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Messages - jvh

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1
Hello Mike,

I have no problem with this. I understand what is the problem and therefore I mentioned "sharper angle grinding" option in my previous post. All deviations caused by hollow grind are calculable and if you take them in account you can eliminate their impact, eg. you can grind microbevel on the flat stone or directly on the Tormek.

A brittle edge indicates a problem with the bevel angle being too sharp. But it's not the fault of grinding - there you can set what angle you want to grind - this is due to the rather inappropriate use on too hard material/wood...

Why should I grind / hone over the complete height of the chisel bevel if I know that resulting angle will be wrong?

jvh


2
My main point was that between what you call the apex and the edge heel, the soft iron layer will be thinner...  that's all...   And if you have experience with Japanese blades (especially high quality ones, not the junk that is generally sold through the western tool dealers...) you would know that the wrought iron layer is integral to the support of the thin blue or white steel layer...  and the risk of tapping out a Japanese kanna blade is high enough without thinning out the layer...  (and if you never tapped out a blade, you aren't using the plane very much, or have one of the junk blades that has a huge flat on the edge of the ura...)  You don't tap out a blade at the edge heel, you tap it in the middle, between the apex and the edge heel...  where it would be thinned out...

I'm not saying that you -can't- grind a Japanese blade on a Tormek...  just that I wouldn't (and neither would any of the guys that I know that use high quality Japanese tools...) ever grind a $600 hand made blade, and wouldn't see any reason to grind a cheap one either...  a hollow grind would structurally change the blade, and not for the better...

JH

Hello,

I must repeat that the soft iron layer will be thicker after hollow grinding (for the same apex angle). And for a thin layer of blue or white steel the rounding of the hollow grind is negligible, even if you grind a sharper angle as shown in Example 2 in my previous post. Other possible problems are described here too.

Please look at the enclosed picture what is difference between flat and hollow grind in higher zoom.

Can you explain how a hollow grind would structurally change the blade?

My post is not meant to be offensive, I'm just trying to verify if the information makes sense and if it's not another myth about grinding...

jvh

3
You really don't want a hollow grind on a Japanese kanna blade (or Japanese chisel blades either...)  The blades of Japanese tools are made from two different types of steels...  there is a very hard steel that is brittle (the cutting edge...) laminated to a much thicker and softer iron...  the thicker iron keeps the more brittle cutting edge supported, and if you use a Tormek to hollow grind the bevel, you will be significantly reducing the thickness of the supporting iron...  mostly because of the thickness of the overall blade, and the length of the bevel...  (most of my kanna blades are around 25 deg. or so, and almost a half inch of bevel...)  Same goes for Japanese chisels...

On western blades, the whole blade is the same type of steel, so hollow grinding isn't a problem...  but I would think that if and when you go to tap out the blade (which you will have to do at some point...) it's stressful enough to do it with the full support of the softer iron, but I would think that the possibility of cracking the hard steel would go up many times with a hollow grind...

Also, the main advantages of a hollow grind being to keep a narrower bevel "stable" when honing and not needing to hone as much steel on each sharpening pretty much go away with Japanese blades...  I've found that the wide bevel makes it very easy to keep the blade flat on the stones, and the softer iron hones so easily that they are much easier to sharpen on stones than western blades...

I use my Tormek all the time for western blades and knives...  but wouldn't touch one of my good kanna blades on it...

Also, no micro bevels or ruler trick bevels on the back on Japanese blades... 

Hope this helps...

JH

Hello,

no, that's not true. If you will have 25° at the apex you will have more material at the edge heel due to hollow grind. You can see what's happening during flat and hollow grinding in this video.

In example below are calculations for chisel with edge heel thickness 5 mm, chisel (single bevel) grind, angle 25°, wheel diameter 240 mm. Hollow grind depth is in that case 0,122 mm, but there is no reducing the thickness of the supporting iron.

The problem with the hollow grind is that the apex angle is 25°, but the angle between the apex and the edge heel is 27,579°. Compared to flat grinding there is "unground" material on the edge heel (due to the rounding of the wheel), which does not allow the blade to be tilted below 27,579°, because it would not cut as the apex does not touch the material. This makes the cut more aggressive because the edge is directed more into the material. This also affects the subsequent re-sharpening on a flat stone, where the minimum angle 27,579° is also ground (if the apex and the edge heel are touching the stone).

