TormekCalc3 - Advanced grinding calculator

[Ken S]

JVH,

I am glad that you have correctly noticed the usefulness of the tool rest SVD-110. I believe it is an underutilized tool, and even more useful in its homemade small platform versions. Sadly, these platforms to not fit in the Tormek "jig controlled sharpening" philosophy.

Ken

[jvh]

Hi JVH,
This is just the shot of my front page of the spreadsheet inspired by yours. To calculate the different USB height needed for the inverted jig: I use an angle finder to get 'Total angle between primary bevels' and then take that angle off the 'delta k' for the and then recalculate to give me desired bevel angle with new USB height. I then divide the difference in USB heights by 0.3 to give me the number of numerals to raise.

The eccentric cam can be similarly calculated but it is still prone to human error so I am currently focusing on a jig that holds Vee section blades in alignment as this removes the need to remember to do anything between sides but not yet settled on a solution. I do not see how the shimming methods can work as they still maintain the error in angle orientation and shifting the blade parallel to the jig makes no difference at all (IMHO)

Tonight, I experimented trying to get an even bevel width around the curve of a blade and when  I moved the jig towards or away from the tip of the blade, as suggested in the Tormek manual (P53 of v. 10.5) it made NO difference to the bevel width! So, I then used a laser guide-line across the stone while using the SVM45 and successfully kept an even bevel around the curve of the blade by keeping it on the laser line. This removed the black magic of how much to lift and rotate the blade.

Hello Merx27,

by turning the eccentric sleeve, one side of the jig is raised and the other is lowered. The axis of the top of the jig moves and this centers the blade. The aim is to obtain a symmetrical clamping before grinding and no further adjustment is required during grinding. The method I use is described below.

Shims method works the same way but from other side. Keep in mind that the work axis does not have to pass through the tool axis all the way, as this is not necessary - for correct adjustment the axis must pass through the axis of the blade and through the jig center in the point where it rests on the support.

I can confirm that the method described in the Tormek manual (P53 version 10.5) has a visible effect, at least on knives from a length of approx. 15 cm.

jvh

[Merx27]

Hi JVH,
This is just the shot of my front page of the spreadsheet inspired by yours. To calculate the different USB height needed for the inverted jig: I use an angle finder to get 'Total angle between primary bevels' and then take that angle off the 'delta k' for the and then recalculate to give me desired bevel angle with new USB height. I then divide the difference in USB heights by 0.3 to give me the number of numerals to raise.

The eccentric cam can be similarly calculated but it is still prone to human error so I am currently focusing on a jig that holds Vee section blades in alignment as this removes the need to remember to do anything between sides but not yet settled on a solution. I do not see how the shimming methods can work as they still maintain the error in angle orientation and shifting the blade parallel to the jig makes no difference at all (IMHO)

Tonight, I experimented trying to get an even bevel width around the curve of a blade and when  I moved the jig towards or away from the tip of the blade, as suggested in the Tormek manual (P53 of v. 10.5) it made NO difference to the bevel width! So, I then used a laser guide-line across the stone while using the SVM45 and successfully kept an even bevel around the curve of the blade by keeping it on the laser line. This removed the black magic of how much to lift and rotate the blade.

Hello Merx27,

by turning the eccentric sleeve, one side of the jig is raised and the other is lowered. The axis of the top of the jig moves and this centers the blade. The aim is to obtain a symmetrical clamping before grinding and no further adjustment is required during grinding. The method I use is described below.

Shims method works the same way but from other side. Keep in mind that the work axis does not have to pass through the tool axis all the way, as this is not necessary - for correct adjustment the axis must pass through the axis of the blade and through the jig center in the point where it rests on the support.

I can confirm that the method described in the Tormek manual (P53 version 10.5) has a visible effect, at least on knives from a length of approx. 15 cm.

jvh

Thanks again JVH, you are helping me to get my head around all of this  . I relooked at the eccentric bushing idea and see now that it is a good way forward so I will resin-cast a 12mm tube against the inside of another larger tube (18mm) and then experiment with a scale to aid set-up.

