I've started seeing plastic staples in some of the Lowes construction lumber. Found one nail and one HUGE spike but missed two smaller ones so we ate two blades during our last Woodmizer day.
Alan, watch them yard tress 8-O - you'll be sawing along, all is going well, then wham you hit something in the log and the blade explodes. The queue is when the mill stops singing it's song and starts screaming, hit the clutch fast... Out comes the chain saw to figure out what the heck is in there. The blade usually makes it through a few nails without exploding. It's larger chunks of metal, rocks and glass can be a problem if your not quick on the clutch...
Even if you peel back the bark there could still be stuff hidden inside that the tree grew around when it was young. I have yet to hit anything in the logs I've sawed that we purchase from logging companies. But still do at times when someone brings logs in to be sawed. I make it very clear up front my sawing rates do not include damaged blades or additional labor to chain saw chunks out of a log to get ride of trash. If there's to much trash I won't saw the log. I'm almost thinking I might change to an hourly rate + damaged saw blades for customer brought logs. If the logs are clean they would come out ahead of the game, but if the logs are trashy they would pay a little more and I think it would be fair for everyone.
A few other things to kinda be on the look out for with yard trees, is pith location and wind shake.
If the pith is not close to center and pushed off to one side you got a problem. Depending on how far the pith is off center you may be looking at usable lumber from only 1/2 the log. Off centered pith usually results from a tree growing on a hillside, alone not surrounded by other trees or growing up against something like a building. The other 1/2 will be good for boat planks or fire wood, because the boards will bend up, no matter what you do to them. I saw this picture in your photo gallery which is a classic example of pith off center.
A wind shook tree will have a lot of stress and will twist like there is no tomorrow. Wind shake is very common with yard trees, there are no other trees around to protect it from the wind and it's constantly being shook, the tree builds up a lot of stress in the main log. You'll notice wind shook right away when the board twist as you cutting them off the log or if the log it's self wants to raise up off the bed of the mill as your cutting. I've seen wind shake so bad that the log actually split after taking a few boards of it.
blah blah blah - enough already jeff...