I bought one of these trimmers and I'm very happy with it but it falls just a bit short on the light brush. I wanted to try some kind of a bush blade. The hardware is (for the most part) easy to find.
In the background is the blade I chose. It has a 1" hole.
1. Looking at the trimmer it looks like these vanes are to cool the motor - we'll need that feature. This means you're going to have to sacrifice a trimmer head to make this work. After buying a new one I went to work on the old.
2. OEM hardware
3. 1/4" fender washer (1" OD)
4. 1/4" fender washer bored to 5/16 ID NOTE: It was just a shade bigger than the 1" OD needed. I snugged the washer on a 5/16" bolt, chucked that in a drill and ran it over a file until it was a snug fit.
5. 5/16 shoulder washer (thicker than the OEM part, same OD)
6. (not shown here) 5/16 fender washer - greater than 1" OD.
Need to cut off all of the string head but the base. This initial setup was wrong. You need to cut on the line in the pic removing about half of the raised boss just below the square hole
I shouldn't have to remind you that the number of fingers you have should be the same before and after you complete this step.
Now you have this and the center section needs to be brought to the same height. Sandpaper on a flat surface and work carefully, rotating often, checking for square. If this isn't square your blade is going to wobble. Take your time.
Brought down to the same height as the 5/16 shoulder washer. (#5)
Assemble with the cut trimmer head, the spacer, 5/16 fender washer(6) and ..... there isn't enough thread engagement. Especially with the flatted shaft.
You could cut away half of the hex portion of the OEM fastener and you might get enough thread....
You could also space some washers and use a nut and locknut....
I think the best option here is a coupling nut. You would have to bore into it a bit for the unthreaded part of the shaft but you would get the most thread engagement and protect the threads as well.
This is an 8mm thread on the shaft same as a standard M8 bolt.
When I can test it I'll post something but for now it runs straight and true with no vibration.