When you use several progressively finer grinding wheels to sharpen a knife, and these wheels are not of the same diameter, as you move to the next wheel you have to adjust height of the Universal Support to maintain the same grinding angle.
For example, to sharpen a knife I may use 3 grindwheels: Tormek 220 grit SG or SB, aftermarket 800 grit, and 4000 grit SJ or aftermarket.
My T7 wheels diameter at the moment is anywhere between 235 and 250 mm, and aftermarket between 252 and 254 mm.
(If you use Tormek wheels only, this happens as you move between SG or SB and SJ.)
I used to have a funny procedure to adjust the US height as I change wheels, till Jan pointed out inaccuracies in my approach.
Jan started me thinking, and since then I have changed grindwheels matching to calulated absolute values for the US height.
Universal Support height for a given grinding angle can be calculated by Pithagorean theorem, where hypotenuse is calculated by Ton Nillesen's (Dutchman) formula F0, and the other right triangle side is a constant horizontal from the US centreline to the shaft centreline (51 mm in my T7).
I borrowed a sketch from the Ton Nillesen's work to illustrate the right-angled triangle used in the calculations - in red.
(http://home.exetel.com.au/dropbox/sketch.jpg)
Universal Support height from its base to the top of the support bar = the calulated value for the vertical cathetus - constant vertical from the shaft centreline to the US base (i.e. the Tormek's housing top - 29.3 mm in my T7).
Theoretically, I should get exact angle match when I change grindwheels.
Practically, as measured by AngleCube and AngleMaster where applicable, a nice match.
To eliminate the blade width variable, I checked with a knife that is 2.5mm thick at the spine where I clamp it, so its edge is exactly at the jig centreline.
The US height was set with the help of a calipers depth probe.
E.g. having changed a 244mm stone to 253mm, AngleCube relative reading of the bevel angle was 0.1 degree (the AngleCube accuracy is 0.2 degree). A knife sharpened at 15 degrees grinding angle on three stones 244mm (#220), 253mm (#800) and 243mm (#4000), showed exactly 30 degrees on laser goniometer.
When I sharpen a batch of knives at the same angle, and keep the distance between the adjustable stop and knife edge constant as I change knives, I recalculate the US height for a given stone only after truing.
If for whatever reason I change that distance, or have to sharpen at a different angle, I recalculate the US height.
Time-wise it is quick, since I put the formulas in a simple script.
Generally speaking, the above script is just another application of the cosine rule to Tormek that we have been watching on this forum in the succession of:
- Dutchman's tables;
- Kenjig designed to set the grinding angle by distance from US to the stone;
- and this script for setting the grinding angle through US height over the Tormek case.
Wootz,
Your work is awesome! Using theory you, Jan, and Dutchman (plus Herman) understand and I accept of faith, I think we can interject some low tech kenjigs here.
If we simplify things by using a fixed projection length (the well known by now "139mm" distance). we can calculate kenjigs for different wheel diameters. For example: Start with one for the 600 grit wheel, say 252mm. 250mm would be a logical next jig. Then go down in five mm intervals. Make up a series of kenjigs with the groove cut for the various diameters. Label the jigs, for example, "fifteen degree bevel with 252 mm diameter wheel".
The total length of each of the jigs could match the diameter of its calculations, or, if longer, pencil marks could notate that length.
Doing the calculations for these jigs and the simple woodworking involved in constructing should require very little time. The kenjigs will become part of your permanent Tormek kit.
One of the things I appreciate about this forum is being able to piggyback my simple ideas with high powered math which is beyond my training. Thanks.
Ken
ps We are not limited to any one projection distance. It just simplifies both the math and the set up. In fact, a second projection distance for paring knives with just the regular knife jig or for a Chinese cleaver using Robin's extended universal support would be very useful.
Wootz, thank you for posting your new method for matching grinding wheels of different diameter. :)
Your new matching method is based on generally valid geometrical rules and so can be used for grindstones of arbitrary diameters.
