How to Sharpen a Posthole Digger

[garry]

I recently purchased a used Husky 3 point post hole digger. It works fine in regular soil but I need to dig some holes in shale. I sharpened the point and that works very well. The cutting teeth just ride in top of the shale. I tried turning the cutting points upside down but that didn't help. so my question is how should I sharpen the the removable cutters. Should I sharpen at a certain angle? Should I sharpen the top side or the bottom side. Should I grind a relief behind the cutting edge? I seems line a waste to buy new points if I have a grinder, I just need to know where to grind. If anyone has a picture of new cutters I certainly would appreciate seeing them.

 

[kneedeep]

buy new points

 

[oosik]

Sharp teeth or not. I wonder if a post hole digger is really designed to bore thru shale.

 

[Diggin It]

^^^ With no downforce and no impact, I don't see how it would be possible. Hard soil and gravel will stop them. Neighbor tried to dig my red rock gravel with a fairly large tractor and PHD and got nowhere, not even six inches. I had to resort to an air chisel to loosen the gravel and use a manual clamshell to lift it out.

Shale will need to be broken/shattered before it can be removed.

 

[Have tractor did travel]

Years ago we were holing into North Carolina clay. We lashed a pole on to the boom portion of the post hole digger. That pole extended out to the rear of the digger by about 6 feet. My helper then hung on the pole, giving us down pressure. I don't think that will help with shale.

 

[Wyobuckaroo]

One time I bought a used PHD with a well used auger.. I could not get replacement teeth for that auger so I made homemade teeth out of 3/8" flat stock..

I made several sets that I re sharpened as I could and replaced when necessary... It got the job done..

 

[tracracer8867]

I sharpen all the usual yard, landscaping stuff for some of my neighbors on my block. I wish I could persuade folks to put those implements away properly, instead of leaving them in the weather. I usually scape and oil all the wooden handles, including wheelbarrows, too. It is irritating to find a recently sharpened and oiled spade, with the blade buried in the soil, leaned against the fence. And brooms, resting on the bristles, in the weather. Teeth clencing, growling.
When I was younger, I moved into a new house and put up a fence. Dug about twenty post holes in dry decomposed granite, with a clamshell type. The clamshell was considerably cheaper to rent than the powered auger. But the auger would have made the same twenty holes in a few hours instead of a day and a half. Get a better hole with an auger, too.

 

[Jchonline]

In CO I would tell you to start with a pick axe (and safety glasses). Wonder if a pick axe will work to break up that shale? Do you need a perfect hole?