I installed a vent in a shingle roof. I used "How to Vent a Bath Fan Through the Roof | This Old House" video and the instructions that came with the vent as a guide. At the end of the day, I'm confident the vent is installed properly.
However, there were problems with drilling the 4.25" hole. I purchased a Milwaukee General Purpose Bi-Metal Hole Saw. I have been using a Ryobi drill that has treated me well for two years. The youtube video removed the top layer of shingles. The instructions said to remove no shingles, just drill the hole. I removed no shingles.
After cutting through the shingles and a little bit of wood, the bit was somewhat hot and gummed up. I removed the gummed and continued to drill. It took three batteries and 20 minutes to cut that hole. Insanity!
I know getting the bit too hot can cause it to dull. I assume that's what happened. Is cutting through a couple shingle layers seriously all it takes? A brand new bit is dull and trash because of that? What's going on???
I assume there was no permanent damage to the drill. Maybe some life removed from the batteries since they were drained so quickly??
I can remove the shingles completely in the future, but I'm just new to this and shocked. Thanks in advance.