Hello
As many of you have been noticing, the SVM-45 jig gives different angels once a knife depending on thickness. The jigg is constructed for one thickness of the blade, if you want the exact angle on both sides.
What is that exact thickness?
What is Tormeks rekomendations to compensate for this problem?
Is there any plans to make a pivoting jigg?
Based on my measurements and considerations it is the thickness of 2.5 mm.
If the blade is thicker than 3 mm (1/8") or thinner than 2 mm the side asymmetry starts to be visible (for people who are aware of it). For thin blades you can compensate it using suitable shims, while for thick knifes only Wootz's solution can resolve the problem.
https://forum.tormek.com/index.php?topic=2962.msg16395#msg16395
Jan
P.S.: Based on my recent geometrical modelling incorrect knife mounting in the knife jig can result in bevel asymmetry much larger than the one caused by excessive blade thickness.
Welcome to the forum, Lape.
Your observation about the bevel angle variation with blade thickness is correct. Jan's observation about greater variation being possible with how the blade is placed in the jig is also correct.
How much variation should we expect or tolerate? In the world of metal machining, things are never "exact". The closest we come to exactness is "within tolerance". Tolerances vary depending on many factors. One would expect tighter tolerances with a Rolex than with a Timex. Even an object which reads right on with a precision tool like a micrometer is limited by the precision of the tool.
Knives could be sharpened with much more precise bevel angles than the standard Tormek jigs produce. However, how much demand would there be for a jig which cost several hundred dollars? Or, for a sharpener charging fifty dollars at a farmers market?
I think Wootz' modification of the Tormek knife jig is a real improvement. I can see where a collector with a knife which needed to be resharpened would be willing to pay a premium for very exacting sharpening. If Tormek made a self centering very precise knife jig, I would be willing to purchase one. So would a few forum members and professional sharpeners. Tormek makes a superb drill bit jig, the DBS-22, in that class. They also sell the 4000 grit SJ 200 and 250 grinding wheels in that cost range. I suspect the forty dollar knife jig outsells the two hundred forty dollar drill bit jig more than substantially.
I first began using a Tormek in 2009. Since then, much of the Tormek line has continued evolving. The T7 had numerous improvements, the most notable being the stainless steel EZYlock shaft. The T3 made a giant leap and became the T4, much improved. The T7 evolved into the T8, with many substantial improvements. Almost all of the jigs and accessories have been redesigned and improved.
The standard knife jig was redesigned with zinc machining and a new locking mechanism. I would not be surprised to see Tormek produce an upgraded, self centering version someday. I certainly have no inside information about this; it just seems a logical step forward. Recently the Tormek engineering staff has had a very full plate. We have seen the new T8; a much improved SE-77 straight edge jig; more minor redesigns of several jigs now made of machined zinc; plus a new website. That is quite a workload for a very small company.
Looking back at the entire history of the Tormek, innovation and change has been continual. Knife sharpening is a primary market, especially in Europe. Tormek has always been the premier leading company in wet grinding innovations. The redesigned gouge jig is an outstanding example of this. The older model was the state of the art. In my forum review of the new jig, I expressed the opinion that I felt many turners long satisfied with the older jig would want to switch to the new jig. That opinion has bern echoed by forum turners. I can foresee a day when I will have the same opinion about a new redesigned Tormek knife jig. I look forward to that day. In the meantime, the present Tormek knife jigs offer very adequate accuracy for general sharpening.
For very fussy work, grinding one bevel and then reversing the blade before final grinding of the second bevel should improve consistency.
Ken
As an alternative to grinding part of the jig (Wootz's solution) for thicker knives... could you not also shim the blade so it is canted slightly in the jig? (Basically alluded to in Jan's "incorrect knife mounting" statement).
Recently I have seen a belt sander sharpener with a knife jig which may be self-centring the blade.
Jan
Most of the guided clamp systems have come up with a self centering clamp of some sort. (In fact, I have one that may be adaptable to the Tormek, see picture).
