Size of auger needed.

[Shaneard]

If you want three posts to be in a perfect line, one of them is going to need some modifying with a clamshell digger. The more you put in, the more that you will need to modify. I have a six and a 12 inch auger. The six inch is worthless. Just realize that the smaller hole you drill with your tractor, the more work it will take to modify it so the posts line up by using the clamshell digger. Be sure to get the very best that you can find. My favorite one is all metal and twice as heavy as the wood handled one.

I have an 8" and a 12", as far as I know the 8" has never been used.

A 6" post in an 8" hole isn't going to be much concrete and it will be hard to get all your post straight like Eddie said with only an inch of space all the way around.

 

[QRTRHRS]

Looks like I can get a PhD w 8 inch auger at a good price. So looks like that should suffice.

Posts will have 1 bag quick Crete dumped in hole and then filled w dirt.

Like I said, you need to "settle" the Crete, ie; get the air out of it. A piece of 1/4 inch rebar works great. You still need to tamp the backfill over the concrete.

 

[QRTRHRS]

If you want three posts to be in a perfect line, one of them is going to need some modifying with a clamshell digger. The more you put in, the more that you will need to modify. I have a six and a 12 inch auger. The six inch is worthless. Just realize that the smaller hole you drill with your tractor, the more work it will take to modify it so the posts line up by using the clamshell digger. Be sure to get the very best that you can find. My favorite one is all metal and twice as heavy as the wood handled one.

I set my corners then run a tight string to align the line posts to. I have had occasion to work with either a big dip or a big rise. For the dip, I hang a weight on the string then set a post or two somewhere along that row until I finally get them all aligned. For a rise, I find a long pole or pipe and temporarily secure it to a post so I can see over the rise. String or not, wood posts need a visual check as well. I will support an unbackfilled post then step away a couple of post spacings or so and do a visual. But then when it comes to fencing, I am fussy!

 

[747driver]

I use a 9" auger for 6" post. To big a hole and you end up using alot of concrete. The 9" gives you just enough wiggle room for concrete. I make a concrete mushroom at the ground level for water to drain away from the post.