"139mm"

[Ken S]

I originally chose 139mm to be the standard projection length of the knife in one of the Tormek knife jigs with the kenjig. I based that on Dutchman's tables and used 250mm as the grinding wheel diameter. I knew that would need to be changed somewhat eventually as my grinding wheel wore.

I had not calculated on the extensive sharpening work I have done this fall in preparation for and actually demonstrating the Tormek at a woodworking show. I measured the diameter of my SG-250 grinding wheel this week and was surprised to see it was only 240mm. my wheel has plenty of useful life remaining.

I have reached the point where I need to alter the kenjig to account for the smaller grinding wheel. I could sand off one millimeter from the bottom of the tool, thus making 139mm into 138mm. Eventually I would need to gradually remove more as my wheel wears.

Some time ago I had reached the realization that my SG-250 grinding wheel is a consumable. It will do a lot of work as it gradually wears down, but like a set of brake shoes, it will eventually need to be replaced. I now realize that my kenjig is also a consumable. Fortunately, making a replacement requires only another cut off from my wood pile and a few minutes.

There is an alternative to changing the 139mm projection distance. The slot for the distance between the universal support and the grinding wheel can be lengthened to accommodate the wheel wear. Jan has done such an outstanding job with his angle setter. It is based on the 139mm projection distance. It makes sense to me to leave the 139mm as a constant. In Jan's version of the angle setter, the tool automatically compensates for wheel wear with the two contact point mechanism of the TTS-100. in my more primitive wooden version, a couple saw cuts easily deepen the groove.

For the record, I believe there is room for both angle setting tools. Jan's version is certainly more sophisticated and precise. However, my simple wooden version is certainly adequate for the task and is stone simple.In a more contemplative scholarly environment, I prefer Jan's method. In a more hectic sporadic application, I think the humble woodie holds its own. I like having choices.

Ken

[Jan]

Agreed, Ken. Both angle setting techniques work fine and provide the same result. 



Support setting with Ken's simple wooden version is quicker and more robust, but depends on the wheel diameter. Support setting with the modified TTS-100 requires more diligence, but does not depend on the wheel diameter. 

The red dot between the metal contact discs, near the 30^o groove, shows the position where the edge meets the wheel.

Jan

P.S.: Tormek statement "The strength of the TTS-100 Setter is that it works irrespectively of the stone diameter", is not entirely correct. The stone diameter cannot be smaller than some 145 mm (5¾"). This is because small wheel hollows deeper between the metal contact discs than a large wheel. Clever design of the TTS-100 does not allow its usage with too small stones, because such a stone will collide with the lower edge of the TTS-100 between the metal contact discs.

[Ken S]

Good comments, Jan.

One of the fascinating things about the Tormek for me is its versatility. It can function quite well with either a simple wooden tool or a much more sophisticated tool or both, depending on the application need.

Interesting observation about the jig preventing using too small diameter grinding wheels.  Clever, both to design and to notice!

Ken