Tormek T7 problems

[Jan]

Thanks, Jan. It means a lot to me that you, with your formidable math background, recognize my practical little tool.

Ken

Honour to whom honour belongs, Ken. You have recognised the potential of Ton Nielsen paper Grinding Angle Adjustment for our forum and suggested your practical little tool – the kenjig. 

This geometrical concept removes all difficulties with setting an edge angle for thin knives and knives with tapered blades provided the blade is properly centred in the jig. 

Jan

[Ken S]

Thanks for your kind words, Jan.

My original motivation for the kenjig was to assist an older member who was having difficulty using the Anglemaster because of his eyesight. Improving set up time has been a nice by product. The Anglemaster, while an essential accessory, can be difficult to use in poor light and with small bevels. Unless some sort of presets are used, it also must be used with every tool to be sharpened. This can be tedious.

The admonition in the handbook to use good light should be in large bold type! I experienced this epiphany years ago when I set up my Tormek on a Workmate outside. The light was bright and soft that day. I was on the north side of my primitive garage/workshop. I was astounded how much easier the Anglemaster was to see. Since that day, I have strived to improve the task lighting in my new shop.

The difficulty with small bevels is improved with a black marker. It can be eliminated by using a substitute target. I made up a substitute target out of a rectangular piece of steel 25x40x3mm. Grind a single bevel from the long side to less than fifteen degrees. For greatest accuracy match the ideal thickness of the jig jaws (2.5mm). Measure the protrusion of the knife in your jig. Replace the knife in the jig with the steel substitute target set to the same protrusion. You now have an easy to measure large, flat target.

Standardizing the Distance between the universal support and the grinding wheel AND the Protrusion of the tool in the jig from the universal support has several advantages:

1) It simplifies sharpening for beginners and infrequent users. This allows the user to focus on the actual grinding.

2) It eliminates the tedium of continual remeasuring with each tool to be sharpened.

3) It makes set up very fast for busy sharpeners.

4) When Prutrusion is carefully chosen (I chose 139mm), it allow very quick changes between knife sizes (paring to chef to slicer) with little or no jig adjustment and no Distance changes. The Distance remains constant. The Protrusion needs only occasional tweaking to bring it to 139mm. (I use three jigs and a small blade tool for efficiency. I could do it all with just one regular knife jig.)

Again, thanks for your kind words, Jan. You fully understand the process.

Ken

[Jan]

Ken, you are welcome! 

For your single bevel substitute target I would recommend a thickness of 1.25 mm = 0.05" which would guarantee that its edge is centred with respect to the jig axis. 

Jan

P.S.: Your 3 mm thick substitute target will not cause a large error in edge/bevel angle but it is breaking the knife jig flip symmetry.   

[Rem]

A most interesting thread !!!  Apparently, I've been doing this all wrong.  Several times in this thread there has been reference to "halving the angle" as measured on the Angle Master for a double bevelled blade.  I sort of missed that the first time around.  I prefer using the written manual for these things, and upon review, I cannot find any reference to this concept in the owner's manual.  They use a single bevelled tool as the primary object of the discussion. 

I then went back to the video and, sure enough, right at the very end, they briefly refer to this concept. 

Am I correct that this is not mentioned in the written word (owner's manual)?  If I am in error, I would appreciate being straightened out.   If I'm not, this definitely needs to be elaborated on in the owner's manual.  I can't find it, but HEY, I'm old and it's early. 

Anyway, I think I have it now.  When determining the blade angle of a double bevelled blade, you set the Angle Master at 1/2 of the desired final angle.   Someone please confirm for all of posterity.   Thanks.  Great thread.   R   

[Rem]

Apologies ......  I just found one brief reference to this (see previous post) on page 55 of the Owner's Manual, under the Knife Jig SVM-45 chapter, under "thin knives".    As this appears to be a fundamental concept for the use of this machine, I still feel it is under emphasized.   But that's just me.    Anyway, I think I have my answer.   I've been doing this all wrong.  It's hard to be cool when you don't read the fine print !!!  Things should be more better from now on.   R   

[Jan]

The "halving the angle" method on p.55 is used for thin knives and also for knives with small bevels where the bevel is too short for alignment of the angle setter. The "halving the angle" method works as described in the handbook when the sides of the blade are parallel, but it requires correction when the blade tappers towards the edge. 

Jan

[Rem]

Thanks, Jan.  This is a bit ahead of my learning curve right now, but at least I'm aware of it.  I'll try and read up on it some more.   Thanks again.  R

[Ken S]

Ken, you are welcome! 

For your single bevel substitute target I would recommend a thickness of 1.25 mm = 0.05" which would guarantee that its edge is centred with respect to the jig axis. 

Jan

P.S.: Your 3 mm thick substitute target will not cause a large error in edge/bevel angle but it is breaking the knife jig flip symmetry.   

Jan,

You are correct. The substitute target works best if the thickness is on the center axis of the knife jig, 1.25mm. That was my intention from the start. Thanks for assisting my math.

Rem,

I think we can all benefit from a quiet morning or afternoon with an insulated mug of coffee or tea, a highlighter, a dark pencil, and the Tormek handbook. I try to do this periodically, and have benefitted everytime. I will continue to to this.

