PHD technique in rocky soil?

Marks481 · Jun 25, 2005

Any rcommendations for techniques for digging post holes in rocky soil.

I have the 9" inch, and I make it down about 6-12", and pretty much stops going any farther due to fist size (and smaller) collection of rock. So I muck/pry those out with a shovel, and then keep drilling. Pretty slow going. I have been flooding the holes with water to try to help loosen the soil.

Marks481 · Jun 25, 2005

What a PIA. I resorted to a combination of mini backhoe, shovel, and PHD. I can generally get 6-12" at a shot with the PHD before it bogs down on rocks, then clear it out with the shovel, and attack the big rocks (between pineapple and pumkin sized).

Makes me glad I jumped up to the PT422 from the PT180 (which I did solely on the basis of being able to run the minibackhoe... okay, the oil cooler is kind of nice too...). Haven't run out of power yet.

JerryG · Jun 25, 2005

The best thing that you can do with that type of soil is to put the holes in early in the spring or really late in the fall. The dirt is easier to dig then.

DML · Jun 25, 2005

This is actually why I haven't purchased this attachment. Not that I don't have confidence in the tool, I just don't think it would be the right tool for my soil. I have thought about it, and thanks for the post. It is also why I delayed buying the trench digger. The trench digger, though, actually has served me well, so far. Some rocks it actually cut through, others it knocked out, and still some I had to attack with a pick hammer! It is a lot easier to attack them with a pick hammer in a trench than a post hole, though.

Marks481 · Jun 25, 2005

Where I chose to put the first hole was a bad choice. After digging out about a dozen cantalope size rocks with the minihoe, I hit the mother lode. With an ever increasing hole size, I mapped out a rock about 3x4 foot (at least), which pretty much sat right where I wanted a post (inline with the back of the house, 8' from the house). I don't think that baby is coming out... back to the planning board. The hole just kept getting wider and wider.

So I started from the other end. The auger cut through the soil like butter. 32" deep in about 15 minutes (I had to pull the auger out of the ground half a dozen times to liberate softball sized rocks). Hopefully the next four will go this smoothly.

When I hit a rock, the auger starts thumping up and down. I raise the auger a bit, and let it sit there and vibrate the rock for a few minutes. If it is small (baeball size or less), it will work it's way free and pop up to the top.

I am loving my PT422. The PTO seems to be working just fine, but I will wait on running the mower deck until I get the replacement spool, since I am guessing that the mower deck will require a higher flowrate of hydraulic fluid to spin it (and with the spool sticking halfway open, I am guessing I will get suboptimal results).

Marks481 · Jun 25, 2005

( The trench digger, though, actually has served me well, so far. Some rocks it actually cut through, others it knocked out. )

While I was sitting there with the auger jumping up and down while it tried to take care of a rock, I was thinking that the trenching attachment would probably work well, since the vertical motion of the chain would probably pull rock out alot easier.

I considered buying teh trencher instead of the auger, but I already bounced way over budget by going with the 4n1 bucket instead of the LMB, and the $1700 trencher vs $1100 PHD just wasn't in the works.

FOURTEEN · Jun 26, 2005

( Where I chose to put the first hole was a bad choice. )

 I have clay soil without rocks! If you will tell me the number and size holes that you need, I will send them to you if you will pay the freight!! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

PS: /forums/images/graemlins/blush.gif Sorry! /forums/images/graemlins/blush.gif It's early Sunday morning, and I'm feeling a bit giddy!! /forums/images/graemlins/crazy.gif

Marks481 · Jun 26, 2005

the good news is shipping wont cost much, since they are lightweight.

catsco · Jun 26, 2005

It is true that holes are not only lightweight, but very low in cost.

Installation, however, can be expensive! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

Mark H.

Kioti3054 · Jun 26, 2005

Hi Tim, I'm in New London and dig a lot of holes for contractors. I use a cheap 3 pt hitch PHD on my Kioti. It works ok but I go through a lot of shear bolts. I am thinking on converting it to hydraulic drive to have more control and to be able to reverse the auger. But in some areas around here I use my backhoe with a 9" trenching bucket its faster and easyer with the rocks. Plus with the 9" bucket I can keep the holes pretty tight. I also find that some times running a 12" auger works a little better. Sometimes it loosens up the rock better.

Dave

Marks481 · Jun 26, 2005

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 · Jun 26, 2005

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 · Jun 26, 2005

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 · Jun 26, 2005

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 · Jun 26, 2005

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 · Jul 11, 2005

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.

Link

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

KentT · Jul 11, 2005

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 · Jul 11, 2005

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 · Jul 11, 2005

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 · Jul 11, 2005

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