Digging post holes has never been easier than with the Seymour adjustable auger. The 21-inch hard-maple cross handle gives you the leverage you need to turn the auger with ease in a variety of soils. Boring 6-, 7-, or 8-inch holes is accomplished by adjusting the yoke, which is secured into position with a locking bolt. The high-quality construction features heavy-gauge steel blades riveted to the cast-iron yoke and a steel tee welded to a high-tensile steel tubular shaft.
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I did start the hole with a post hole clamshell digger for two reasons. One was to collect the chunk of sod in one piece. The other is that while the auger will chew through the sod, it wanders around a bit and requires more work to get into the sod than it takes to dig the rest of the entire hole.
This tool is built very well and looks like they have been making it the same way for 80 years (cast parts, beefy looking).
Another benefit of this design is that you can extend the handle with common black pipe. Last winter I dug a 7.5' deep hole with it. You're only limited by how much weight you want to lift and how high you want to lift it.
VS a clam-shell post hole digger, this is a MUCH more efficient design. I do wish they mad one that was 10".
I use mine in combination with a standard clam-shell. I find it easier to start the hole with the clam shell (breaking through turf and such) and then auger in! Once I'm to depth, the clam-shell is helpful for shifting the bore profile ... make it a little bigger here, there, etc. I have an 18" galvanized pipe (black pipe works too ... any 3/4 pipe thread will do) on it as an extender... that lets me get plenty deep.
We have a tractor mounted auger that we don't use ... its not as accurate in its placement of the hole, makes a much larger hole, is lousy at clearing said hole, threatens to suck in any loose clothing.... A major benefit of this auger is evident when go to pack gravel or concrete around your post ... the amount of fill material required is greatly reduced!