don griffith

[don griffith]

Well, I remember quite well this post. I’d pulled the cork on a bottle and was feeling a little loose and lippy–clearly I hadn’t pulled enough corks….
Since you’ve elected to dredge it up (things better left unsaid…let sleeping dogs lie…quiet, you’ll wake my dad…), I suppose I’ll have to give it a go with full faculties.
In its common non-technical usage, accuracy usually means ‘how well will this thing tell me what I want to know’. In the more technical setting, it is usually associated with a value range (tolerance; specification) that represents how well the user can expect the instrument/tool to display the expected, or true, value. Since the true value cannot be known, error (or accuracy, if you will) cannot be known, only estimated, hence the ‘±value‘ for a symetric specification.
Now to the crux of it. By definition, accuracy is a qualitative indication of the ability of a measuring instrument to give responses close to the true value of the parameter being measured (ref. VIM, International vocabulary of basic and general terms in metrology, para. 5.18; also The Metrology Handbook, 2nd Ed., Jay Bucher PhD, Editor, ASQ Quality Press 2012, pg. 470), and many more. No matter how it is used, accuracy is a metrological term, and thus defined in metrological terms. 🙂

Also, see the link above in post 10561 for a look at an Angle Cube test.

Cheers

[don griffith]

….(This sort of raises the question of “how accurate is accurate?” but that’s probably for another day and another thread!)
-Pie

Bah. Easy Peasy. Why wait.
Always know that accuracy is a qualitative term, not quantitative. So, very accurate, quite accurate, good-enough-for-government-work accurate, and this-thing-ain’t-worth-a-crap-because-every-time-I-lay-it-up-against-my-knife-it-changes accurate and so forth are all accuracy statements. Period. No numbers required.
Precision, error, repeatability and reproducibility, on the other hand, are all quantitative terms and are expressed numerically.
So the question we really want to ask is: “How much error can I tolerate?”
See? Easy Peasy.
:silly:

[don griffith]

Rather than start a thread, I thought I’d revive a revival…

My angle cube tells me a different angle almost every time I lay the stone against the bevel. I mean, even if I just lift the stone and re-set a second later, I get a slightly different reading. For example, I will see like 25.2 then 25.4, then 25.2, then 25.3, etc. I know the accuracy is +/ 0.1 degree, but is this how it should really behave? And I am holding the stone at the exact same spot every time, so it’s not variance on my part.

-Pie

For an idea of the capability of the Angle Cube, you could try this older thread. It looks at the accuracy (yep, it is) and precision (yes, it has some) in a semi-rigorous test.
http://wickededgeusa.com/index.php?option=com_kunena&func=view&catid=2&id=363&Itemid=63#363

[don griffith]

Not really relevent for sharpening, but if you were constructing something or grading your yard, you might want to know the slope of the ground so the rain water runoff didn’t end up at your back door. Some parameter might tell you the desired grade or slope, like when building a roof, instead of the angle.

[don griffith]

Clay, et al,
I see you suggest a water and soap mixture instead of oil or other lubricant. Since soap is/contains surfactants is there a concern that it will migrate to the backside of the stone and eventually loosen the adhesive bond?

I have been away from sharpening for a while and am playing catch-up. I unboxed and used my new 12-1600 stones for the first time last night and noticed that they had a bad case of dandruff… now I know why. 🙂

[don griffith]

As one who doesn’t consider himself a good sharpener, I have no trouble raising–and we say raising because the burr seems to stick out from the edge on the side opposite–a burr with the WEPS. If you’ve ever opened a tin can of beans or tuna and felt the edges then you know what to look for. It doesn’t seem likely that you haven’t raised one yet based on what you’ve said so far. :huh: Forget the magnifier, you can raise an easily felt burr with 100 stones after 5 minutes of scrubbing, especially if your initial marker line has been ground away.
Try using fingernails instead of fingertips with moderate pressure and see if they scratch up, stroking from spine to edge.

[don griffith]

Has anyone tried the suction-nozzle thing yet? I mean a set-up similar to a woodshop where sawdust is vacuumed up as soon as it is generated.

Well, I tried taping the hose of my vacuum cleaner to the stones, but the tape kept getting cut on the knife blade, and the hose was swinging wildly around…. :silly:

I suppose if one had the room that a ‘fume hood’ arrangment could be useful. Something similar to that used on benches where a lot of soldering is done or chemicals are used, but usually they are noisy.

We could also let our nose hairs grow out to perform their natural filtering duties more effectively. It’s more likely that the handkerchief spotting came from the nasal passage mucus membranes and hairs (doing their job), not the lungs. If you’re coughing it up, then that would be more reason to worry.

I’m wondering if some of the ‘airborne dust’ is also from the binder matrix as it erodes away.

[don griffith]

But, but… NO PHOTOS???

Those are tied to his other two cylinders that don’t fire so well. Perhaps some hi-test gas (ANYONE WHO REMEMBERS WHAT THAT MEANS, RAISE YOUR FEEBLE ARM… IF YOU CAN HEAR ME…:silly:) will get them going.

[don griffith]

My 2 cents on the cube. Just so you know, the cube measures the angle “in space” not relative angle.