Just to add a bit to my earlier post, if I had a knife that was, 3.5mm thick... where the Wootz solution is to use a jig he ground .5mm from... could I not shim the base of the blade .5mm (on the base level side) ... which would essentially tilt the blade down? I know that part of this would depend on how wide the blade is (spine to edge), but for most knives, it should be close enough to negate the difference you're trying to correct for. (May actually be a thinner shim, since the angle is really what is being compensated for).
May not be ideal in a commercial environment, where speed is a factor, but for the home user an alternative solution.
Cbwx34, your procedure may require juggler skill. ;)
It would be probably easier to compensate the side asymmetry by suitable turning of the knife jig adjustable stop at each upside down flipping of the jig.
One turn of the adjustable stop typically corresponds to 1.5° change in the bevel angle.
Jan
Ha... you may be right.
So, is there a recommended angle change (using the Adjustable Stop) based on blade width?
Cbwx34, full bevel angles symmetry for thick blades requires some effort. I do not do it often.
I have no general recommendation concerning the angle change of the Adjustable stop because it also depends on blade protrusion, stone radius and bevel angle.
To estimate the suitable angle change of the adjustable stop use the Tormek Angle master. Set the angle for the first side, flip the knife jig and estimate the angle change necessary to get the same angle for the other side also.
Jan
Ok. Thanks. I took a 3.8mm thick blade and tried to measure the angle difference on it (with the Angle Master and a digital gauge)... came in between 1.4-2 deg. So guess 1 rotation would adjust for it.
Just to satisfy my curiosity (throwing a wheel in the mix has always thrown me off a bit)... the 1.5° change you mentioned earlier would also be affected by stone radius, correct? (I know it's probably not much... just seeing if I got it right in my head). :)
Thanks again!
Cbwx34 you are welcome! You are correct, the change is small.
For 125 mm wheel radius, shortening of the blade protrusion in the Knife jig by 1 rotation of the Adjustable stop, results in bevel angle increase by circa 1.5°.
For 100 mm wheel radius, shortening of the blade protrusion in the Knife jig by 1 rotation of the Adjustable stop, results in bevel angle increase by circa 1.8°.
In both cases I have assumed bevel angle 15° and kenjig protrusion 139 mm.
Jan
Very useful information. If desired, we could even subdivide the rotation, essentially making the threaded end stop a micrometer. We would certainly not need twenty five or fifty divisions, however, a half, quarter or eighth turn might be useful.
Interesting thought path.
Ken
Thanks to all of you for very good answers. I have tried the shims. Works great.
Hello again.
According to my recent measurements the jigs center is aligned with blades exactly 2 millimeter thick.
Hmm?
Lape, originally I have thought also that the Knife Jig works symmetrically for 2 mm thick blades, but was aware that the accuracy of this figure is limited.
Later I have specified this thickness to 2.5 mm based on logical arguments. 2.5 mm is the thickness of the steel guide bar (1) of the Small Knife Holder. This thickness guarantees that the Small Knife Holder inserted in the Knife Jig works symmetrically and the same is true for the knife blade of the same thickness in the Knife Jig.
Jan
Here are my measurements. Sorry for the bad drawing.
As shown, the center is 1 mm above the bottom plate of the jig.
Not a solution for most I know, but I was able to rig up the clamp from the KME by adding a larger washer, and nut, to sorta mimic the Tormek jig (see attached pic). (The KME clamp is self-centering).
The jig actually rides on the nut across the Universal Support. Which got me wondering if something could be added to the standard jig at the Support area, to "ride on" when a slight angle change is needed for thicker knives? Might be an alternative to grinding jigs or making a manual adjustment every time the blade is flipped. Just an idea.
Cbwx, be careful not to scratch the USB.
I have dealt with similar considerations as you, but without a specific output. The form of the adjustable stop was designed for easy sharpening of typical knife belly.
Jan
Quote from: Lape on July 26, 2017, 04:44:07 PM
Here are my measurements. Sorry for the bad drawing.
As shown, the center is 1 mm above the bottom plate of the jig.
Lape, I do not doubt your measurements at all. I have got similar results. But keeping in mind the limited accuracy of my measurements I have accepted the thickness of 2.5 mm based on deduction and not on direct measurement.
