Metal in trees is a fact of life, unfortunately.  Fortunately, hitting metal with the Wood-Mizer bandsaw is neither a disaster nor dangerous.  At worst, the metal has made a stain which ruins your board, or you incur a blade charge due to a dulled or ruined blade.

A blade charge between $5 and $20 for blades is made depending on whether the foreign object has just dulled, or ruined the blade, or something in between.  This is inexpensive compared to hitting metal with a large expensive circular blade, and is one of the advantages of portable sawmilling. 

Trees which have grown a long time near buildings are more likely to have metal in them than ones grown in the woods.   Being able to cut yard trees is an advantage of my equipment. 

Using a metal detector can save sawing time.  Sometimes metal is found near the surface and can be removed easily.  Cutting off the end of a log to get rid of metal or avoiding cutting low-value logs with metal in them are also options.    High value logs, however, are usually are sawn without removing the metal.  A 2" thick, 18" wide walnut board 15 feet long is worth the extra $20 risk of a ruined blade.  Digging for metal is usually a losing proposition which ruins wood and wastes time.  Once a nail or screw eye is sawn through, it can be removed with much less damage to the wood than digging a big hole to find it (or not find it).

I use two kinds of metal detectors.  Whole logs can be quickly scanned off the mill with my Rens 4000 detector which can detect a 3" nail near the center of a 30" diameter log.  This detector can quickly identify if metal is present and approximately where it is.  Logs need to be on the ground away from the mill (the metal detector will always find the sawmill (!!!).    If the ground has metal in it, it sometimes is difficult to detect whether the metal is in the ground or the log.

A second scanner is the Lumber Wizard wand-type scanner.  This much less sensitive scanner can be used on the mill, and detects nails 1-2" below the surface opf the wood.  When metal is suspected, scanning the surface can judge whether metal is likely to be hit in the next cut.  If the surface "sounds clean" it usually is. If metal is present, one can choose to dig for it, or not, or to put on a "blade second" to make the suspect cut. I usually carry "seconds" blades which were resharpened after hitting metal or being damaged some other way.  These blades may produce a rougher cut than usual but still cut straight, which is what's most important.  If we hit metal which ruins a "blade second"  the cost will be lower (or no cost) compared to  ruining a regular blade.

Once you have hit metal in a log your view on pounding nails or putting screw eyes in trees will be different!!!