This is a prototype knife-sharpening jig that I built out of scrap wood and metal that was lying around my workshop. It was inspired by looking at various store-bought systems and thinking "I'm not paying $100.00 for that plastic toy".
The blade is held on a hinged bed, by clamps made of aluminium bar, 5/16" bolts, and wing-nuts. The bed angle is adjusted by a sliding block which also locks in place with bolts and wing-nuts. In both cases, the wingnuts are on the underside of the board.
Sharpening angle is set by changing the bed angle. The wooden blocks that guide the sharpening stone slide on the vertical post and, after bed angle is changed, the blocks must be moved until the stone guide is level. The lower block is held in place by a grubscrew (a piece of 3/16" brass rod in this case), the upper block swings freely.
The "stone" is a piece of plate glass with silicon-carbide "wet & dry" sandpaper attached with spray-glue. I actually have 3 pieces of glass with paper on each side, giving me 6 grades of abrasive. I sometimes clip a bastard file to the guide block, for rough shaping or repair of dodgy edges. For more information on sharpening with abrasive paper, see Scary Sharp World Headquarters.
In the pictures below, the bed is at 25°, for sharpening plane irons. I just stuck the knife in there to give you an idea of how it works, for knife sharpening the actual angle used is lower.
This is just a rough job, and covered in steel filings to boot, but it produces that authentic ScaryTM sharpness. I cut my thumb just touching the edge of one of my sharpened plane irons.
I plan to change a few things in the next revision. In particular, this version is no good at sharpening chisels, and the clamps are rather tedious to use.
This page was created after I mentioned my jig on Usenet and a few people asked for more information. Send e-mail if you want to know more. Beware that if you plan to make a commercial product, the field of sharpening is heavily mined with patents.
Crikey, I'm #1 google hit for 'knife sharpening jig'. How embarrasing given that this page has languished unmaintained for 6 years (kids happen).
I painted the jig, and still use it. I'd recommend diamond plates over scary-glass for the rough shaping, now that they're so cheap.
I'll try to get some updated pix up RSN.
There are now some commercial products that resemble my jig (which I never claimed was original anyway), eg.:
p.s. Massive apols to the senders of several unanswered messages about this page---I just discovered my spam filter got them.