sharpmaker - visual aid for maintaining vertical?

[ahains]

I've been contemplating how I can make it easier for me to get very accurate angles when sharpening. First I wanted to see how much the knife has to move before I have gotten "somewhat inaccurate".

My target angle recently was 12* per side. If I estimate that the height of the knife blade is 1" from spine to edge, I can find out how far the spine of the blade should be from sharpening stone with the tangent of the angle.
So if I take the tangent of my target angle (12*), and the tangent of a "bad" angle (17*, since I'm assuming a 5* variance is costing me in edge quality), then I can figure out how far I would need to accidentally move the spine off-track to hit my bad angle.
The formula can be written as tan(degrees) = distance_stone_to_spine / knife_blade_height

My trusty calculator shows:
tan(12*)=0.21255656167002212525959166057008
tan(17*)=0.30573068145866035573454195899655

So assuming my knife edge is 1" high for simple math, a little algebra gives us:
0.21255656167002212525959166057008 = distance_stone_to_spine / 1
distance_stone_to_spine = .213"
0.30573068145866035573454195899655 = distance_stone_to_spine / 1
distance_stone_to_spine = .306"
=> so movement of the top of the blade for a 5* variance is about 1/10 of an inch.

I'm not a great sharpener, so I would think it is quite likely I will at least be 1/10 of an inch off of my target when trying to sharpen. This led me to contemplate how I could give a greater effective height of the blade. One possibility is to stack a pile of magnets on the back of the spine. Perhaps the simplest idea would be to hold a length of music wire between my thumb and the delica handle, with the wire sticking straight up. Then I can use this extension of the knife as a visual aid to keep it closer to vertical.

If I use a 10" length music wire and plug this into the formula:
0.21255656167002212525959166057008 = distance_stone_to_spine / 10
distance_stone_to_spine = 2.13"
0.30573068145866035573454195899655 = distance_stone_to_spine / 10
distance_stone_to_spine = 3.06"
=> movement for 5* variance is nearly 1 inch

I think that gives me a better chance of keeping near vertical with a visual aid like this.

One last thought I had was to attach a laser pointer to the top of the spine, pointing straight up. Then I can check where it falls on the ceiling.. this would be like a 5' extension to the blade. I think it would be difficult to look back and forth from the blade to the ceiling.

I know it is going to be a bit of extra hassle to try and watch an aid that is away from the knife, but I think it may not be too bad. I only need this approach for the microbevel, so it doesn't take many strokes to set this. I think if I'm very accurate in my angle, then the number of strokes will be even less.

Does anyone have other suggestions for visual aids?

[ahains]

Oooohhh I just had another idea.
I'm still visualizing a length of music wire that sticks up from the handle. Then at the top of the music wire is a loop with a string tied to it. Hanging from the end of the string is a small/simple weight, that hangs just above the level of the knife. Then I can have the point of observation be right at the knife, instead of looking up at the top of the music wire to try and figure out if its vertical. If the weight is dangling directly above the knife then I know I have it vertical.

Following the curvature of the blade might be tricky, since the weight would fall forward of the knife. This still may be useable though. I may just have to try it out and see how it works.

Crazy?

[rycen]

If you are that concerned you should get the Edge pro.

[gldfshkpr]

If I get what you're saying, you want to change the angle from 15 to 12 degrees per side using the inclusive 30 degree back bevel guides on the Sharpmaker. I've heard of people putting a book or some object underneath one of the sides of the unit while keeping the knife blade vertical to achieve a lower degree. I suppose you'd have to rotate the unit to do the other side of the blade just using the one stone. Does that help or am I missing the point?

I'd love to see pics of what you're doing. That would make it more clear to (at least) me.

[ahains]

If I get what you're saying, you want to change the angle from 15 to 12 degrees per side using the inclusive 30 degree back bevel guides on the Sharpmaker. I've heard of people putting a book or some object underneath one of the sides of the unit while keeping the knife blade vertical to achieve a lower degree.

I didn't explain very well, and I'm sure you're right that a picture would be worth a thousand words. :)
I do use a pencil underneath the middle of my sharpmaker to get a steeper angle, but that is not what this post was about. This post was me wondering "how close do I need to get to perfectly vertical, to keep the blade within some tolerance?"
It turned out that if I accidentally wiggle the spine of the knife .1" off of perfect vertical, I'm imparting about 5* of error off of my intended angle. This is a pretty tiny wiggle IMHO. So although my sharpmaker is 12*, I can very easily hit 17* by mistake.

