3pt Post Hole Digger Geometry and Operation

[tonys55]

Hi all,
I'm not sure I am making any sense here but...
I have been reading many posts and watching many videos about how to operate a 3pt post hole digger and the frustrations of getting the auger stuck. Some of the techniques others have used to avoid this, or to free a stuck auger, are pulling up and clearing often, rocking the tractor, a pipe wrench, engine rpms, and 3pt depth control - to name a few. One that stands out is moving the tractor forward as the auger diggs down. This makes perfect sense as its the only way to keep the auger plumb and relieve binding. The boom moves in an arc so moving the tractor relieves the binding. But forward only works up to the point the boom is parallel to the ground. I haven't heard anyone mention moving the tractor backwards as the boom drops below parallel to the ground. The illustration below has been drawn to a scale of 1" = 1'. Now it isn't perfect but close enough to make a point. The point is when the boom moves below parallel to the ground, the auger is also moving towards its maximum contact with the ground. If the tractor doesn't move backwards, it seems the binding friction will be much greater and more difficult to power through than when above parallel and the tractor isn't moved forward as you dig. It follows that once the auger moves towards maximum depth and friction, the tendency would be to screw itself into the ground, stall the tractor or shear a bolt. Some soil conditions might be more forgiving and the tractor can just power through. With binding and increasingly higher friction in mind, pulling up and clearing the auger more frequently as you dig down deeper and deeper, might be a good idea.
I recently purchased a properly sized post hole digger for my 1025R. Haven't installed or used it yet, and have only used a manual digger in the past. I am a complete novice on the subject. Which is the reason for posting and asking for thoughts...or maybe some folks might keep this in mind during subsequent digging and find it helps. Honestly, I don't think moving the tractor forward and then backward is very practical, but it is the only way to somewhat keep the auger plumb and the hole round. This seems easier said than done. Moving the tractor as you dig down would also require moving the tractor when lifting out the auger. So, it seems an oblong, out-of-plumb hole is inevitable. How oblong or plumb depends on whether or not the tractor is moved as you dig. Again, there seems to be no practical way to keep the tractor in the ideal position at all times.
Anyway, below is what I am talking about. I haven't seen anyone talk about below parallel. It's worth keeping in mind...or maybe not. How you deal with it is up to you in your situation.
And yes, the 3pt auger is inherently a bad design. A different auger design that digs straight down would be much better. We are talking 3pt here.
Am I way off here? Thoughts? Thanks.

 

[RustyA]

Start your hole by taking a divot out with pointed shovel, auger doesn't skip around as much when starting. Have a spotter help you keep the auger perpendicular as you are drilling. My auger has a hole in the back of gearcase a piece of long round bar stock can slide into for spotter to help keep auger level left and right. Be sure your three point arms are adjusted for minimum sway left and right. Clean auger out every foot or two. If Rocky soil be sure to have plenty of shear bolts and a pointed rock bar to bust rocks up so auger can finish.

 

[RjCorazza]

I do much better with projects that I roll around in my head well in advance. In your case, you may be over thinking the post hole digger operation... But better to over think than to jump in like a bull in the China shop.
When I had a 3 point auger, I would generally operate slightly above idle, raise and clear out the hole every foot or so, creep forward a few inches once about 1/2 way down, and finally.... Keep my hand on the 3 point lever to prevent the auger from screwing into the ground. You'll only do that once!
I currently use a loader mounted hydraulic auger, and the down pressure and reversing makes the job much easier.

 

[TerryR]

What's the problem if the hole is a bit oval? You're going to fill it back in anyway after you place the post.

I think as RJ says, you're over-thinking this.

 

[Ricn]

Bought a used PHD on a 35HP ford, got so irritated with using it I sold the whole outfit buying a newer tractor with BH attached, then sold that outfit and bought an excavator, very happy now. When ground is very rocky I found the PHD to be a real PITA!

 

[camshawn]

I put the bucket , 1/2 curled into the ground and use the bucket to move the tractor forward and back as needed to keep the digger going plumb into the ground.