After cutting hardox with my angle grinder i have discovered the best set of cutting discs for the job. I progressed up from Silverline which just didnt do diddly, bough some norton ones from Screwfix and they were pretty good but the best ones i have used are Eng-Weld cutting discs. they go through hardox with ease and last twice as long as norton and 30 times longer than silverline. so there you have my tip of the day