I have a 4 1/2" angle grinder and I bought this blade because I need to cut some concrete bricks for my patio.

With the blade I received a small disk that fits in the hole of the diamond disk and it seems to be some sort of adapter so that the blade can match the size of the arbor.

When I tried to attach the blade that seemed to be the only way to attach it (by using this small disk) but when it did not really work, the blade did not seem to attach firmly to the arbor even after I tightened the screw that was supposed to press both the blade and the adapter (the piece with three small wholes in the picture)

I am talking about the yellow disk labeled "Adapter" below. (I represented this based on what I remember about it, I don't have the tool in front of me)

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What am I doing wrong?

Edit: I have checked and indeed if you flip the nut then the nut presses on the disk. If the nut is not flipped the nut pressed on the adapter. The nut in this last mentioned position is used when you have a recessed blade that you use angled for grinding.

The adapter is needed to center the blade on the arbor BUT it has not role in in the tightening mechanism that keeps the blade in place. That it the role of the nut if it is flipped

4 Answers 4


Depending on the thickness of the blade, you flip the locking nut over. Also, it may or may not need the adapter for different disks.

  • The adapter came with the disk, I am just wondering why the disk still rotates when the adapter is in. The adapter seems to match the arbor size perfectly. I will try to flip that nut when I get home, I did not look at that :-) thanks
    – MiniMe
    Jul 16, 2015 at 16:06

I don't have either tool directly in front of me, but...

I'm pretty sure the arbor size on a circular saw is 5/8" and the disc fits that exactly. I'm pretty sure the spindle size on a typical angle grinder is 5/8", but the discs' holes are 7/8" meaning the arbor size for an angle grinder is 7/8".

Without any disc on your angle grinder, there are two metal pieces: the one closest to the motor (I'll call it the top) and the one that screws on the end (I'll call it the bottom).

The top piece is kind of a flat cone. You want the opening of the cone facing away from the motor (towards the "bottom").

The bottom piece is a kind of like a thick washer with screw threads in the middle. But there is a tiny lip on one side of that disc!

When I switch from a grinding disc to a cutting disc, I typically have to flip the bottom piece over.

Do not use the insert.

The insert is for use with a circular saw. The discs I use for my grinder do not fit tightly around the threads, at all.

Try screwing on the bottom piece flipped both ways and see which way it "sits" best.

The disc is spun by the clamping force, not contact with the spindle.

  • 2
    The insert is needed to center the disk!
    – MiniMe
    Jul 17, 2015 at 1:17

The 5/8 arbor insert is needing to be knocked out. I don't know how to do it correctly or safely, but I know how I do it. I put the disk on the grinder with the threaded nut flipped flat against the disc. Needs to be really tight. Give the button a few hits, letting it spin just a second with each. Then unplug or pull off battery and wiggle the blade side to side until it feels loose. Un thread the nut and pull off the disc. You should see the disc and the arbor insert separated. Take the insert out and now your disc should have 7/8 arbor .

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. Jan 31, 2020 at 23:35

The only reason those rings exist is to provide one with a means of operating the tool using a blade with a bigger accepting hole diameter than the thinner, less girthy in circumference acceptor shaft If the tool you plan to operate the blade inside, preventing centrifugal forces from borking the rotational integrity of the blade and causing it to spin like shut and be, like really dangerous. You can also use the rings to separate two like blades that operate in tandem on the same acceptor shaft provided that the hole and shafts are of congruent diameter, and the diameter of the ring Bridging the two wheels exceeds that of both the hole and shaft.

  • Though I do not recommend this *
    – user125431
    Nov 8, 2020 at 2:58
  • Hello, and welcome to Home Improvement. It's really hard to understand your answer; would you edit it to clarify? And, you should probably take our tour so you'll know how best to contribute here. Nov 8, 2020 at 3:57

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