Author Topic: EdgeCalc - what's happening on the knife-edge...  (Read 1590 times)

Offline jvh

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EdgeCalc - what's happening on the knife-edge...
« on: November 08, 2019, 01:54:47 am »
Hello everyone,

for precise outputs and for an idea what's happening on the knife-edge during grinding I made EdgeCalc - Excel spreadsheet which lets you calculate deviations caused by roundness of grinding wheels. I plan to add this functionality to TormekCalc in the future but this solution is much faster.

EdgeCalc contains drawings with dimensions for better visualization and it will help you if you want to validate used math in formulas. I tried to describe all, but there can be problems with used terminology. If you have better idea please write it here and I will release updated version. Any ideas for improvement are welcome as well as questions.

Table is locked by default (without password), only three green input cells are editable. Feel free to unlock it if you know what you are doing.

Enjoy!


jvh

Note: File is compressed to zip format (forum restriction), you have to unzip it before using.
« Last Edit: November 08, 2019, 01:40:08 pm by jvh »

Offline jvh

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Re: EdgeCalc - what's happening on the knife-edge...
« Reply #1 on: November 08, 2019, 02:37:35 am »
Screenshots...

Offline smurfs

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Re: EdgeCalc - what's happening on the knife-edge...
« Reply #2 on: November 08, 2019, 10:17:47 am »
That's excellent work jvh and thank you for providing the maths for deriving the bevel heel and chord angles.

Just one thing though. I don't think it is correct to describe the angle variations that occur along the bevel as 'errors caused by roundness'. To me this terminology suggests the angle calculations are wrong or approximate which is not the case as the maths is precise.
« Last Edit: November 08, 2019, 12:09:57 pm by smurfs »

Offline Jan

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Re: EdgeCalc - what's happening on the knife-edge...
« Reply #3 on: November 08, 2019, 01:22:44 pm »
JVH, thanks for further details from the tip of the blade.


Just one thing though. I don't think it is correct to describe the angle variations that occur along the bevel as 'errors caused by roundness'. To me this terminology suggests the angle calculations are wrong or approximate which is not the case as the maths is precise.

I fully agree with Smurfs. The term 'errors caused by roundness' is not adequate for our situation. The change of the angle along the hollow grind occurs as a consequence of using a round grinding stone. There is no error in this approach.

Jan

Offline jvh

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Re: EdgeCalc - what's happening on the knife-edge...
« Reply #4 on: November 08, 2019, 01:39:53 pm »
Just one thing though. I don't think it is correct to describe the angle variations that occur along the bevel as 'errors caused by roundness'. To me this terminology suggests the angle calculations are wrong or approximate which is not the case as the maths is precise.

That's true, "errors" has been changed to "deviations". Thank you.

Offline Jan

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Re: EdgeCalc - what's happening on the knife-edge...
« Reply #5 on: November 08, 2019, 04:10:20 pm »
Dear Tormekers, as it is my habit, I have independently checked some of the calculations made by JVH.

I have used a formula derived prof. Verhoeven and I can ensure you that it gives numerically the same angle of the chord as calculated by JVH. I have also successfully verified the real length of the grind.  :)

The angle of the chord is important for practice because this angle we get by angle protractor measurements which “overbridges” the hollow grind.

Just out of curiosity in geometry those angle relations are given by the inscribed angle theorem which is very useful for the wheel geometry.  ;)

Jan
« Last Edit: November 08, 2019, 04:12:39 pm by Jan »