Tormek opinion is here as reply #7: https://forum.tormek.com/index.php?topic=2577.0
Jan
Quote from: Jan on July 26, 2017, 09:44:43 PM
Cbwx, be careful not to scratch the USB.
I have dealt with similar considerations as you, but without a specific output. The form of the adjustable stop was designed for easy sharpening of typical knife belly.
Jan
Haven't noticed any scratches... but I'll keep an eye out. Thanks.
I agree about the stop, and thought about trying to modify the KME jig to see if I could fit it on there... but decided probably not worth the effort. (Maybe later).
I can set a knife to just "lift the handle" of the knife in most cases, to adequately cover the belly/tip area, (although I know rotating is usually the better option).
This problem with the knife jigs is not on the Tormek folks radar. These jigs are very old and antiquated and no one is concerned enough even though they do have issues with symmetry. There are solutions that have been shown from various folks out there and it would be nice if Tormek would make an upgrade. There are a plethora of these old jigs and change is hard cost etc... every manufacturer goes through growing pains. They have made great strides with their jigs and machines. Now to move on to the new innovation of the knife jig. :D
Quote from: Edgesup on April 01, 2018, 02:26:12 PM
This problem with the knife jigs is not on the Tormek folks radar. These jigs are very old and antiquated and no one is concerned enough even though they do have issues with symmetry. There are solutions that have been shown from various folks out there and it would be nice if Tormek would make an upgrade. There are a plethora of these old jigs and change is hard cost etc... every manufacturer goes through growing pains. They have made great strides with their jigs and machines. Now to move on to the new innovation of the knife jig. :D
👍👍👍 ;D
Edgesup,
While I am not blind to the possibility of improvements to the knife jigs, I feel your criticism is too harsh and undeserved.
I may be known as the head cheerleader on this forum. I also believe I am the chief critic. Tormek traditionally introduces new items at the Spring Fair in Cologne. This year was no exception. The three new diamond wheels have far exceeded my expectations. I believe they will revolutionize the Tormek.
To be honest, I was expecting a new knife jig, not diamond wheels. To continue being honest, in my opinion, the benefits of a redesigned knife jig pale in comparison to the potential benefits of the three diamond wheels and the new multi base.
I have no inside information, however, I would be surprised if Tormek was not working on redesigning the knife jigs. I think "band aid" may be a bit harsh, however, Tormek did not change the jig designation, as they did with the redesigned SE-76, now the SE-77. The redesigned SVD-185 became the SVD-186. The SVD-45 remains the SVD-45. I think we will see redesigned knife jigs when the resources of a small company permit. I would expect any company to make the best use of its existing products. That certainly does not mean that improved products are not being developed or that the company does not care.
Since I bought my first Tormek in 2009, The T4,8, and 2 have been introduced. The T4 in particular was a radical improvement. Several new grinding wheels have been introduced. The DBS-22 drill bit jig, truly new, has been introduced. About half of the jigs have been upgraded or redesigned. Tormek remains the leader in wet grinding innovation.
Ken
Quote from: Ken S on April 01, 2018, 04:29:16 PM
Edgesup,
While I am not blind to the possibility of improvements to the knife jigs, I feel your criticism is too harsh and undeserved.
I may be known as the head cheerleader on this forum. I also believe I am the chief critic. Tormek traditionally introduces new items at the Spring Fair in Cologne. This year was no exception. The three new diamond wheels have far exceeded my expectations. I believe they will revolutionize the Tormek.
To be honest, I was expecting a new knife jig, not diamond wheels. To continue being honest, in my opinion, the benefits of a redesigned knife jig pale in comparison to the potential benefits of the three diamond wheels and the new multi base.
I have no inside information, however, I would be surprised if Tormek was not working on redesigning the knife jigs. I think "band aid" may be a bit harsh, however, Tormek did not change the jig designation, as they did with the redesigned SE-76, now the SE-77. The redesigned SVD-185 became the SVD-186. The SVD-45 remains the SVD-45. I think we will see redesigned knife jigs when the resources of a small company permit. I would expect any company to make the best use of its existing products. That certainly does not mean that improved products are not being developed or that the company does not care.
