Flattening a Plane Sole with Aluminium Oxide Finishing Film
This Juuma No. 4 smoothing plane had a slightly hollow sole, and encountered a piece of metal against its front left edge while planning (see image.) The resulting dent on the front led to a small bulge on the bottom edge. This provided an opportunity to use our new Alox finishing film while dressing the sole.
We selected a sheet of Alox finishing film
with 100 µ particle size (about 150 P) for the initial flattening, and a sheet with 40 µ (about 400 P) for polishing out the grooves which were caused the coarser sheet. The sheets have a size of 230 x 280 mm and are comparable in size to normal sanding sheets. Since no matching glass plate was at hand, we decided to use an available granite measuring plate
with dimensions 457 x 152 x 51 mm. This also allowed us to have both sanding sheets adhered simultaneously on the surface. Since the surface of the granite slab is a little smaller than the area of ??two abrasive discs, we cut on the rough sheet to 150 x 280 mm and the fine sheet to 150 x 170 mm, and adhered both to the slab. The Alox Finishing sheets have a self-adhesive backing, but one should definitely make sure that the surface the sheets are being adhered to is completely flat and free of grease.
Now, a few drops of water were put on the finishing film we were ready to go. We moved the plane in a circular motion over the magenta grinding surface with 100µ grain size.
After about 15 minutes the plane sole looked like this. The dark stripe along the side of the sole shows where the abrasive has abraded the surface, and where not. So there was still a lot to do, especially since the area of ??the plane's mouth must engage the abrasive across its entire width. It is worth mentioning that the progress is increasingly slower. This has 2 causes: first, the surface that is contacting the abrasive is increasing. And second, the abrasive grains have been wearing down. So it's time to change the sheet.
The spent leaf was easy to remove smaller remnants of glue were removed with a spatula and alcohol.
After adhering a new sheet, we continued. As you can see we temporarily removed the frog (the steel screws) to prevent, through capillary action, water getting between the frog and the rest. That was to avoid rusting later. Look at the bright spots at the middle of planning mouth, and the larger light strips in the middle of the back, where the abrasive has not yet abraded the surface. What appears on the front of the sole as bright spots is diffused light, which shows that the abrasive rubbed very well there. The black strip at the edge is swarf (grinding sludge.) It is clear that we are already making really good progress, but it's just not quite ready yet. Also, it was at this stage once again much slower for us and even a little difficult. Now we decided to change sheets.
After the deepest point is by the planer mouth is abraded the abrasive, I switched from the circular grinding motion - even on the coarse magenta sheets - to a back and forth motion to obtain a uniform groove pattern. Then the plane was placed a little further to the right and with the same movements - back and forth - we continued with the fine sanding on sheets with a grain size of 40 µ (about 400 P.)
The finished planer: you can still see a dark stripe at center back. There, the abrasive has not abraded the sole. The inward curve is no longer measurable with our board, since it is less than 1/50 mm, and most of the sole has a very good finish. I decided at this point to stop because more work would not improve the performance significantly. The plane at this point would experience no restrictions in terms of its function. Of course you can smooth out the last piece at the rear also, the drive for perfection has no limits. After you have flattened your plane, dry it well and lubricate it so that rust is prevented. The whole process as illustrated took about 60 minutes. Time allocation you can control yourself; if it is to go faster, you can move the sanding sheet, but the process will be a bit more expensive.