Sharpening knives, grinding into or trailing?

[AlInAussieLand]

If 6 to 8 minutes are only 10% of the time needed on other devices, then either those devices are very ill-suited to knife-sharpening, or maybe you're only using the #6000 grit belt/stone 

Remember that I do this for personal use and family & friends.
Also, the Edge Pro stone usage is normally 220 > 300, if the knife needed "re-setting of the edge, then you would start with 120 > 220 > 300. If using a high quality knife for an even better edge...220 > 300 > 600. Even higher finish...add the 1000 stone.....mirror hair popping finish..now add the tapes on glass ..polish tapes 2000 and 3000.
Also they use their own type of grading. They have a chart where as an example, the Edge Pro 600 stone is 3000 > 5000 grade with anybody else and I can confirm that as I have other sharpening stones.

So the Edge Pro will give you ultimate precision but can be tedious and time consuming. It still requires its own skill set (so you can still mess things up until you have got a bit of experience).
The T8 is a lot quicker as you can achieve faster results with the same stone by varying its grading and using different pressures.

With the little time I have got on the T8, I can see that I will use it 80% of the time and use the Edge Pro on very expensive knifes as I have a lot more experience on the Edge Pro and it gives me that bit more control for more extreme cases.

[tgbto]

That's a fair point, but remember you need to compare apples to apples. You should compare the time it takes to sharpen with the T-8 with the time required to get the same finish on an edgepro. If you want to compare based on the Edge pro with glass stones and polish tapes (and I would add leather strop to really deburr cleanly) you should compare it to the Wootz version of the T-8, with the addition of the japanese stone and 3 different stropping compounds.

Two remarks AFAIAC :
- The difference between a T8 and edge pro is bigger as the blade gets longer.
- The mirror polish hair splitting finish you get when finely polishing the blade does not translate in kitchen-world edge retention and perceived cutting performance. A SG with honing on leather wheel is sufficient for most applications, as is the Edge Pro with the 600 stone and leather strop.

[Ken S]

I am reminded of two sayings:

The first, attributed to Prussian General von Clausewitw, "The enemy of a good plan is the dream of a perfect plan".

The second: "There are many roads to Dublin".

There are many good ways to sharpen. I happen to prefer the Tormek; however, if I needed to sharpen something where I was away from my Tormek, I would not hesitate to use whatever sharpening tool was at hand. Also, I do not expect my Tormek, or any other tool, to be the universal best tool. I would try to use the "right tool for the right job" (borrowing a phrase from Star Trek Engineer Scotty).

ken

[AlInAussieLand]

Two remarks AFAIAC :
- The difference between a T8 and edge pro is bigger as the blade gets longer.
- The mirror polish hair splitting finish you get when finely polishing the blade does not translate in kitchen-world edge retention and perceived cutting performance. A SG with honing on leather wheel is sufficient for most applications, as is the Edge Pro with the 600 stone and leather strop.

Yes, absolutely...:-)
My wife knows how to use the knifes, to the point where I barely need to give them a touch up every couple of months.
Hair popping sharpness is just an exercise in ability, proving that I can do it, but has no practical application in the real world of usage in kitchen or other general usage. One cutting session and that extreme sharpness is gone.
In the real world, on the Edge Pro, even on higher quality knifes, 220 grid and sometimes going to 300 grid is more then good enough to shave the hair of you arms or cut paper with ease.

Just finding my feet on the T8. I have a few cheaper general purpose and kitchen knifes to get practise on. Just like the Edge Pro, the T8 requires its own skill set and they can not be gained by just watching videos.
I have already done a trouble some 8 inch carving knife with very good results on the T8 that has given me years of trouble on the Edge Pro, for what ever reason.
This knife would micro chip, no matter what method or stone used.
With the T8 I finally got the micro chips out and back to a factory edge, while at the same time causing a hollow grind in the middle section.....grrhh. 
Lots more practise needed.....

[tgbto]

This knife would micro chip, no matter what method or stone used.
With the T8 I finally got the micro chips out and back to a factory edge, while at the same time causing a hollow grind in the middle section.....grrhh. 
Lots more practise needed.....

For the carving knife, the steel might be quite brittle and will hate the kind of lateral impact with a hard stone it gets with the edge pro. The T8 edge leading, along with the finely controlled way you lay down the jig, will minimize this phenomenon.

