I got a 45mm. I think it was about a week total turnaround. A 1" bulkhead has about a 1/2" wide flange on each side, so I couldnt see .15mm on each side making a difference. Also, I dont think the tolerance on bulkheads is very low. Mine fit the hole pretty snug, had to work it a little to get it to slide in. I dont think theyre cut to exactly 1 3/4.
Mine has also cut tile... like a knife through butter. I'd offer you mine, but I'm really not sure what condition my dad using it to cut holes in the tile floors for gas lines has left it.
I was going to have a glass shop or something cut the holes, but with all the DIY work I did, $10 for a saw seemed a much better deal than $20 a hole. If I had to pay $50 for a saw, I may have just had a glass shop do it.
All told, it was pretty easy to cut the holes, and I just used a hand power drill.