Author Topic: Finishing with SJ-250  (Read 4566 times)

Offline Sharpco

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Finishing with SJ-250
« on: October 22, 2017, 04:55:01 am »
Tormek said......"Since the surface left by the Japanese Waterstone is so fine, we do not recommend honing afterwards on the leather honing wheel."(https://www.tormek.com/international/en/accessories/grindstones/sj-250-tormek-japanese-waterstone/)

But in my experience, the SJ-250 finished knife is not sharp enough. There is a big difference compared to the honing wheel.

Is your experience the same?

Offline wootz

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Re: Finishing with SJ-250
« Reply #1 on: October 22, 2017, 07:34:13 am »
Tormek honing compound and SJ abrasive particles are similar in size, yet the difference is expected.
Do you mean you get a sharper knife using the honing wheel instead or after the SJ?

Offline Sharpco

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Re: Finishing with SJ-250
« Reply #2 on: October 22, 2017, 09:03:40 am »
Yes. I could get a sharper edge using the honing wheel after the SJ-250.

Offline wootz

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Re: Finishing with SJ-250
« Reply #3 on: October 22, 2017, 10:49:02 am »
You must either be setting an angle on the SJ too steep, or overhoning the edge.
Try the following.

Having ground an edge on your  SG wheel, change to the SJ, and adjust the US height to the edge angle as accurately as you can, by whatever method you use.
Then LOWER the US by 1 digit.
This way you will spare the very edge apex from the impact.

Starting on the side with the burr from the SG, make just two alternating passes on the SJ - check sharpness to decide whether to continue or not - number of passes needed depends on the steel hardness.

Not to overwork the edge is crucial at this point.
If you can shave your forearm smoothly or even better get a hair violin sign, stop there as you hardly can refine the edge further by edge-leading honing on SJ.

I've just tried all that on an ATS-34 knife, and got an edge at 130-115 BESS that shaves, fillets paper and plays violin with a hair.


« Last Edit: October 22, 2017, 12:17:40 pm by wootz »

Offline Sharpco

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Re: Finishing with SJ-250
« Reply #4 on: October 22, 2017, 01:39:53 pm »
wootz.

Thank you so much. I will try again.

I have a question. What is the BESS result after you have used the Honing wheel?

Offline cbwx34

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Re: Finishing with SJ-250
« Reply #5 on: October 22, 2017, 04:30:32 pm »
I would be interested in a few more things, like how you're testing for sharpness, how you're using the SJ wheel now, what differences you're seeing, etc., so if wootz advice doesn't give you the results you're seeking, you may want to provide a bit more info. 

I would add "light pressure" to wootz's suggestions.  You should be able to get at least as good an edge off the SJ wheel as the honing wheel.  You might try honing away from the edge (if not already), and see if that makes a difference.  I would also marker the edge... make sure you're hitting the bevel properly, and that nothing is changing between the wheel switch... even a subtle change can affect the outcome.
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Offline wootz

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Re: Finishing with SJ-250
« Reply #6 on: October 22, 2017, 09:59:12 pm »
wootz.

Thank you so much. I will try again.

I have a question. What is the BESS result after you have used the Honing wheel?

That's an easy question, as I keep BESS records of all sharpening sessions: from 75 to 110.
Just mind that you should NOT use the leather wheel WITH the Tormek honing compound after SJ, as the abrasive particles are of the same 2-3 micron size in both - that is why Tormek doesn't recommend that.
When I have to do final honing on the leather wheel after SJ, I do it with 0.5 micron diamond spray, and now and then condition the leather with oil-based CHROMOX, which is pure Chromium Oxide of 0.5 micron in size (so I actually have a mix of them on the wheel).

Note that Green Rouge is not the same as Chromium Oxide, Green Rouge has varying abrasive particles 0.5 to 3 micron in size, and gives you no advantage using after SJ.

EDIT:
The benefit of commenting is that having answered someone's question, I understand things better for myself.
This time I realized I've never tried a combination of 0.25 micron diamond spray and CHROMOX on the Tormek leather wheel.
Tried this on that ATS-34 knife, and after 4 alternating passes got BESS score 60.
From a hair violin sign, the edge has improved to splitting the hair, and even whittling it on one portion of the edge.

The truth about diamond sprays is that they are graded by average size, and the 0.5 micron spray will certainly have larger than that particles among.
I've known that for long, but only today it dawned upon me that if I want a true 0.5 micron honing mix, I should be using 0.25 micron diamond spray.

