Post Holes: Danuser EP6 and which augers???

FatTire · Apr 5, 2014

Thinking seriously about buying a hydraulic auger, most likely the Danuser EP6, for use with my Kubota MX5100 (9 gpm). Where I get hung up is selecting the auger(s). We have 6 to 20 inches of top soil, and then clay, and plenty of rocks ranging in size from 4 inches up to several feet in diameter. When digging a post hole by hand in this rocky ground, there is less than 50% chance of completing any hole that I start, which is painful when you have 20 minutes or half hour into a hole and then hit a big rock. ( I've been known to "misread" 24 inches as "30 inches" from time to time, rather than "give up".)

My main question is what happens with a rock bit if you hit the edge of rock? For example if drilling hole, and happen to hit the edge of boulder that is sticking out into the path of the hole, does the rock bit cut into it, or does it try to push the auger (and FEL) sideways? Also- Am I going to want both a dirt auger and a rock auger?

Any feedback on this auger question, along with FB on the Danuser EP6/EP10 units is appreciated.

texasjohn · Apr 5, 2014

I have experience in ground similar to yours. My very strong recommendations are...

Get rock bits...these work fine when you don't hit any rocks and make 100% difference in penetration when you do hit rocks.

Get a digger with down pressure capability. You WILL need this ability.... the regular weight of the post hole digger itself is insufficient when you hit rock. You will need down pressure when you hit rocks...and it can really help when you hit hard clay.

When the auger hits stuff, how it behaves depends on what it hits. I have a Danuser auger, no down pressure, I added 200 lbs weight to it, 12 inches. Wish I had down pressure.

When it hits a flat slab of rock, auger will bounce and bounce on the rock and the rock bit will grind into the flat slab. Sometimes, it can chip away enough to crack and grind enough to make its way thru a slab down to clay underneath. Sometimes not. When it goes no where, you have a hole with a rock bottom well scored where the teeth went round and round.

If you are going thru a mix of various sized rocks, the auger will pound away at them and when one breaks loose it will make its way to the top of the hole and out. If there is a big rock with just a jagged corner sticking into the hole...you can end up with a PROBLEM. The end can get caught in the auger and pull the auger into the ground but the rock is too stuck to come up....so the auger gets hung....only solution is to disconnect the auger and wind it backwards out of the hole.

Hitting a big rock on its side can cause the auger to slide to the side and go down the edge of the rock. This results in a slant hole.

The most important thing to learn is to not try to drill too deep at one time. Up and down, up and down, up and down.....each time you come up, the spoils spill out. If you go too deep, it can be come too heavy to lift out and you get stuck....but this won't happen if you keep the hole kinda clean as you drill down.

Finally, I recommend you use metal T posts for line posts... as few wood posts in drilled holes as you can...use the FEL to drive the T posts in.

FatTire · Apr 5, 2014

Thanks, that's what I wanted to know. Sounds like I could get by with just 1 auger, something like 10 inch rock bit. The EP6 is hydraulic, so I imagine I'd be able reverse flow to pull out of hole when it jams.

Ken45101 · Apr 6, 2014

Yes, as long as you have the hydraulics set up, you can reverse the auger and back it out. That's a big advantage of a hydraulic auger AFAIK.

As for auger size, well, what size posts are you going to put in and how will you backfill? An oversize hole either needs concrete to fill the hole, or a compacted dirt fill. Compacting fill dirt by hand with a spud bar is not fun IMO. I tend to keep the hole only a few inches bigger than the post so there is less backfill and more solid ground. If I was really sure of a vertical hole, I would use an auger very close to the post size (e.g. a 5" auger for a 4" post).

My PHD is three point but I have 4, 8 and 12" augers depending on what I'm putting in. IMO, a 10" auger is a poor choice for 4 or 5" posts.

FatTire · Apr 6, 2014

I have to put in some 6x6 with concrete sono tubes, but more often 5" diameter round posts. If you only leave an inch (or less) gap around the post, how do you pack it?

These rock bits are a grand or more, so I will get only one. Even with a 10" auger, I would have to widen out the hole manually to make it wide enough for the sono tube. (6x6 is about 8.5" across the corners, so even a 12" tube is tight.) For round posts we do not use concrete, just backfill with dirt/clay.

texasjohn · Apr 6, 2014

get the right size auger to start with. I have trouble getting a straight hole...always seems to slant off some way for some reason. thus, putting a pole straight in a slant hole requires a larger diameter hole to start with. I use a tamping bar to tamp in dirt/clay...and I agree, if only an inch gap it is very difficult to get a good firm tamp all the way around the post. If I were going to do a number of posts, I think I would get some gravel to shovel in around the post. finding the right size material to flow evenly around a post at the dig site is often a problem. On occasion when using a mix of rock/clay, I have had to transport water to the hole and water in the material to get it to settle down and around the pole.

rd_macgregor · Apr 7, 2014

I have a Belltec hydraulic auger with 9" and 15" bits (with 2" hex shaft mount). It works pretty slick and the reverse is handy both for backing out a stuck bit, but also it helps in clearing the soil off the bit when you pull it out of the hole. Rocks can be a nuisance, but type of rock can make a big difference. Ours is relatively soft sandstone and, with a bit of down pressure, a good bit can grind right through it. I suspect something like granite would be a bit more of a challenge, plus, breaking up or forcing aside cobbles would be a whole different story than trying to drill right through boulders or bedrock!

Obviously, if you are casting concrete posts, you need to drill a bigger diameter hole. For PT wooden posts, I've wondered if it wouldn't work to drill a slightly undersized hole and then push or drive the post into the hole...voila, no back-tamping!

Also, standard bits are nominally 4' long; I'm planning to get an extension, probably 18" in case I decide to do my own pole barn pole-holes.

A final note on visibility. The Belltec is centered on a QA plate, and I can not quite see the exact spot where the bit touches the ground. I'm thinking of getting a magnetic trailer hook-up camera to stick on the FEL arm so I can see precisely where the bit is landing and what's going on there. This rig might also be handy for monitoring rear implements in tight clearance situations.

Bob

gdanuser · Apr 7, 2014

The "Rock" Augers are good for solid rock or concrete. The EP6 and the Kubota do not have enough torque or down force to operate the "Rock" Auger effectively. I would recommend the "Cast" Augers. They will power through the dirt, clay, and rocky soil. Industrial Augers | Danuser

texasjohn · Apr 7, 2014

He knows what he's talking about, not just trying to upsell you. He knows his equipment. It might be worth it for the OP to engage in a phone discussion with gdanuser regarding the equipment, its abilities and the nature of the task to be done. Just an idea. Danuser reputation on TBN is excellent. Seldom posts, but watches and contributes positively when his equipment is being discussed.

gdanuser said:
The "Rock" Augers are good for solid rock or concrete. The EP6 and the Kubota do not have enough torque or down force to operate the "Rock" Auger effectively. I would recommend the "Cast" Augers. They will power through the dirt, clay, and rocky soil. Industrial Augers | Danuser

gdanuser · Apr 7, 2014

texasjohn said:
He knows what he's talking about, not just trying to upsell you. He knows his equipment. It might be worth it for the OP to engage in a phone discussion with gdanuser regarding the equipment, its abilities and the nature of the task to be done. Just an idea. Danuser reputation on TBN is excellent. Seldom posts, but watches and contributes positively when his equipment is being discussed.

texasjohn, thank you for the comments! We do try and watch when customers need advice or troubleshooting with Danuser Equipment. Feel free to call or email. Thank you!
Glenn Danuser