Dc-250 - Df-250 - Sg-250?

[Swemek]

Hi all,

I have two Tormek diamond wheels, course and fine. I also have SG-250 wheel which has never been graded course, so it still has the 250 mm dimension since I only use it as the final step after the diamond wheels, used as Tormek Japanese water stone, if you will, but with courser grit.

Many times DE-250 (grit 600) is the final step, this give me good enough result.

Wanted to ask you all if you see any reason to have the 1200 grit diamond wheel, as long as my SG-wheel keep it's dimension but also remains true?

To my eyes the result from SG-250 (graded very fine, with a finer grit than the fine git side of the Tormek grading stone) gives a beautiful edge to finalize on my leather wheels.

Is there any practical or theoretical pros with using diamond (or CBN) as the last step of sharpening super steel's like m390, rather than traditional aluminium oxide stone?

I I'm aware that deburring on diamond can give high vanadium steels better edge retention.

Thanks!

[Ken S]

One overlooked solution is to make the final pass or two with your DF-250 with VERY light pressure. This is demonstrated in the online class covering the T2, but can be applied to any Tormek. This is very fast, not involving any wheel changing. It is also very cost efficient, as no extra expense is involved. It gently transfers the initial honing from the leather wheel to the grinding wheel.

Ken

[John_B]

I think many users worry unnecessarily about consuming the SG-250. When I have knives that need more material removed I do not hesitate in using the coarse side of the grading stone. I also in the camp that trues the stone fairly often rather than letting it go and removing a lot of material less often. Unless you are using a dial indicator to measure runout it is often hard to detect an out of round condition.

When chasing the sharpest edge I personally look at whose knife it is that I am sharpening. It is not too difficult to obtain an edge that is better than almost every out of the box knife. This can be achieved with the SG-250 and leather wheel. For my knives and a couple of customers I will use a second leather wheel with 1µ diamonds. I also look at the time required to change wheels to a progressively finer grit when doing multiple knives when few appreciate the knifes sharpness beyond out of the box.

[Royale]

From my personal experience with my Tormek T8... I see the matter in terms of matching the abrasive to the steel type.

For cheap and soft steels with low carbide content, I use the SG-250 for speed.

For harder steels alloyed with more carbides, I still use the SG-250 for reprofiling (because at this stage I'm not bothered with carbide tear/fall out), but all follow up sharpening is done with diamond grindstones (DF-250, DE-250) because I want to cut through both the supporting ferrite matrix and carbides together. Takes a longer time, but often a "Do it good, do it once" type of situation.

Long story short, seeing the dimension of grit size only, may leave you missing out on a bigger part of the workflow.

Hope that made sense.

[John Hancock Sr]

Many times DE-250 (grit 600) is the final step

The DE is 1000 grit.

Is there any practical or theoretical pros with using diamond (or CBN) as the last step of sharpening super steel's like m390, rather than traditional aluminium oxide stone?

Your abrasive needs to be harder (MOHS) than your steel or you will simply glaze your wheel. This is the process whereby the sharpening process rounds over your grit and leaves it blunt, thus making the wheel less effective and deforming rather than scratching the steel. I am assuming that you are dressing the SG otherwise you are leaving it glazed and not working efficiently.

[Rossy66]

I thought this was a great video and helped me make me final decision on what wheels to buy.

https://www.youtube.com/live/Gg4R9jxtKfI?si=iwhJu9dNjfk5vHAd

[Swemek]

One overlooked solution is to make the final pass or two with your DF-250 with VERY light pressure. This is demonstrated in the online class covering the T2, but can be applied to any Tormek. This is very fast, not involving any wheel changing. It is also very cost efficient, as no extra expense is involved. It gently transfers the initial honing from the leather wheel to the grinding wheel.

Ken

Thats interesting, since I read somewhere that a quick light pressure pass on df-250 would minimize the burr. Maybe it was one of your posts in fact. It's a part of my routine however.

