What Constitutes "Light Pressure" for the new Diamond Wheels?

[RickKrung]

I've read and heard that "light pressure" should be used with the new diamond wheels and to "let the diamonds do the work". 

Well, I am wondering just what does that mean "light pressure".  That is very qualitative, as what is light pressure to one may be heavy pressure to another.

Can "light pressure" be characterized in some standardized manner, or quantitatively, such that every user can correctly interpret it and use the appropriate pressure on the wheels.  Does it constitute just the pressure of the weight of the jig and tool being sharpened?  Just a light touch with a finger or two, or a very light "lift" for tools that do not contact the wheel by their own weight? 

My knife edge sharpening testing instrument (Edge On Up's PT50#)(http://www.edgeonup.com/index.html)  measures in grams of force required to sever a standardized media and sharpness is rated according to an accepted standard (BESS scale of sharpness)(http://www.edgeonup.com/eou_new_2016_008.htm).  (My PT50 happens to the the "A" model which measures in 1 gram increments.  The others are 5 and 20 grams.)

I wonder if grams of force could be a standard way to characterize the necessary pressure for the diamond wheels. 

I wonder if the PT50A could be rigged in such a way as to measure the force (grams) applied by just a tool/jig resting on it, and then with a finger of pressure, etc.?

I am asking sincerely, as I am spending a bunch of money on the wheels and sure as heck do not want to abuse them and dull them prematurely. 

Rick

[Grizz]

since I use the SJ-250 a lot, I learned what light pressure is. just barely more than the weight of the knife being sharpened. I just tried your theory on a PT-50-A. The weight of the SVM-45 placed on the DCB 10 base and holding the jig with the forefinger in front of where it would rest on a USB bar, the weight should be around 175g.
press lightly until you reach about 250-260g. this would be my interpretation of light pressure.

[Grizz]

just tried without the jig, just used my finger on top of the dcb-10 base, seems like anywhere from 50-75g is about right.

[Ken S]

Rick,

You are asking a serious and timely question. The Edge on Up PT 50 uses a high tech postal type scale, especially your model, the top of the line PT 50, with its one milligram accuracy. While an ordinary postal scale should be adequate for this task, your PT 50A should do the job extremely well.

Steve Bottorff uses a postal scale to teach proper grinding pressure when sharpening knives freehand with the Tormek.

I just finished reading the new online edition of the handbook ("hot off the press"). Unfortunately I found no reference to grinding pressure beyond "very light" in the latest handbook. The handbook is a fine reference for a Tormek using the original SG grinding wheel. However, one has to read very carefully to learn how to use any grinding wheel beyond the SG. My computer skills are not advanced enough to know if it is possible to highlight words and passages on the uploaded version. If this highlighting is possible, anyone using any grinding wheel beyond the original SG should do it. The handbook was essentially written for the SuperGrind with the SG-250. While basic information about new jigs and accessories has been added over the years, the technique portions of the handbook have not changed.

Someone like you, an experienced machinist and sharpener, would know which parts of the handbook to ignore when using diamond wheels (or the blackstone). I am concerned for beginners.

Ken

[Grizz]

Ken, I think you are very right. we all need to comply with what Marie said in this statement in the following.
https://forum.tormek.com/index.php?topic=3622.0

[RickKrung]

I am not at all satisfied so far.  I'm not sure the PT50 scales are the right instrument for measuring in this case, but it is what I have that measures over the range we are talking about. 

I just ran some trials with four knives, 1) a piece of junk cheapo, very light & thin (108g), 2) a modest quality, heavier one (175g), 3) a cleaver (230g) and a long heavy one (292g).  That is a range of almost 300% on the weight of the knife.


Combining each knife with the SVM-45, the dead weights were: 435, 491, 551 and 616g. 

But dead weight of the knife and jig combination is not what the grinding wheel sees.  That combo is set at an angle, on the USB.  I measured the weight on the wheel of those four combinations (at about 45º), making 10 measurements each and averaging them.  1) 231, 2) 260, 3) 286 and 4) 354g.  That is range of over 100g just in the resting weight of the knife/jig combination. 


Adding a finger can add 50-100g and adding both hands, one to grip the jig/USB and the other to grip the knife can add even more, but it can also reduce the weight.  Given the range of weights of the combos, some level of lightly pressing down for small, lightweight knives is likely required, where lifting lightly might be needed for heavier knives. 

But therein is the question.  What is lightly pressing or lifting? 

I think with all the development and testing that Tormek has to have done to bring the diamond wheels to market, you would think they know more about how much pressure is appropriate in more definitive terms than "low pressure" or "very low pressure", to quote Marie in two remarks the same paragraph in the linked message Grizz posted.  (BTW, I get an empty PDF screen when I click on the Tormek spec sheet link, so I can't look to see if there is any info provided there.  I suspect not, otherwise someone would have mentioned it.)

I am left wanting.

Rick

[BobD]

These are some of the tools I use to measure pressure and sometimes consistency while sharpening. I also use bands in various circumstances to maintain a preset pressure against a device. The push and pull springs allow measuring in both grams of force and Newtons and with increments of 5 grams or .5 N. They are available in much higher resistances as well. They can be used with the blade while in free hand sharpening and through use of jigs. They can be used not only to preset a desired amount but held during the process to confirm consistent pressure

[RickKrung]

Very interesting, BobD.  Welcome to the forum. 