Why 0.5? - because the abrasive grit size and the edge apex width you get with that abrasive are related by about an order of magnitude, i.e. grit #1000 (15 micron) gives you about 1 micron edge, and honing/stropping with a 0.5 micron abrasive refines your edge to 0.1 - 0.05 micron, i.e. to a DE razor range.

And a final note: Neither woodworkers, nor straight razor users like the gritty feeling the diamonds give to the edge, but this is that toothy trait that is appreciated in knives.

« Last Edit: October 23, 2017, 03:54:13 am by wootz »

Offline thansen

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Re: Finishing with SJ-250
« Reply #7 on: October 29, 2017, 12:35:30 pm »
You must either be setting an angle on the SJ too steep, or overhoning the edge.
Try the following.

Having ground an edge on your  SG wheel, change to the SJ, and adjust the US height to the edge angle as accurately as you can, by whatever method you use.
Then LOWER the US by 1 digit.
This way you will spare the very edge apex from the impact.

Starting on the side with the burr from the SG, make just two alternating passes on the SJ - check sharpness to decide whether to continue or not - number of passes needed depends on the steel hardness.

Not to overwork the edge is crucial at this point.
If you can shave your forearm smoothly or even better get a hair violin sign, stop there as you hardly can refine the edge further by edge-leading honing on SJ.

I've just tried all that on an ATS-34 knife, and got an edge at 130-115 BESS that shaves, fillets paper and plays violin with a hair.

This is my first post in this friendly forum :)

I just want to thank wootz for this advise.
I am fairly new to sharpening with the Tormek, and I had problems getting my knives razor sharp.

Before I always had to use the leather wheel after the SJ stone, to get my knives sharp. But I read somewhere that it wasn't necessary to use the leather wheel after the SJ stone, so I must have done something wrong.

I then read wootz' advise and tried following his advise, and surely I paid of, now I have razor sharp knives without using the leather wheel.

Thank you again wootz  ;) I'll buy you a beer if you ever comes to Denmark  ;D   

Offline Sharpco

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Re: Finishing with SJ-250
« Reply #8 on: October 29, 2017, 12:58:05 pm »
You must either be setting an angle on the SJ too steep, or overhoning the edge.
Try the following.

Having ground an edge on your  SG wheel, change to the SJ, and adjust the US height to the edge angle as accurately as you can, by whatever method you use.
Then LOWER the US by 1 digit.
This way you will spare the very edge apex from the impact.

Starting on the side with the burr from the SG, make just two alternating passes on the SJ - check sharpness to decide whether to continue or not - number of passes needed depends on the steel hardness.

Not to overwork the edge is crucial at this point.
If you can shave your forearm smoothly or even better get a hair violin sign, stop there as you hardly can refine the edge further by edge-leading honing on SJ.

I've just tried all that on an ATS-34 knife, and got an edge at 130-115 BESS that shaves, fillets paper and plays violin with a hair.

Wootz.

I'm using SJ-250 towards the edge. Does honing direction matter?

And Why should I pay attention to overwork?

Finally, what is mean 'hair violin sign'?
« Last Edit: October 29, 2017, 01:51:25 pm by sharpco »

Offline wootz

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Re: Finishing with SJ-250
« Reply #9 on: October 30, 2017, 12:22:44 am »
You must either be setting an angle on the SJ too steep, or overhoning the edge.
Try the following.

Having ground an edge on your  SG wheel, change to the SJ, and adjust the US height to the edge angle as accurately as you can, by whatever method you use.
Then LOWER the US by 1 digit.
This way you will spare the very edge apex from the impact.

Starting on the side with the burr from the SG, make just two alternating passes on the SJ - check sharpness to decide whether to continue or not - number of passes needed depends on the steel hardness.

Not to overwork the edge is crucial at this point.
If you can shave your forearm smoothly or even better get a hair violin sign, stop there as you hardly can refine the edge further by edge-leading honing on SJ.

I've just tried all that on an ATS-34 knife, and got an edge at 130-115 BESS that shaves, fillets paper and plays violin with a hair.

Wootz.

I'm using SJ-250 towards the edge. Does honing direction matter?

And Why should I pay attention to overwork?

Finally, what is mean 'hair violin sign'?

Towards the edge = edge-leading, and the above my advice is for that.
Saying overwork, I meant grind/hone too much, past the apex where the two sides of the edge meet, dulling it.

