Ionut's Small Knife Jig

[ionut]

Hi Herman,

The length and thickness become an issue in relation to the allowed angles and clearances, when the small platform is being fixed on the Tormek jig.
If clamping it doesn't give you the clearance or you want a more definitive solution that would allow you more flexibility I would suggest routing at the place where your bolts are , two lengthwise slots right through the platform, one with a ½ " bit and one with ¼ bit. The ½ one would be probably only 1/8 deep but the ¼ one would go all through the platform in the center of the first one. That would allow you to use T-slot screws that would be flush with the upper surface of the platform, and you could have underneath some wing nuts or anything similar and you will be able to move the platform closer or further away from the stone depending on what you want to achieve. I believe 2" long slots would give you enough adjustment for almost anything you want. Before getting the UMHW you could try to experiment with the wooden version, before you commit for a definitive solution and se what is fitting your needs better.

Ionut

[Elden]

I have my rough version mostly done . Welded the spacer block to the 3/8" pipe, bolted the plate to the spacer block with countersunk screws. Drilled and countersunk 2 extra sets of holes so that the plate extension length can be changed.

[Elden]

Congratulations Herman!

[Elden]

Sometimes a person can get thick scrap plexiglass at places that handle glass. I got a piece of 1/4" free from a lumber/farm supply store.

[Rob]

Can you post pictures Elden?

[Elden]

Not yet, but am working on it.

[Rob]

What's the problem?

[Herman Trivilino]

What's after hero......galaxy class?

Why, super hero, of course.

Thanks everyone!

[Herman Trivilino]

If clamping it doesn't give you the clearance or you want a more definitive solution that would allow you more flexibility I would suggest routing at the place where your bolts are , two lengthwise slots right through the platform, one with a ½ " bit and one with ¼ bit.

Good ideas, Ionut.  I think clamping gives me all the flexibility I'll need.

I did some whittling on the wooden platform tonight in preparation for the next prototype.  I plan to make a more refined version tomorrow and will post pictures.  This wooden version could then be used as a model for the plastic version.

Does anyone see a need for grinding bevel angles smaller than 10^o?  On a typical knife this would give an edge angle of 20^o. 

In Ron Hock's book he says "For tough chopping [...] an included edge angle as large as 50^o or 60^o may be needed, while the slicing of fish or vegetables may call for an edge angle as small as 10^o."

This would be a bevel angle of 5^o unless that's expressed poorly and he's referring to a bevel angle of 10^o.

Especially confusing because he goes on to say that a good kitchen will have a variety of knives ground at different angles for different purposes, but then on the next page he states that the angle for a kitchen knife is "rarely critical".

[Ken S]

A good illustration of the need for different blade angles in a kitchen is the recent post about the knife missing a large hunk of the blade due to using it to cut a lobster. (The choice of knife might have been done more carefully as well.)

A Sawzall blade which routinely had to cut through nails as well as wood would be a poor choice for cutting dovetails.  Likewise a dovetail saw would be easily destroyed by a nail infested 2x4.

My Chinese cleaver used for slicing vegetables can and should be sharpened to a different angle than the heavier chopping cleaver of a more carnivorous  person.  Vegetables are boneless.

A paring chisel should be ground to a finer bevel than a dovetail or mortising chisel which is hit with a mallet.

Is the exact angle critical?  I think we live in a world of tolerance ranges.  If I needed a chisel for paring in a size that I only had one sharpened for dovetail chopping, I would use it.  Being very sharp covers a multitude of sins.  It might not be the ideal tool, but it would work.

One of the joys of skillful sharpening is the ability to adapt edges to specific uses.  We can grind a knife or chisel specifically for very light, intricate paring.  We can grind the same tool for more utilitarian use.  A good chef or woodworker would want that flexibility.

I believe a "compleat" sharpener also uses the edges he creates and maintains.  Whether the blade is a chef's knife, chisel or for a lawn mower, the person who sharpens that blade should have a working knowledge of how the tool behaves under different degrees of sharpness.  The true test of a sharp kitchen knife is on the cutting board, cutting whatever the intended use is.

I am one of the forum who regularly proclaims the value of being able to sharpen a simple chisel edge.  That is an important foundation block in sharpening.  I would not minimize it.  However, once the basics become solid, there is a whole range of options to adapt the tool to the job and the individual worker.  I believe both the satisfaction of doing basic work well and the creativity of choices add to the satisfaction of the sharpener.

Ken 

[Rob]

Gentlemen

I've just this morning posted a new topic which addresses some of the ambiguity and confusion in this area.

