Drilling fence posts into granite

[Saddlebronze]

I have to drill holes for about 16-30 1 1/2 steel t posts into granite. Do I have any options other than a compressor and a rock drill? I have a backhoe, but no other equipment on site

 

[oldironman]

core drill.

 

[NCWayne]

Probably not what you really want to hear but an actual rock drill or a core drill are about the only two options you've got. Personally I'd rent the smallest hand held rock drill I could find and still carry a bit large enough to bore a hole the post will fit in. I've used both types of drills and in the majority of cases the rock drill is going to be way faster than a core drill will be. Not to mention you don't have to worry about trying to break out the center chun and getting it out of the hold like you do with a core drill.

 

[Jerry/MT]

I"d find another way to put fence in! A jack leg fence would be easier.

 

[Puddles]

What about welding a plate on the bottom of the post with 4 holes in it. Use a rota-hammer and wedge anchors?

 

[Russ from MN]

I have a $60 hammer drill from HF that would do it, but I don't know how many! The land where our cabin is has some exposed bedrock along the back property line. One of the previous owners built a fence by stacking large flat rocks atop each other with a barbed wire in between each rock.

 

[jackinok]

bought a four ft carbide tipped drill bit to do mine,thought it would fit my drill but it wont so now i'm watching around auctions for a used hilti drill.I dont have granite ,but hard sandrock. what i intend to do is simply drill a hole,knock the plate off the posts and drive them in.thought the long bit would help because i have quite a few ,and could drill them standing up. another project on a rapidly growing list.

 

[Rich_WI]

Puddles idea is best, weld up some brackets that attach to the post and use smaller anchors to go into the granite. Its cheaper, faster and easier but not quite as strong. Can always redo it though and it might be 20 years or it might be 100 before it needs it.

My next choice would be a big hammer drill but even just renting a 2" bit will be expensive. Not a bad job though: hammer drill the hole, blow out the crumbs, add the post and some rapid rock or epoxy and done.

Core drill will work but with that many holes you need water on site too or the bit expence goes threw the roof and it wasnt cheap to begin with.

 

[Saddlebronze]

Thanks for the suggestions guys. This is for a vineyard and it is the only place on the acreage it can go. I brought in the dirt with my backhoe, but getting the posts in has been a challenge. I tried a Bosch electric jackhammer, but since the bit does not rotate, it just gets jammed in the hole. I then tried a Makita roto hammer drill with a core bit, but it was way too slow. (they did not have a working star bit to rent) I will probably go back and rent it again when they have the star bit, but the welded plate I had not heard of. Couple hundred to rent the rock drill and compressor for a day, so it may come to that.

 

[tn terry t]

(quoted from post at 07:54:28 12/21/11)
What about welding a plate on the bottom of the post with 4 holes in it. Use a rota-hammer and wedge anchors?

at work we those wedge anchors all the time up to 1-1/2 so they make bits big enough for the rotary hammer to do your job just hang on to that drill or it will beat the crap out of you