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It should be easy enough to make one out of 12 mm rod.  The only tricky part would be the weld. 

Take a look at the SVA-170 Axe Sharpening jig.

http://tormek.com/international/en/grinding-jigs/sva-170-axe-jig/

I've never used it but have thought about getting one.  Do you have the scissor-sharpening jig?  I've used the portion of that jig that attaches to the universal support to sharpen stuff like that.

Yeah, that seems excessive to me, too.  It took me several years to put 50 mm of wear on my first stone.  I'm not a commercial user, but I sharpened all kinds of stuff with that stone, from shovels to lawn mower blades and of course lots and lots of knives.

Have you by any chance been using the truing tool a lot?  That'll wear your stone down quick because, well, that's what it's designed to do.

Check out this thread:  http://forum.tormek.com/index.php?topic=930.0

In addition to the method I describe there, I've also in the past used the universal tool rest along with a c-clamp attached to the blade to keep the grinding angle constant.

Well, if you've had only moderate success with bench stones, then the Tormek may suit you.  I have the equivalent of the T-7 and don't have any experience with the T-3.  I bought mine several years ago and it's a big improvement over bench stones.

The Tormek claims to have a 1000 grit stone when properly graded.  Using the jig, you get a smooth bevel because the angle stays constant.  Using a bench stone takes more skill to keep the angle constant.  But, if you could pull this off, theoretically, you'd get a smoother bevel with the 4000 grit water stone.  I doubt it'd make a difference on any of the knives I use, though.

A used machine can be a good cost-saver.  Check the grind stone diameter to see how much wear it has.  When my machine got old it was in need of a new grind stone and a new main shaft.  These machines are made well and can be repaired quite easily.  I would buy a used machine if it appeared to be well cared for and was available at a good price.  Things I'd look for, in addition to the amount of wear on the grind stone, would be a good-running motor, and a main shaft that's not bent or rusty.

You can read about my repair adventures by following this thread:  Rusty Main Shaft http://forum.tormek.com/index.php?topic=929.0

Are you using the the T3 or the T7?  The only thing I can think of that would cause this "step" would be having the chisel too far to the right or left, so that a decent portion of it is not in contact with the grindstone.

If, as you say, you're moving the tool back and forth across the grindstone, then I can't imagine what's causiong it.  Maybe I don't know what you mean by a "step".

Is the vibration accompanied by a loud chatter?  This happens, it's just a condition known as resonance.  Change the amount of force you're applying to the tool, or just remove the tool from the wheel and make contact again.  This usually happens to me when the tool is very close to being sharpened, or has already been sharpened to the point that additional contact with the wheel won't make it any sharper.

I think you're obsessing about the scratches.  Getting that mirror finish is possible, and it's good showmanship when selling the product, but the fact is, you don't need it!  Those chisels are as sharp as they can be, and they're a joy to use when they're sharp.  The same is true of plane irons.

I have a couple of old planes that my Dad had in his garage.  It was obvious that the irons hadn't been properly sharpened for a very long time.  I got them sharpened, and it's the first time I've ever used a truly sharp plane.  They work like magic.

So do the chisels.  You should be enjoying them.  They're not going to work any better just because you got the scratches out.

The shape of the blade is a factor, too.  Some blades have cutting edges that are curved.  I could never do a good job of sharpening those.

When it came time to buy a new mower, one of the factors I considered was the shape of the blade, and in particular, the shape of the blade's cutting edge.  One of the first things I did after buying the mower was purchase an extra blade.  It's a Bolens MTD 742-0642 twenty-two inch blade.  The factory edge on these blades is terrible.  I measured the bevel angle to be 25 degrees, and after using the blades for a while with moderate success, I perfected a technique.

I use the knife sharpening jig (SVM-45).  I set the angle to 22.5 degrees.  I use the same technique as I'd use to sharpen a wood chisel, with some modifications.  The first thing I do is clean the blade using a wire brush.  Just like a wood chisel, there's a side with a bevel and a flat side.  Keeping the flat side flat is essential.  I take sandpaper and clean the portion of the flat side that's near the cutting edge.  If necessary, I use a file on the flat side to make sure it's flat, removing any damage that may have been caused by the mower blade hitting something.  Then, using the SVM-45 jig I sharpen the bevel side using the same technique that I'd use to sharpen a chisel, with the following modification.  I take the blade over to my bench grinder and remove some of the steel on the bevel, but I'm careful to stay away from the region of the bevel that's close to the edge.  In other words, I remove some of the steel from the heel of the bevel.  This saves wear on the Tormek grinding wheel.  I move back and forth from the bench grinder to the Tormek machine, inspecting the edge each time.  Finally, I finish it off on the Tormek machine.

Now comes the tricky part.  It's hard to remove the burr with the honing wheel, so I developed a new technique.  I use a small sharpening stone, like the type you might use to sharpen a pocket knife.  I clamp the mower blade in my bench vise, and with a little oil as a lubricant, I gently polish the bevel, and the flat side near the bevel.  This works quite well.

And now, be careful.  You've got a very dangerous instrument in your hand, capable of doing some real damage to your skin.  I've got a nice slice in my finger to remind me that I need to be careful around sharp mower blades.

Does the grinding stone wobble when it's spinning?  If so, you probably have a bent mainshaft.  That's the only thing I can think of that might cause the truing issue you describe.

As far as the bevel being wider on one side than the other, you have simply ground too much on one side of the knife than the other?

Have you watched the video clips of Jeff sharpening the knife?  (You can find them on this website, or just do a YouTube search).

BTW, how much did you pay for your used Tormek?

I've never used the T3, but the problem of not getting square chisels is not unique to the T3.

If your conclusion about the tolerances not keeping the tool rest precisely parallel to the surface of the grindstone is true, you can make sure they're parallel by using a anything as a gauge block.  Take, say, a scrap piece metal or wood and place it between the tool rest and the grindstone, and slide the tool rest down until it traps the gauge block between the grindstone and the tool rest.

Slide the block back and forth along the surface of the grindstone and check to see if it's really not parallel to the grindstone.  If there's enough slop in the the tool rest mounts you should be able to adjust the tool rest until it is parallel.  If there's not enough slop, and the grindstone is true, then you should be able to get a refund.

Insert a long 1/2" bolt through the hole and fasten with a pair of nuts.  Let the bolt prutrude slightly past the nut on the side with the bevel, so that it can rest on the universal tool support.  You should be able to rotate it so that you get the same angle bevel all the way around.

I don't know if this'll work, but I'd give it a try.

I don't know if galvanized steel would perform any better than powder coated steel.  My Supergrind 2000 is about 7 years old, and I too had to replace a rusted main shaft.  There are places where the steel casing has started to rust, and the coating has flaked off.

Installed the new main shaft today, and am happy to report a wobble-free grindstone.  Now, I should be ready to go another 7 years!  Longer, probably, because I won't have to worry about rust on the main shaft. 

The MSK-250 doesn't include the right-handed nut that secures the drive wheel!  Is this intentional?