If you count with this you can start grinding with a sharper angle to get the angle between the apex and the edge heel equal to 25°. Second picture shows that you have to set initial grinding angle to 22,17° (= apex angle) and this slighly reduce thickness thickness of the supporting iron - hollow grind depth will be 0,146 mm. Is it too much?
But this is not the end, now you can continue on the flat stone - when the apex and the edge heel are touching the stone you will grind 25° angle + you will reduce also hollow grind depth while grinding. Other possibility is to grind 25° microbevel on Tormek too. 

Personally, I see no reason why Japanese chisels could not be sharpened on the Tormek. It will only be better to use advanced grinding techniques...

jvh



4
Knife Sharpening / Re: sharpening apps question
« on: June 10, 2021, 07:19:18 pm »
I have a question about knife sharpening apps. It is not my intention to compare apps or discuss their value. I have watched a number of well done videos about using these apps. These videos all seem to focus on sharpening one knife. I understand that this simplifies the learning process; it is an effective teaching technique.

What I have not seen is a video showing a typical sharpener situation with ten to twenty (or more) knives to sharpen in a morning. In a hypothetical ten knife batch, how many would receive the computer "treatment"? I realize there is no simple stock answer. I am just curious, not critical.

Ken

Hello Ken,

as I know, there is no such app except TormekCalc2 / BatchCalc module. Sharpening of up to 6 knives / tools in one go is supported at current version, but that can be easily increased. The main reason why there are only 6 positions is that you need the same amount of jigs for batch grinding.

Another unique feature of this module is that the height difference between the individual steps is converted to the required turns of the Tormek Micro adjust nut. I can say, from my own experience, that this method of setting up is fast and very, very accurate.

Unfortunately, the BatchCalc module is not freely available for several reasons, the main one is that the implementation of such functionality is not trivial at all and there is a lot of work and know-how behind it.

Video how it works is here: https://youtu.be/9qtyTKqQb1g

jvh

5
Knife Sharpening / Re: Tormek Excel cal spread sheet
« on: May 31, 2021, 09:10:25 pm »
@ Rick & Mike:
Thank you for your posts.  :)

@ Alf:
Please look at help in cell comments, functions should be well documented here. I will try to add more instructional videos to my YT channel in the future, unfortunately I have a lot of other work at this moment.
If necessary, you can also send me a private message and I will try to answer specific questions directly.

jvh

6
General Tormek Questions / Re: Need Advice.
« on: May 28, 2021, 11:52:11 pm »
Jvh, but will by looking only, one can check the sharpness?
Alf

Alf,

it depends. Sharpness for what? For the lowest BESS or for real use?

Sharpness is only one part of the problem. You have to consider also the real use, edge toughness, edge retention, corrosion resistance. You have to remove burr completely.

BESS shows you the sharpness in one point of the edge at a given time. When you repeat the measurement the next day you will get a value ca +20 g higher due to the oxidation of the edge. The BESS value will increase significantly after a few cuts etc.

With a good microscope... what do you think, is it sharp? (And you can still use cigarette paper, hair etc.)
https://youtu.be/QG_z9ynBht8?t=122
https://youtu.be/NXz7WB_qhqk?t=92
https://youtu.be/8LS17P0k4hw

jvh

7
General Tormek Questions / Re: Need Advice.
« on: May 28, 2021, 09:36:22 pm »
Hello,

why do you need to measure BESS value? I'd rather invest in a good microscope - you'll see what's going on on the whole edge, not at single/few points...

jvh

8
General Tormek Questions / Re: Suggestion for water spillage
« on: May 27, 2021, 09:41:46 am »
Hello,

something like this? (Not my ideas, taken from CZ forum.)

jvh

9
JVH,

Thanks for the screen shots.  They are helpful.  I tried replicating your examples, but don't get the same results, at least with some of the jig parameters that my version of the spreadsheet had as defaults. 