I still cannot see how shims work unless they are used to rotate the blade in the jig, please see my attachment.

It is likely that the Tormek manual method has a small effect but for me, all it does is change how much I lift the handle of the blade. I will stick with the guideline approach (laser or otherwise) as this suits me and gets excellent results

Thanks again for your help

[jvh]

Thanks again JVH, you are helping me to get my head around all of this  . I relooked at the eccentric bushing idea and see now that it is a good way forward so I will resin-cast a 12mm tube against the inside of another larger tube (18mm) and then experiment with a scale to aid set-up.

I still cannot see how shims work unless they are used to rotate the blade in the jig, please see my attachment.

It is likely that the Tormek manual method has a small effect but for me, all it does is change how much I lift the handle of the blade. I will stick with the guideline approach (laser or otherwise) as this suits me and gets excellent results

Thanks again for your help

Hello Merx27,

a shim can help, but must be placed at the end of the jaw only (or have a triangle profile). An eccentric bushing is also very helpful here because the correction with shim is very rough and the bushing allows fine adjustment.

Other way is special jig. Although it looks weird, the blade is well centered. There is different angle on each side but also different protrusion length, so you get an even grind when you flip it.

See the photos for a better idea...

jvh

[Merx27]

Thanks again JVH, you are helping me to get my head around all of this  . I relooked at the eccentric bushing idea and see now that it is a good way forward so I will resin-cast a 12mm tube against the inside of another larger tube (18mm) and then experiment with a scale to aid set-up.

I still cannot see how shims work unless they are used to rotate the blade in the jig, please see my attachment.

It is likely that the Tormek manual method has a small effect but for me, all it does is change how much I lift the handle of the blade. I will stick with the guideline approach (laser or otherwise) as this suits me and gets excellent results

Thanks again for your help

Hello Merx27,

a shim can help, but must be placed at the end of the jaw only (or have a triangle profile). An eccentric bushing is also very helpful here because the correction with shim is very rough and the bushing allows fine adjustment.

Other way is special jig. Although it looks weird, the blade is well centered. There is different angle on each side but also different protrusion length, so you get an even grind when you flip it.

See the photos for a better idea...

jvh

Hi JVH
I found shims very fiddley and sensitive to tiny movements, especially when the blade also tapered towards the tip. I could make them work but it took so much time to set it up. Have you a source for tapered shims, that would make like very much easier? Instead, I considering making different angle rebates in a couple of my SVM-45s but without a machine shop, this was likely to be a little uneven. I thought about using a homemade jig to hold the bottom jaw against my belt sander...

I like the look of the adjustable jig - did you make that? My fear, when considering something similar, was that the pivot between the shaft and the jaws might not be strong enough with a large knife but you have inspired me to reconsider. I'm not sure how the different protrusion lengths help but it may be that I haven't got my head fully around how you use it.

Thanks for sharing your experience, you are way ahead of me. I have received my casting resin and will get onto the eccentric bushing as soon as I finish the 5 Global knives and a food processor blade that came in today.

[jvh]

Hi JVH
I found shims very fiddley and sensitive to tiny movements, especially when the blade also tapered towards the tip. I could make them work but it took so much time to set it up. Have you a source for tapered shims, that would make like very much easier? Instead, I considering making different angle rebates in a couple of my SVM-45s but without a machine shop, this was likely to be a little uneven. I thought about using a homemade jig to hold the bottom jaw against my belt sander...

Hello Merx27,

Yes, that's right - fiddly, time consuming...
I haven't any source of tapered shims. I am using a piece of cable tie as shim + double side tape if I need it.

I like the look of the adjustable jig - did you make that? My fear, when considering something similar, was that the pivot between the shaft and the jaws might not be strong enough with a large knife but you have inspired me to reconsider. I'm not sure how the different protrusion lengths help but it may be that I haven't got my head fully around how you use it.

