Since joining the Tormek forum, for some odd reason I thought the "General Tormek Questions" sub-forum was the only
sub-forum. I only discovered the other sub-forums in the last couple of days and have enjoyed "catching up" on all the old posts I've missed!
One of the threads that caught my attention was Robin's, regarding the SE-76 and getting a square edge with a variety of different tools. I had some of the same concerns and thought I'd post a couple of thoughts for anyone who might benefit.
The first and foremost thing you must do IMO, is to check your work often. If you do this, your eyes will detect any non-squareness while it's still a non-issue and easy to correct. If you simply chuck the chisel/iron/whatever into the jig and start wailing away until you think you're done, there's a good chance you'll end up with a skewed edge; not because the SE-76 is bad or defective, but because few tools are truly perfectly straight and parallel on the long edges - including high end tools that are advertised to be just that. It only takes the tiniest bit of wave in the long edge of a tool to cause the edge to be ground out-of-square when using the SE-76.
Does this negate the whole purpose of the SE-76? Not at all. You simply need to realize that the manufacturing process of your tools will result in a certain amount of imperfection. By the way, I've also found new high end tools where the long edges actually were
straight and parallel, but the cutting edge
was ground skewed from the factory - in which case you want
your first grind to appear to be skewed, in order to fix the new blade!
So what's the secret to knowing what you really have? Because you have to know what you're starting with in order to know if you're progressing in the right direction as you grind. The secret is a good small square. It doesn't have to be super expensive, although I can't help but to recommend Starrett for any such tools. But it does have to be square, and there are a lot of them out there that aren't really even close. A good square will tell you exactly how to chuck the blade into the jig, where more or less material needs to be removed, where any imperfections in the tool are located, etc.
Along with that, I found that a slight improvement can be made to the SE-76 itself. If you look at the front of the jig, in the area around where the tool projects from it, you'll see that it wasn't intended to serve as a precision surface. It's kind of rounded, probably has a bit of mold seam, etc. This is the outside of the jig and isn't meant to register against anything - so there isn't supposed to be a need for it to have a precision surface. However, I've found that by flattening that entire front face of the jig (using sandpaper on a granite plate), I can use that surface with my square as an additional check for squareness when the blade is mounted in the jig.
In the photo above you can see where I flattened the front of the jig. When doing that, I checked my progress by registering the square to the inside of the jig and the front of the jig; this effectively told me that I had the front face perfectly square to the blade registration surface.
With the front of the jig flattened, it now serves as an additional point from which to check for squareness. If you look closely, you can see that although this old Stanley 720 chisel is registered into the SE-76, it's not quite perfectly square:
And by holding the square up to the registration edge of the chisel, you can see why. With a strong light behind, you can see that there's a very slight wave in the edge of the chisel. That's all it takes to throw off your squareness (in this case I had to slightly adjust the chisel in the jig to account for this):
I'm interested in hearing your thoughts on this, and any other suggestions for grinding square edges.