When using bi-metal Hole Saws it’s easy to not follow the proper directions and become disappointed with the lack of performance. No matter what brand you are using there are some basic things you can do to extend the life of any Hole Saw. First have you ever looked at the proper RPM chart for your hole saws based on size & material? …What Usage Chart?
All Hole Saw Kits or Individual pieces should come with a chart of some kind that gives the proper RPM for Wood, Aluminum, Mild Steel, Stainless Steel, Etc. Since that packaging is probably deep in a landfill somewhere just keep a few numbers in mind. For a 2” Hole Saw the recommended RPM for wood is 2000, the recommendation for Stainless Steel however is 85 RPM. For a 5” Hole Saw the numbers are even lower 800 RPM for wood, 30 RPM for Stainless Steel (or 1 revolution every 2 seconds). Obviously no big deal on wood but that’s pretty slow for the steel and easy to way over do it. Other types of metals such as Aluminum or Mild Steel you can go a little faster but not like you are zippin through a 2×4 of pine. If you should fine that handy cutting guide you will also probably notice a disclaimer that says “Cutting Oil Recommended” and if you want to extend the life of your Hole Saw you should probably use cutting oil with any metal cutting.
The slow speed and cutting oil both help to keep the Hole Saw cooler, over heating will kill any Hole Saw no matter what the brand, price or fancy selling features. For serious cutting in metal you might also want to look at Annular Cutters that will work in standard drills and do a much better job.