DISCLAIMER: First let me say that its not recommended to use a circular saw blade on a brush saw.
For starters, that’s not what the blade was intended for. Secondly, the arbor hole on the blade is larger that the shaft on the brush cutter.
I recycle my circular saw blades to use on my brush saw. Its s bit of balancing act because the blade hole is much bigger than the shaft on my Stihl FS 250. The picture below shows it in a good position to tighten. What I do is put on the big washer (shown further down in another picture) and tighten the nut just enough to keep the blade in place. Then I slowly spin the blade to see if its still centered. Usually it isn’t and requires a slight movement in one direction or another. Once centered, tightened down the nut.
Then I start the saw. If the blade is centered, I will not feel any (or very little) vibration in the shaft. If there is vibration, its back to square one with re-centering the blade.
Once its centered and in place, I can cut for hours the tall grasses, weeds, bamboo, hardwood sapling up to an inch in diameter and bigger. I’ve even felled softwood spruce and fir up to 2 inches in diameter. Its a great saw. Though there are times when cutting poplar (popple) sapling which grown in clusters, the saw can get caught up and wedged amongst a cluster, that’s usually when the blade gets knocked off center (or worse, bent out of shape). I’ll know it because the brush cutter shaft will start to vibrate right away. Time for tool maintenance. Below is picture of what the blade would look like when off center. Compare it to the photo above.
The solution would be some sort of spacer. I did make an attempt some time ago to file down a washer but it didn’t go so well so I had given up on the idea for a spacer. After a while the idea came back to me to try again. It just popped into my head to try a piece of copper pipe. Well lo and behold, the outside diameter of the pipe is a perfect fit for the circular saw blade.
However the inner diameter of the pipe is still larger that the shaft. BUT, it does fill in significant space. Yes, the copper metal is soft but its worth a try.
As you can see in the photos above and below the copper is higher than the blade. I wanted to file the copper ring down enough for a snug fit under the OEM spline washer.
I installed the parts and ran the saw but it still vibrated. Rather than work on the copper ring some more, I thought about maybe using something else, maybe a thick piece of brass. I have a box full of brass parts in the workshop.
I found a brass coupling that was the perfect fit for the diameter of the hole in the blade, but again, some work would be needed to get it to fit over the shaft.
I ground down the excess with the grinder and had to file the inner hole a bit with a bastard file. I had a snug fit, so I pushed it onto the shaft by tightening the lock nut onto it. Well that was a bust. The brass being so soft, it cracked.
So its back to the copper pipe as a spacer. I spent some more time at it, filing it down until it was just the right height. Its now a snug fit, the saw runs well and I’ll be testing it out this weekend. I see no reason why it should not help in preventing the blade from going way off center.
AGAIN WITH THE DISCLAIMER: BE ADVISED THAT THE USE OF CIRCULAR SAW BLADES ON A BRUSH SAW EQUIPMENT IS NOT RECOMMENDED. BUT IF YOU DO, ITS UP TO YOU TO THINK SAFE AND WORK SAFE. EYE PROTECTION SHOULD ALWAYS BE USED ALONG WITH HEARING PROTECTION.