As for the hollow grind, it is a very common problem at first. The most useful advice I could find so far are :
- Put a bit more pressure when the heel is on the stone to compensate for the fact that it will see less stone time overall compared to the middle section (in a video by Wootz)
- Round the shoulders of the stone significantly. Else when you lay down your knife, if it is ever so slightly tilted towards the tip, it will severely overgrind the middle portion.
- As you said, practice, practice, practice.

[AlInAussieLand]

So having now tested grinding a knife using the trailing method.
The main reason for trying that, was to overcome the hollow grind in the middle of the dead straight edge practise knife.

Trail grinding without a doubt gave a larger burr, but gave me (at this) stage more control. This burr was easily reduced to the same level as leading edge grinding by giving the knife edge 2 ~ 3 very light final swipes per side on the Grind stone. From there normal honing on the honing wheel gave the same edge/look sharpness with no left over burr.
Did the trail grinding fix my hollow grind in the middle section?....NO..
Lots and lots more practise needed.

[cbwx34]

...... fix my hollow grind in the middle section?....NO..
Lots and lots more practise needed.

It's better to fix the hollow grind before sharpening.  If you're trying to sharpen and make the repair at the same time, you'll mostly likely just chase the problem.

If you want to fix it on the Tormek, (and don't want to freehand it), try setting the angle as high as you can, that should make it easier to repair.  Once the repair is made, you can lower the angle and sharpen in a new bevel/edge.

You can also use the flat-side of the wheel freehand (again at a higher angle) to fix it.

[AlInAussieLand]

...... fix my hollow grind in the middle section?....NO..
Lots and lots more practise needed.

It's better to fix the hollow grind before sharpening.  If you're trying to sharpen and make the repair at the same time, you'll mostly likely just chase the problem.

If you want to fix it on the Tormek, (and don't want to freehand it), try setting the angle as high as you can, that should make it easier to repair.  Once the repair is made, you can lower the angle and sharpen in a new bevel/edge.

You can also use the flat-side of the wheel freehand (again at a higher angle) to fix it.

Great tips...thanks
Good thing is that I am trialling all this on a cheap practise knife.

[Ken S]

This morning, I carefully reread this whole topic and finally realized what was confusing me. I remember, going back to the 1970s, when it was quite popular to add a hollow grind using a round grinding wheel, as opposed to a flat grind using a bench stone. The round wheel was almost always a six inch diameter high speed electric grinder, either run around 3450 RPM or 1725 RPM. These small grinders produced the desired hollow bevels which were easily resharpened by sharpening just the tip of the edge and the back end of the bevel. Those who were concerned about this hollow grinding merely added three degrees to the bevel setting. Care was required not to grind fully to the apex to avoid overheating the edge. This was why final sharpening was done on bench stones.

This was less laborious than regrinding the entire bevel. It was also unnecessary with the Tormek. The large ten inch grinding wheels produced bevels which, for practical purposes, were flat. Being water cooled, overheating was no longer an issue. The motor of the Tormek did the work, so fully grinding to the apex was not a problem.

With knife sharpening, there was another potential issue. If the middle of the knife curve was overground, a low spot was produced. This was often called "the green onion effect" when the low spot prevented clean cutting. This low spot was man made trouble, caused by inadvertently grinding the middle of the curve. It was frequently done by earlier sharpeners. It is easily detected by rocking the knife gently over a flat surface. I agree that this is best corrected before actual sharpening. Checking and correcting this should be a standard part of good knife sharpening. This and the related bolster reducing should be "part of your custom" and go a long way with customer satisfaction.

Ken

[AlInAussieLand]

With knife sharpening, there was another potential issue. If the middle of the knife curve was overground, a low spot was produced. This was often called "the green onion effect" when the low spot prevented clean cutting. This low spot was man made trouble, caused by inadvertently grinding the middle of the curve. It was frequently done by earlier sharpeners. It is easily detected by rocking the knife gently over a flat surface. I agree that this is best corrected before actual sharpening. Checking and correcting this should be a standard part of good knife sharpening. This and the related bolster reducing should be "part of your custom" and go a long way with customer satisfaction.

