New Tormek Online Class MB-100 on Mai 12th, 2021

[tgbto]

Hey guys, I just came across this https://www.youtube.com/watch?v=3r_1mZ9XjIs

[Ken S]

TBG,
Thanks for posting this. I must have been asleep at the switch. I encourage our members to watch this online class, as I plan to.

Please post your impressions after the class.

Ken

[tgbto]

Ken, it's okay, it's only fair that we share watch duty !

[Ken S]

Thanks, TGB.

For years I have enjoyed the innovative ideas shared by forum members. In fairness, Tormek has also produced some innovations, also. This online class with the Multibase finally explains some of its  innovative potential. I believe it is limited only by the user's imagination. I used mine to reshape a straight skew to Lacer grind. It worked well. Other than that, it has sat on the shelf.
It is time to put it on active duty!
Please share your experiences.

Ken

[Ken S]

Perhaps you are thinking, I do not have the diamond wheels which can grind flat bevels with the MBS-100 Multibase. Why should I bother to watch this video?

Good question. Here is a good answer. As an example, one of the frequently asked questions is about the dreaded "hollow grind". Near the beginning of this video is one of the best explanations of the amount of hollow grind left by a Tormek wheel I have ever seen. Using a 250mm diameter grinding wheel set to a 20º bevel and a 2mm thick blade, the deepest part of the hollow is .03mm, or roughly .001". That is roughly one third of the thickness of a single sheet of copy paper. That is small enough that I do not worry about it for my chisels, plane blades and kitchen knives.

Most of the online classes have parts like this which apply to several areas. Don't sell yourself short by watching only those classes which you think only apply to you.

Ken

[jvh]

Hello,

I would like to thank Wolfgang, Sébastien and Victor for next part of the Live Sharpening Class, it was excellent again.

Perhaps you are thinking, I do not have the diamond wheels which can grind flat bevels with the MBS-100 Multibase. Why should I bother to watch this video?

Good question. Here is a good answer. As an example, one of the frequently asked questions is about the dreaded "hollow grind". Near the beginning of this video is one of the best explanations of the amount of hollow grind left by a Tormek wheel I have ever seen. Using a 250mm diameter grinding wheel set to a 20º bevel and a 2mm thick blade, the deepest part of the hollow is .03mm, or roughly .001". That is roughly one third of the thickness of a single sheet of copy paper. That is small enough that I do not worry about it for my chisels, plane blades and kitchen knives.

Most of the online classes have parts like this which apply to several areas. Don't sell yourself short by watching only those classes which you think only apply to you.

Ken

Hello Ken,

0.03 mm is really small, but it's only one part of a more complex problem. It is indicated in the video (ca. 4:45), but it is not explained exactly.

Wolfgang said: "Force, of cource, is a little bit aggresive, it will dig in little bit faster..."
This is because in the example shown, the apex angle is 20°, but the angle between the apex and the edge heel is 21.26°. Compared to flat grinding there is "unground" material on the edge heel (due to the rounding of the wheel), which does not allow the blade to be tilted below 21.26°, because it would not cut as the apex does not touch the material. This makes the cut more aggressive because the edge is directed more into the material, and this is IMHO the main thing that should be taken into account.
This also affects the subsequent re-sharpening on a flat stone, where the minimum angle 21.26° is also ground (if the apex and the edge heel are touching the stone).

This problem increases with blade thickness, sharper angle and smaller wheel diameter. It is usually negligible for knives, but may not be the case for tools...

jvh

P.S." The picture shows a thickness of 4 mm, but this is because the calculation is performed for symmetrical blades. The example shows a chisel grind, from which you get a "symmetrical" by multiplying the thickness by two.

[Ken S]

JVH,

Thank you for your reply.

I appreciate the technical expertise members like you bring to the forum. I see the value of this refined technique, especially since with no false modesty, I admit that I have not developed it myself.

Two things heavily influence my thoughts on hollow grinding:

First, I believe many associate hollow grinding with the small diameter grinding wheels common several decades ago. One of the few advantages of old age is remembering things like this. My 1972 vintage dry grinder, six inch (150mm) diameter, is typical of the time. Two point grinding using the distinct hollow with water stones was very popular.

Second, and related, is the time when I held a straightedge against a freshly ground chisel bevel. I can easily see the hollow of a chisel ground with a six inch diameter wheel. I have to look very hard to see any hollow with a 250mm Tormek wheel.

I realize that these thoughts are not very scientific. They are, however, aligned with my present expectations. If I can make my woodworking tools and kitchen knives very sharp, I am content. I do not believe the old English language idiom that "you can't teach an old dog new tricks". I am learning new tricks. After decades of using film cameras and working in a darkroom, I have become comfortable using my digital camera. I am comfortable with basic digital image manipulation. My computer literacy has advanced beyond beginner status. I have a lot more to learn in all of these areas. There are many new tricks for this old dog to learn. Among these new tricks to learn is your computer assisted setting program.

I do appreciate your sharing.

Ken

[Arthur]

some more use cas MB-100

[Ken S]

Well done, Arthur. Good thinking!

Ken

[Rimu]

some more use cas MB-100

Arthur,

What's is the shell you have mounted in the photos, and where did you get it?

[Arthur]

some more use cas MB-100

Arthur,

What's is the shell you have mounted in the photos, and where did you get it?

The photos show a grinding wheel for the Makita 9820 Horizontal Wheel Wet Blade Sharpener. There are three grinding wheels in total. A-69048 1000 grit, A-69054 6000 grit, A-69032 60 grit.