Hair violin sign - the edge cannot cut the hair yet, but the hair "plays violin" with the edge.
This is due to the hair cuticles catching the edge, which is not sharp enough to penetrate. You can sense the violin-like vibrations.
Your knife starts playing violin at 115 BESS or at 0.2 micron edge apex width.


Offline Sharpco

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Re: Finishing with SJ-250
« Reply #10 on: October 30, 2017, 12:29:44 am »
wootz.

Thank you for your reply. I'm learning a lot from you.

Offline wootz

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Re: Finishing with SJ-250
« Reply #11 on: October 30, 2017, 12:41:15 am »
@ Thansen - no worries.
Though very fine, the SJ eats metal away like a hog.
It is easy to hone past the apex on it, and dull the edge rather than refine it.

@ Sharpco - not much left to learn, if any. :)
You are there already, and your customers will appreciate that.
« Last Edit: October 30, 2017, 12:52:16 am by wootz »

Offline cbwx34

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Re: Finishing with SJ-250
« Reply #12 on: October 30, 2017, 03:30:31 am »

Though very fine, the SJ eats metal away like a hog.
It is easy to hone past the apex on it, and dull the edge rather than refine it.


Have you ever honed away from the edge with the SJ wheel?  (And if so... differences?)

I've been using it that way.... and "eats metal away like a hog"... I don't see that.

p.s. (By differences, I also mean with your testing results).
« Last Edit: October 30, 2017, 04:05:25 am by cbwx34 »
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Offline Ken S

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Re: Finishing with SJ-250
« Reply #13 on: October 30, 2017, 07:42:56 am »
A while back, we had some difficulties defining the bevel angle versus the included angle. In the interest of clarity, I would like us to use Tormek's terms for grinding direction, as shown below from page fifteen of the handbook. (Sorry, the diagrams did not copy.) I am not saying that Tormek's terminology is any better, however, we can all refer to it in the handbook. It should prevent any confusion.

Grinding is either towards or away. With the standard universal support bar, that means using the vertical sleeves is towards and using the horizontal sleeves is away.

I think this is a most useful topic, and want to be sure we have our direction terminology correct.

Ken
                                                                                                                                        Grinding Direction
The question whether to grind away from or towards the edge is probably as old as the art of water cooled grinding. Many experienced and skilled craftsmen state that one should grind away from the edge whilst others, equally ex- perienced, maintain that one should grind towards the edge. Conventionally dry grinding at a high rpm is always carried out towards the edge.
Our tests show no noticeable difference between the two methods in relation to the sharpness of the edge. There are however some practical and essential differences in the grinding operations.
You achieve a higher grinding pressure and thus faster grind- ing when grinding towards the edge as the rotation of the grindstone helps to press the tool towards the stone. When grinding away from the edge the grindstone tends to lift the tool and decrease the grinding pressure.
Grinding towards the edge tends to activate the grindstone and reduce the risk of a glazed stone surface. The burr de- veloped during grinding is shorter and stiffer compared to grinding away from the edge, when it is longer and thinner.
A disadvantage when grinding towards the edge, is the risk that the tool can accidentally dig into the stone. This can be eliminated if the tool is mounted in a grinding jig. Vibration can also occur at steeper edge angles, which is not the case when grinding away from the edge.
Grinding away from the edge is preferable when you need a light grinding pressure, e.g. when grinding small and delicate woodcarving tools. In this direction you can easily control the grinding operation and observe the burr developing as no water  ows over the edge.
Free-hand grinding is best done with the stone running away from the edge. With the Tormek system you can grind both towards and away from the edge. In the chapter “Which Jig Should I Use?” there is a recommendation of the grinding direction for various types of tool.
Grinding away from the edge.
    Grinding towards the edge.
                                      Grinding towards the edge increases the grinding pressure.
                 It should be noted that this question of grinding away from or towards the edge must not be mixed up with the question whether the grindstone should rotate away from you or to- wards you. This depends on how you position the machine. The Tormek machines can be positioned either way.
Grinding away from the edge decreases the grinding pressure.
15

Offline Sharpco

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Re: Finishing with SJ-250
« Reply #14 on: November 07, 2017, 02:19:01 am »
I have tried many times with the way wootz told me. Certainly, I was able to get better results than before. Thank you. wootz.

But after honing with SJ, I was able to get a sharper edge using the leather wheel.