Since I bought my first Tormek in 2009, The T4,8, and 2 have been introduced. The T4 in particular was a radical improvement. Several new grinding wheels have been introduced. The DBS-22 drill bit jig, truly new, has been introduced. About half of the jigs have been upgraded or redesigned. Tormek remains the leader in wet grinding innovation.
Ken
Or, not harsh enough. ;)
Kidding, but from my understanding, the "collar lock" was eliminated because users were over-tightening and breaking the collar, or stripping the threads. So, while the redesign might not be considered a "band aid" solution, I think it would be hard to argue that the O-ring is as secure. (Maybe a better solution would have been an insert for the screw?). So, IMO, less secure = step backward.
To be fair... maybe some of this is Tormek just needing to "catch up" to what some knife sharpeners are now expecting? Not that long ago, a knife would be considered "sharp" if it sliced a piece of copy paper, cut a ripe tomato, or shaved some arm hair. Now it's "tree topping" arm hair, cutting phone paper, etc. And, not as much attention was paid to things like "symmetrical bevels" or measuring angles (in fractions) as they are now. And, to be fair, not all sharpeners do all of the above.
But, those who look to purchase a sharpener, in particular, a guided one, now seem to pay more attention to this. In addition, there is a wider variety of knife styles, as well as higher end knives.
I don't "harp" for "self centering clamps", redesigned collars, etc. because I can't get a knife sharp with the current jig... I can. I do it for the times I want some of the above features... and to make edges even better.
Hope that makes a bit of sense. :o
Quote from: cbwx34 on April 01, 2018, 10:00:32 PM
from my understanding, the "collar lock" was eliminated because users were over-tightening and breaking the collar, or stripping the threads.
Adjusting the collar used to be necessary for fine-tuning the angle, but that was before the micro-adjust feature was introduced. The SVM-45 is an ancient jig, but it's not clear how the suggested improvements could be engineered. The Tormek will allow one to easily adjust and measure the edge angle to within a couple degrees or more, and for me that's more than enough precision. I usually change the edge angle on a kitchen knife by 5 degrees if I want to alter the way it performs.
Slicing papers and arm hairs is all for show, although it does indeed demonstrate sharpness. It's the amount of roughness on the surface of the bevels that determines how a knife will perform in the kitchen. Sometimes you want the edge polished; but sometimes you want it rough, with a "tooth" to it. The Tormek allows for this variation well enough for me.
Quote from: Herman Trivilino on April 01, 2018, 11:40:21 PM
Adjusting the collar used to be necessary for fine-tuning the angle, but that was before the micro-adjust feature was introduced. The SVM-45 is an ancient jig, but it's not clear how the suggested improvements could be engineered. The Tormek will allow one to easily adjust and measure the edge angle to within a couple degrees or more, and for me that's more than enough precision. I usually change the edge angle on a kitchen knife by 5 degrees if I want to alter the way it performs.
Slicing papers and arm hairs is all for show, although it does indeed demonstrate sharpness. It's the amount of roughness on the surface of the bevels that determines how a knife will perform in the kitchen. Sometimes you want the edge polished; but sometimes you want it rough, with a "tooth" to it. The Tormek allows for this variation well enough for me.
The collar still turns, so if the micro-adjust made it unnecessary... seems they could have locked it in place? There are numerous examples of the suggested improvements (although Tormek would probably have to come up with its own variation).
You're right... the tests I described are examples to demonstrate sharpness level. As for precision, look no further than examples in this forum, where some are measuring in tenths. ;)
My knife set up technique is different than most users. I do not use the micro adjust and I rarely adjust the projection of the knife jigs. With the kenjig, I set the support bar distance with a groove to the desired angle. It is fixed at 80mm, following Dutchman's tables. As my grinding wheel wears, I will increase this distance as dictated by the tables.
I have standardized on a projection of 139mm. By using three knife jigs (SVM 45/100/140), I do not have to adjust the jigs. Any minor compensation can be compensated by knife placement in the jig.
I have not noticed any slippage in my newest SVM, which has just the O ring. If I do, I will apply a layer of tape. I sharpen only my kitchen and pocket knives, therefore, I have not encountered thickness problems.
