When sharpening chisels, should the SJ 250 be used trailing edge, turning away from the edge?
Derek,
That is the way I use it. I am not keen on potentially digging the chisel's edge into the grindstone.
Rich
Also, I've read that the SJ 250 should be trued and I've read that it doesn't need trying. Which is it?
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
I agree with Ken.
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.
https://youtu.be/141hD1d1zj0
This is what you are looking for.
Ken
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.
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
Quote from: darita on April 30, 2023, 10:18:42 PMWhen 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.
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.
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.
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.
Quote from: darita on May 02, 2023, 02:53:55 PMThanks 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.
Quote from: darita on May 02, 2023, 06:50:59 PMSo 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
Quote from: RichColvin on May 03, 2023, 03:27:20 AMQuote from: darita on May 02, 2023, 02:53:55 PMThanks 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.
Maybe "like a sponge" was a bit dramatic. How do you true your SJ?
The traditional Tormek technique as laid out in the handbook was based around using the SG-250. Even though the SB and SJ wheels were introduced more than ten years ago, they shared only a paragraph in the handbook.
Over the years, I have noticed a lot of what I call high speed dry grinding and bench stone thinking trying to be applied to Tormek thinking with mixed success. I would include trying to apply SG thinking to the SJ (and SB) with these not always successful crossovers. The SG, SB, and SJ wheels are all useful tools for their intended purposes. Each has pros and cons. I believe it is a mistake to try to use the same technique with all three of them.
Ken
OK...this is weird. I trued the SJ with my TT-50, then graded the surface with a 400g flat diamond stone. The wheel wasn't truly true, however can someone explain this result after using the SJ on two chisels? I used it after a 1200grit wheel. Has anyone else had this happen?
(https://i.imgur.com/l2m0EFX.jpg)
(https://i.imgur.com/UKKkwRQ.jpg)
Hmmm...just guessing, but that looks like a constant oscillation pattern that might be related to manufacturing? Did you notice any oscillation while truing with the TT-50? It would be interesting to run a dial indicator over that stone while rotating it by hand on the motor shaft. I would send those photos to TORMEK product support to hear if they have a good explanation.
Quote from: TireguyfromMA on May 05, 2023, 07:52:07 AMHmmm...just guessing, but that looks like a constant oscillation pattern that might be related to manufacturing? Did you notice any oscillation while truing with the TT-50? It would be interesting to run a dial indicator over that stone while rotating it by hand on the motor shaft. I would send those photos to TORMEK product support to hear if they have a good explanation.
I did notice some vibration, but not enough to be of concern at the time. Using the TT-50, I didn't notice any vibration other than that created by grinding. I think I will email support on this.
Interesting, could you give the reading taken with a tape measure in between two stripes on the wheel ?
A 50hz phenomenon with a 248mm (trued) wheel would give 1.5 cm.
I don't have the inner diameter of the drive wheel in mind, but it could also be something that happens with every revolution of the drive shaft, it can be easily computed.
I wouldn't rule out that it has something to to with your grading. First off, 400g seems quite coarse to me, that's something I would use for grading my SG, not my SG. Vadim used to recommend 1000g for the SJ. That being said, it's like the stone has been smoothed out by something wobbly...
Quote from: tgbto on May 05, 2023, 05:39:27 PMInteresting, could you give the reading taken with a tape measure in between two stripes on the wheel ?
A 50hz phenomenon with a 248mm (trued) wheel would give 1.5 cm.
I don't have the inner diameter of the drive wheel in mind, but it could also be something that happens with every revolution of the drive shaft, it can be easily computed.
I wouldn't rule out that it has something to to with your grading. First off, 400g seems quite coarse to me, that's something I would use for grading my SG, not my SG. Vadim used to recommend 1000g for the SJ. That being said, it's like the stone has been smoothed out by something wobbly...
Best I can do is, it's about 8mm peak to peak on average on the second photo. Also, on that photo, I did try 1k diamond. I did send a note with photos to Tormek Support. One thing...after using the TT-50, the surface was higher on the inner surface than the outer. I noticed that when I mounted the 400g diamond in the SE-77 to smooth the surface.
I've got a thick, heavy, 160g flattening diamond plate. Can I simply rest that against the USB to grade the surface of the SJ? Seems like that is doing the same thing as the SE-77, just eliminating the middle man.
I don't see why you couldn't use the USB as a rest for stone grading, provided the plate is stiff. But I think 160 grit is way too course for the SJ stone.
Quote from: 3D Anvil on May 07, 2023, 06:17:01 PMI don't see why you couldn't use the USB as a rest for stone grading, provided the plate is stiff. But I think 160 grit is way too course for the SJ stone.
Yes it may be, however I wanted to try it since I use that same diamond plate to flatten all of my other water stones and ceramic stones.