Help! Suggestions/advice please for installing posts for yard fence in rocky ground?

I'm looking at having to replace the wooden fence enclosing my backyard. It was built at the same time the house was built (back in the late eighties/early nineties). Aside from the fact that this fence was never built very well to begin with, it has rotted to the point to where I have no choice but to replace it before next winter. Wouldn't be a big deal except that I will have to install all new posts, which means the digging of new post holes in ground I painfully only know too well to be riddled with large "auger-stopping" rocks. Having used a power auger on more than one occasion to sink holes in the yard (once so as to sink concrete pier-columns for a deck; plus on three other miscellaneous 4x4 post-related occasions) I have learned that for every two holes attempted, one hole will have at least one huge rock in the way requiring excavation and removal by hand-shovel; a very labor intensive and time consuming process for just one (out of shape) person such as myself. Therefore I'm currently trying to find out if there might not be a less labor intensive process I could use in dealing with these auger-stopping rocks? A couple of ideas for example: For use with a demolition or breaker hammer (jackhammer), might there exist a chisel attachment of ultra long length (pardon my grammar) such that it could be used to reach down as much as say three feet below the ground surface in order to be able to simply break up such rocks as they are encountered while augering a hole? Or, might there be such a thing as post-hole digging equipment, which, while reasonably affordable and portable enough to rent, would be somehow capable of simply cutting through such rocks? (One can see I'm scrounging for ideas here. <g>) Any help/advice/info/references-to-such would be appreciated.
TIA, Ken
* FYI: The fence _posts_ themselves have to be replaced for two reasons: 1) The builders buried the posts only two feet deep into the (soft, except during summer) ground, and the result has been that the whole fence has had a problem remaining upright since before we bought the place. 2) The builders did not (or so it appears) use rot resistant -e.g. pressure-treated, etc.- posts and therefore these will only have to be replaced eventually in any event.
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I have the same rock problem. I plan on digging what I can, and when I hit a rock, using a rockdrill to drill out 1/2" holes to epoxy rebar. Then you can drop your posts on top of the rock and pour cement aound it. Another method is to use a bigger rock drill bit (like 5" for 4x4 posts), drill into the rock and then drop your posts in the hole and fill with cement or epoxy.
Let me know what ends up working best for you, since I have to build a deck and fence on a rockledge.
tim1198
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tim1198 wrote:

Depth is important because it keeps the post upright. But you can also use a large disk of concrete on the surface to achieve the same effect. Or, you could use two long pipes, stronger than rebar, at right angles drilled through the wooden post.
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Get a 5 inch diamond core bit, it can be driven from a heavy regular electric drill, it cuts just the edge with diamond and can goi thru granite. they are available good used for about 25 bucks or less per inch, if you need a source e mail me.
with your location its a good investment for future projects and is useful for things like going thru concrete too.
a buddy had this trouble thats how i know..........
this bit is used for granite countertops
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Rock drill, eh? Thanks. I'll check further into this.
Ken
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On 5/2/06 2:26 AM, in article snipped-for-privacy@news.supernews.com, "Ken

I'd rent a small excavator to dig the holes if there's more than say 10.
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Find a company that rents tents for large functions, and see if you can get them to drive your fence-posts with their pnuematic tent-stake drivers? Those things hit hard enough to mushroom the end of #12 rebar.
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This approach can be employed with a special hydraulically powered farm-tractor add-on device, that shoots cone-pointed round-posts (or poles) into the ground. From what I've been told, this method doesn't work with square posts though. Plus I simply wouldn't be allowed to bring in machinery the size of a tractor into our small yard since it would severely damage many of the shrubs, bushes, small trees, flower gardens, trellisses, arbours, walkways, and extensive other ornamental effects that the lady of the house has lovingly 'toiled' a long time to develop.
Ken
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Lotsa rock here too, some over 3 foot sided cubes. Put up a perimeter fence around the house. Over 400 ft long. Used standard pasture/field fencing with 3X2 squares. 4X4 ACQ corner and tensioning/bracing posts. Steel t-posts. Built exclusively to keep the dogs on the property. I dug all the holes with a rock bar and a diamond tipped masonary drill to help breakup the bigger rocks for the corner and tensioning/bracing posts. They're all 2.5' in the ground with concrete footings. T-posts, had to drill out some rock sometimes. Used the heaviest pounding tool for the T-posts. Took over 3 weeks to dig, and set all the posts.
In retrospect, should have hired out the same people that drilled out the holes for the footings for the piers for the house. They used a commercial type driller for setting utility poles. Just use a smaller diameter auger bit.
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Jonny



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I pose this more as a question than suggestion- dynamite, anyone? I know farmers used to keep some sticks around the shed for nasty jobs like this. Don't know what the current laws are on this- obviously not practical if there are neighbors. Anybody know? Course you'd still have to drill the bore holes.
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At one time dynamite wasn't too hard to get a hold of. Back during the depression, my grandfather was known to use dynamite to fish with (highly illegal, but this was at a time when people were desperate just to keep from starving to death). He'd light the fuse of a stick and throw it in the water... BOOM!!! All the fish in the vicinity killed by the resulting underwater shock wave, would then float to the top, from where he'd simply gather them... taking them to feed his otherwise would-be hungry family.
I would imagine that today though, legitimate access to dynamite is much more tightly monitored and controlled while being restricted to a carefully licensed and closely regulated professional elite. [I make this comment merely as a casual "guess", and hence in no way to be taken as informed opinion, much less, known fact.]
Ken --
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given terrorism dynamite probably isnt available
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