I am well aware that a minority of users who are higher volume sharpeners must deal with these problems. If Tormek wants to cater to high end business users, change is inevitable, and the sooner the better. I believe many users would embrace (purchase and use) these improved knife jigs.
We must remember that Tormek has constraints as a business that we as individuals do not have. I have made no secret that the kenjig is based on Dutchman's tables. Dutchman has never threatened to sue me for using his work. In fact, we enjoy occasional friendly emails. Nor would I think of complaining or bringing legal action when other members use and improve it. These ideas are freely offered, as are ideas like Herman's platform jig.
Tormek does not such luxuries. Tormek, like all businesses, must deal with the financial and legal realities of business. Originally I had hoped that Tormek might incorporate the kenjig into its product like. It would be a logical extension of the TTS-100. However, I soon realized that because I had posted it on the forum, Tormek would not use it because of the possibility of prior use legal action.
We have noted that other manufacturers jnife jigs are self centering. Why not Tormek? For Tormek to produce a self centering jig, they would have to invent a new and patentable way to do it, no easy task. They would also have to consider whether an improved, but more expensive product would be profitable. No matter how useful a product is, it must help make psyroll to keep a company afloat.
Ken
Quote from: Lape on July 26, 2017, 02:37:40 AM
Hello again.
According to my recent measurements the jigs center is aligned with blades exactly 2 millimeter thick.
Hmm?
My value is 2.2mm, I use Rick's method detailed here: https://forum.tormek.com/index.php?topic=3445.msg21498#msg21498 (https://forum.tormek.com/index.php?topic=3445.msg21498#msg21498)
Variation may depend on the jig issue, we still have a few old, you may have new.
And our current values are here http://knifegrinders.com.au/05Equipment_jigs.htm (http://knifegrinders.com.au/05Equipment_jigs.htm)
Instead of shims we now use layers of cloth tape at the clamping site, just easier.
Good post, Wootz.
I like precisely delineated problems with practical. low tech solutions.
Ken
Quote from: cbwx34 on April 02, 2018, 12:15:22 AM
Quote from: Herman Trivilino on April 01, 2018, 11:40:21 PM
Adjusting the collar used to be necessary for fine-tuning the angle, but that was before the micro-adjust feature was introduced. The SVM-45 is an ancient jig, but it's not clear how the suggested improvements could be engineered. The Tormek will allow one to easily adjust and measure the edge angle to within a couple degrees or more, and for me that's more than enough precision. I usually change the edge angle on a kitchen knife by 5 degrees if I want to alter the way it performs.
Slicing papers and arm hairs is all for show, although it does indeed demonstrate sharpness. It's the amount of roughness on the surface of the bevels that determines how a knife will perform in the kitchen. Sometimes you want the edge polished; but sometimes you want it rough, with a "tooth" to it. The Tormek allows for this variation well enough for me.
The collar still turns, so if the micro-adjust made it unnecessary... seems they could have locked it in place? There are numerous examples of the suggested improvements (although Tormek would probably have to come up with its own variation).
No one is saying that the micro-adjust made adjustments of the collar of the SVM-45 unnecessary. It is still needed for some adjustments, but the micro-adjust makes it not critically necessary for fine adjustments of the angle.
QuoteAs for precision, look no further than examples in this forum, where some are measuring in tenths. ;)
No one has ever demonstrated that they can use the SVM-45 to create an angle that's uniform to within a tenth of degree along the length of an edge. Not even close. I would bet that the best, most experienced sharpeners couldn't even achieve one degree, probably a few degrees is the best they could do.
Making a measurement that's accurate to within a tenth of a degree is not the same thing as being able to reproduce something to that level of precision.
Quote from: Herman Trivilino on April 06, 2018, 11:57:53 PM
Quote from: cbwx34 on April 02, 2018, 12:15:22 AM
Quote from: Herman Trivilino on April 01, 2018, 11:40:21 PM
Adjusting the collar used to be necessary for fine-tuning the angle, but that was before the micro-adjust feature was introduced. The SVM-45 is an ancient jig, but it's not clear how the suggested improvements could be engineered. The Tormek will allow one to easily adjust and measure the edge angle to within a couple degrees or more, and for me that's more than enough precision. I usually change the edge angle on a kitchen knife by 5 degrees if I want to alter the way it performs.
