What size auger for my post hole digger?

[Sarahlane]

If anyone lives in Ontario or near or needs an affordable Post Hole Digging service you can contact MSG Post Hole they are very good with their services they just recently finished my work before the estimated time.
I am satisfied just wanted to appreciate their work.
They have some good machines.

 

[CasterHQ]

I've learned from experience that when you use an auger a bit smaller than your post, there's initially some looseness. This gradually fixes itself as the soil settles in.

And about the auger size for your post, the nine-inch ones are probably the best. They're not just good for digging, but their size also gives you room to correct any misalignment, ensuring your post stands just right.

 

[EddieWalker]

I have a six inch and a 12 inch auger. The six inch is useless. Total waste of money. I use the 12 inch for everything. If I want to put a one inch pipe in the ground, I'm using the 12 inch auger. I'm not changing it for different sized post. I use it for 4x4 square posts, 6x6 square posts and 6 to 8 inch round posts. Most of the time it's fine, but if I need to install a bunch of posts in a straight line, every 8 feet, I'm going to need my clam shell digger to modify half of the holes I drill. The auger will either angle off to one side while drilling, or hit something a foot down and slide the entire hole over.

In the last 20 years of installing fence posts, and moving them to other locations when I change my mind, I've learned that the most solid fence post is the one set in concrete. It takes everything my full sized Loader/Backhoe has to pull them out of the ground!!!! They don't want to come up, not for nothing. And the posts that I set in the ground with just dirt packed around them all pull out easier then T-Posts. I don't know of anything that pulls out easier then a post that's had dirt packed in around it.

 

[RjCorazza]

I have a six inch and a 12 inch auger. The six inch is useless. Total waste of money. I use the 12 inch for everything. If I want to put a one inch pipe in the ground, I'm using the 12 inch auger. I'm not changing it for different sized post. I use it for 4x4 square posts, 6x6 square posts and 6 to 8 inch round posts. Most of the time it's fine, but if I need to install a bunch of posts in a straight line, every 8 feet, I'm going to need my clam shell digger to modify half of the holes I drill. The auger will either angle off to one side while drilling, or hit something a foot down and slide the entire hole over.

In the last 20 years of installing fence posts, and moving them to other locations when I change my mind, I've learned that the most solid fence post is the one set in concrete. It takes everything my full sized Loader/Backhoe has to pull them out of the ground!!!! They don't want to come up, not for nothing. And the posts that I set in the ground with just dirt packed around them all pull out easier then T-Posts. I don't know of anything that pulls out easier then a post that's had dirt packed in around it.

I use a 9" auger, but at times wish it was 12" for the fudge factor with fence post holes. In hindsight, if I were to choose one size it would certainly be 12".
I concreted my gate posts and corner posts 25 years ago. Replaced the fence 2 years ago using just packed dirt and it was fine (mostly clay). Pulling the concreted posts was a challenge, and due to a stupid mistake in rigging, I did $2k damage to my tractor's 3 point where it attaches to the case. I still saved a lot of money doing it myself though.