SE-76 - random thoughts on grinding a square edge, and a slight modification

[Mike Fairleigh]

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.

[Ken S]

Excellent post, Mike.  Good thoughts and photos well done.  I'll need some time to think it through.

Ken

[RobinW]

I agree - very good post. You have well illustrated some of the minor items that cause major impacts in using the SE76. After all my struggles previously logged, I found the best way of checking I was on track was the combination of a good small square and repeated application of felt tip marker to the ground surface.

I had the same problem with trusting the front face of the SE76 for reference as it was not a machined surface and not at 90 degrees to the inside edge against which the chisel is aligned. Next time I'm having a chisel session I'll consider dressing the front face see if I can get it 90 degrees to the inside edge.

[Ken S]

This is getting very interesting.  Very good posts, Mike and Robin.

I don't believe the Tormek was originally designed to be a precision tool.  By that I mean to work within acceptable tolerances to a machinist or tool and die maker.  That is nothing negative against the Tormek.  If is was designed that way, it would probably cost $6000 or much more instead of $600.  It does provide a high level of repeatability and accuracy at a reasonable price.

That stated, I don't think the original idea foresaw the versatility the Tormek has today.  Ten years ago, while chugging along nicely sharpening knives, chisels and plane blades very well, who would have imagined being able to customize four facet edges on drill bits, let alone retouching carbide bits?  Who would have imagined interchangeable grinding wheels?

My workaday  bench planes are century old Stanley Bedrocks I have owned for forty years.  They have served me well, and I would not trade them for new Lie-Nielsen or Veritas planes.  Are the old Bedrocks the equal of today's premium planes?  Certainly not.  However, with skill and some fine tuning they can get very close.

I believe that, like the old Bedrocks and Baileys, the Tormek can get closer to the precision of an industrial grinder.  Skill and experience are certainly the main ingredients.  Jeff is certainly the example of that.  there is no substitute for years of day in, day out using the tools.  I have no doubt that Jeff is continually honing his skills and not just going through the motions.  (Read the "sweet spot" post in wheel alignment.)

We can all work on "operator error on inexperience".  We would do well to also think like machinists.  We certainly don't need lab accuracy granite surface plates.  We would be very well served by a good "B" grade small surface plate. (B grade is typically used on the machine shop floor for workaday tasks.)  I agree with Mike about Starrett quality.  If you have not used a Starrett Satin Chrome rule, you don't know what a fine rule can do.  Buy a six inch Satin Chrome 3R graduated rule with end gradations.  You will use it all the time and love it.

Back to Tormek.  I think Mike's idea of tuning the surface of the SE-76 is a very solid improvement.  How much of an improvement?  I don't know, but within the area of worthwhile.  Add it to careful dressing of the wheel and checking the alignment of the Universal Support Bar and we are getting closer to a precision tool.  Truing the front surface is a one time operation, like flattening and polishing the back of a chisel.  It takes time and patience to do it well.  It will make a better tool for the life of the tool.

Will future Tormek SE-76 jigs come from the factory with ground edges?  Possibly.  The second T7 I purchased came with the new EZYlock shaft and water trough.  My first unit came with a regular shaft, but made of stainless steel, an upgrade.  The SE-76 itself is an upgraded jig.

I know from personal experience that this forum is read by people at Tormek AB in Sweden. I hope the engineering staff have either considered grinding the front surface in the past, or will consider it.  If they feel it would be a cost effective improvement, they will probably introduce it.  It would be very nice if they posted their thoughts.

If they choose not to grind the surface, it does not mean it is not a good idea.  I think my idea of a half size flat surface jig is a definite improvement for very small blades.  I also realize that the demand for it would not be enough to justify the cost of manufacturing it as a separate product.  Any business must consider the bottom line or perish.

Robin and Mike, keep up the good work.  We can all benefit.

Ken 

[Herman Trivilino]

I think that even if all the surfaces of a chisel are true and square, you'd still not get a square end when sharpening with the SE-76 unless you check your progress frequently and adjust accordingly.  Simply applying more force with your hands to one side or other of the chisel will alter the angle.

[Ken S]

Good thought, Herman.  I do believe Mike's modification will certainly help, although there is no substitute for careful and checked work. 

Ken

[Mike Fairleigh]

Absolutely!  Careful and frequent checking of progress is a must, regardless of anything else.

[rsaygv]

I use my little engineers square to mark a line on the back (unground side) of my square blades, a few millimeters from the end, with a fine point permanent marker. It makes it very easy to monitor the squareness while sharpening.

[Ken S]

Good idea, Ron.  A small engineer's square is useful for many things.

Ken