Unfortunately, we have no guided path for the learning curve. An indepth basic training video from Tormek would be a great help. The top email on the Tormek General subforum was my attempt to do this. The topic grew too much. I still think a 3/4" chisel is the best training tool to learn the basic Tormek, even if the user never intends to sharpen chisels. The chisel is a great trainer. Most of the initial difficulties we all experience with the Tormek seem unnecessary to me with some good training. Hang in there. You will soon be doing fine.

Ken

[Jan]

Thanks, Jan.  This is a bit ahead of my learning curve right now, but at least I'm aware of it.  I'll try and read up on it some more.   Thanks again.  R

Rem, I think that being aware of certain pitfalls is the right approach. 

It is not good to study in advance all possible future difficulties. "For everything there is a season, and a time for every matter under heaven: ..."

Jan

[SharpenADullWitt]

REM,

This is why I still recommend JF video's, even for a new Tormek owner (T-8).  The tool may have changed a bit, but what he teaches is technique and he covers things so well, that stuff will get missed the first time viewing.  I watched it the first time, and then the first time I went to do a knife, I had the jig and knife with me, and caught his video, telling to put the edge of the jig, parallel with the edge of the blade, NOT the knife back.  Makes a world of difference.

[wootz]

Guys, it is way easier to set grinding angle by the Universal Support height than with the WM-200 AngleMaster.
As a matter of fact, I haven't used the AngleMaster since I developed a computer script for this.
And since you are reading this you also have a computer and can use this script.
Using this method you needn't bother about the blade taper.

The method was elaborated here http://forum.tormek.com/index.php?topic=2969.0
Despite the topic caption, you can use it to set a desired grinding angle even if you use only one grinding wheel.

Rather than reading through the lengthy concept, just copy the script from that thread to the Notepad on your PC, save, and change the file extention from .txt to .vbs

Double click to run, and follow the prompts to get the Universal Support height.
For a double-bevel knife the "target grinding angle" is your desired knife edge angle divided by 2, e.g. to get a 30 degree cutting edge, the grinding angle is 15 degrees per side.
The script will calculate the Universal Support height from the Tormek case top to the top of the Universal Support bar for a given edge angle.
Then set the US height with the help of a callipers depth probe, or a combination square.

(Note that constants in this script are for T7. For T2000, T4 and T8 you have to measure and edit values of the ConstantHorizontal and ConstantVertical.)

I validated this method with laser goniometer on so many custom knives... you can trust it.

T7 has its peculiarities and limitations in knife sharpening, but all have been addressed in this forum; older threads are well worth studying.

[Jan]

Yes, the Wootz approach is another geometrical method to set an edge angle. I have tested it carefully this spring and can confirm that it works correctly. It is immune to blade taper problem. I can definitely recommend it. 

From the geometrical point of view it is another successful application of the cosine rule to Tormek grinding geometry. Wootz approach is based on setting the edge angle through the USB height over the Tormek housing while the kenjig approach is based on setting the edge angle by the distance between the USB and the grindstone *. Both methods depends on the grindstone radius. 

There is only one edge angle setting approach which does not depend on the grindstone radius – the modified TTS – 100 jig. Currently it exist for a predefined set of bevel angles and fixed protrusion 139 mm.
http://forum.tormek.com/index.php?topic=2639.30
http://forum.tormek.com/index.php?topic=2639.60

Jan

* P.S.: The kenjig concept is based on the original Dutchman approach which involves small approximation concerning the way we measure the distance between the grindstone and the USB.

Wootz approach is not burdened by this small approximation. For this reason Wootz script provides even more accurate results than the Dutchman tables.   

[Herman Trivilino]

The "halving the angle" method on p.55 is used for thin knives and also for knives with small bevels where the bevel is too short for alignment of the angle setter. The "halving the angle" method works as described in the handbook when the sides of the blade are parallel, but it requires correction when the blade tappers towards the edge. 

Regardless of the method used, the shape of the blade, or the thickness of the blade, the bevel angle will be half the edge angle on any conventional knife that is sharpened on both sides.

[SharpenADullWitt]

Guys, it is way easier to set grinding angle by the Universal Support height than with the WM-200 AngleMaster.
As a matter of fact, I haven't used the AngleMaster since I developed a computer script for this.
And since you are reading this you also have a computer and can use this script.
Using this method you needn't bother about the blade taper.

The method was elaborated here http://forum.tormek.com/index.php?topic=2969.0
Despite the topic caption, you can use it to set a desired grinding angle even if you use only one grinding wheel.

Rather than reading through the lengthy concept, just copy the script from that thread to the Notepad on your PC, save, and change the file extention from .txt to .vbs

Double click to run, and follow the prompts to get the Universal Support height.
For a double-bevel knife the "target grinding angle" is your desired knife edge angle divided by 2, e.g. to get a 30 degree cutting edge, the grinding angle is 15 degrees per side.
The script will calculate the Universal Support height from the Tormek case top to the top of the Universal Support bar for a given edge angle.
Then set the US height with the help of a callipers depth probe, or a combination square.

(Note that constants in this script are for T7. For T2000, T4 and T8 you have to measure and edit values of the ConstantHorizontal and ConstantVertical.)

I validated this method with laser goniometer on so many custom knives... you can trust it.

T7 has its peculiarities and limitations in knife sharpening, but all have been addressed in this forum; older threads are well worth studying.

So you measure to the center of the support bar, or the bottom or top of the support bar?

[wootz]

The calculated Universal Support height is in mm from the top of the support bar down to the housing.