Slicing papers and arm hairs is all for show, although it does indeed demonstrate sharpness. It's the amount of roughness on the surface of the bevels that determines how a knife will perform in the kitchen. Sometimes you want the edge polished; but sometimes you want it rough, with a "tooth" to it. The Tormek allows for this variation well enough for me.
The collar still turns, so if the micro-adjust made it unnecessary... seems they could have locked it in place? There are numerous examples of the suggested improvements (although Tormek would probably have to come up with its own variation).
No one is saying that the micro-adjust made adjustments of the collar of the SVM-45 unnecessary. It is still needed for some adjustments, but the micro-adjust makes it not critically necessary for fine adjustments of the angle.
QuoteAs for precision, look no further than examples in this forum, where some are measuring in tenths. ;)
No one has ever demonstrated that they can use the SVM-45 to create an angle that's uniform to within a tenth of degree along the length of an edge. Not even close. I would bet that the best, most experienced sharpeners couldn't even achieve one degree, probably a few degrees is the best they could do.
Making a measurement that's accurate to within a tenth of a degree is not the same thing as being able to reproduce something to that level of precision.
I guess I read "used to be necessary" as "no longer necessary". ;)
I'll let the person who claims "
edge angle controlled with 0.1 degree accuracy" defend that one, (or maybe it doesn't apply in this case). 8)
Hi all,
This is my first post in this forum. I bought a T8 a few months ago and have so far only been reading in here, learning from all the experience gathered. I must admit my expectations have not been met with this machine. Being used to sharpen knifes with water stones I expected to sharpen knives fast and precise right away. That didn't happen :). So far I am still learning but the results are getting better even though sharpening a knife still takes me forever.
The reason why I am replying to this inactive thread is that it is the newest I could find that deals with the asymmetry of the SVM-45. In this thread and another (https://forum.tormek.com/index.php?topic=3445.msg21408#msg21408 (https://forum.tormek.com/index.php?topic=3445.msg21408#msg21408)) Lape and RickKrung measure the jig. You both measure the thickness of the flat to around 9 mm. This figure is then used to calculate the offset to the jig centerline and you both get around 1 mm and it is then concluded that a knife with a blade thickness of 2 mm will be symmetrical placed in the jig.
I have done the same measurements as you guys and I get the same numbers. However I believe that the measurement of the flat thickness (9 mm) is measured at the wrong place giving a wrong result. What I did was to place the SMV-45 bottom part on a flat surface. I measured the distance from the top of the shaft to the flat surface in each end and as it was the same, I concluded that the centerline of the jig was in parallel with the flat surface. Then I measured the distance from the flat surface to the top of the flat in the same place where you have measured it, and I also got 9 mm. However when measuring the distance from the flat surface to the top of the flat at the end of the jig where the knife is resting the distance was 9,4 mm. If you look at the plane where the knife is resting, in each side of the jig the surface is a little big higher (sorry for my bad vocabulary :(). This is also visible on the 3rd picture in RickKrung post in before mentioned thread.
A distance of 9.4 mm leads me to conclude that the offset to center line is only 0.6 mm and that my jig (I know there are several versions) is made for a blade thickness of 1.2mm. I have checked this with control measurements with the angle master and they verify this. If I mount a knife with a blade thickness of 2 mm in the jig, I get a smaller angle on the side of the knife that rests on the bottom part of the jig relative to the other side.
As many of my knifes are around 2mm thick, this leads me to conclude that I need to take some material off the SVM-45. This seems drastic as all of you (except Wootz) are talking about inserting spacers instead. So if any of you guys still have an interest in this, please comment. Am I overseeing something? I will postpone the modification for now :).
Thank you all for sharing your knowledge in here guys. I have learned a lot from you and there is still a lot more to learn :).
PS Sorry for the orientation of the picture. I can't get it right.
Torben, Denmark
Torrent,
I like the picture you drew, and the math seems to be right. I'm interested in what others with more knife sharpening experience have to say.