It finishes with a table which we could all evolve until we have a definitive list of bevel/included angles for blades aimed at a specific job. A quick reference if you like to save us having to wade back through all the knowledge references. I plan to keep mine taped to the Tormek when complete

[courierdog]

Herman I would like to know the physical dimensions of the plate.
My current sharpening project is my Japanese Kitchen Knives which use an angle of 10-15 degrees depending on the knife and the cutting application.
I followed your post and also watched your video as well.
I have the three current grinding wheels.
The jig you have devised seems to meet my requirements however it would be better if I had physical dimensions and a simple procedure to set the correct grinding angle.
Thanks for your effort and posting to encourage people like myself.

[courierdog]

This worked great.  I had perfect control.

Herman While I agree with you on the lifting of the blade, I do not like working over the rotating wheel.
To many mistakes can be made when any part of the body is over the top of any rotating device no matter how slowly it is turning.
I am currently working on a Reverse Jig Plate which will allow the Universal Support to be held on the back side of the machine.
This is necessitated for the use in sharpening my Metal Lathe Tool Bits.
Once I learn how to post pictures it will be much easier to explain, I am sure

[stevebot]

I am quite late commenting on this thread but:
There are two key features to a jig of this type:
1. It is only as wide as the wheel so you can grind up to the bolster on either side.
2. You grind into the edge so your pressure opposes the grinder pressure.

Almost all tool rests including Tormek's are too wide for rule 1. If you cut them to the proper width you discover A: the tongue is too short, or if you turn it around, B: the Knob is in the wrong position. I suggested the correct design to Torgny years ago but it never made it off his desk.

If you ignore rule 2. the wheel will lift the blade off the guide and pull it away from you.

[Herman Trivilino]

I am quite late commenting on this thread but:
There are two key features to a jig of this type:
1. It is only as wide as the wheel so you can grind up to the bolster on either side.

I discovered that myself. It also helps if the jig is thick enough so that the bolster doesn't hit the universal support rod when sharpening curved tips of shorter knives. About 12 mm seems to do the trick. 

2. You grind into the edge so your pressure opposes the grinder pressure.

Almost all tool rests including Tormek's are too wide for rule 1. If you cut them to the proper width you discover A: the tongue is too short, or if you turn it around, B: the Knob is in the wrong position. I suggested the correct design to Torgny years ago but it never made it off his desk.

Page 18 of the Tormek Handbook (which can be downloaded for free once you register at http://tormek.com/international/en/account/register/) explains perhaps why Tormek hasn't developed a tool rest like our homemade version.

Tool Rests and Grinding Jigs
To achieve an even and sharp edge, the tool must be held steadily and with a consistent
grinding angle to the wheel. This is obtained by resting the tool on a tool rest or clamping
it in a grinding jig.

A common tool rest on fast running bench grinders is a bent plate which is usually too short
to support the tool properly. This simple tool rest can be replaced by a larger and more sturdy
support to enable you to hold the tool steadily towards the grinding wheel. The tool rest can
also have a fence which is guided in a slot, so you can keep the tool at 90° or at a specific
skew angle to the grinding wheel.

These type of tool rests have been developed for high speed grinders, where you work with a
low grinding pressure due to the high rpm. However when mounted on a water-cooled grinder
which requires a higher grinding pressure, they do not work satisfactorily. This is because
the pressure which you apply to the tool does not reach the grinding spot but instead goes
to the tool rest. (Picture no 1).

To obtain the required grinding pressure, you also need to push the tool from the handle direction
towards the wheel. Then the tool tends to climb up on the grindstone and the precision
is lost. (Picture no 2). You need to push the tool both towards the wheel and downwards so
that it does not lose its contact with the tool rest. In practice this is not possible.
This effect appears when grinding narrow edge angles and when grinding both towards and
away from the edge. The disadvantage is more severe when grinding turning tools, as they
are often made of HSS-steel which is hard and requires a high grinding pressure.
For turning scrapers which are ground at larger edge angles, this type of tool rest works
satisfactorily on dry or water-cooled grinders. The reason that these types of tool rest work
fairly well on high speed dry-grinders, is that they require a lower grinding pressure and
therefore the disadvantages can be overcome.

I have discovered, though, that lots of pressure (actually force is the more correct term here) is not needed when sharpening knives. Unlike an axe or perhaps a chisel or other tool, when sharpening a knife it's not necessary to remove lots of steel. Perhaps Torgny won't budge from what he considers a basic design principle of his Tormek.