PHD technique in rocky soil?

[Marks481]

I could see the larger auger actually working better then my 9" auger, since it probably would be able to pull out larger rocks. Of course, the downside is that it would find more rocks cause the hole is larger.

You are almost right next door to me, as I am in Mystic.

 

[egb6550]

After trying to use the trencher to dig some holes and having it bounce all over and go crazy I ordered the post hole digger. Fortunately I don't have the rocks you do and the only problem I've had is tree roots. It has been great but I do need a manual post hole digger to pull out the loose dirt. I do wonder whats the best angle (what do you call the angle control right to left on the stick?) for the thing and how to keep it straight as you go deeper.

 

[Dakar]

While we are on the topic, does anyone have any experience using the PHD on sandstone? I would like to get one for my PT, but the area that I need to fence is very close to some large sandstone outcroppings. I am certain to hit some for several of the holes I would need to dig. I am wondering if the auger will go through the rock with enough patience. Any thoughts? (Oh yeah, there is currently a mesh fence there, and some one managed to drive steel posts into the ground there, which gets my hopes up.)

 

[Marks481]

I think you will wear your self out before you break throught the sandstone. THe bottom of the PHD is a blunt, rounded extension with no real cutting edge. I have hit several flat rocks square on, and the only way you know is all of a sudden the PHD wont go any deeper... since it is a flat surface, it doesn't jump around or anything.

So where is the PT rock drill? Come on, PT makes minimg equipment, so I gotta think they have one available. What about the hydraulic jack hammer? Both would work far better for breaking through limestone.

 

[BAGTIC]

I have the PT425 with 14" & 30" augers.

I have the same problem as my soil is clay/rock. Some or my rock is limestone and some is chert or flint. It makes great sparks. The problem is that these augers are really 'earth augers' and are not designed to dig rock. When I hit a flat tilesized flat , like a paving stone, piece the fishtail point just spins like a top without biting in. I have even considered buying a carbide toothed 'rock auger' bit from another source.

On the round 'potato sized rocks' I can sometines offset the auger a few inches to the side and complete the hole. I haave been trying to build a fence for my chosen orchard site and it looks like a snake with a bellyache. I am almost ready to hire someone with some HEAVY equipment to come in and set the posts for me.

The large 30" aauger does fairly well lifting small rocks but bogs down quickly in the sticky clay, not enough torque or tractor weight. It takes off no more than 1/10 inch, or less per revolution. The clay flakes look like little fat red potato chips. Nonetheless it has proven handy as it is doing what I bought it for, digging flower beds for bulbs (iris, daffodils, daylilies, lilies, hyacinth, etc.). Usually 12-15 inches is plent deep for that purpose and 30'' makes for a nice sized clump.

 

[Marks481]

As luck would have it, the first post hole I tried to dig was square in the middle of a rock about 3' wide, 2' thick and who knows how high. I worked it with PHD and minihoe, then gave up and successfully dug the rest of the fence without hitting any rocks bigger then a watermelon (a large one...).

And then back to the big rock. No luck, still stuck. I finally rolled the sucker about half way over after some serious excavating with the minihoe. I REALLY REALLY want to put a fence post there. Maybe I will finally get it moved tomorrow. Anybody know how much weight the minihoe will lift? I am thinking that I might just have to dig a big enough hole to slide it out of the post hole target zone and rebury, cause I don't know if the PT will lift it out.

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MikePA: Changed inline picture to link. Inline pictures are not modem friendly. /forums/images/graemlins/smile.gif

 

[KentT]

Just an alternative suggestion... you might want to consider going with the flow:

1. Washing that big rock really well to get the dirt off,
2. Use it as a base for your fencepost, and cut the post to length
3. then use some "bonding agent" on it, then pour concrete to encapsulate the rock and the base of your fence post.

I've successfully used the bonding agent to join a fresh concrete pour to OLD stone retaining walls. I see no reason why it wouldn't work here. The stuff is pretty expensive, though, about $10.00 for a quart bottle -- but you'd only need one bottle, while I used several.

 

[Highridge]

Yep, that's a big one. I had one about that size the other day to pull out. The 1430 handled it fine. I don't know if the 422 would handle it, but the worst that could happen is the rear end would lift up. Just take it nice and slow and if you feel rear moving up drop it back down.

 

[Marks481]

If it was a post in the middle of the fence, I probably would have settled for anchoring the post to the rock. Unfortunately, the post will be supporting a gate, and I think that it wouldn't last long unless I plant it deep enough.

 

[KentT]

If you encapsulate both the post and that rock on the bottom of it in one big chunk of concrete, it would likely hold up a telephone pole... /forums/images/graemlins/wink.gif