Deferred Maintenance

I have read of woodworkers who spend the first 30 minutes of each shop session on tool maintenance. Predictably, their chisels and planes are always sharp, everything is always put away, and their major machines are in perfect adjustment. But the rest of us... well, we use things until they work so poorly that we have no choice but to take time to maintain them. My jointer was like that:

A jointer is a tool to make wood flat on one side. Under the guard in the center of the machine is a spinning head that holds three knives, each 6" long. This almost-antique Craftsman jointer was decades old when I got it, and the blades had never been sharpened. Surprisingly, it still worked pretty well for rough work. But as I used it, the cut got worse and worse, until finally I had to do something about it.

Recently I had taken a stab at adjusting the knives, and found that they were really, really stuck in place. I had to do some pounding to get them out, and then I found the inevitable: they were as dull as marbles. It was time to sharpen, but I didn't have time right then so I stuck it back together and unplugged it.

Today, I was looking for a project that could be completed in one go, and I decided to try again. What I needed was a fixture to help me sharpen those long blades - it's essentially impossible to do it just holding them in your hand. Fortunately, the web is full of schemes to accomplish this, and I picked one as the basis for my solution. First, you take a piece of wood and with the table saw tilted to 45 degrees, you make a cut like this in one edge:

The important thing is that the cut is 1/8" wide, the same as the thickness of the jointer blades. I accomplished that by using an outer blade from a dado set. I used a long blank for safety, and then crosscut it a bare 1/16" shorter than the blade length.

Next (and final) step was to route a basic handhold on the "push" end, and add small clamp pieces on either end. I used some short pieces of aluminum for the clamp.

The idea is that the blade is held in the fixture by the clamp pieces, and then the fixture can be slid along a fence. The bevel edge of the blade is 90 degrees to the fence, so it can be sharpened by an abrasive face below. Here's how it looks mounted in the fixture:

And here's the complete setup. I used my table saw fence as a guide, and prepared four pieces of very flat marble tile with strips of sandpaper in the grits I had handy: 100, 150, 240 and 320. The fixture slides along the fence, and only the bevel edge slides along the sandpaper. I stuck the paper down with spray adhesive, and also clamped it from the corner to keep it from sliding.

By bumping the fence to the right every 15 or 20 strokes, I can use the entire "near" width of the paper, and then rotate it to use the rest. Ever frugal!

If you've done some sharpening, you might be surprised that I started with such coarse paper. But at that point, I wasn't sharpening, I was grinding a new bevel to erase nicks in the edge of the blade. A common mistake is to start with too fine an abrasive, or to change to a finer abrasive too soon. Almost all of the work was done on 100 grit - about 10 minutes of grinding per blade. After than, each successive grit was only used to erase scratches from the prior grit, and it only took about a minute per piece. After the 320 grit, I removed the blade from the fixture and moved to two grades of ceramic stones, honing the back to remove the burr left by the coarse abrasives, and polishing the bevel a bit more. In a blade that wide, light polishing on the bevel is easily done handheld.

Then, it was time to reinstall the knives (actually I sharpened and reinstalled each knife before moving to the next one, just to take a break from the grinding). That is the part that is really difficult to get right, and is the reason why the world is full of jointers with dull knives. There are all kinds of fixtures that are supposed to  hold them in place, and various schemes to ensure that the knife is exactly aligned with the outfeed table. The problem is that the knife moves in a circular path, and you have to set it with the knife at the exact top of its swing.

I started using a dial indicator in a magnetic holder, but it was almost impossible to use it effectively - the point was too small. Then I got the idea to use my digital height gauge, because it has a wide foot. That let me rotate the knife until it was at the top of its swing, as shown on the indicator, and then use the adjustment "jack" screws to zero things out relative to the outfeed table:

It's still problematic, because the Craftsman's design uses a wedge (called a gib) to hold the blade in place, and it's hard to tighten the gib without the blade shifting a bit. But finally, I had all three set to zero across their length and tightened.

So, time for a test. I made a few very shallow cuts on a narrow edge, and all seemed fine. So I cast around for a piece of wood with a lot of grain figuration - those are often hard to joint successfully. I jointed the face of a piece of quarter-sawn oak with a lot of cross-grain rays, and was rewarded with a very fine cut. I wiped it with mineral spirits so you can see the complicated grain pattern better:

One more test - jointing a 2 by 4 at the deepest cut the jointer can make, 1/8". Worked great!

All in, about four and a half hours to take a machine that was basically unusable and tune it up to a fine performer.  So now I can say, FOR SALE! This 6" jointer is fine, but I have my eye on an 8" jointer with a long bed and a super-sophisticated spiral cutterhead, and also with the ability to hook to my dust collection system. I'll even throw in the sharpening fixture and the pieces of tile so you can keep the blades sharp.