Knife jig aid

[wootz]

This knife jig aid is not for every knife, but yet for the larger portion of knives, which profile is a normal sweeping curve, like most hunting and cook's knives, sheepsfoot and wharncliffe knives.

For this type of knives, the movement to keep the blade on the stone must be axial to the shaft of the knife jig.
Any shifting other than vertical results in uneven bevel.
I use a 1/2 inch shaft locking collar, locked at 12mm from the jig stop (the flat black plastic part), to ensure the jig slides on the Universal Support perpendicular to the stone, vertically rocking on its axis following the blade taper, and not shifting horizontally (or you may say not shifting laterally or forwards/backwards).

I have it on the jig at all times, and when I sharpen a blade of a different profile, e.g. curved etc, I unlock the collar and slide it away.

[brettgrant99]

I like it

[Ken S]

Make that two likes.

Ken

[Hatchcanyon]

That might be a good solution - will give it at try.

Rolf

[wootz]

Rolf, if you do, the Universal Support weld will need some filing for the collar to slide past, as in the picture, just be careful not to nick the horizontal bar (I did it with a Dremel).



It is funny to remember how I came to it. My 9 year old son wanted to sharpen his kids' bowie himself on Tormek, and I thought how to make it fool-proof, or child-proof for this case.
Added the collar, set his bowie in the jig, and let him do it, and his first grind on Tormek gave a perfectly even bevel.

It also helps with S-shaped knives: with the adjustable stop at the concave trough, I lock the collar at the convex crest, getting an extra reference point to maintain the S-blade  in the same line of contact as I sharpen it.

[Herman Trivilino]

Added the collar, set his bowie in the jig, and let him do it, and his first grind on Tormek gave a perfectly even bevel.

I'm a big fan of letting kids do these kinds of things. Learning at a young age embeds skills in a way that has no substitute. I liken it to spreading mulch on a garden.

[Ken S]

Nice image, Herman. We need to allow our children (and now grandchildren) to grow in skill and creativity.

Ken

ps That creative growth should not be limited to the young. 

[Jan]

My eldest granddaughter, who is now 13 years old, has lively interest in some affairs of the Tormek forum. She already knows many of you by name (e.g. Ken, Herman, Steve, Wootz, Elden, Rob, Stig ...) and she always asks what's new. 

I am her math and physics tutor. Now we repeat the tangent and the chord to a circle and maybe later we will touch the definition of bevel angle also. She understands quite well the BESS scale, because she already distinguishes between mass and weight and also between force and pressure. 

She is mostly interested in images, links and somewhat controversial topics, not the ones where there is a consensus.

Jan

[Ken S]

Jan,

What a joy that you and your granddaughter share a love of learning. Memories of your tutoring will enrich her entire life and give added meaning to your studies.

Almost all of the interests I have enjoyed for many years, some since boyhood, began as shared activities with family members. The interests themselves have long ago fused with the emotional bonds with loved ones. I believe the real legacy we pass on to the next generations is memories and values.

I look forward to ongoing progress reports from both of you! Both of you will learn from this special shared experience.

Very best wishes,

Ken

[Jan]

Ken, thank you for your kind words, greatly appreciated. 

Jan

[Herman Trivilino]

She understands quite well the BESS scale, because she already distinguishes between mass and weight and also between force and pressure. 

Keep in mind, Jan, that the definition of weight as a force is something unique to the fields of physics and engineering. In the medical fields, and in particular in the definition used for legal trade, mass and weight are synonyms. Children need to understand this if they are to make sense of the conflicting usages that await them as they explore human knowledge.

Most introductory physics books fail to point this out. They will, for example, define the pound as a unit of force. It is in fact defined as a unit of mass, and has the exact value of 0.453 592 37 kg. At least that's the case with the pound used in America. I realize that there are other definitions for the various different types of pounds, but they too are all definitions that establish the pound as a unit of mass. There is no officially-sanctioned definition of the pound-force, despite the fact that it's used in many legal documents such as NASA contracts.

What I tell people is that the word weight means different things to different people, and that the important thing to understand is not the distinction between weight and mass, but the distinction between force and mass. I rarely use the word weight as a noun, but instead always refer to the weight force, using it as an adjective.

Interestingly enough, the Scandinavian countries, as I understand have two separate words, one translating as the weight force and the other as the mass.

The important thing to know is that if it's measured in newtons, it's a force; and if it's measured in kilograms it's a mass. (If it's measured in pounds, you have to figure out from the context if it's a mass or a force). The BIPM officially removed the use of the kilogram as a unit of force way back in 1960, I think it was, but its use still persists. People still measure force in grams, for example, despite that fact the kilogram-force definition of 9.806 65 N was abandoned when BIPM took that action.

[Jan]

Herman, thanks for your consideration of the concepts of mass and weight. 

As a teacher, I'm in a pretty good situation because my granddaughter already knows Newton's 2nd law F = m.a. So it is straightforward to say that weight is a force caused by the Earth gravity field, which gives bodies an acceleration g and write Weight = m.g. Because she understands, that our weight on the Moon would be circa six times smaller than on the Earth, I am quite sure she distinguishes the different concepts of mass and weight.

It makes me happy because I spent many years as geophysicist interpreting very tiny anomalies of the Earth gravity field for oil and mineral exploration purposes.

Jan

[Ken S]

Jan,

With my very limited science background, many years ago I watched a fictional video about Einstein working with a third grader. It was very well done. From it, I learned that C=the speed of light. It helped me understand that Energy=Matter moving at the speed of light squared.

Would you help me understand the two Newton Laws you quote by defining ma and mg. I would like to understand them.

Thanks,

Ken

[brettgrant99]

m = mass
a = acceleration
g = gravity

Most people don't do dimensional analysis, but it is pretty important to keep your units straight.

[Herman Trivilino]

Would you help me understand the two Newton Laws you quote by defining ma and mg. I would like to understand them.

Newton's Second Law tells us that the net force exerted on a particle equals the mass of the particle times the particle's acceleration: F=ma.

It follows from that law that for a particle in free fall F=mg where g is the free fall acceleration. It has a value of about 9.8 m/s² or 32 ft/s².

Acceleration is the hardest part of this to understand. An acceleration of 9.8 m/s² means the velocity of the particle changes by 9.8 m/s ever second.

So what Newton's Second Law tells us is that a constant force results in a changing velocity. A concept particularly resistant to understanding.