This sander is another great product from Arbortech, although when I first saw a picture of it my first thoughts were that it would be spinning too fast and would probably burn the wood. I was proved wrong. Even spinning at 1200rpm on the angle grinder I attached it to, the 50mm flexible disc orbits rather than spins in contact with the wood.
The extension shaft supplied is similar to the one that comes with the Mini Turbo and has an M14 internal thread on top for attaching to larger angle grinders. This is called the random sander attachment. An adapter nut that screws into the M14 thread allows you to screw it onto a 10mm angle grinder shaft. Also in the kit is a flexible rubber disc that accepts self- adhesive stick-on discs. Five discs each of 80,120, 180 and 240 grit supplied. Initially 60 grit was supplied but this proved too inflexible to hug curves. The finer grits are much better for getting into tight spots.
The random sander attachment also has a separate shaft set into a bearing that is off-set about 1mm off centre. The bearing is held in place with a circlip. In the shaft there is an M4 internal thread that takes the screw on the rubber sanding pad.
The offset of the bearing gives the 2mm random sanding action, just like other random obit sanders we use in our workshops. This orbit is about half of most other sanders, which is why it does not leave orbit marks. The 50mm diameter sanding pad is flexible on the outer 6mm which allows it to flex into tighter curves.
I trialled the sander on two different sculptural pieces, one in grey ironbark, one in Huon pine. I was quite surprised how quickly the sanding action removed rough marks with 80 grit discs, obviously slower on the ironbark, but quickly with the Huon. Swapping to a 120 grit disc on the Huon pine cleaned up the surface a lot smoother without sanding marks. I tried it in some of the tighter curves on the sculpture but found it was not the right sander for the tight channels. On the more open curves like the back of my wall piece, it does a great job.
The supplied self adhesive disc has a peel-off back which can be replaced if you want to swap to a finer grit and before the abrasive has worn out. The adhesive used seems to be industrial disc cement which holds on really well. The discs never seemed to heat up and soften the adhesive in use. I found myself looking for finer grits to polish my wall piece and on checking with Arbortech, learned that they are working on producing the finer grits up to 600. The inventor, Kevin Inkster told me he was amazed with the results of using a 600 grit disc on jarrah. He said he had never sanded anything to 600 grit before, but is now converted.
You might think using an angle grinder with a long shaft would be a little cumbersome and vibration might be a problem, but it is quite comfortable to use and has little or no vibration. The attachment very well machined and presented, just like other Arbortech products. It is one of those products that all woodies need for the curved sanding applications that we run into.
Available from Arbortech: www.arbortech.com.au or phone (08) 9249 1944.
Words and photos by Neil Scobie. First published in Wood Review, issue 84.