Always kept them on cylinder or lens side up on the table when in use. When done with the job I put them over the brow tines on random antler mounts on the wall.
Good God it's a mower deck not the space shuttle. Weld it up grind it down , drill a pilot hole and run a car reamer thru it. Certainly doesn't require 2 tons and 10,000$ of machining equipment to fix an egged out hole.
Sounds like your using a blade with too high of a teeth per inch count. Chips are likely not getting pulled out of the cut. No such thing as a one size does all bandsaw blade
5/16" floor screws? I use a 17/64" bit for those. Problem is that rusty scale is ruining the bit before you start. Needle scale or grind the scale off where you want the hole. I use either Viking or Norseman black and gold bits with lots of pressure and usually use the CRC cutting oil.
Vevor offers a set of bearing press plates in increments. It's in metric o.d. but goes pretty large in size. Last I checked the set with a couple arbors was around 70$
Keep in mind most of not all dual shield only comes in a 12" spool. Dual shield runs HOT and will destroy the standard mig gun in a hurry especially with c-25 gas. Co2 offers a little more cooling which can help with duty cycle. If it's just 1/4" material I would stick with 70s6 wire and c-25