Yes, one of the prototypes. It is robust enough for such a task, but the precise setting can also be time consuming.
I made several designs and there are different ways how to make the adjustable version. In the end, when I compared the price, versatility and speed and accuracy of the settings, I ended up again with an eccentric bushing. But I don't give up, I have some more ideas how to made a perfect jig...

jvh

[jvh]

Hello,

I released a new video where you can find an answer to the question of whether the blade thickness affects the resulting grinding angle. It also briefly introduces EdgeCalc - next module in the TormekCalc2 - its using and capabilities.
The bonus part focuses on verifying the results using a goniometer (laser protractor).

Link: https://www.youtube.com/watch?v=vG_MmPIUPss

jvh

[cbwx34]

Hello,

I released a new video where you can find an answer to the question of whether the blade thickness affects the resulting grinding angle. It also briefly introduces EdgeCalc - next module in the TormekCalc2 - its using and capabilities.
The bonus part focuses on verifying the results using a goniometer (laser protractor).

Link: https://www.youtube.com/watch?v=vG_MmPIUPss

jvh

Nice job (as always).

Probably worth pointing out (or correct me if I'm wrong), 😑 that these are scale drawings that validate the formulas, not just drawings made with numbers inserted.

[Dutchman]

... [snip]
I released a new video where you can find an answer to the question of whether the blade thickness affects the resulting grinding angle.
... [snip]
jvh

I do not agree that the sharpening angle is not affected by the thickness of the blade when the blade is clamped in the jig resting on the USB.
During the sharpening process, the tip of the blade will lower towards the stone, while the resting point of the jig remains on the USB. This will cause the jig to tilt towards the stone, changing the angle.
I described that in my publication "More math for the Tormek grinder" after CBWX34 reported that problem to me. See https://forum.tormek.com/index.php?topic=1849

[jvh]

Nice job (as always).

Probably worth pointing out (or correct me if I'm wrong), 😑 that these are scale drawings that validate the formulas, not just drawings made with numbers inserted.

Hello cbwx34,

you are right, the dimensions are "live", they are from parametric CAD, not static images. I drew 3D models of my T-8 and some jigs and use them to verify the calculated results.

jvh

[jvh]

... [snip]
I released a new video where you can find an answer to the question of whether the blade thickness affects the resulting grinding angle.
... [snip]
jvh

I do not agree that the sharpening angle is not affected by the thickness of the blade when the blade is clamped in the jig resting on the USB.
During the sharpening process, the tip of the blade will lower towards the stone, while the resting point of the jig remains on the USB. This will cause the jig to tilt towards the stone, changing the angle.
I described that in my publication "More math for the Tormek grinder" after CBWX34 reported that problem to me. See https://forum.tormek.com/index.php?topic=1849

Hello Dutchman,

no, this is something else. It is caused by excessive grinding. If you grind over the axis^*) the grinding angle will rise as the jig protrusion length will shorten. It is also mentioned and showed in my video HERE. But it has nothing to do with the thickness of the blade.

jvh

*) Meaning the axis of the blade in this case, as the calculations in TormekCalc2 are performed for symmetrical grinds by default.

[tgbto]

I would tend to agree with JVH. Most of the blades we intend to sharpen are not a knife blank, and even in this case we would probably try not to grind through the axis. So whether the blade is extremely thin or thick will not matter with regard to the grind angle... as long as the blade is centered in the jig.

The only actual effect due to blade width that I can see today is the effect on the assymetry of the grind due to the assymetry of the jig.

As I don't have jvh's machinery skills, I am more thinking of drilling through the jig handle close and parallel to the axis and setting a blind nut which would allow me to correct by adding just enough offset on the long side to make sure the knife sits on the laser line on both sides. It is probably not perfect but it is the only doable thing I can think of with my skills, the excentric bushing and the like being out of my league.