Yes
It's clear I used the wrong terminology, my bad.
It is the over-grinding of the middle section that is causing me all the problems.
We replaced a middle range quality long blade carving knife with a new high quality unit.
The old one is going to my youngest son who has (finally) moved out and with his girlfriend have started their own household.
It's the medium quality carving knife that had the issue with micro chipping that I simply was unable to remove with other sharpening methods. It just alluded me. Other knifes from the same manufacturer and same steel did not show this problem...go figure.
So with the T8, I was finally able to get rid of all the micro chips...hurray..and created a whole new problem. As the blade steel is a lot harder, the over grinding of the middle section is minor, but still noticeable if you look at it closely. So this knife has a 200mm blade length and a very long straight section which is at least 80% between the heel and the start of the curvature towards the tip.
So setting the knife vertical with its edge down, you can see light through at the middle section.

This is when I grabbed my "practise knife". This is a simple straight blade 100mm blade length knife used by Linesman and electricians. Soft stamped steel, designed to be roughly sharpened with a file or similar.
I can for the life of me not stop the over grind in the middle section 
The T8 original stone is trued and the edges have been rounded. Despite all this, even being super careful and controlled slow with light pressure, it still happens.
When I get to the middle section, I can feel the stone "bite" suddenly.
By the way, this doesn't happen with the Chefs knife or any other knife that has at least some curvature across the length of the blade.

[Drilon]

Do you always sharpen in one direction from the heel to the tip or do you sharpen back and forth? Sharpening in two directions would over-grind the middle part of the knife.

[AlInAussieLand]

Do you always sharpen in one direction from the heel to the tip or do you sharpen back and forth? Sharpening in two directions would over-grind the middle part of the knife.

Good point. I will try sharpening one direction only, from heel to tip and see how that goes.

[3D Anvil]

I think this issue is often caused by insufficient grinding of the heel section of the blade.  If you start at the heel, as I think most do, that section of the blade gets very little wheel time.  It's on the wheel, and then you draw it straight off and that's all the grinding it sees.  In contrast, the part of the blade that's on the opposite side of the wheel traverses the entire width of the surface.

At the speed I normally go, the extreme heel would be on the wheel for less than a second, while the section that was on the other side gets 3-4 seconds of grinding before it comes off.  That causes a high area at the heel and a dip in the section after. 

One way to deal with that is to hold the heel section on the stone for a few seconds before you start moving the blade.  What I've been doing for a while now is actually starting an inch or two ahead of the heel, then moving back to the heel, and then across to the tip.  Works for me.

The belly section can also get short shrift for the same reason.  Any time you have a curve, only one point on the blade can contact the stone at any given time.  As you lift your elbow to bring the bevel in contact with the wheel, each point on that belly spends a brief moment in contact with surface.  In the case of the belly it's mitigated a bit by the increased pressure that comes with the small contact patch.  I find I get better results going a bit slower on the belly section.

[cbwx34]

I think this issue is often caused by insufficient grinding of the heel section of the blade.  If you start at the heel, as I think most do, that section of the blade gets very little wheel time.  It's on the wheel, and then you draw it straight off and that's all the grinding it sees.  In contrast, the part of the blade that's on the opposite side of the wheel traverses the entire width of the surface.

At the speed I normally go, the extreme heel would be on the wheel for less than a second, while the section that was on the other side gets 3-4 seconds of grinding before it comes off.  That causes a high area at the heel and a dip in the section after. 

One way to deal with that is to hold the heel section on the stone for a few seconds before you start moving the blade.  What I've been doing for a while now is actually starting an inch or two ahead of the heel, then moving back to the heel, and then across to the tip.  Works for me.

The belly section can also get short shrift for the same reason.  Any time you have a curve, only one point on the blade can contact the stone at any given time.  As you lift your elbow to bring the bevel in contact with the wheel, each point on that belly spends a brief moment in contact with surface.  In the case of the belly it's mitigated a bit by the increased pressure that comes with the small contact patch.  I find I get better results going a bit slower on the belly section.

Good point.  I used to have a video saved (can't find it now) that showed a sharpener fixing an accidental recurve just by working the heel area behind the recurve, which corrected the problem.  He also showed (on a flat stone) similar to what you said, that the heel doesn't get enough "stone time".  Your point about the belly to tip area is good too.

One reason to make sure a burr is formed along the entire edge when checking for it.