This is part two of my restoration of an I. Sorby tenon saw. For part one, you can read my earlier post by clicking here.
Before I move on to cleaning the saw plate, I think I had better address the saw nuts that were just removed.
As you can see, they are quite dirty and in need of some serious clean up. The backs had a lot of green tarnish and sticky gunk on them. To clean these, I use several methods. I have a very soft wire wheel on my bench grinder that removes this build up very quickly. I am hesitant to use a wire wheel with brass this soft, but I have found that if you turn the grinder on for just a second and power it back off before it gets up to full speed, the inertia in the spinning wheel is enough to clean the parts without the fear of the wire eating right into the brass. I only use this method on the back side of the parts.
The medallion has a lot of fine detail and should be cleaned carefully. I have found that the best thing for cleaning all of the crud out of this is a soft nylon nail brush, warm water, and Bar Keeper’s Friend.
I love this stuff. It cleans up brass parts beautifully. I also use it to clean the brass depth adjustment wheels when I restore Stanley bench planes.
The split nuts also need some work. The slots in them need to have well established side walls for the split nut driver to engage or the soft metal will strip and deform when you try to re-install them. To accomplish this, I use one of my needle files that is the same width as my split nut driver, to deepen and clean up the kerf or slot in the split nut. I lay the split nut on a flat surface and carefully file the slot so that it has a clean uniform slot.
This new re-defined slot will make it much easier to re-install when everything else is done. In the below photo you can see that the split nut on the right now has a clean and well-defined slot while the one in the middle still looks a little chewed up.
The last thing that I do with the split nuts is clean the faces. To do this, I use a strip of 320 grit self adhesive sandpaper on a granite slab.
Simply rub the face gently on the sandpaper to clean them and restore the brushed look to the brass. It looks much better if you take the time to ensure that your sanding marks are parallel to the slot in the split nut. Once the saw nuts are cleaned and the slots re-defined, I put them in a small container, like a jar, so that they wont get lost until they are needed again later.
Next we need to address the saw plate. I use a razor scraper, a soft sanding block, pressure sensitive adhesive (PSA) backed sandpaper, and a light oil for lubrication.
I used a sharp razor scraper and carefully scraped away as much rust as possible. You have to use caution to prevent the corners of the razor blade from putting any deep scratches in the saw plate as these can be hard to remove later. It is surprising how much rust and gunk this method removes and it is way faster than going straight to the sanding.
Next, I use PSA backed sandpaper on a semi-soft sanding block. I get the sandpaper from Klingspor’s Woodworking Shop in various grits. Each roll is 2 3/4″ wide by 10 meters long and lasts quite a while. I love this stuff. I use it as my primary sandpaper for just about everything that I do. It works great when stuck to my granite reference surface for flattening parts, lapping the backs of chisels and plane irons, or even lapping the sole of bench planes. I also bought the sanding block from Klingspor’s. You can find it here. For oil, I use either a 3-in-1 household oil or a very light weight motor oil like 5W20.
I usually start with either 100 or 120 grit. I first squirt oil on the saw plate and then begin to sand in straight lines along the length of the saw plate. The oil quickly turns to a nasty brown sludge, but I find it is far easier to wipe this up with paper towels than it is to deal with rust dust all over the place. Add oil as needed. I try to sand until I have a nice uniform look all over the saw plate and any signs of surface rust are gone.
I then wipe the saw plate clean and switch to 220 grit paper. I sand the whole plate again with oil wiping up and adding oil as I go. You should not expect to get a bright shiny look that you would see on a new saw. You’re not going to get it and it would look out-of-place. On a steel backed saw like this, I also sand the spine to remove the surface rust.
Most old saw plates will have some pitting. To what extent and how deep will vary widely. By sanding with a semi-soft block, I find that I can achieve a more consistent and smooth surface but will not be able to sand down into the bottom of the rust pits. I’ll address those spots in the next step. Using a sanding block like this is also a very good technique to use when trying to lightly clean a saw plate without removing any remaining etching. It’s not foolproof, but sanding with finger pressure on the sandpaper alone is far more likely to remove the etching. I don’t know if this saw ever had an etched saw plate, but it was so dirty and rusted that I was not concerned about the possibility of removing it when compared to the need to get it clean and usable. As it was, during the cleaning process, I did not see any evidence of the plate ever having been etched.
The surface rust has now been removed but the rust down in the pits needs to be dealt with or it will continue to deepen over time and eat away at the plate. If I can’t get at this rust to remove it, the next best thing is to neutralize it. To treat the rust, I first had to remove any traces of oil that were left on the plate from the previous step.
Once I had sanded the saw plate, I wiped it down to remove as much of the dirty oil as I could. I then sprayed it down with a quick drying brake parts cleaner and wiped it again with paper towels. The plate now looks quite clean and much better than it did when I started. The next step however is going to mess all of that up.
To treat the rust, I bought some OSPHO rust neutralizer from my local hardware store. They had it in their marine supplies section and it cost about $9. According to the company’s website, “OSPHO causes iron oxide (rust) to chemically change to iron phosphate – an inert, hard substance that turns the metal black.” I thought it was worth trying.
I poured some of it into a glass jar and used a disposable chip brush to paint it on. Like the brake parts cleaner, I did this outside to avoid breathing any fumes. I found that to get good coverage I had to keep brushing it on and spreading it around for a few minutes. Otherwise it has a tendency to bead up and only treat the parts that remain wet. By constantly spreading it around, the result was more even.
After a few minutes, the saw plate starts to turn brown and looks terrible. Don’t worry, I’ll fix that later. I treated the whole thing, plate and spine, since they both had rust pits.
After spreading it around to ensure evenness I left it for about 30 minutes. The chemicals continue to react and the saw plate really starts to blacken. The first time I did this, I was concerned at how bad it looked and thought I might have screwed up. It cleans up later.
After allowing time for the OSPHO to work, I dried the saw plate and sprayed it off with the brake parts cleaner again. Here it how it looks at this point:
At this point, any remaining rust that was it the pits should be neutralized. However, the saw looks terrible but that’s easy enough to fix. I again sanded the saw plate and spine with the semi-soft sanding block and oil for lubrication. I started with 220 grit and repeated the process with 320 grit. This dramatically brightened up the saw plate but remember it’s not going to look like a new saw, the black iron phosphate that is in the pits is there to stay.
That is about as far as I am going to go with the saw plate. To prevent any rust from returning, I wiped the saw plate down with a light oil for protection. You can also use paste wax, or both.
In my next post, I will explain how I polished the spine of the saw.