Author Topic: Polishing angle calc  (Read 569 times)

Offline Gilles

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Polishing angle calc
« on: May 15, 2020, 06:21:50 pm »
Hello everyone,
It makes several months, I am reading with very much interest, the different posts and I have learned a lot about sharpening.
This is my first post on this forum and I would like fist to thank all the contributors for sharing their knowledge.
My first Tormek was a T3, and I didn’t like it because the USB support was not strong enough to keep the blade of a planer perfectly perpendicular.
Later on, I found a very cheap Tormek 4000, all in stainless steel. I try it in a dark area and I didn’t realize that the stone was not a Tormek stone and that the shaft was twisted! After a while, I found someone to make me a new shaft and I bought a second hand Japanese wheel SJ250. This purchase was finely a very good one.
So now I have a SG200 wheel to sharpen knifes and I have a wider wheel to polish them (before the leather wheel).

I have tried to use the TormekCalc² to keep the same angle with the 2 stones but I realize that it was not possible. The second wheel was always grinding the edge heel instead of the edge tip.

I wanted to find the lowest possible knife angle that would polish the tip.
I have spent some time to understand all the formula of the TormekCalc² of JVH.
What is nice with the Tormek problem is that everything can be analyzed through triangle geometry. It is no more mathematic, it is only geometry, nice geometry, and I have solved my problem of polishing angle.
I share with you this spreadsheet that does the same calculation as the TormekCalc² and some more calculation; however this is done with a totally different objective. TormekCalc² is a very user friendly tool (Thank you JVH) and I don’t want to compete with it. My aim is to do a very simple spreadsheet so that everyone could understand every formula and modify them as they need.
I took the liberty of using as much as possible the same letter and the same name as in TormekCalc² so that people could understand the drawing and the formula more easily.

I have also study the impact of the knife thickness and the tapered knife on the real grinding angle.
It gives me the idea to realize a Jig centering bushing before I realize that JVH has already realized it.
I have added a sheet dedicated to that.

I hope that my calculations are good. The first trial I have done was OK with a flat piece of steel of 3mm with a single bevel grinding. With the same angle as the grinding wheel, I could see the polishing of the hell and with the correction of the angle, I could see the polishing of the tip. I am happy. It works for that!

I do not have a very tapered knife so I was not able to validate my calculation for that. 
 
Now that I understand how to use the Tormek, I need to go to practice and play with it.

Kind regards

Offline cbwx34

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Re: Polishing angle calc
« Reply #1 on: May 16, 2020, 01:30:15 am »
Hello everyone,
It makes several months, I am reading with very much interest, the different posts and I have learned a lot about sharpening.
This is my first post on this forum and I would like fist to thank all the contributors for sharing their knowledge.
My first Tormek was a T3, and I didn’t like it because the USB support was not strong enough to keep the blade of a planer perfectly perpendicular.
Later on, I found a very cheap Tormek 4000, all in stainless steel. I try it in a dark area and I didn’t realize that the stone was not a Tormek stone and that the shaft was twisted! After a while, I found someone to make me a new shaft and I bought a second hand Japanese wheel SJ250. This purchase was finely a very good one.
So now I have a SG200 wheel to sharpen knifes and I have a wider wheel to polish them (before the leather wheel).

I have tried to use the TormekCalc² to keep the same angle with the 2 stones but I realize that it was not possible. The second wheel was always grinding the edge heel instead of the edge tip.

I wanted to find the lowest possible knife angle that would polish the tip.
I have spent some time to understand all the formula of the TormekCalc² of JVH.
What is nice with the Tormek problem is that everything can be analyzed through triangle geometry. It is no more mathematic, it is only geometry, nice geometry, and I have solved my problem of polishing angle.
I share with you this spreadsheet that does the same calculation as the TormekCalc² and some more calculation; however this is done with a totally different objective. TormekCalc² is a very user friendly tool (Thank you JVH) and I don’t want to compete with it. My aim is to do a very simple spreadsheet so that everyone could understand every formula and modify them as they need.
I took the liberty of using as much as possible the same letter and the same name as in TormekCalc² so that people could understand the drawing and the formula more easily.

I have also study the impact of the knife thickness and the tapered knife on the real grinding angle.
It gives me the idea to realize a Jig centering bushing before I realize that JVH has already realized it.
I have added a sheet dedicated to that.

