SJ250 Question

[darita]

When sharpening chisels, should the SJ 250 be used trailing edge, turning away from the edge?

[RichColvin]

Derek,

That is the way I use it.  I am not keen on potentially digging the chisel's edge into the grindstone. 

Rich

[darita]

Also, I've read that the SJ 250 should be trued and I've read that it doesn't need trying. Which is it?

[Ken S]

Good question, Darita. I have trued mine, and would do so again if it needed it. That said, I trued mine very gently. Now, I would start by using the stone grader to radius the two edge corners slightly. With that done, I take VERY light cuts with the TT-50, no more than half a microadjust number.

I believe it is more important to keep the SJ clean. Buy a set of rust erasers. Use the fine grit eraser frequently. You will find many uses for the set.

The SJ is a polishing stone, not a sharpening (grinding) stone.

Ken

[RichColvin]

I agree with Ken. 

[darita]

Somewhere, but I can't find it, I seem to recall Vadim demonstrating using diamond plates to true the SJ-250.  Do you recall anything like that?  Rather than the stone grader, using different grits of diamond plates makes sense to me.

[Ken S]

https://youtu.be/141hD1d1zj0

This is what you are looking for.

Ken

[darita]

Got it!  Thanks.  Don't know why I couldn't find it.  Now I see the plates are used for grading mostly, rather than truing, although Vadim states the stone can be graded 5 times before having to true again. 

[Ken S]

To be fair to the stone grader (all of this is my opinion, and not necessarily Tormek doctrine), the stone grader was originally designed for the SG. The SG is more coarse than the original natural sandstone wheel. This made improved faster grinding, but not as smooth finish.

I think the SB and the SJ, both introduced later, were determined to "also work" with the stone grader, adequate, but perhaps not ideal. Diamond plates, as recommended by Vadim, are inexpensive and will not damage the SJ (or SB).
I suggest you try them.

Ken

[John Hancock Sr]

When sharpening chisels, should the SJ 250 be used trailing edge, turning away from the edge?

Tormek recommend sharening with the stone towards the edge. This produces a smaller burr apparently. With the jig secures ther eis no danger of digging into the stone.

[tgbto]

From what I've seen under the microscope, edge trailing will leave a tiny yet discernible foil-like burr.

Using the SJ edge leading, the burr is not visible with my small microscope. But there still is one that I need to hone, as BESS testing showed, along with the indentation the BESS test medium left on the edge.

I agree that edge-leading, especially with narrow chisels, one has to be very careful to press the jig against the USB at all times. For someone who does this very occasionally (like me), i'd go with edge trailing.

[darita]

Thanks all for the replies.  Since the edge will be refined whether edge leading or trailing, I'll play it safe and go edge trailing to prevent damage to the very delicate SJ.  I know how the SJ absorbs water like a sponge and gets extremely soft after doing so. 

[darita]

So Ken, I'm finding it difficult to figure out how to setup a trailing edge configuration using the TTS 100 and SE 77.  Things just don't seem to line line up correctly.

[RichColvin]

Thanks all for the replies.  Since the edge will be refined whether edge leading or trailing, I'll play it safe and go edge trailing to prevent damage to the very delicate SJ.  I know how the SJ absorbs water like a sponge and gets extremely soft after doing so. 

The SJ is not particularly delicate.  Rather, it can chip easily.  

Also, the SJ does not absorb water "like a sponge". In fact, I find that it absorbs it very little water.

Finally, I've not experienced it becoming spongy. But, I only leave the SJ grindstone in water during the time I'm using it.  Once I'm done, I remove the water from the stone.  

[Ken S]

So Ken, I'm finding it difficult to figure out how to setup a trailing edge configuration using the TTS 100 and SE 77.  Things just don't seem to line line up correctly.

Darita,
I recommend edge leading for chisels with all grinding wheels. The chisel is held securely in the jig. Start with light pressure. As you gain confidence, you can add pressure.
When setting the Distance with hole B in the TTS-100, the SE-77 is not in use. After the Distance is set, put the TTS-100 aside. Then mount a chisel in your SE-77. For a 25° bevel, use a small rule and set the tip of the edge 45mm from the jig. Measuring the Projection this way is probably the easiest way.

Keep us posted.

Ken