I think many users worry unnecessarily about consuming the SG-250. When I have knives that need more material removed I do not hesitate in using the coarse side of the grading stone. I also in the camp that trues the stone fairly often rather than letting it go and removing a lot of material less often. Unless you are using a dial indicator to measure runout it is often hard to detect an out of round condition.

When chasing the sharpest edge I personally look at whose knife it is that I am sharpening. It is not too difficult to obtain an edge that is better than almost every out of the box knife. This can be achieved with the SG-250 and leather wheel. For my knives and a couple of customers I will use a second leather wheel with 1µ diamonds. I also look at the time required to change wheels to a progressively finer grit when doing multiple knives when few appreciate the knifes sharpness beyond out of the box.

Since I got the diamond wheels I have found new use of the SG-wheels. But when I only had the original wheels. I also trued sg-250 often and many times to make sg-250 aggressive and to remove steel as quick as possible. I sharpen a bit of axes for people, sometimes I true before and after.

So it makes sense, I do have two SG-250 one that I true often and I got a very good deal on two diamond wheels and then I had already invested in a new SG-250, which I now use as final step.

Many times DE-250 (grit 600) is the final step

The DE is 1000 grit.

Is there any practical or theoretical pros with using diamond (or CBN) as the last step of sharpening super steel's like m390, rather than traditional aluminium oxide stone?

Your abrasive needs to be harder (MOHS) than your steel or you will simply glaze your wheel. This is the process whereby the sharpening process rounds over your grit and leaves it blunt, thus making the wheel less effective and deforming rather than scratching the steel. I am assuming that you are dressing the SG otherwise you are leaving it glazed and not working efficiently.

I meant DF-250. I do not own EF-250.

I'm not sure I understand what you mean. But do you mean that aluminum oxide won't cut mentioned steels? Thats not my experience. In this case, and since I have no way to measure the results, like Bess device, it is easy to see that that Sg-250 which never been dressed other the finest grit possible get gives the bevel a very different finish, rather than using DF-250 as the final stone. What I don't know is if the SG-250 as described actually makes the knife sharper or gives it better edge retention.

My philosophy is to use just enough steps and as few passes as possible, thinking to many passes and steps grit-wise also can lead to errors that gives a worse result.


Maybe I am missing something or using wrong terms in my fist post.

This thread a bit splitting hairs, since the results I get DC and DF-250 with any steel I have sharpen this far gives me fantastic results and on very short time.

[John Hancock Sr]

I'm not sure I understand what you mean. But do you mean that aluminum oxide won't cut mentioned steels?

Yes and no. It is a matter of hardness. More specifically MOHS hardness. There are different forms of harness but it is MOHS hardness which determines the abrasive for each material. In the MOHS hardness cscale each material is given a number form 0 to 10, 10 being diamond and 0 being talc. For an abrasive to be able to sharpen it has to have a higher MOHS hardness that the material being sharpened.

For steels it depends on the composition and the temper. Different steels of ther same composition will have different harnesses depending on the temper. Knives often consist of several different steels so you may easily be able to sharpen the casing but have difficulty with the core.

Aluminium oxide has a range of MOHS hardness depending on the impurities but in general it can harden carbon steels but not so much high speed steel. So it will vary. When I was sharpening a very hard Japanese knife, my HSS thicknesser blades or my HSS drill bits the SH wheel glazed rapidly. It did cut the steel but was very slow and the wheel had to be constantly graded. It proved to be extremely inefficient. The issue was that the steel had a higher MOHS hardness than those steels. It may have been that the steel fell into the range of the softer to harder particles within the SG wheel this glazed rapidly.

The glazing happens when the steel being sharpened breaks the grit down since it is harder than the grit and you end up with a smooth wheel unable to cut the steel. This is an indication that the wheel is too soft.

Bottom line is that for efficient sharpening you need a harder grit that the material being sharpened.