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I am attempting to determine the proper safe configuration for using a 4 1/2” tile cutting blade with my metabo hot angle grinder. I have seen lots of folks utilizing angle grinders with these cutting wheels in order to cut curves or notches from tile.

I’ve read through the manual for my angle grinder and it says nothing about cutting wheels, it only mentions grinding wheels. Moreover, it prescribes a specific type of “depressed center” grinding wheel (type 27).

How do I ensure that my grinder and cutting wheel are a proper match In order to safely complete this job the grinder is new so I can return the grinder or wheel in order to obtain a compatible product. It does appear that there is a sort of but on the grinder so I doe, but again no information on utilizing that with a cutting wheel.

Also, the grinder manual states only use grinding wheels of at least 13,300 rpm despite the fact that the grinder’s own not load rpm is only 10,000. Originally the cutting blade I picked up was only 13,000 rpm. I have found a more expensive cutting blade with 13,300. The original blade also seemed to not match the arbor size. I’ve attached photos.

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enter image description here What is the best practice here? I really only need to make one notch cut and then cut around the toilet flange. I think I could get around the toilet flange with nippers if it came down to it, but imagine the grinder is the best tool for the job.Any help would’ve appreciated.

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  • The bump on the hub of that nut is a feature to help hold thick grinding discs centered on the shaft - install it with the bump facing toward a thick disc. When working with a thin disc such as those pictured, install the nut so that bump faces away from the disc.
    – Greg Hill
    Commented Jan 20, 2020 at 17:32

2 Answers 2

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13,000 rpm blades are fine. While centrifugal force does mount quickly as rpm increases, 3,000 is adequate headroom. The concern is that the blade's mass tears it apart at maximum tool rpm.

The key to reasonable safety is making sure that the blade is both centered on the arbor and secured to the motor. If your blade arbor closely matches the arbor diameter, and you can securely sandwich it using the supplied nut along with washers of almost any kind, there's not really a problem using the tool like this. If you feel any wobble or imbalance, evaluate the situation before proceeding.

I've used the same AvantiPRO Turbo blade in my 7" grinder to cut hundreds of concrete pavers with great results.

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  • Do all grinders specify depressed center wheels, and folks just use the flat cutting wheels anyway, or should I look at another grinder? Does it matter which side of the spindle but I abut to the wheel?
    – Brian G
    Commented Jan 20, 2020 at 14:00
  • I can't say what all grinders specify, but that's a common thing. I've never seen a diamond wheel that fits that shape, though, nor is it clear why they have that requirement. I suspect that it's related to the structural integrity limitations of abrasive discs, which are obviously less robust than steel.
    – isherwood
    Commented Jan 20, 2020 at 14:05
  • @BrianG, There was a question about offset disks here, but that was specifically about abrasive disks, and I'm not sure how much translates to a metal disc.
    – JPhi1618
    Commented Jan 20, 2020 at 15:29
  • Based on that other post it sounds like it has to do with the design and safety of the guard as well. Different guard types for type 27 versus type 1 discs. Currently trying to ascertain which grinders are specifically designed to handle type 1 cutoff
    – Brian G
    Commented Jan 20, 2020 at 15:55
  • Given the shape of your guard it will be OK to use a flat wheel, some guards don't have enough clearance behind the plane of the depressed center wheels to allow for flat wheels. The outer flange can be reversed to clamp the cutoff wheel.
    – Phil G
    Commented Jan 20, 2020 at 16:09
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Those warnings are primarily regarding the pressed resin disks, which are quite a bit more flexible and fragile than metallic disks. Without the depressed center you can push the resin disks up into the guard and shatter them. With your grinder I'd always opt for type 27 grinding and cutoff wheels if they were resin.

The diamond ones are a different story because the metal flexes less and doesn't shatter. You've got the clearance for them already built in or you'd have a note in the manual. The biggest things you should avoid are using a flat grinding (rather than cutoff) wheel which is forbidden in the manual and using a formed resin wheel (grinding or cutoff) for the opposite of its stated purpose. That's a good way to break them.

Regrading your comment no handheld grinders are specifically designed to handle type 1 cutoff wheels; they're designed for cutoff tools. The wheel type is part of a standard system for classifying abrasive wheels. Type 6 is a straight cup, for example.

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