What to dig post holes with in rock?

[bdhsfz6]

I don't bother trying to dig holes in solid rock to hold a post. I use these square post anchors and fasten them to the rock ledge with four masonry bolts. 10 minutes with a cordless drill & masonry bit and their as solid as the rock their bolted to. Take advantage of the rock rather than fight it.

They can get pricey if you need a lot of them, so I make my own by welding a piece of square stock to a 6" x 6" x 1/4" plate.

Most times, they outlast the fence post. I have some that have been in the ground for 20 years.

 

[Gomer pyle]

I don't bother trying to dig holes in solid rock to hold a post. I use these square post anchors and fasten them to the rock ledge with four masonry bolts. 10 minutes with a cordless drill & masonry bit and their as solid as the rock their bolted to. Take advantage of the rock rather than fight it.

View attachment 2097000
They can get pricey if you need a lot of them, so I make my own by welding a piece of square stock to a 6" x 6" x 1/4" plate.

Most times, they outlast the fence post. I have some that have been in the ground for 20 years.

Makes since. Do you use these for corner or gate post also?

 

[bdhsfz6]

Makes since. Do you use these for corner or gate post also?

I have one corner post where I had to use a larger 12' x 12" plate with 6 bolts. It's held well for several years now but I don't over tension the wire.

Not sure how it would work with a heavy gate though.

 

[Hay Dude]

I'm not sure what that is

 

[M59]

8-9" posts. Some of mine start rock on top of the ground, some are a foot down before it starts.
I have rented skid steer augers when I have a few to do and like it. All the ones I've rented have dirt augers. I just want to make sure that one will do the job before I invest that much money

Looks like you have several options for posts. The bolting to exposed rock is an option but limestone is relatively soft stone so side loading such as a gate may cause anchor failure but use in a straight fence line would work well. Have you considered smaller diameter posts such as iron "T" posts or 2" fencing posts so your holes are smaller and require less effort. Boring a 4" dia hole would be much less work than a 12" dia hole using a rock auger.
An electric rotary drill and 2" dia carbide tipped bit would bore holes in limestone really quickly ( expect less than a minute per 12" deep hole ) but may not be feasible given your indicated your back injury.

Would contracting the job to someone with proper tools be considered?

 

[BlueKnife]

8-9" posts. Some of mine start rock on top of the ground, some are a foot down before it starts.
I have rented skid steer augers when I have a few to do and like it. All the ones I've rented have dirt augers. I just want to make sure that one will do the job before I invest that much money

A standard dirt auger will not go anywhere in the conditions you describe. I've not used a rock auger on mine yet, but I'll probably end up with one eventually. I'll be curious to hear how it works for you if you get one.

 

[BlueKnife]

I don't bother trying to dig holes in solid rock to hold a post. I use these square post anchors and fasten them to the rock ledge with four masonry bolts. 10 minutes with a cordless drill & masonry bit and their as solid as the rock their bolted to. Take advantage of the rock rather than fight it.

View attachment 2097000
They can get pricey if you need a lot of them, so I make my own by welding a piece of square stock to a 6" x 6" x 1/4" plate.

Most times, they outlast the fence post. I have some that have been in the ground for 20 years.

How are you attaching the post to that base?

 

[MAX-24-Dean]

I use the method that @M59 stated above, I've gotten to the point where I can't work with the vibration of my SDS- Max rotary hammer for very long due to physical pain in my wrist. So I changed to a core drill with no hammer action. It works fine, just takes a little longer. Hole diameter is drilled so the T-post is tight going in.

I knock off the wings on the T-posts, add cementall to the hole then install the T-posts.
Some of the T-posts have been in the rock for 14 years using this method and still doing there job.

 

[BlueKnife]

I use the method that @M59 stated above, I've gotten to the point where I can't work with the vibration of my SDS- Max rotary hammer for very long due to physical pain in my wrist. So I changed to a core drill with no hammer action. It works fine, just takes a little longer. Hole diameter is drilled so the T-post is tight going in.

I knock off the wings on the T-posts, add cementall to the hole then install the T-posts.
Some of the T-posts have been in the rock for 14 years using this method and still doing there job.

How do you get the "core" out of the hole? If it's solid rock, it would still be attached at it's base.

 

[MAX-24-Dean]

Run a bit down the pilot hole.

Then vacuum out the leftovers.