Here's a Quick Tip to Grind a Inside Fillet Weld to a Smooth 90

Here’s a quick tip on how I grind a inside corner fillet weld. This doesn’t come up all that often but sometimes its necessary. Here’s a before and after photo.

A flap disc or skinny wheel would be most welders choice to remove this but as you can see the attack angle and disc design makes it hard to grind out the weld correctly without gouging the surrounding base material.

The solution I’ve found that works the best is the combie click system from pferd. Its design works great to grind flat because of the backing pad. As you can see it allows the grinder to get the correct angle and only cut the weld. The disc is stiff so it can grind at the very edge without bending or flexing.
The fast switch between grits makes clearing the bulk of the material out with a 36 grit then switching to a 60 or 220 once you get close to the base material.

Hope this tip helps you get those pesky inside welds cleaned up.
You can find the discs and backing pads here. Black pad for curves, Blue for flat surfaces.


So what kind of milage are you getting out of one of those 36g discs? Do you sell just the disc without the backer?

The lower grit discs go pretty far. They are ceramic so you get your money’s worth. You need the backing pad to make it work with the grinder. Yes you can just by the discs when you need more. I like this system for finish grinding.

I have never used this combo, but about to wave some in to try. You prefer this combo over a pferd polifan disc? I have yet to try one of the polifans as well, but by the looks of it, seems like it is purpose built for this application?

I use the combie click system for all the finish work. I use it to grind around the tube not just the inside fillets.

I have a video coming soon showing my welding and grinding process to achieve the finish in the first photos.