I looking for what other parameters are different,  I see that some of the jig dimension parameters differ for the SE-77 in BevelCalc, but these are values I can't alter on this tab. I've tried changing values in the Jig tab, and while that does change the displayed values, I still don't get the same Bevel Angle as you.  The differences are very minor and immaterial, I think.  Probably some other parameter differing in decimals. 

What would be the reason for the different jig parameters?  I am curious how you measured those jig parameters as they require some careful alignments and could make a difference in results.

I believe I get your point and can use BevelCalc. 

Rick

Hello Rick,

sorry, I used my version of TC2 while I experimented with another support with different diameter, so calculated results was for USB dia 15,3 mm.
I changed the pictures in the previous post, you should get the same results if you use the same machine constants.

jvh

10
Hello CB,

thank you, I couldn't be here for a few days...


Thanks, CB.  I guess that helps.  It took me a while to figure out the number of significant digits makes some difference and how to set it to display correctly (T USB).  It appears VUSB is a required input in BevelCalc for the Bevel Angle to calculate correctly.  I took that value from TormekCalc, but if I have to measure it as well as T USB, I don't want to bother.  That is one reason I am using T USB, so I don't have to measure VUSB. 

Hello Rick,

VUSB is not required input, you can enter T USB dimension (Top of USB to wheel surface T [mm]) in BevelCalc too. But if you enter T USB only, you get angles in all Bevel angle Δ [°] cells, because this dimension is the same for all USB types and it is not clear which one you are calculating.
You can also enter T USB and VUSB together (or HUSB / FUSB) dimension, then VUSB dimension has higher priority and it will override calculated angle for VUSB. Take a look at the attached pictures for a better idea.

jvh


11
Knife Sharpening / Re: TormekCalc2 - Advanced grinding calculator
« on: May 18, 2021, 09:57:29 pm »
Great 😊 I'll give it a shot, dusting off the old excel skills. Great tip btw. I'm guessing it will be possible to save the offset angle for honing for specific knives/steels.

Hello,

You can save the offset angle to Notes for knives/tools and Sharpening notes for materials.

I do not plan to load these values automatically, because I consider this concept to be problematic. As you may have noticed, I don't automatically follow the suggested procedures, instead I try to verify them and find out what they really are. My experiences suggest that the correct grinding technique and more precise settings between the individual steps have a significant effect on the formation of burrs, which can be eliminated during grinding and subsequent honing at a higher angles is not necessary.

jvh

12
Knife Sharpening / Re: TormekCalc2 - Advanced grinding calculator
« on: May 18, 2021, 12:00:10 am »
Wow just found this and it's a game changer!

Is it possible to add data for felt wheels and recommended honing angles like knifegrinders recommend? Understand if this is only for Tormek specific products^^
Would you be interested in adding Swedish language to the Excel file? I might be able to provide this if so. Cheers!

Hello LarK,

yes, you can add data for any wheel or machine. There are 3 slots for custom wheels in hidden columns, but you can also change unused wheels data specification to something else. For honing at higher angles is designed "Grinding angle shift ±Δ [°]" function, see picture.

Any translation is welcome, if you do it you will become a contributor. Please use the "Language5" column on the Languages sheet, send me a PM for help if necessary, as there are formulas in some cells.

jvh

13
Knife Sharpening / Re: TormekCalc2 - Advanced grinding calculator
« on: May 17, 2021, 08:10:02 pm »
Hello everyone,

new public and non-public version of TormekCalc2 is available (v2.67).

Main News:

  • CompCalc [New non-public module]

    Allows calculation of the grinding angle compensation if wheels with different diameters are used for grinding.
    It is a problem which, as far as I know, was first described by Gilles in this post and calculated using the Polishing angle calc, which is still available there. CompCalc is based on Polishing angle calc, all credit belongs to Gilles.

    Although this phenomenon may not be visible on wheels with a similar diameter and small blade thicknesses, it can cause problems with thicker blades (eg. chisels) and when switching from a smaller wheel to a larger one (eg. 200 mm coarse wheel on T-4  and 250 mm fine wheel on T-8).