Kind regards,
Rich
Quote from: TorbenDenmark on April 15, 2019, 11:00:59 AM
Hi all,
...snip..
As many of my knifes are around 2mm thick, this leads me to conclude that I need to take some material off the SVM-45. This seems drastic as all of you (except Wootz) are talking about inserting spacers instead. So if any of you guys still have an interest in this, please comment. Am I overseeing something? I will postpone the modification for now :).
Thank you all for sharing your knowledge in here guys. I have learned a lot from you and there is still a lot more to learn :).
PS Sorry for the orientation of the picture. I can't get it right.
Torben, Denmark
Three things:
1) I struggled with the orientation of images for a while also. It has to do with the orientation setting within "Properties" of your original image, as taken. I found I have to take the photo in "landscape" in order to get it to display properly. I tried editing that property field but that did not work. Now what I do is take the photo in landscape, moving back far enough to get the whole object in view and then in my editor, crop the image down to include just what I want.
Another very helpful edit is to reduce the image size to 640x480 pixels so it displays the whole image in the browser, to eliminated the unnecessary action of scrolling oversized images.
2) There is a raised "Tormek" logo on the back of my jigs, which could cause the difference in readings you report. If the raised logo is present on your jig, it will NOT be resting parallel with your reference base. I think you may need to rest the jig on some precision parallels to get it level before you take the measurements.
3) I HAVE modified some of my jigs, as Wootz has, to enable the use of shims for getting blades more centered. I have four SVM-45s. Two are unmodified. One is modified by removing 0.5mm, another by removing 1.0mm. I also shortened a set of feeler gauges so they are only slightly longer than the SVM-45 jig is wide. This really helps when blades are narrow and/or short enough that full sized feel gauges interfere with getting the bevels to the grindstone.
For the time being, using these modified jigs and shims has somewhat alleviated my need for a true self-centering jig, although I am still pursuing such a jig.
Rick
Quote from: TorbenDenmark on April 15, 2019, 11:00:59 AM
Hi all,
...snip...
However when measuring the distance from the flat surface to the top of the flat at the end of the jig where the knife is resting the distance was 9,4 mm. If you look at the plane where the knife is resting, in each side of the jig the surface is a little big higher (sorry for my bad vocabulary :(). This is also visible on the 3rd picture in RickKrung post in before mentioned thread.
A distance of 9.4 mm leads me to conclude that the offset to center line is only 0.6 mm and that my jig (I know there are several versions) is made for a blade thickness of 1.2mm.
...snip...
Torben, Denmark
Quote from: RickKrung on April 15, 2019, 08:55:20 PM
...snip...
2) There is a raised "Tormek" logo on the back of my jigs, which could cause the difference in readings you report. If the raised logo is present on your jig, it will NOT be resting parallel with your reference base. I think you may need to rest the jig on some precision parallels to get it level before you take the measurements.
...snip...
Rick
I drafted this out in my CAD program.
The distance from the bottom rear of the fixed jaw to the close side of the raised logo is 39.63mm (1.560") (I did this in inches and rounded the mm's so there may be some slight discrepancies in the mm numbers). The distance from the bottom rear to the front of the jaws is 84.84mm (3.340").
I drew a parallel line at length 39.63mm and then another offset 0.18mm (0.007") which is the height of the raised logo. I then drew a line from the bottom rear point to the raised logo height point. And THEN projected that angled line to 84.84mm to represent the front jaw height. The offset of that front jaw point from the parallel line was 0.38mm, which if rounded yields 0.4mm.
0.4mm is exactly the number you got with your measurements.
Rick
The uncertainty in the offset estimation lead me to estimate the value by a deductive way.
I have assumed that the Small Knife Holder works symmetrically with respect to flip. Because the steel guide bar (1) of the Small Knife Holder has a thickness of 2.5 mm, I have deduced that the jig offset is 1.25 mm.
https://forum.tormek.com/index.php?topic=2577.msg15232#msg15232
Jan
cbwx34 and Rick thank you for your messages and effort to investigate my observation. I will post a reply here soon...