It may be that my whole concern is unfounded. Maybe it doesn't really matter if I have that much variance while sharpening. I'm going to have to buy some piano wire and give it a try. If I do, then I'll take a picture or video and post it.

[yablanowitz]

Probably the most helpful suggestion I've ever seen for the SharpMaker (next to the Sharpie trick) is propping a mirror up behind the unit so you can see the reflection of the blade in the mirror. It is a lot easier to see if you are holding it vertical if you are looking at the blade end-on than if you are just looking at the spine, especially on full flat grinds. Saber grinds are easier if you pay attention, since the flat above the grind will become visible when you get off vertical a degree or so, assuming you watch with one eye and keep that eye centered behind the knife.

The very best advice is simple: Practice. Practice. Practice.

[chuck_roxas45]

Since I've been on the forums I've seen several threads about using trigonometry and other higher mathematics for sharpening. The best guys at sharpening get scary sharp edges by feel alone.

[spoonrobot]

Hot glue a micro-level to the spine of the blade. Doesn't work for all models but it does work for quite a few.

ETA: I guess that's specific to sharpening with the Sharpmaker on a level surface using the supplied angles.

If you want to use a more acute angle it appears one of the easier ways is to use an adjustable jig to raise one end of the Sharpmaker to the appropriate angle, do one stroke and then rotate and do the other stroke. There were some pictures posted of such a set-up over at Bladeforums. I'll see if I can find them.

[bh49]

Probably the most helpful suggestion I've ever seen for the SharpMaker (next to the Sharpie trick) is propping a mirror up behind the unit so you can see the reflection of the blade in the mirror. It is a lot easier to see if you are holding it vertical if you are looking at the blade end-on than if you are just looking at the spine, especially on full flat grinds. Saber grinds are easier if you pay attention, since the flat above the grind will become visible when you get off vertical a degree or so, assuming you watch with one eye and keep that eye centered behind the knife.

The very best advice is simple: Practice. Practice. Practice.

+1
Regarding 12 degrees setting: you can put rubber bend over top of rods, it will squeeze rods to 12 degrees per side.

[chuck_roxas45]

+1
Regarding 12 degrees setting: you can put rubber bend over top of rods, it will squeeze rods to 12 degrees per side.

What are those pink rods?

[araneae]

Whoa that post gave me flashbacks to high school trig. Scary. Too much math for knife talk. :eek:

[bh49]

What are those pink rods?

These are Congress Tool Ruby 1/2 Tri. x 6. I have them in 80, 150, and 320 grit.

http://www.congresstools.com/congressto ... &parent=24

[Simple Man]

For the the proof is in the pudding. I sharpen away as intended w/o additional gadgets and get awesome results. If I want to go better, I go to the belt sander/strop.

[Slick]

If you are that concerned you should get the Edge pro.

Yes

Got one but remember to flaten the stones as needed.

I still want a Sharp Maker.

[chuck_roxas45]

These are Congress Tool Ruby 1/2 Tri. x 6. I have them in 80, 150, and 320 grit.

http://www.congresstools.com/congressto ... &parent=24

Thanks. That sure would make re-profiling a breeze.do they fit the sharpmaker as is?

[AKWolf]

These are Congress Tool Ruby 1/2 Tri. x 6. I have them in 80, 150, and 320 grit.

http://www.congresstools.com/congressto ... &parent=24

Wow , thanks BH , seems like a great solution for coarser alternatives for the

SMaker and well priced . :spyder: :spyder: :spyder:

[bh49]

Thanks. That sure would make re-profiling a breeze.do they fit the sharpmaker as is?

Most of them :eek:
Please, keep in the mind: these stones were not made for sharpmaker. 1/2" is correct size, but it looks like their tolerance is quite wide open, which can create few issues: some rods may be will not fit, some can be loose (angle will be 1-2 degrees bigger, which can create a little reporfiling on medium rods), two rod, which fit can be quite different. For me Congress Tool is a local company, so if I need I go there with my base and try stones before I buy them. Still I missed than one of my Ruby stones smaller than others and when I reprofiled my knife, one edge come out much wide than other (but it is not driving me crazy, like some others).
I use these stone for several years and like them: very inexpensive and can get them in very coarse grits, which will remove steel much faster than Spyderco diamonds.
For somebody else, to avoid these issues I would recommend to buy flat Congress stone like 1/4x1"x6" and clamp them to sharpmaker rods with binder clip.