From the context it is clear, that your method was developed for the US in vertical sleeve, nevertheless it would not be difficult to modify it for the horizontal sleeve.
Your basic script for US height calculation works fine. The only difficulty I faced was the decimal marker. In this country we use comma as symbol for decimal marker. I had to change "." for "," in the script and everything was OK. This gave me opportunity to see how nicely your script is written and admire sophisticated string commands.
I have checked your matching method on my T7 for wheels with diameters 240 and 220 mm and can confirm that it works correctly.
Congratulations to the invention of a new procedure for setting the US. Great job. :)
Jan
Ken, Jan, thank you for kind words, but you are giving me too much of credit.
The maths is not mind-bending, and the script is nothing fancy.
What really deserves credit, is the constructive criticism, and inspiring atmosphere of this forum.
If not for everything that has been said here before, I wouldn't even look in this direction.
Wootz,
I think of the forum as a pulling boat (a term from my Outward Bound days, more commonly known as a life boat.) The oarsman on the port side does a better job if there is an oarsman on the starboard side. Both do better with someone minding the tiller and a navigator. I think we are a great team!
Ken
Wootz, you are a very humble person. :)
I think that programming scripts still does not belong to ordinary skill of a knife sharpener. The Cosine and the Pythagorean theorems are certainly not astonishing, but thank God if their proper application leads to the desired goals.
Writing scripts requires some skill also, because "the devil is in the detail". I saw it with my decimal comma problem, until fixing it, the script was delivering meaningless figures.
So congratulations are definitely in place. :D
Jan
Quote from: Jan on March 30, 2016, 01:04:06 PM
... The only difficulty I faced was the decimal marker. In this country we use comma as symbol for decimal marker. I had to change "." for "," in the script and everything was OK.
... "the devil is in the detail". I saw it with my decimal comma problem, until fixing it, the script was delivering meaningless figures.
Thanks for drawing my attention to this, Jan.
I think I could reproduce what you are saying on my PC, and modified the script to make it work for both comma "," and "." as the decimal.
The above script has been updated.
Could you do me a favour, try the updated version on your computer and tell me if it works right?
Wootz, I have tested the updated version of your script and it works fine also with comma as decimal marker. :)
It provides slightly different figures compared with the initial script, because you have changed the ConstantHorizontal from 51.4 to 51 mm.
I have again admired your programing skill in overcoming this issue. Thank you in the name of potential "decimal comma" users. :)
I was wondering if suitable format specifier could do the job as well?
Jan
Hi Jan,
Thank you for testing the script, it is finished, as Ken joked elsewhere, for both hemispheres now.
As to the ConstantHorizontal, I went to my local dealer with a caliper, and asked his permission to measure the display Tormek T7, and two more T7s he had in for repairs - they all showed 51mm.
I thought this value is better suited for general use.
I cannot do without this script because AngleMaster does not work for aftermarket oversized wheels, including the paper wheel of 254mm.
(Obviously for the script to work for my paper wheel setup, I had to edit the constants ConstantHorizontal and ConstantVertical.)
Wootz,
You need to leave the comfortable world of high tech and Mr. Euclid and venture into the depths of low tech! :)
Just because Tormek ends the diameter correction scale at 250mm does not mean that we cannot add a few millimeters with a sharpie. Just eyeball it or use a rule for layout. At this point, we may have three choices:
1) Remove the locking screw. Move the arrow to your new 254 mm mark and tape it in place. You are good to go!
2) Use your calipers and measure the change in the diameter compensator. Make a shim that thickness and place it under the diameter compensator when you measure.
3) (the nuclear option :-[) File the groove enough to allow the arrow to point to your 254 mm line. If this totally fails, a replacement part is available for $3.73 US.
Regards from the low tech land,
Ken
Quote from: wootz on March 31, 2016, 01:15:06 PM
Hi Jan,
Thank you for testing the script, it is finished, as Ken joked elsewhere, for both hemispheres now.
