Ira wrote:First, how the heck do I make that two step hole with a standard drill? Just use one bit to make the small one, then go with a bigger bit but shallow? Or do I HAVE to buy a forstener bit?
Drill the larger hole first. The hole left by the point of the larger bit will align the smaller bit. I used forstner bits but a plain old spade bit is sufficient.
You don't really need to drill the smaller hole though for mounting fenders. I used the two step hole to increase accuracy of the insert because the bolt threaded into it was supporting a cam that operates the lifting mechanism for the mobile base of my saw. If the insert securing a fender is a few degrees off of 90 no one is going to notice.
Ira wrote:Also, how do I accurately align the holes in the fender with the holes in the frame? In other words, if the fender is already fully assembled, it's not like I can fit my drill in there to drill it at a straight angle through both the fender and frame at the same time to at least align the holes accurately.
Drill the the holes in your fender. Clamp the fender against the teardrop side (use 200mph tape if you have to or get someone to hold it). Use a pencil to mark the location of the fender holes. Drill the teardrop for the inserts. Insert inserts then mount fender. If you drill the fender holes a bit over size you don't need to get everything perfect. It is why they invented fender washers.
Also you are going to want to seal the end grain exposed by drilling the holes in the teardrop. After drilling slather in some diluted wood glue or varnish. I'd use a stainless bolt and washer.
When fenders on cars used to be bolted on a fender welt was used to hide gaps and stop the fender from rubbing the body. You can still buy it but I'd just use a strip of foam tape.