Instructables

Knife sharpening jig

Picture of Knife sharpening jig
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This is a knife sharpening jig I made recently. i have no photos of the building process. If anyone wnats any details just ask, and i will provide any detail about the build. I'm pretty happy with the results i've been getting, it is very effective and precise.This saves me a lot of money, I spent some 10 €, but I had the plastic and a few parts lying around. I guess for less than 20€ you can make something similar.



Specs:

Materials: rainylon base (easily substituted by plywood, acrylic, aluminium etc)
30cm length
made to accept off the shelf hand sharpening stones
easily  adaptable design
angle from 10 to 25 degrees
takes big knives ( the one in the picture is a 30 cm blade) and small knives
easy to use

Design and use considerations

    The slotted angle regulator allows for any angle between 15º and 25º
    The length of the base makes it easier to sharpeng big knives, as it is more stable
    The knife clamp must be made from a thin, strong bit of metal, if it's too thick the stone will be riding on it, scratching the stone and possibly ruining the knife( or at least giving you a load of work reprofiling the blade
    The edge must be worked on only when it is 'flush' with the end of the base, to keep the angle consistent
    Using a sharpie or similar is a good technique to avoid grinding too much or too little, wich is VERY bad because you will be effectively changing the curvature of the edge, or worst, making it irregularly curved
    I currently have one 100 grit stone, one 220 grit, and various grits of sandpaper ( i use the stones as a sandpaper block, the stone holder acts as a clamp)
    Took about one afternoon to make.
    depending on the knife type and its intended use, you should adapt the grit you gring the blade to, for example:
             Vegetable knife, for slicing tomatoes ( you want a slight burr) 100 - 220 - 400 grit sandpaper - 600 (optional) - steel
             Filet knife ( you want it sharp, polished) 100 - 220 - 400 - 600 - 1000 - 1200 - steel
Use oil with oil stones, water with water stones and nothing with dry stones. the same applies for sandpaper.
A magnifying glass is useful for checking progress during the sharpening.
Before sharpening make sure you have the whole thing stable, a kinfe falling on your lap blade first with the whole thing behind it must hurt.

this info was based on my own observations, this has been effective for me and I use my knifes intensely almost every single day. the knife in the pic cuts through raw vegetables almost without exerting pressure, and keeps sharp for a long time.
Do not sharpen knives you aren't sure need it, sharpening removes metal and that effectively lowers the service life, sometimes properly steeling the knife brings it right back to shape.
 
Any knife ( sharp or not) is magically effective at cutting through your soft, fleshy bits( fingers, etc). Proper care and precaution must be taken for you own and other's safety.



Thank you for watching.
Suggestions and improvements are welcome
legamin4 months ago

super clever! There is a pre-made kit three level system that is pretty much the same here in the USA on the market for about $20.00. A bit bulky to Cary around and not as satisfactory when it comes to creating your own custom angles.

I found, by watching video of myself then using a standard goniometer to find the angle of my average stroke that I sharpen at about 20.5 deg. angle. I reduced this to 17 degrees and found my edge much more satisfactory in hardened then tempered steel blades, though not in softer stainless.

I'm going to try your kit using my stones and some plexiglass and aluminium threaded rod (to keep it light for packing). Thanks for the idea.

jimmymmorris9 months ago
This looks like the same concept as the Lansky knife sharpeners. You did a good job of scaling it up for larger stones or sanding blocks. I like it.
matosmeister (author)  jimmymmorris9 months ago
Essentially it was inspired by the lansky, but the purpose-made stones really bugged me so i made this
If the stone holder is made so that the guide rod is in the same plane as the active surface of the stone, then the angle stays constant over the stroke. It is not clear from the photos of this is the case. Good idea regardless.
matosmeister (author)  gumby_kevbo1 year ago
I have the guide offset, but parallel altough the guide can be bent in a way that makes it coplanar to the surface,like so:
00O|##########|_
|##########| \_______________
what really matters is that the guide and surface remain parallel, even if the guide is offset it can be accounted for when doing the math.If I'm not mistaken, it's as follows
a= stone^blade angle
A= base length
O= stone- guide offset
B=guide height(uncompensated)
V=vertical compensation
total height=B+V
B=A*tg(a)
V=O*tg(a)

total height=(A+O)*tg(a)
making the height reamin directly proportional to the angle ( A and O are known)
and so, you only need to change the markings on the slotted angle adjustment piece
matosmeister (author)  matosmeister1 year ago
the 'picture' is supposed to be
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