Jan thank you for your input. I have seen your post before about this. I respect your way as I have also realized that this is more complex than I first thought it would be :). But... 1.25 mm seems like a lot to me. When I mount my 2 mm thick kitchen knife in the SVM-45 jig and I compare the angles on each side of the blade with the anglemaster, the anglemaster tells me that the side of the blade in contact with the bottom part of the jig is sharpened at a slightly smaller angle than the other side. This is, according to my understanding, caused by the center of the knife blade being above the centerline of the jig, meaning that the knife is too thick for this jig. Your estimation says that the jig should sharpen a 2.5 mm thick knife symetrically. I do not own a 2.5 mm thick knife but I expect the asymmetry would be significant. Does this work for you? And if yes, can our jigs vary that much? I saw a picture in here of a SVM-45 where the shaft was not straight at all.
I am aware that the way I mount the knife and tighten the jig can also influence the angle but I pay attention to this and I do it as advised in this forum.
Torben
Torben, from your reply I see you understand that really in depth! :)
Your estimation, that your jig works symmetrically for blade thickness of 1.2 mm riddles me. I consider this value for anomalous one.
Since I have accepted the value 2.5 mm, I use standard SVM-45 knife jig for all blades with thicknesses from 2.0 to 3.0 mm. With a naked eye I am not able to see any asymmetry in the edge width. I was not diligent enough to study the edge width under the microscope.
For thicker blades I use now my prototype of a self-centring knife jig.
Jan
Quote from: Jan on April 16, 2019, 05:05:59 PM
Torben, from your reply I see you understand that really in depth! :)
And then clearly not :). cbwx34 has been so nice to inform me that I got it backwards. So to save some honour I hereby state that I have not got it backwards, I just wrote the opposite of what I mean :). What I meant was...
I put a 2 mm thick blade in the SVM-45 jig. The angle master tells me that bottom side of the blade (in touch with the bottom part of the jig) is sharpened at a higher angle than the top side. This leads me to conclude that the blade center line is above the jig center line and hence the knife is too thick for the jig.
Hope I got it right this time.
Jan just like you, my (little) experience with this machine also tells me that I will not be able to see these small difference with a naked eye. But I find it quite funny analysing and maybe optimizing these small things. It makes me feel I'm in control of the sharpening process. I hope it is ok to enter nerd mode once in a while. I can see I am not the only one doing it in here :)
Torben
Quote from: RickKrung on April 15, 2019, 09:44:09 PM
I drafted this out in my CAD program.
The distance from the bottom rear of the fixed jaw to the close side of the raised logo is 39.63mm (1.560") (I did this in inches and rounded the mm's so there may be some slight discrepancies in the mm numbers). The distance from the bottom rear to the front of the jaws is 84.84mm (3.340").
I drew a parallel line at length 39.63mm and then another offset 0.18mm (0.007") which is the height of the raised logo. I then drew a line from the bottom rear point to the raised logo height point. And THEN projected that angled line to 84.84mm to represent the front jaw height. The offset of that front jaw point from the parallel line was 0.38mm, which if rounded yields 0.4mm.
0.4mm is exactly the number you got with your measurements.
I see your point about the TORMEK logo on the back side of the jig Rick and the fact that you are able to derive the same 0.4 mm difference as I measure, verifies that the difference is caused by the raised logo.
I was aware of the logo when I did the measurements. However as you have now derived that the raised logo lifts the end of the jig where the knife rests by 0.4 mm, I would also expect the other end of the jig (the shaft) to drop. I measured the distance from the ground surface to the top of the shaft - in each end of the shaft (see attached picture), and found the distance the same in both ends. So I concluded that the shaft was in parallel with the ground plane and hereby the centerline of the jig too. This I still don't understand.
After reading your post I have remeasured the shaft and also measured on the jig when I push the raised logo just outside the surface that the jig rests on, with the purpose of cancelling the effect of the logo. I have measured many times but I must unfortunetaly conclude that I am not able to achieve consistens accurate results. I do not posses the proper measuring equipment and maybe also the skills to do this. So I have to stop here. It bothers me to leave this without fully understanding, but without being able to make accurate measurements I will not get any further.
Thank you for your effort and response cbwx34 and Rick.
Torben