Geometry and Kinematics of Guided-Rod Sharpeners

Legacy Forum Archive thoughtstheoriesscience-related-to-sharpening
41

Hi Clay, Everyone,

More experiments with a CCD flatbed scanner (Epson V33). All of the images were scanned at 600dpi, and are un-edited except for being resized to 800 pixels for their long dimension. Using “adjust curves” one could have improved the contrast if needed. A clear transparency sheet was used to protect the glass platen.

Learn something every day: I was wrong about flat-bed scanners having absolutely no perspective effects! :ohmy: See below for details.

First I scanned a bunch of knives at once, hoping to save time. Cardboard background didn’t work so well. Top to bottom, the knives are a Victorinox Pioneer Pruner (Silver), Spyderco Dragonfly Salt, Leatherman Wave, Kershaw Cryo, and a Spyderco Paramilitary 2 in M390.

Next, I tried the same thing with white graph paper as the background. Pretty reasonable, very usable, although the Swiss Army Knife is a bit dark.

At this point, I noticed something odd about the scan of the Blue Paramilitary 2: It is not a pure side view of the knife! You can actually see the top of the knife. So I tried scanning just Blue PM2 at several different positions in my scanner.

I’m using my flatbed scanner in “landscape” layout, and the scanner head is a vertical line that moves from right to left.

First, bottom of the landscape. You can see the top of the knife.

Next, mid way between top and bottom of the landscape. Looks good! Pretty much a dead-on side view.

Top of the landscape. You can see the bottom of the knife.

That was pretty interesting, so I tried the same thing going from the right to the left of the landscape.

Right side of the landscape. Looks normal for the most part.

Mid way between left and right of the landscape. Looks normal.

Left side of the landscape. Looks normal.

Conclusion:

In landscape mode, my particular scanner (Epson V33), has perspective effects going from top to bottom, but no perspective effects going from left to right. Pretty interesting!

So I think the moral of the story is:
For flat bed scanners, place your knife in the middle of the platen.

That being said, the distortion is probably too tiny to matter when we use a flatbed scanner. I suppose if you were absolutely crazy, you could scan a bunch of identical cubes (say 5mm per side) which were distributed over the entire platen, and then compare their images to measure the distortion. Personally, I’m too lazy to do that! So I’ll just scan in the middle of the platen.

If any of you test your scanner, let us know how it went.

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I am really enjoying this thread… learning a lot but not too much to offer by way of help, but…

The other night I was watching a gun review show on the Outdoor channel. Talking about a holster manufacturer, they showed how a holster for a new gun was introduced.

First, the gun is run through a 3D scanner.

Second, a sample holster is printed that fits it near-perfectly.

Third, minor adjustments made.

Fourth, production.


Then, I thought about this thread.  Scan a knife in 3D and then the program could perform near perfect calculations and placement, right?

I don't have a 3D scanner.

So, I was wondering if there are already 3D scans of many of the most popular knives?

I found this website:  http://www.turbosquid.com/3d-models/global-knives-max/728173 

The page refers to a 3D rendering of some Global knives.

So, there must be many sites that already have 3D knife files.  Here's another one:  http://grabcad.com/library?per_page=20&query=knife.

With 3D files already in a standardized format, can you import the dimensional data from those type of files?

Perhaps, eventually, the Wicked Edge knife database will have programmatic elements on file about the knife so we can download the knife’s precise settings!

Or, the program could be used centrally and the precise correct settings for any knife could be authenticated, approved and then published.

Sounds cool. Very, very, cool…

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Wow, neat! :slight_smile: Thanks for your post.

I don’t have access to a 3d scanner, but that’s a great idea.

It’s certainly possible to import the data from 3d CAD files directly.

It’s also possible to just take the 3d CAD file and use it indirectly: You could use computer graphics to render an orthographic side view of the knife. For example, you could have a white background and the knife silhouette is black. This image then could be easily traced either by hand, or by software.

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You guys must have much better scanners than I .
I took one scan of my Edcs

with my HP then I took a photo using a Canon 50d with an EF 50mm lens.
I have to say the scan pictures were a waste of time clearly my scanner is no good

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45

Gib,

That’s great, thank you! We use 3D knives all the time in our renderings but we have to draw them ourselves and it’s very time consuming. Having access to 3D files of some nice knives is great.