As to the ConstantHorizontal, I went to my local dealer with a caliper, and asked his permission to measure the display Tormek T7, and two more T7s he had in for repairs - they all showed 51mm.
I thought this value is better suited for general use.
I cannot do without this script because AngleMaster does not work for aftermarket oversized wheels, including the paper wheel of 254mm.
(Obviously for the script to work for my paper wheel setup, I had to edit the constants ConstantHorizontal and ConstantVertical.)
Wootz, you have internationalized your scrip. :)
Bellow there is a map from Wikipedia showing where the comma and point are used. https://en.wikipedia.org/wiki/Decimal_mark (https://en.wikipedia.org/wiki/Decimal_mark)
(http://img18.rajce.idnes.cz/d1802/11/11982/11982115_ca941ed2f566d26ff045b1eb4d031b15/images/Decimal_marks.jpg?ver=0)
For us in countries with decimal comma, the decimal point is not a problem, because we take it as the common "international" notation used in computers. The problem occurs only when programs do not ask the operating system for the decimal mark selection. Some commands than can generate incorrect results. Wootz has overcome this issue in an original way.
Wootz, more accurate value for the ConstantHorizontal* is fine with me. It has minimal impact on the US height, only 0.1 mm for the default input values. But just that little difference 0.10 mm alerted me, because the devil is in the detail, however after a while I heard the angels sing. :D
I will correct the ConstantHorizontal in my Autocad model where I am using approx. value 52 mm.
Jan
P.S.: * Explanation. Wootz uses the ConstantHorizontal = 51 mm to tell the script what is the horizontal offset of the vertical sleeve from the shaft.
Jan,
Fascinating post!
Ken
Quote from: Ken S on March 31, 2016, 05:41:25 PM
Wootz,
You need to leave the comfortable world of high tech and Mr. Euclid and venture into the depths of low tech! :)
Just because Tormek ends the diameter correction scale at 250mm does not mean that we cannot add a few millimeters with a sharpie. Just eyeball it or use a rule for layout. At this point, we may have three choices:
1) Remove the locking screw. Move the arrow to your new 254 mm mark and tape it in place. You are good to go!
2) Use your calipers and measure the change in the diameter compensator. Make a shim that thickness and place it under the diameter compensator when you measure.
3) (the nuclear option :-[) File the groove enough to allow the arrow to point to your 254 mm line. If this totally fails, a replacement part is available for $3.73 US.
Regards from the low tech land,
Ken
OMG
... and only when I went to the 'nuclear option', I realized the AngleMaster lower scale has a 10" mark. Shame on me, I should better know my instruments.
Ken, I was delighted to read your advice for oversize wheels. :)
You showed almost the same inventiveness as Wootz by internationalization of its script. ;)
Jan
Jan,
I would like to see a map showing where apostrophe is still used in the English language. I dont think there would be many areas showing in North America. :)
Thanks for your kind words about my oversize wheel thoughts. I have read that the other wheel company was given ten inches instead of 250mm as the design spec, hence the slight oversize.
Truing the wheel will eventually solve the oversize dilemma. :)
Ken
Quote from: Jan on April 01, 2016, 03:22:25 PM
Ken, I was delighted to read your advice for oversize wheels. :)
You showed almost the same inventiveness as Wootz by internationalization of its script. ;)
Jan
Ken, you are generally correct, English speaking countries use decimal point. The exception is South Africa. In Canada they use decimal point when they are using English.
I do not have the exact figure, but the majority of people in the world use decimal point, however this is given by the fact that China and India do.
Jan
Jan, I must not have been clear. I was referring to the all too common (lazy) habit of many English speakers of ignoring the apostrophe in contractions. "Don't", a contraction for " do not" becomes just "dont". I am sure that as a native Czech speaker you were taught proper English. Sadly, too many of my countrymen have forgotten how to properly speak our own language. :-X
Ken
OK Ken, sorry for my misunderstanding. :-[
Jan
"Dont worry", Jan. I was just commenting on the state of English by native speakers. :(
Actually, your comment about the use of commas and periods in math is fascinating.
