View Full Version : My sharpening tool
06-17-2012, 06:27 PM
I just finished this knife sharpening tool. On the left is a pivot point. Basically a piece of threaded bar with a nut for height altering, on a hinge. Then to the right, comes a linear bearing, then the mechanism for setting the right angle, and then another pivot point for flipping the knife over, and then the jaws. It works really well and is easy to operate, and the sharpening angle will keep the same all the way.
I have 220 - 400 - 1000 - 3000 and 10,000 japanese water stones, and not a proper stropping leather / paste...
Can you give me advise on sharpening? I use a 10 degree angle, and on the last moves, per stone, the movement is into the stone, so the bur goes away. At the end I stropped at a simple piece of leather at a slightly steeper angle.
My results were quite ok, shaving and cutting paper were easy, and was better then the free hand sharpening I did before. But I can't put my knife on a tomato and cut it by the weight of the knife. The smallest width on the primairie bevel is 0.4mm, damascus chef's knife, 60 HRc, 1.2842 and 1.2767 toolsteel.
Johan van Zanten
06-17-2012, 09:04 PM
06-17-2012, 09:11 PM
Would love to see a video of it working if you have one...
It does look like a nice piece of work. I suspect it has the same inherent flaws as all other devices consisting of an arm rotating about a single fixed axis.
At 10 deg per side, and 10k finish, you should be able to pass the tomato test. Perhaps you can lighten the pressure at the end.
06-18-2012, 10:30 AM
+ 1 on the video request. Something like this needs to be seen in motion.
As for sharpening for the tomato test: try very light pressure at the end and edge traing strokes only.
Same thing when you're stropping: light pressure with more passes and also try and angle LOWER than the stone angle. If had the stone at 10deg, try something in the 6 to 9deg range. If you are going for crazy sharp, not durability, the idea is to round off / micro convex the edge as little as possible. The strop is going to give and flex and wrap around the edge, so you want an angle and pressure where it's just barely "kissing" the edge.
06-19-2012, 04:31 PM
@tk59, you could look at this like a vector with it's tail fixed, and besides that all the freedom of movement. What flaws do you mean? What is irritating me so far is the weight of the arm, I think i'm going to install a spring under the arm.
@ Justin, what are edge traing strokes? Strokes pointing the edge into the stone?
I will make a video about the tool, and another video about how I sharpen right now, after the weekend.
Thanks so far.
06-19-2012, 05:08 PM
Edge tailing, means that the edge is not going first into the stone as its being dragged. Instead you hold it at the angle you want and sweep backwards, usually with light pressure.
06-25-2012, 10:55 AM
ah ok. I'll try it with lighter pressure.
Here's the video:
06-25-2012, 12:03 PM
This may be the first jig I've seen that JUST holds a consistent angle and doesn't restrict otherwise. It's basically a human arm with a locked wrist.
06-25-2012, 01:39 PM
06-25-2012, 03:22 PM
Very slick. I would never be able to come up with an idea like this, let alone build one of these, but a friend of mine suggests that some thumbscrews might be handier, to replace the wrenches.
06-25-2012, 08:08 PM
Sir I am a noob when It comes to sharpening. But my 2 cents says that I like it. I am not sure about how the tip is taking enough or to much off. Other than that I can't see anything wrong.
Btw Welcome to the forum.:dance:
06-25-2012, 10:14 PM
nice job! and thanks for the video
A+ for creativity.
It looks like once you set up you device sharpening will come out just about right. My only concern would be safety, In video shows blade and device are not so easy to attach with each other and many moving parts, other than that GREAT job.
07-01-2012, 12:44 AM
Very, very cool. Thanks for the video and sharing your project.
This system is doing the same basic thing as the edge pro system, except it's kinda flipped upside down (or is it right-side up?) and is moving the knife and not the stone. However, it does have a few big advantages: such as the ability to use any stone (although you will still need to make adjustments for each stone of different thickness) and the fact that the arm is much longer so the arc that it moves in has a much larger radius and becomes less of a factor.
You've obviously put some thought into it, so these suggestions are just because thinking about design and engineering is fun and are by by no means criticism:
- a way to lock/ immobilize each of the pivots and hinges (this would make adjustments and clamping the blade much easier).