I hope that my calculations are good. The first trial I have done was OK with a flat piece of steel of 3mm with a single bevel grinding. With the same angle as the grinding wheel, I could see the polishing of the hell and with the correction of the angle, I could see the polishing of the tip. I am happy. It works for that!

I do not have a very tapered knife so I was not able to validate my calculation for that. 
 
Now that I understand how to use the Tormek, I need to go to practice and play with it.

Kind regards

A very nicely laid out spreadsheet... looks good to me.  Now I need help understanding how you use it?  (It always takes me a while).

So, for example, I look at the "Polishing Angle" page.  If I use the angle of 12° for the 200mm wheel, then look down at the 250mm wheel, I see 12.65°.  So do you then take 12.65°, and put that back into the "USB Height" page (along with the wheel size difference), to obtain the answer to set the USB?

Again, nice job! Thanks.

Offline Gilles

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Re: Polishing angle calc
« Reply #2 on: May 16, 2020, 09:37:12 am »
Hi cbwx34,
you perfectly understand how to use it.
regards

Offline Jan

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Re: Polishing angle calc
« Reply #3 on: May 16, 2020, 11:21:27 am »
Gilles, welcome to the forum!

Thanks for sharing with us your very nicely done Excel spreadsheet. It is well documented with formulas and drawings and it covers wide span of tasks related to the geometrical aspects of sharpening. I find it valuable and inspiring.

I have validated your page “USB height” and can confirm that it works accurately!

My comment to this page is, that many people use the USB top to stone distance for setting the grinding angle. It is machine independent value.

Your “Polishing angle” page, reminded me the central angle theorem which relates the grinding angle, chord angle and heel angle. Your values are in compliance with this theorem.

Jan
 

Offline Gilles

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Re: Polishing angle calc
« Reply #4 on: May 16, 2020, 11:51:49 am »
Hi Jan,

Thank for your comment,
You make me understand why people are using the USB top to stone distance. I will add it in a future release.
I didn't knew the existance of the cental angle theorem, I will have a look at it

Kind regards

Offline Jan

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Re: Polishing angle calc
« Reply #5 on: May 16, 2020, 12:19:07 pm »
Chord angle = ( grinding angle + heel angle ) / 2

Jan

Offline cbwx34

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Re: Polishing angle calc
« Reply #6 on: May 16, 2020, 02:34:56 pm »
...
My comment to this page is, that many people use the USB top to stone distance for setting the grinding angle. It is machine independent value.
...

I already added it to my copy of his spreadsheet. ;)

...
I will add it in a future release.
...

I sent you a PM... if you make changes... a couple of minor things I noticed.

Offline Jan

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Re: Polishing angle calc
« Reply #7 on: May 16, 2020, 03:58:53 pm »
Gilles, in my understanding the condition for minimum grinding angle is, that the chord length is the same for both wheels. In your example the chord length is 11.4 mm. Also the angle of the chord will stay the same (15.3⁰) for both wheels.

CB, you are quick!  :)

Jan

Offline RichColvin

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Re: Polishing angle calc
« Reply #8 on: May 17, 2020, 02:41:59 am »
I've added this to the calculators available from the Sharpening Handbook.  Here is the page link:  https://www.sharpeninghandbook.info/indexCalc.html

Kind regards,
Rich
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Offline Gilles

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Re: Polishing angle calc
« Reply #9 on: May 17, 2020, 11:34:33 am »
Thank you Rich. I think it is a good idea

Offline RickKrung

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Re: Polishing angle calc
« Reply #10 on: May 22, 2020, 05:00:04 pm »
Beautiful spreadsheet.  Very nicely laid out with all the formulas, etc.  Way beyond anything I could have done, even in my prime of using Excel.  Just getting started looking at it and trying to understand it a bit.   

I do have some questions, and perhaps a request or two. 

It appears to me that the spreadsheet is sort of "hard wired" for a Supergrind 2000.  On the first sheet, "USB Height".  Variables "Constand HV" and "Constand VV" (for both the "Vertical Side" and "Horizontal Side") are derived from distance values in the figures, but most of the these are specific to a Supergrind 2000. 

I have studied the figures and formulas enough to figure out how I could measure some of these for my T8 and input the values.  You have documented most clearly.  Your spreadsheet shows the computation for Constant VV (Parameter AA')(cell C16) on the Vertical Side, which is =23+12/2 (cell D16).  To my spreadsheet, I have added the values for the computation of Constant HV (Parameter AB)(cell C15) to the adjacent cell (D15), which is: =119.6+12/2-63-25/2.