Ken
Wootz, I again dealt with your program for matching grindings wheels of different diameters and I would like to propose to appoint you and Dutchman for Professors! :) http://forum.tormek.com/index.php?topic=2969.msg15686#msg15686 (http://forum.tormek.com/index.php?topic=2969.msg15686#msg15686)
The reason is simple, I have compared your script with a similar formula published by John Verhoeven and I found that yours works much better. (Experiments on Knife Sharpening by John D. Verhoeven can be downloaded as PDF from https://www.wickededgeusa.com/wp-content/uploads/2012/10/knifeshexps.pdf)
The study referenced above presents in appendix 2 a formula (Eqn. 1) derived by R. Homer, which is biased by several degrees. Instead to found a bug an empirical correction constant was introduced that approximately corrects the bias. :-\ (The problem is not in its own calculation, but in oversimplified geometry of knife sharpening using TORMEK jig and USB.)
Because both authors are emeritus Professors, I think that you deserve to be Professors also. :)
Respectfully yours.
Jan
Thank you, Jan. Knowing your university background, and how meticulous you are, I and Dutchman should hold your praise in high regard.
I understand Verhoeven couldn't get the formula predictions work because of the knife jig offset from the centreline, and actual results varied with the knife thickness. Verhoeven attributed this offset to a manufacturing flaw. If he realized it is on purpose, he would have mentioned the thickness of the knife blade in his work.
No wonder though he was mistaken, as Tormek doesn't clearly state the lower jaw offset from the jig centreline, and regular users centre the blade in the jig by guess-work.
It was your, Jan, elegant solution to find out the offset is to center 2.5mm thick blade, which got further confirmation in Tormek's Improved Knife Jig description saying "Knife 2.5 mm thick" http://tormek.com/international/en/grinding-jigs/svm-45-knife-jig/ (http://tormek.com/international/en/grinding-jigs/svm-45-knife-jig/)
Any knife outside this ideal thickness would require a correction to the formula to get the predicted angle.
Well, we all understand the practical importance of these calculations is not in achieving the exact target edge angle, but in maintaining the same grinding angle as we move the blade to a stone of a finer grit, and to the honing wheel, as this is the only way to get it sharp.
Since the script was developed, I use only it to set the same grinding angle by the Universal Support height as I move from the #220 grinding wheel to finer wheels, and then to the honing paper wheel, and always get ultimate possible sharpness. I can't even remember when I last used AngleMaster or marker for adjustments.
Quote from: Ken S on April 01, 2016, 10:25:20 PM
Jan, I must not have been clear. I was referring to the all too common (lazy) habit of many English speakers of ignoring the apostrophe in contractions. "Don't", a contraction for " do not" becomes just "dont". I am sure that as a native Czech speaker you were taught proper English. Sadly, too many of my countrymen have forgotten how to properly speak our own language. :-X
Ken
I think the reason of not using the apostrophe is purely laziness to change keyboard layout or fast writing. And now it got so common and accepted, so it is OK for the new gen as they don't know else.
Wootz, I have appreciated your answer! :)
The original Dutchman approach involves a small approximation concerning the way we measure the distance between the grindstone and the USB.
Your approach, Wootz, is not burdened by this small approximation. For this reason your script provides even more accurate results than the Dutchman tables even though you are using the Dutchman formula also. ;)
Jan
I appreciate having the technical back up of the Forum Mathematics Department. Being able to be more precise than might be needed helps true up the whole process, just like working with a well trued grinding wheel.
I do think we need to differentiate between precision and consistency. I believe most users will be quite content as long as the bevels appear to be consistent and the bevel angles visually approximate the desired fifteen degrees or or whatever the desired angle is. (We have an idiom in English, "It looks good from the road")
While we can not achieve exactly our mythical fifteen degrees, I am in favor of anything material or mathematical which helps us approach it.