- the spring idea to reduce the effective weight of the arm is a good one, but I think that a tension spring which pulls the arm up might work better than a compression spring under the arm. It would be easier to calibrate / adjust on the fly and would be more tolerant of the way that the arm swings. You could extend a post up from just behind the pivot to anchor the spring and then stretch it down and attach it to the non-extending (underside) of the arm.
- adding shims or some of height adjustable platform under the stones would allow you to compensate for different thicknesses without adjusting the entire arm.
- adding rubber / padding to the clamping jaws would be easier than trying to wrap a loose pad around the knife.
- some way to mark reference points on the angle and height adjustment.
- if you wanted to completely negate the issue of the arm radius all together, you could add another horizontal pivot just behind the free-spinning bearing on the blade clamp. That would add another degree of freedom and would allow you to pivot counter to the direction of the main arm pivot. Thus, cancelling it out and allowing you to keep the vector of the motion of the knife the same as you sharpen the different sections of the blade.
Oh yeah: nice knife by the way! If a dammy Kramer is your "test knife", I'd love to see the rest of your collection.
07-01-2012, 01:25 AM
Sir I am a noob when It comes to sharpening.
That being said, it looks like it will solve the sharpening dilema for someone....prolly me!
...- if you wanted to completely negate the issue of the arm radius all together, you could add another horizontal pivot just behind the free-spinning bearing on the blade clamp. That would add another degree of freedom and would allow you to pivot counter to the direction of the main arm pivot. Thus, cancelling it out and allowing you to keep the vector of the motion of the knife the same as you sharpen the different sections of the blade...Yes. However, with the extra degree of freedom, you would introduce a need for a little more skill and probably defeat the purpose. You'd need to be able to "program" the curvature of the blade into the device or perhaps you can simply position the blade so the less acute angle is at the heel for tough chopping jobs and the more acute angle ends up at the tip and call it good...
07-01-2012, 11:53 AM
position the blade so the less acute angle is at the heel for tough chopping jobs and the more acute angle ends up at the tip and call it good...
WHOA...that is a golden nugget to a dummer like me. Makes perfect sense.
THANK YOU for that one Tinh!!!!
07-03-2012, 06:02 AM
I like your suggestions. I had the idea about the rubber, but didn't had any usable rubber layin around ;-)
What is your idea about the post with the tension spring?
The extra pivot point is a nice idea. I also figured that the bigger the radius (arm length) the easier the sharpening. An extra pivot would able you to turn the knife a little when sharpening the tip for example. But I don't think that is a big advatage. And like tk59 said, it might overrun the purpose a little...
The knife is made by me. I made it to get a feeling for kramers knives. I've got my own design ready now (primarily focusing on the right convexes right now ;-)
07-03-2012, 05:00 PM
07-03-2012, 07:05 PM
haha thnx, how do you know i'm dutch?
12-06-2012, 12:52 PM
haha thnx, how do you know i'm dutch?
Hey, just noticed this again. Of course you're Dutch: your name, your accent ... although I do hear Led Zepplin in the background and not Golden Earring.
Anyway, my dad's Dutch so it was a cinch.
12-11-2012, 03:04 PM
Haha I see :-D Yeah Led Zeppelin and Golden Earring are both great for in the shop!
This is an excellent thing you've made. I agree on the idea of shims or a way to raise or lower the platform the stone sits in. Of course this would be a good idea for the people who like to buy all choseras for instance. I think with the long radius it shouldn't be a problem unless you have a really long knife but still I think shorter learning curve than an edge pro. I think it's more like an upside down Gizmo as it used full size stones. Anyway great engineering
02-02-2013, 11:27 AM
Yes. However, with the extra degree of freedom, you would introduce a need for a little more skill and probably defeat the purpose. You'd need to be able to "program" the curvature of the blade into the device or perhaps you can simply position the blade so the less acute angle is at the heel for tough chopping jobs and the more acute angle ends up at the tip and call it good...
Isn't the fact that the blades gets thinner towards the tip - if you keep the blade at a constant angle to the stone - you do just the opposite - a more acute angle at the heel ?
I can't get the right picture in my mind about this question so would appreciate your input.
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