Telephone/utility pole anvil stand question

[Joshua R. D.]

To start, I'd like to apologize if this question has already been addressed before as I attempted to look for a similar topic/comment that answered it but couldn't find one.

Anyway, if have several 20 ft lengths of telephone/utility poles (whichever you prefer calling them) left over after building my smithy. (Well, it's more of a small pole barn at the moment, but I'm planning to add 4.5ft cobble "half" walls as wind breaks... eventually. I digress) I've used 6ft sections of utility poles as anvil stands before with 3ft buried in the ground... but that was in florida, where rocks and clay didn't exist. I can't remember where I read/heard it from, but 2/3 feet of telephone pole in the ground helped make a "smaller anvil work like a heavier one" (of course I know there are a lot of factors that go into what makes a proper anvil but this is just a simple way of saying it's adding more "mass" and making it a more solid piece... I think that's the proper explanation... I'm rambling now.)

 

Long post short: how long of a section do I actually need and how much of it do I bury? The type of ground it'll be in is, if you're familiar with gettysburg pa, brown clay, rocks, (specifically: predominantly diabase, granite, slate [red, black, grey], quartz, to a [lesser extent but still present] iron [bog, limonite, hematite, magnetite] and other minerals/rocks I can't remember off the top of my head.) Oh, limestone and dolomite, so lots of calcium carbonate, if that particularly matters.

 

thank you to anyone that takes the time to read and respond to my "long winded" post and eventual question (which I apologize for)

 

Again, thanks, Josh.

[ThomasPowers]

Stability and resistance to downward forces are the important factors, not some random number.  If you dig down and hit a big rock; well if you have enough depth to hold it against sideways motion then your fine!  If you dig down and hit pure soft sand, then you may have to dig deeper!  (My shop's foundation ranged from rocks they had to use the backhoe to remove to one corner where you could push a rod 6'+ down in pure soft sand.)

So how deep to keep the pole from being shifted sideways under heavy work?  (Note that a smaller anvil may "work" like a larger one; but you still can severely damage it with a missed sledge hammer strike!)

[JHCC]

As ThomasPowers notes, resistance to sideways movement really is the important thing here. Two to three feet is a good general rule, but if the ground is exceptionally soft, you want to dig it wide as well as deep, so that you can pack a lot of rocks etc around the sides as well.

[anvil]

I live in the rocky mtn west, and they are named that for a reason.  As has been said above, 2'-3' is good.

[ThomasPowers]

If you dig to the  Mohorovičić discontinuity you have gone too far!  Things get softer after that!

[Joshua R. D.]

Rocks most certainly arent a problem when I say clay and rock, I mean cobbles you could build a wall out of. In fact, my smithy is built up against a rock wall from the 1800's. Probably all the rocks and boulders they dug up when making the foundation for the house and yard.

Anyway, sideways movement isnt a problem with all the clay and rock.

[anvil]

Still working on mancos shale.  insidious stuff! 

[Charles R. Stevens]

1/3 to 1/2 the length of the post works around here being that Your taking about 30” above the ground shoot for a 60” post down to a 45’’ one