described.
The only difference between his and mine is that mine are four inches long.
I tried an experiment today. I took a slice of rock from a previous attempt and drilled three holes, one 5/8" and the other two 3/4". All three hole where 5 inches deep. The piece was about 18 inches thick, looked like a section from the an orange.
I put a set of F+W in hole #1 (5/8") and the rock cracked after 6 good taps.
I put a set of F+W in hole #2 (3/4") and they stuck.
I put another set in hole #3 (3/4") and added a 1/8" shim between the F and the W and it spit after about 8 or so good taps.
Then I proceeded to smash the dickens out of the remain section trying to recover the F+W and doing so I broke the handle on my little sledge!
I'll look up Swensens Granite Works tomorrow and see what they say.
I'm also going to call the company I bought them from and see what they say.
Thanks