Dr., haven’t you wondered what that 3rd button was for…? 🙂

A couple of quick reactions. I thought that the Angle Cube has a zero set button so that you can place it against what you are using as vertical (or horizontal) and set it to 0, then against the stone being used on the WE to get a relative angle?

This is correct.[/quote]

Isn’t this the theory?

Put it on the slab.
Press the first button.
Then press the 3rd button to zero out, enven if your table/slab is 20 degreed off to zero out.

I’m I missing something?[/quote]I don’t think so.
For those that may be new to the Angle Cube, the Cube is a gravity-driven instrument (a level with digital display), and will show the angle with respect to Z, which is the local gravity vector. As Matt put it, “free space”, but tied to Z.
If the WEPS base says 0.00 when looking left/right and fore/aft, then it is level in X and Y. We assume the jaws, when the WEPS is mounted correctly, are parallel with Z and perpendicular to X and Y.
All angle measurements made on the paddles will be true when leaned against the jaws, and any blade properly clamped.

If the base is not level, the angle measurements will be offset by the amount of unlevelness (technical term…:)) because the jaws are no longer parallel to Z.
The “Zero’ button allows you to set a new reference for subsequent measurements by subtracting the ‘Z offset’, and the angles measured on the paddles will now be ‘true’ with respect to ‘Z offset’.
Fortunately, the Cube does the math for us and reads 0.00.

You know, the WEPS angle setpoints work in a similar way. They are tied to the WEPS base, and even if the base isn’t level, it’s still the same angle when read on the bar. The trick would be to get the blade centered and edge parellel to the jaws.

Sorry for the diatribe, but as a Gov’t employee, I’m required to find something to do when there’s nothing to do…

[don griffith]

Thanks, but I’m not complaining about anything, just wondered what others do, and what would you fix? You can’t change the OD of the arm nor the ID of the paddle. I suppose the taper pins could be removed with a drift punch and small diameter non-metallic washers installed to take up the gap between the arm and link. Which end of the pin is the small end? 🙂
Otherwise, no worries.

[don griffith]

My 2 cents on the cube. Just so you know, the cube measures the angle “in space” not relative angle.

Dr., haven’t you wondered what that 3rd button was for…? 🙂

A couple of quick reactions. I thought that the Angle Cube has a zero set button so that you can place it against what you are using as vertical (or horizontal) and set it to 0, then against the stone being used on the WE to get a relative angle?

This is correct.

[don griffith]

Question about the CATRA Laser Goniometer. It gives specs of measuring knives up to 1.7″. I have chef’s knives with 2″ wide blades. Is there any way of using the goniometer to measure such blades, i.e. some sort of work-a-round?

Grinder…?

You could try taking a band saw and cutting out the ring between the ±5° marks, but you’d have to make sure the ring didn’t change dimension.

The Angle Cube can give the angle of the final edge of a knive you’ve just sharpened, but the goni might be better at finding the approximate angle on a knife edge that you haven’t sharpened yet.
The Hobbigoni is ±2°, and the uplevel Portable is ±1°, but the cost is 4x+ (too much for my blood) the Cube and the Cube has better precision and accuracy.

[don griffith]

Was thinking that if the handles were made in such a way as to be able to swap out the different medium. That way you have a generic handle and people could just snap in the stones they wanted.

That way it will keep the costs down as people won’t have to buy handles for every 2 grit.

Also for those that have multiple mediums for different steels it would just be a matter of sawpping the stones out.

Some of us are color blind, and need the printed labels on the handle. Some of us are illiterate, and need the colors on the handle. 🙂

[don griffith]

Hi Mark
I have had similar problems with the goniometer…
Sorry. guys. but I’ve never used one
I believe that the problem lies in the fact that the meter requires a flat facet to reflect the laser so it points to the correct reading. In a fully convexed blade, as the edge approaches zero the job for the meter becomes more and more difficult until a point is reached near zero when the laser reflects not only from the actual edge but even more from the steel at the base of the edge.Big sprays of red laser light all over the dial.
By ‘edge approaches zero’, do you mean as the blade width approaches zero as it gets closer to the very edge?
The reading I see there is very unclear but my best guess is between 4 and 6 degrees.
On one side, but looks indeterminate on the other. Is there a chance the knife was not ‘straight’ in the V?
You might try the following…turn the knife in the slot so it rests flat on one of the V sides…take a reading of the laser at its furthest reach…do the same with the knife lying flat on the other side of the V…if the readings are the same then you are at zero or approaching zero. If there is a difference e,g, one reading is 30 degrees and the other is 35 degrees then the angle is 5 degrees.
Not following here.
Having said all that I may be full of baloney.
Don’t think so. Is there a chance that the convex edge was simulated by sharpening 1° at a time? There seems to be step-changes to the laser light at about 1° increments. Could be illusion. The right side with bigger splash might indicate that the sides are asymmetric or the knife isn’t aligned with the V. CATRA does have other models that are for thicker knives. Could be that this one is too thick for this model
I will trust that those with more scientific minds than mine will see this just that or maybe not!!
Trust no one…

[don griffith]

So much for flying under the radar… maybe I should take out an ad, put my name in lights on Broadway, or hire a skywriter, eh, Leo? Maybe my name should have been allcars. Get it? Calling allcars… 😛

Sorry, Leo, just having some fun at your expense. 👿

I will look at it, mate.

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