As a newbit to woodworking a year and a half ago, I saw the jigs and thought the angle was critical, but what I've learned is this:
You don't need a fancy jig to sharpen a chisel properly
You don't need a powered machine to sharpen a chisel or edge tools
You don't need an exact angle, you need roughly 25 to 30 degrees, some say closer to 30 for hardwood will keep it sharp a little longer and closer to 25 is slightly better for softwood, though either will work fine with either. Even 24, 23, or 22 degrees will work.
You need only set your angle one time when you prepare a tool the first time(like an antique) with a wood block at the desired angle sitting on the tool rest of a belt sander to rough out the angle and rough out the flat side.
Rule one is to flatten the backside of the tool.
I use the cheapest method around now, sandpaper sharpening on glass. I bought a 3foot piece of 1/2 inch or 3/8 min glass at a glass shop for $16 with the edges beveled and smoothed. I made a frame for it from scrap MDF. it lays on the benchtop. Then bought Pressure sensative adhesive (PSA) sandpaper in 80, 150, 220 grits and lay 12 inches of each on the glass. Then flatten the back side moving from coarse to finer paper, removing all previous coarser grit scratchs and cleaning in between grits so that you don't transfer any coarse grit to finer. Keep the paper swept clean with a brush. This process is all done dry by the way and you can never over heat a tool like with a machine because you can never get it hotter than you can hold. After the three grits, cut some 600, 800, and 1000 grig wet dry paper like you get at the autobody supply store (or pepboys, I prefer 3M or Norton paper). You don't need adhisive for this paper, just cut it to the right size and lay it on the previous paper on the glass (lay the 600 over the 80 grit, 800 on the 150 etc. and the grit of the underlying paper will hold the wet/dry paper in place. work down to 1000. Now your getting pretty sharp. You can try to polish finer if desired. You can play with wet stones but don't necessarily need them. Once you've done this process on your chisels and get them in shape, you don't need to do this much work every time -to resharpen just a quick run through with the finer grits. I learned from a 30 minute DVD Called Sandpaper sharpeing, it's the second item on this page:http://www.thewindsorinstitute.com/bvd.html
Here's a video I just found online. http://www.woodsmith.com/issues/165/videos/sandpaper-sharpening/
In this online video they spray water on the wet dry paper and use an angle guide. They also talk about using 1/4 inch plate glass. I recommend 3/8 min. You don't need either. I posted this online video link just to show that just sandpaper will do the job well. The Sandpaper sharpeing video by Mike Dunbar shows how to hold and rotate the chisel to the bevel angle and sharpen 90 degrees to the axis of the chisel. This sandpaper method is nearly as fast as a machine, but has far more control and is more forgiving. Chipped edges are no problem for the sandpaper method. The Sandaper sharpeing video by Mike Dunbar also shows how to sharpen edge tools with curved edges.