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Messing around with a couple of cameras here. Knife is Spyderco Manix 2

length overall 8 " (203 mm)
blade length 3.375 " (86 mm)
blade steel CTS-BD30p
length closed 4.625 " (117 mm)
cutting edge 2.875 " (73 mm) weight 5 oz. (143 g)
blade thickness 0.125 " (3 mm) handle material G-10

First the Canon:

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Next the Sony:

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48

Clay, those photos look great! :slight_smile:

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Here’s one from my scanner. I just can’t get any clarity from it:

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Here’s one from my scanner. I just can’t get any clarity from it:

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Hi LeoBarr, Clay,

Wow, those flatbed scans of each of yours didn’t come out very well. I see what you mean. btw, LeoBarr, nice camera!

Hmm… My guess is that your scanners use CIS sensors? That might explain the blurriness for everything not touching the glass.

Sincerely,
–Anthony

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For my use the scanner is fine for papers & what I cannot scan I will photograph the best knife photos are out doors the one I did was with natural light I also think in general the pictures are best in cloudy conditions since the light is diffused so no problems with glare.
Your scan pictures are very good.

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Clay what is the max size photo you can upload to the site in pixels I have been working on 500 pixcels obviously I can go a shade wider is it 550/600?

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Good question Leo, I’ll ask the webmaster how it’s set. Those are 1500px wide.

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I have been setting mine at 500 pixels max width or height whichever is greater I kept finding my images were too large so bored of that I opted for that but they miss a lot at 500 pixels especially when I have taken the trouble to photograph using a real camera over the iPhone.

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I’ve been poking around a bit more.

Naive me. I assumed that knifemakers would, these days, already have these 3D files of their knives and that, as sharpeners, they would likely be available to us. Wrong.

What I found out is that the knifemakers I got in touch with who had files guarded them as corporate “secrets” and weren’t even close to considering giving the files away. After being told “no way” by SOG & Buck, I didn’t try to contact any custom makers. I did read some opinions on other blade forums and they all doubted there would be ease of access freely given to the files.

Afterall, who would want end users printing out their own modified Bob Loveless or even a Gryptillian? So, I kind of see the makers point of view.

I would love a Loveless but the 3D printing technology isn’t up to printing in the quality of steel required. So, scanning is ahead of direct, local printing.

It also seems a losing battle with the ease of access almost anyone has to 3D scanning & printing these days. From what I saw, $50 - $100 to scan a knife sized object – a little spendy but still accessible.

Anyway, it’s been an interesting little side jaunt on this fascinating thread… looking forward to the next instalment…

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Here’s another:

ZT 0560

Overall Length: 8.75"
Blade Length: 3.75"
Blade Thickness: 0.16"
Blade Material: Elmax
Blade Style: Drop Point
Blade Grind: Hollow Blade
Finish: Stonewash
Edge Type: Plain
Handle Length: 5.00"
Closed Length: 5.125"
Handle Thickness: 0.58"
Handle Material: G-10 Handle
Color: Black Liner
Material: Titanium
Weight: 5.98 oz.
Pocket Clip: Right/Left Hand, Tip-Up/Down
Knife Type: Manual Opener: Flipper; Thumb Stud
Lock Type: Frame Lock
Designer: Rick Hinderer

*Specs courtesy of BladeHQ.

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Good question Leo, I’ll ask the webmaster how it’s set. Those are 1500px wide.[/quote]

Heard back from our webmaster:

“1mb 800px x 800px”

Oddly, I can always upload pictures that are wider than 800px.

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Fallknieven SK3

Mod. SK3
Total length: 147 mm (5.8")
Blade length: 70 mm (2.8")
Blade thickness: 3 mm (0.12")
Tang: Hidden
Weight (knife): 48 g
Steel: 3G
Blade hardness: 62 HRC
Handle: Curly birch
Sheath: Open top leather

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ESEE-4

Overall Length: 9.0"
Cutting Edge Length: 4.1"
Overall Blade Length: 4.5"
Blade Width: 1.25"
Weight (Knife Only): 8.0 ounces
Drop Point Blade Style
Maximum Thickness: .188"
1095 Carbon Steel, 55 - 57 Rc. (Carbon Steel Model)
440C (Stainless Steel Model)
Removable Handles
Rounded Pommel w/ Lanyard Hole
Ambidextrous Black Kydex Sheath

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