[jvh]

As I don't have jvh's machinery skills, I am more thinking of drilling through the jig handle close and parallel to the axis and setting a blind nut which would allow me to correct by adding just enough offset on the long side to make sure the knife sits on the laser line on both sides. It is probably not perfect but it is the only doable thing I can think of with my skills, the excentric bushing and the like being out of my league.

Hello tgbto,

all you need to make an eccentric bushing is a drill, drill bits and a piece of aluminum rod. I made first pieces this way.

I hope I understand what you mean... but if the knife sits on the laser line on both sides, it does not guarantee that it is well centered, it only means that the protrusion is the same. I check the symmetrical clamping with AngleMaster as described in Reply #61.

jvh

[cbwx34]

Nice job (as always).

Probably worth pointing out (or correct me if I'm wrong), 😑 that these are scale drawings that validate the formulas, not just drawings made with numbers inserted.

Hello cbwx34,

you are right, the dimensions are "live", they are from parametric CAD, not static images. I drew 3D models of my T-8 and some jigs and use them to verify the calculated results.

jvh

Thanks.  I was pretty sure, but wanted to point out the "independent verification" that a CADD drawing provides.  (Sure helped me).

... [snip]
I released a new video where you can find an answer to the question of whether the blade thickness affects the resulting grinding angle.
... [snip]
jvh

I do not agree that the sharpening angle is not affected by the thickness of the blade when the blade is clamped in the jig resting on the USB.
During the sharpening process, the tip of the blade will lower towards the stone, while the resting point of the jig remains on the USB. This will cause the jig to tilt towards the stone, changing the angle.
I described that in my publication "More math for the Tormek grinder" after CBWX34 reported that problem to me. See https://forum.tormek.com/index.php?topic=1849

Hello Dutchman,

no, this is something else. It is caused by excessive grinding. If you grind over the axis^*) the grinding angle will rise as the jig protrusion length will shorten. It is also mentioned and showed in my video HERE. But it has nothing to do with the thickness of the blade.

jvh

*) Meaning the axis of the blade in this case, as the calculations in TormekCalc2 are performed for symmetrical grinds by default.

Actually, I think you two are talking about 2 different things.

Dutchman is correct that a thick blade sitting on the stone is at a different angle than a sharpened blade.  But, the calculator gives the "sharpened angle", which is what we want.  So, if I sharpen the thick blade correctly, working both sides and never sharpen past the center line, I will end up with the desired angle.

jvh is correct that if I take that same blade and sharpen past the center line, (think of the extreme where I sharpen one side all the way to the other side, then flip it over), I will shorten the Projection Distance, which will change the resulting angle.

In either event, thickness does not matter in a blade that is correctly sharpened. 

[jvh]

Actually, I think you two are talking about 2 different things.

Dutchman is correct that a thick blade sitting on the stone is at a different angle than a sharpened blade.  But, the calculator gives the "sharpened angle", which is what we want.  So, if I sharpen the thick blade correctly, working both sides and never sharpen past the center line, I will end up with the desired angle.

jvh is correct that if I take that same blade and sharpen past the center line, (think of the extreme where I sharpen one side all the way to the other side, then flip it over), I will shorten the Projection Distance, which will change the resulting angle.

In either event, thickness does not matter in a blade that is correctly sharpened. 

Hello again,

yes, in this example the angle changes and I pointed this problem two times in my video, but it has nothing to do with the thickness of the blade. This is related to the clamping / feeding method (and axis and protrusion length).

When a thick blade is sitting on the stone it means that there is some ungrinded material and you are above the blade axis and not at the point where you should be. The same situation is when you are under the blade axis.

A simple example - let's imagine that we mount the SVD-110 in the opposite way than usual and try to grind the chisels. We will grind chisels with different thicknesses, feeding method is shown by the arrows. As you can see the apex angle always remains the same regardless of the thickness, so how the thickness affects sharpening angle?

jvh