KennK
Silver Member
The wife and I a building horse stalls in a new barn which required digging post holes. Our northern Wisconsin soil is littered with small to fairly large granite "field stones", some the size of a large softball or bigger. Because of this I'll have to admit that I was dreading using the post hole digger - fearing we'd pop shear pins like crazy. I'm happy to report that we were very successful!!
We'd purchased the CountyLine post hole digger with a nine inch auger from Tractor Supply, but hadn't assembled or used it. It went together fairly easily.
We had to dig 11 holes for four stalls (eight doorway posts and three stall corners). The barn floor was built up from the soil with a layer of sharp limestone rocks maybe 3-4 inches across, and then a layer of 3/8" gravel and fines on top of that. I dug the first three holes by hand, and found the hardest part was getting through the limestone rocks, which had been compacted by a large excavator. By the time I was done with the third hole my sore hands told me that it was time to try the post hole digger.
To start, we lowered the auger (at the lowest RPM possible) in the holes I'd already dug to widen them. The first and second hole went fine, but in the third hole ... POP! There went the shear bolt. I pulled out my box of shear bolts under the assumption that we'd go through a lot of them.
After putting on the new shear bolt (Grade 5 5/16" x 3" bolt, per the PHD instructions) we set about drilling the remaining eight holes.
I'm happy to report that the PHD barely blinked at the compacted limestone rock layer. Per the recommendations I'd read here, I was careful to avoid screwing the auger in too deep. I would repeatedly drill in maybe 4-6 inches, and then raise it to loosen the soil. Every once in a while I'd raise the auger 6-12 inches, increase the RPM's a bit, and raise the auger out of the hole to remove debris.
I found that the large granite rocks would cause the PHD to vibrate and chatter. When that happened I would lightly lower the auger and let it spin for a while to see if it would dislodge the rock. If it kept chattering I'd stop the PTO, raise the auger to full height, pull forward a bit, and use a tamping bar to find the rock, pry it loose, and remove it with a hand PHD. I'd use the hand PHD to clear out the debris, and go back to the tractor to continue drilling.
We were somewhat shocked that this process allowed us to finish the eight holes fairly quickly without having to replace another shear bolt.
Use the lowest RPM.
Use the repeated down/up - down/up - down/up approach so you don't simply drill the PHD into the ground.
Watch for the chatter/vibration of rocks.
Ken
We'd purchased the CountyLine post hole digger with a nine inch auger from Tractor Supply, but hadn't assembled or used it. It went together fairly easily.
We had to dig 11 holes for four stalls (eight doorway posts and three stall corners). The barn floor was built up from the soil with a layer of sharp limestone rocks maybe 3-4 inches across, and then a layer of 3/8" gravel and fines on top of that. I dug the first three holes by hand, and found the hardest part was getting through the limestone rocks, which had been compacted by a large excavator. By the time I was done with the third hole my sore hands told me that it was time to try the post hole digger.
To start, we lowered the auger (at the lowest RPM possible) in the holes I'd already dug to widen them. The first and second hole went fine, but in the third hole ... POP! There went the shear bolt. I pulled out my box of shear bolts under the assumption that we'd go through a lot of them.
After putting on the new shear bolt (Grade 5 5/16" x 3" bolt, per the PHD instructions) we set about drilling the remaining eight holes.
I'm happy to report that the PHD barely blinked at the compacted limestone rock layer. Per the recommendations I'd read here, I was careful to avoid screwing the auger in too deep. I would repeatedly drill in maybe 4-6 inches, and then raise it to loosen the soil. Every once in a while I'd raise the auger 6-12 inches, increase the RPM's a bit, and raise the auger out of the hole to remove debris.
I found that the large granite rocks would cause the PHD to vibrate and chatter. When that happened I would lightly lower the auger and let it spin for a while to see if it would dislodge the rock. If it kept chattering I'd stop the PTO, raise the auger to full height, pull forward a bit, and use a tamping bar to find the rock, pry it loose, and remove it with a hand PHD. I'd use the hand PHD to clear out the debris, and go back to the tractor to continue drilling.
We were somewhat shocked that this process allowed us to finish the eight holes fairly quickly without having to replace another shear bolt.
Use the lowest RPM.
Use the repeated down/up - down/up - down/up approach so you don't simply drill the PHD into the ground.
Watch for the chatter/vibration of rocks.
Ken