Ken
Ken,
I agree : consistency is more important than accuracy for me.
Kind regards,
Rich
Rich,
I agree about the importance of consistency, but I would temper that belief with a very healthy regard for accuracy. I think a good marriage of the two is the engine cut hash marks in the Starrett rules. The divisions may only be for 1/2 millimeters or 1/64 or 1/100", however the accuracy of the spacing is considerably more precise. We don't need a micrometer for a rule measurement, but it is nice to have a very good rule.
I think it is always a good idea to have a sense of the measurement accuracy (tolerance) for the job in hand.
Ken
I agree with you all :)
Can we agree to always use Metric and Swedish rules for numbers and measures?
At least it is consistent and politicly correct as we are in "Tormek environment" ;)
WolfY,
I agree with you about using metric measurement. After all, Tormek is an almost all metric. For some reason, the screw on feet of the Tormek Work Station have 5/8 x 11tpi threads. I have no clue why a Swedish vompany chose to have a product made in Germany have feet with imperial threads. However, I agree that the Tormek is essentially a metric machine and logically forum measurements shoild be primarily metric.
Is anyone uncomfortable with that?
I would prefer to use Eastern Danish Rules for Numbers and Measures. I am joking, as I have absolutely no idea of what Swedish rules for numbers and measures are. Would you please explain.
I will hold out for one non metric measurement, the British pint. :) (It's even in the handbook!)
Ken
Ken,
I was exaggerating with the "Swedish" rules and numbers ;)
But for example: the comma for thousands and decimal is like this: XXX XXX,XX
Today's date is 2016-07-01 although it's not relevant for us ;)
Don't remember other rules that really are relevant or important :)
WolfY,
I don't see a problem. In my shop, a busy day might mean several edges, so XXX XXX XX would probably cover several days. :)
As for dates, they have already gone rogue. Look at reply dates before yesterday. (ex. June 16, 2016). Maybe Google Translate could redo them to proper Swedish. (another :) )
All work and no play makes a dull Tormeker...........
Ken
International organizations recommend that a space be used, rather than a comma or period, to separate groups of digits.
So, for example, 75 thousand 4 hundred twenty-one and 45 hundredths is written as
75 421.45
or
75 421,45
depending on the preferences for the decimal separator.
Interesting. I am always learning new things on this forum.
Ken
Thanks Herman,
Looking backwards the thread, I can see I was not as clear as you with the explanation. Kind'a missed something ;)
Quote from: Ken S on July 01, 2016, 04:37:43 PM
As for dates, they have already gone rogue. Look at reply dates before yesterday. (ex. June 16, 2016). Maybe Google Translate could redo them to proper Swedish. (another :) )
The internationally recommended way to write that date would be
16 June 2016
or
16 Jun 2016.
The latter expression is used when it's preferred to have a uniform three-letter abbreviation for each month.
Has the script been removed from the first post? I cannot find any script. If I am an idiot, please explain where I can find the script for using the universal support height for setting grinding angle.
I think we somehow drifted away from the original question about maintaining a constant bevel angle using grinding wheels of different diameters. This is not a complicated procedure, using either Wootz' applet or kenjigs and Dutchman's tables. (One kenjig, cardboard works fine, for each wheel diameter.)
Did I miss something?
Ken
Quote from: ATS on May 22, 2018, 10:12:09 PM
Has the script been removed from the first post? I cannot find any script. If I am an idiot, please explain where I can find the script for using the universal support height for setting grinding angle.
Wootz now sells it as a software package... so he probably removed the script. You can find more information about it HERE (http://knifegrinders.com.au/05Equipment_scripts.htm).
Forum member RichColvin has an online calculator that sets the USB (by measuring to the wheel)... you can find that HERE (http://sharpeninghandbook.info/indexCalcProj.html).
(So... here here I guess). ::)
Good info, CB.
