Just a note on cull logs...
When buying logs, if you can get what you need by passing over those with metal then that is great. But with a bandsaw mill, metal in a log is not the kiss of death. My clients usually already have the logs and didn't have a choice. Here is a 20"x12', perfectly straight and round walnut with obvious metal.
If you look closely you can see that there is a metal stain from 11:00 to 12:00, another from 12:00 to 1:00, and another at 2:00. You can also see that there is a deeper penetration almost to the center at about 12:00. You could almost count the rings and determine how long ago the metal was placed in the tree. I explained the situation to the client and he decided to proceed.
The first metal we hit corresponded to the 12:00 deep penetration, about an 8 penny nail.
It was only about 1' from the butt end of the log, the other 11' were clear. As we got closer to the center we found the other metal, strand of fence wire with staples 11:00, 12:00 and 2:00, also near the base of the log. All metal was dug out and pulled so it was only hit once.
This log was milled for several different projects, 4/4, 6/4, 8/4 and 16/4 boards. Total yield was 272 bf. Hitting metal required two blade changes, both could be resharpened @ $10 apiece so add $20 for blade damage. That represented only 7.4 cents per board foot.
Stain won't tell you where the metal is in the length of the log, my handheld metal detector wouldn't pick it up. Would you have culled out 272 bf of walnut over $20 ? This log represented more than 1/2 of the wood in his tree. Consult with your sawyer and see what they are willing to tackle.