The one that I cannot find values for, to know how you've calculated it is the Constant VV for the Horizontal Side, cell C50 in the spreadsheet.  It is the distance "BC", as shown in the figure.  From the figure for the Vertical Side, the distance from the shaft center to the top of the machine would be =23+12/2 = 29, as shown in cell D16, but you do not show values for how to determined the distance from the top of the machine case to the centerline of the horizontal USB sleeve.  That should be easy enough, with just a measurement from the top of the USB in the sleeve to the machine case, then subtract 12/2. 

My point in torturing this is to suggest that input fields be added so that users can customize the spreadsheets for their own machines, SG, T7, T8., etc. and have those contants computed.  I have not looked deeper to see if this sort of thing might apply to the other sheets in the spreadsheet.  It doesn't appear so, as those other sheets look to be independent of the machine type.

Please do not take my comments as criticism.  This is an amazing piece of work and I thank you for it.  I mean only to suggest some things to make it even more valuable and useful to us much more casual users. 

Thanks for listening,

Rick

« Last Edit: May 22, 2020, 05:04:58 pm by RickKrung »
Quality is like buying oats.  If you want nice clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.

Offline cbwx34

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Re: Polishing angle calc
« Reply #11 on: May 23, 2020, 06:02:58 pm »
...
The one that I cannot find values for, to know how you've calculated it is the Constant VV for the Horizontal Side, cell C50 in the spreadsheet.  It is the distance "BC", as shown in the figure.  From the figure for the Vertical Side, the distance from the shaft center to the top of the machine would be =23+12/2 = 29, as shown in cell D16, but you do not show values for how to determined the distance from the top of the machine case to the centerline of the horizontal USB sleeve. 
...

My GUESS.... he pulled it from the TormekCalc spreadsheet (that this is based on).  😉

Offline Gilles

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Re: Polishing angle calc
« Reply #12 on: May 23, 2020, 08:17:02 pm »
High Rick

Thank you for spending some time to look a my spreadsheet.
I take all the comments as valuable remarks.
I will do a release taking into account all of them.

Concerning the formula I forgot to put in, you found the good answer.

I agree it would be nice to have a sreadsheet with the parameter of every Tormek machines.

Do you know if all those parameters have already been publish on the Tormek Forum or should I create a new subjet to ask the Tormek community to send them to me so that I could include them.


Kind regards


Offline RickKrung

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Re: Polishing angle calc
« Reply #13 on: May 23, 2020, 11:17:31 pm »
...snip...
Do you know if all those parameters have already been publish on the Tormek Forum or should I create a new subjet to ask the Tormek community to send them to me so that I could include them.

Kind regards

Some must know those values, they've developed apps for the machines.  But I know of nowhere that info has been posted. 

You can request users provide you with measurements from their machines.  I have been working on some suggestions on good method of making such measurements, but have I'm not ready to post it yet.  I've been on "Grampa duty" since about about noon yesterday.  My granddaughter stayed overnight at my place last night. We have had a lot of fun, but no time for me to work.

Rick
Quality is like buying oats.  If you want nice clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.

Offline cbwx34

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Re: Polishing angle calc
« Reply #14 on: May 23, 2020, 11:45:01 pm »
...
I agree it would be nice to have a sreadsheet with the parameter of every Tormek machines.

Do you know if all those parameters have already been publish on the Tormek Forum or should I create a new subjet to ask the Tormek community to send them to me so that I could include them.


Kind regards

My 2 cents (and I don't think I'm alone here)... measuring directly to the wheel is the better route.  It's quick, easy, accurate, and machine independent.  No matter what configuration: horizontal, vertical, FVB, etc., or even if you transition to another machine like a buffer with a honing wheel of some sort, you're good to go.

I've gone the route of "measuring to the machine"... and it just causes me unnecessary work, and I don't see any better result.  Measuring to the machine is just a step added after measuring to the wheel, (with a bunch more measurements you now have to account for).

BTW, this doesn't at all "devalue" the work you've done here... it's still a good spreadsheet with some valuable info, just like the TormekCalc2 work.

p.s.  I'm sure at this point you've seen it, but it's worth linking to the original work in these threads...
Simple Adjustment of the Grinding Angle by Dutchman.
« Last Edit: May 23, 2020, 11:51:29 pm by cbwx34 »