Ken
Thank you!
There are two approaches for setting grinding angle in the standard Universal Support position of grinding into the wheel:
The first originates from Ton Nillesen trigonometry for Tormek, and sets grinding angle by distance from the Universal Support bar to the grinding wheel, a free online calculator is available thanks to Rich Colvin: http://sharpeninghandbook.info/indexCalcProj.html (http://sharpeninghandbook.info/indexCalcProj.html)
Kenjig (https://forum.tormek.com/index.php?topic=2803.0) also works on this principle.
The second is Knife Grinders' by vertical distance from the Universal Support bar to the Tormek housing: Computer Software >> (http://knifegrinders.com.au/05Equipment_scripts.htm)
and more here: https://forum.tormek.com/index.php?topic=3501.msg22214#msg22214 (https://forum.tormek.com/index.php?topic=3501.msg22214#msg22214)
Quote from: wootz on May 23, 2018, 06:03:34 PM
There are two approaches for setting grinding angle in the standard Universal Support position of grinding into the wheel:
The first originates from Ton Nillesen trigonometry for Tormek, and sets grinding angle by distance from the Universal Support bar to the grinding wheel, a free online calculator is available thanks to Rich Colvin: http://sharpeninghandbook.info/indexCalcProj.html (http://sharpeninghandbook.info/indexCalcProj.html)
Kenjig (https://forum.tormek.com/index.php?topic=2803.0) also works on this principle.
The second is Knife Grinders' by vertical distance from the Universal Support bar to the Tormek housing: Computer Software >> (http://knifegrinders.com.au/05Equipment_scripts.htm)
and more here: https://forum.tormek.com/index.php?topic=3501.msg22214#msg22214 (https://forum.tormek.com/index.php?topic=3501.msg22214#msg22214)
(https://forum.tormek.com/index.php?action=dlattach;topic=2969.0;attach=2181)
Fun with Cadd! 8)
Update: 48 countries use our software for Tormek!
Our software for setting grinding angle on Tormek is now available in the Apple App Store and Google Play Store.
iPhone and iPad applets - on your iPhone or iPad search the App Store for Grinding Angle Setter.
Our existing customers can obtain the iPhone / iPad applet free of charge - if you purchased our software before, please email Knife Grinders that you also need the iPhone / iPad applet, and we will generate a promo code for you so you don't have to pay for our applet in the App Store.
Our Android version has been upgraded, and all bugs fixed.
Existing customers who need the improved Android version, please email Knife Grinders for a link and get it straight onto your smartphone or tablet.
New customers who want to buy the Android applet only, on your smartphone or tablet search the Google Play Store for Grinding Angle Setter, and look for the Knife Grinders icon
(http://knifegrinders.com.au/Shop/KG_100x100.jpg)
More details on our website http://knifegrinders.com.au (http://knifegrinders.com.au/11Shop.htm)
.
Quote from: wootz on March 30, 2019, 07:13:44 AM
As of today, 41 countries use our software for Tormek.
Our software for setting grinding angle on Tormek is now available in the Apple App Store and Google Play Store.
iPhone and iPad applets - on your iPhone or iPad search the App Store for Grinding Angle Setter.
Our existing customers can obtain the iPhone / iPad applet free of charge - if you purchased our software before, please email Knife Grinders that you also need the iPhone / iPad applet, and we will generate a promo code for you so you don't have to pay for our applet in the App Store.
Our Android version has been upgraded, and all bugs fixed.
Existing customers who need the improved Android version, please email Knife Grinders for a link and get it straight onto your smartphone or tablet.
New customers who want to buy the Android applet only, on your smartphone or tablet search the Google Play Store for Grinding Angle Setter, and look for the Knife Grinders icon
(http://knifegrinders.com.au/Shop/KG_100x100.jpg)
More details on our website http://knifegrinders.com.au (http://knifegrinders.com.au/11Shop.htm)
.
Great Job!