Which grinding disc should I use?

Sometimes the alternative is way more appealing… for me, grinding welds is about as pleasant as trying to unfold Saran wrap after it has clung to itself. Grinding is dusty, loud, and unpleasant. I’d much rather spend time learning to weld better so I didn’t have to grind than taking the time grinding. It’s true, a nicely finished weld is a thing of beauty, but if you can reduce the amount of time you have to spend finishing that weld, you may be further ahead (depending on the direction of the project).

I’ll list a few of the discs I’ve used in the past, as well as their advantages and disadvantages.

This is a hard disc on steroids. The disc is formed with little mountains all over the surface which prevent it from loading up too quickly. It’s also a bit more aggressive because the mountains are almost like little teeth, cutting into the material. This disc will remove material quickly, but it’s not very good at fine finishing. Around the perimeter, a harder material has been added which is almost like a cutting disc. An advantage is the convex face (it looks kind of like a contact lens…) because it means you can pinpoint the area you want to grind by rolling the disc left to right and forwards to backwards.

Here is a 7″ Scotchbrite type pad. It attaches to a Velcro backing disc. It is not for removing material – it will take off slight imperfections, but where it shines is smoothing transitions and taking out grinding scars. One disadvantage is the load-up time – it can get clogged rather quickly depending on the material you’re using it on. Every garage should have these. They’re available in many many sizes, from little 2″ discs for your angle grinder right up to these 7″ pizzas. If there is scale on the steel you’re cleaning, remove that with a hard disc before using a Scotchbrite pad.

A flat hard disc is probably a common fixture in a lot of garages. Personally, I only use these if they’re sitting nearby and I feel sorry for them. They aren’t for fine sanding… it’s difficult to not leave grinding scars or to grind a flat surface. One advantage is their load-up rate – usually they will go quite a while without requiring a change due to cloggage. This disc will do a great job cutting welds or hogging away material using the corner.

The sun shines bright on the last disc in the list. These are called “flap discs”, and that’s a pretty accurate description. There are a bunch of sandpaper strips bonded together, overlapping each other. Advantages include, but are not limited to, the ability to fine grind with a 7″ disc (yes, it will!), the ability to hog away material quickly, and the longevity factor. As you grind, the exposed edges of the paper are gradually removed, uncovering more fresh sand paper. A disadvantage could be the price, but for a disc that lasts so long and is so versatile, I think it’s worth it. Kind of like buying a cheap step-drill… it will last for a few holes and then you’ll chuck it. In the garbage I mean… not the drill. Buy a quality step drill and it will be around for a long time.

If you have any comments about grinding or what disc you like, please add it!


  1. Craig Rathburn says:

    Another disc I like to use is the flat semi-rigid sand paper on a rubber backer. These work great at removing welds from corners while not digging in as much on the flat surface. I use 80 grit on steel parts to blend the weld so it looks like a bend then finish it with a DA. The results are great and fast.

    • DW says:

      Yeah, the DA is something I didn’t mention… I don’t think I had used one when I originally posted that. They give an amazing finish.

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