    You can find more about this phenomenon in this video: https://www.youtube.com/watch?v=h_qRUvSvcLQ


  • BatchCalc [Non-public module]

    The whole module for batch sharpening has been significantly redesigned so that new functions can be built into it.
    The step generation procedure has been completely reworked. Now the grit of the wheels is also taken into account, proceeding from the coarsest to the finest. If grit is not specified (or is not a number), it is assumed to be the honing wheel that is placed at the end. 

    New unique functionality for grinding on wheels with different diameters has been added. It is a compensation layer that automatically calculates grinding angle corrections when moving from a smaller wheel to a larger one. There are two types of compensation, and using this feature brings unexpected grinding benefits...

    You can find more information in the same video: https://www.youtube.com/watch?v=h_qRUvSvcLQ

    Using and capabilities of BatchCalc module can be found in this video: https://www.youtube.com/watch?v=9qtyTKqQb1g

    Attention: For several different reasons, I have decided that these modules will be freely available only to contributors and donors. There is a lot of work, time and know-how behind the development. If in doubt, please compare what the public version of TormekCalc2 (even the oldest) offers compared to commercially available applications. If you have further questions, you can send me a private message or e-mail message (see FAQ sheet in TormekCalc2).


  • Materials

    Added Hitachi GIN-3 and GIN-5 steels to the material table.


Ideas for improvement are welcome as well as feedback. Please feel free to contact me if you need any further information.

Hint: If you have data in Knives or Tools sheet just select all uses rows between column C to AD (included), copy them to clipboard (Ctrl+C) and paste them as VALUES to new version of TormekCalc2.

Enjoy!

jvh



Attention!

Due file size and forum restrictions (maximum individual size is 256 KB) is TormekCalc2 version 2.1+ available only on external web storage.

Download HERE (WebShare.cz, click Download File and then Download slowly).

Current version 2.67
(TormekCalc2_Public_v267.zip, packed size 2 026 804 bytes, TormekCalc_Public_v267.xlsx, unpacked size 2 186 094 bytes + sample pictures in the Knives and Tools folders.)


14
That is my problem, because my manual is in German.  :(

Hello dusmif,

see links.

Manual: Instruction SVH-320 EN

Tormek's video: Tormek Planer Blade Attachment SVH-320
Highland Woodworking review: Tormek Planer Knife Jig SVH-320

jvh

15
Hello,

I would like to thank Wolfgang, Sébastien and Victor for next part of the Live Sharpening Class, it was excellent again.



Perhaps you are thinking, I do not have the diamond wheels which can grind flat bevels with the MBS-100 Multibase. Why should I bother to watch this video?

Good question. Here is a good answer. As an example, one of the frequently asked questions is about the dreaded "hollow grind". Near the beginning of this video is one of the best explanations of the amount of hollow grind left by a Tormek wheel I have ever seen. Using a 250mm diameter grinding wheel set to a 20º bevel and a 2mm thick blade, the deepest part of the hollow is .03mm, or roughly .001”. That is roughly one third of the thickness of a single sheet of copy paper. That is small enough that I do not worry about it for my chisels, plane blades and kitchen knives.

Most of the online classes have parts like this which apply to several areas. Don't sell yourself short by watching only those classes which you think only apply to you.

Ken

Hello Ken,

0.03 mm is really small, but it's only one part of a more complex problem. It is indicated in the video (ca. 4:45), but it is not explained exactly.

Wolfgang said: "Force, of cource, is a little bit aggresive, it will dig in little bit faster..."
This is because in the example shown, the apex angle is 20°, but the angle between the apex and the edge heel is 21.26°. Compared to flat grinding there is "unground" material on the edge heel (due to the rounding of the wheel), which does not allow the blade to be tilted below 21.26°, because it would not cut as the apex does not touch the material. This makes the cut more aggressive because the edge is directed more into the material, and this is IMHO the main thing that should be taken into account.
This also affects the subsequent re-sharpening on a flat stone, where the minimum angle 21.26° is also ground (if the apex and the edge heel are touching the stone).

This problem increases with blade thickness, sharper angle and smaller wheel diameter. It is usually negligible for knives, but may not be the case for tools...

jvh

P.S." The picture shows a thickness of 4 mm, but this is because the calculation is performed for symmetrical blades. The example shows a chisel grind, from which you get a "symmetrical" by multiplying the thickness by two.

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