A few years ago there was a spate of failed bicycle U locks after Kryptonite switched to a disc detainer style lock but had quality control problems. People were calling me every day to remove these busted locks from their bicycles. I could do so in a few minutes using a tool called a battery powered cutoff wheel or angle grinder.
Using an angle grinder one can cut through all but the hardest alloys of metal very quickly. Once lithium ion batteries came out it gave enough power to do this quickly and easily and the angle grinder became the tool of choice for cutting off these locks which in turn became popular due to the prevalence of bolt cutters and special techniques for overcoming cable locks.
Enter the Altor Saf U-lock. The manufacturer claims that this lock can withstand an angle grinder for 30 minutes! I am interested to know if this test includes diamond grit or not. The lock is $300 and weighs 13 pounds (approaching the cost and weight of a decent bicycle when I was a teen).
Note that an angle grinder can still cut through this lock. Angle grinders are really loud and make lots of sparks so you would hope that this would attract attention, maybe people would call the police, etc but unfortunately Seattle is now big and impersonal enough that people now walk past somebody cutting a lock with an angle grinder.
I have personally cut probably close to 100 bicycle locks off using an angle grinder and not once did somebody call the cops or ask what I was doing. In their defense I wouldn’t approach a stranger using a dangerous loud power tool with sparks flying around either. You’d think that at least once somebody would at least call the police or ask why I was cutting a bicycle lock off though.