Your photos appear to show the knife resting on the top of a T8 while you are making some measurements with your devices.  I am not clear on how you use them to measure pressure during use on the grinding wheel.  Also, what are the devices and where can they be had? 

Given that you are able to measure pressure during grinding, what amount of pressure are you striving for and on what grinding wheels? 

Rick

[wootz]

How about by nail bed capillaries of your fingers on the blade?
Stone wheel - 1/5 to 1/4 along the nail edge turns white;
CBN/Diamond wheel - just the rim along the nail edge turns white;
Honing - stays pink.

With CBN wheel I press enough to maintain firm contact of the blade with the wheel; if you press the same "very light" as when you hone on the leather wheel your edge apex will play on the grit because in edge-leading grinding without enough pressure the wheel will push your blade up.
Actually, after years of grinding on CBN wheels, when I have to grind on a stone wheel I do not press hard anymore, I change to a coarser grit or refresh the grains with a diamond plate or grading stone.
We resort to pressing the blade harder onto the stone wheel as it gets clogged, not an issue with CBN/Diamond.

Pressing hard is bad for the forming edge apex. By pressing hard you "apex" the edge quicker but it won't be that sharp as could be.
Mind that we apply macro-forces to the submicron band of steel at the edge of your blade, being gentle pays back.

[cbwx34]

With regular diamond stones, I have the philosophy... think light, then go lighter.  Given that Tormek is putting very low in bold... I would translate it to... just enough pressure to make contact.  For most knives, this should translate to just the weight of the knife/jig... for something heavy, you might even have to lift up a bit.

The few times I've put the diamond wheel on the T-4... I found it takes very little pressure for it to cut well.  I would translate it to what I just said... no more than needed to make contact.... and essentially no "extra" downward force beyond the weight of the knife/jig.

Tormek recently posted an English version of the instruction video for the T-2, but all they say for pressure is... use approximately the same amount you would use to cut something.  They probably shouldn't be quite so vague... especially when it comes to diamond wheels.

I think you'll find it will be easier to address this, when you actually have the wheels... vs. theorizing what force should be used, and/or trying to use a scale to quantify it.  I would just go with no more than what the knife/jig produces (assuming a regular knife)... and while practicing always think "lighter".  (It's what I constantly remind myself of on regular diamond stones).

[Ken S]

Interesting thoughts.

I have become a convert to light grinding pressure. I suspect the heavy touch technique goes back to a marketing strategy to show that the Tormek did not need to be slow.

My plan is to assemble my dozen or so 3/4" sharpening chisels. (see the Tips and Techniques topic pinned as the first topic.) Among them I have two or three which are still in the plastic packaging. I will start with them, using the flat side abrasive to flatten and polish the backs. I will flatten and polish the full length, trying to use all of the side abrasive. This will have the side benefit of breaking in my wheels.

Just like learning to use the TT-50 truing tool, I will begin with very light cuts, in this case, grinding pressure. After several chisel backs, the three sides of the three wheels should have stabilized and I will have started to get a feel for the diamond wheels.

Then on to working on the bevels with "the regular" part of the wheels. Same benefits: the grit made stable and a better feel for the wheels.

I am a true believer in the benefits of learning and practice tools, especially chisels. I can sense you knife people protesting about wasting your time using chisels. In this case, I believe the broader ground area of the chisels will accomplish the break in more efficiently.

Whatever methods we use, I hope we will keep some notes and share our work on the forum.

Ken

ps I will be using the recommended Anti Corrosion Compound.

[Ken S]

With regular diamond stones, I have the philosophy... think light, then go lighter.  Given that Tormek is putting very low in bold... I would translate it to... just enough pressure to make contact.  For most knives, this should translate to just the weight of the knife/jig... for something heavy, you might even have to lift up a bit.

The few times I've put the diamond wheel on the T-4... I found it takes very little pressure for it to cut well.  I would translate it to what I just said... no more than needed to make contact.... and essentially no "extra" downward force beyond the weight of the knife/jig.

Tormek recently posted an English version of the instruction video for the T-2, but all they say for pressure is... use approximately the same amount you would use to cut something.  They probably shouldn't be quite so vague... especially when it comes to diamond wheels.

I think you'll find it will be easier to address this, when you actually have the wheels... vs. theorizing what force should be used, and/or trying to use a scale to quantify it.  I would just go with no more than what the knife/jig produces (assuming a regular knife)... and while practicing always think "lighter".  (It's what I constantly remind myself of on regular diamond stones).

Excellent thoughts, CB. I agree totally. (Please do not tell anyone.)

With the T2 instructions, we have to remember that the target audience is chefs, not sharpeners.

[RickKrung]

Thank you, Wootz, CB and Ken.  That gives me something to work with on several levels.  I agree that it will make better sense once the wheels are here and I can work with them and there is no need or benefit to theorizing or stressing about how many grams.  It will be interesting to see how the fingernail bed method works. 

Rick