Topics

[Best microbevel angle]

Best microbevel angle

Test procedure we used was to set a secondary bevel using a Japanese grit JIS #800 wheel (grain size ~ 15 microns), edge-leading;
then set a microbevel at a larger angle with an SJ Japanese grit JIS #4000 wheel (grain size ~ 3 microns), edge-trailing;
the edge was then deburred*, and sharpness tested with a BESS edge sharpness tester.

We tested microbevels at 0.2 degree interval from +0.2 degree to +1 degree (per side).
In other words, tested edge sharpness where the grit #4000 grinding angle was 0.2, 0.4, 0.6, 0.8 and 1 degree larger than the angle at which the grit #800 bevel was set.
We then repeated the test for the best scoring microbevel to rule out random factors, and tested that range at 0.1 degree interval.

The best edge sharpness gave microbevel of 0.5 degree larger, i.e. 1 degree inclusive.
It scored 50 BESS, which approximates to 0.5 micron edge apex width.

We needed these data ourselves for one of our sharpening methods, but given their practical importance, share here with the knife community.

Full test results follow.
Grit #800 set bevel was 15 degrees per side, i.e. 30 degrees inclusive.

Grit #4000 microbevel angle per side - BESS score on PT50B edge sharpness tester
15.2 - 200 BESS
15.4 - 70 BESS
15.5 - 50 BESS
15.6 - 65 BESS
15.7 - 90 BESS
15.8 - 100 BESS
16 - 105 BESS

-------------------------
Grinder - Tormek T8 (#800), and T7 (#4000).
Knife - SWIBO at 58 HRC from our rental pool.
Edge sharpness tester - PT50B Professional.
*Deburring was done by a single pass each side on a paperwheel with 0.25 micron diamond paste, set at the angle of the microbevel.

[grepper]

This thread continues the discussion started here http://forum.tormek.com/index.php?topic=2831.45 where grepper gave excellent summary on CBN wheels.

My wheel came from http://woodturnerswonders.com/collections/tormek-cbn-wheels/products/tormek-cbn-wheel-600-grit-10-x-2-inch-12mm-arbor

The original stone of the Tormek T7 has a diameter of 250 mm, the CBN wheel has a diameter of 254 mm. At first I thought it is just a little too big for the water trough, but it fits fine, though almost flash, and runs without brushing the trough.

With the width of 50.8 mm, the shaft protrudes just enough to tighten, as seen on the next photo.


The CBN wheel bore matches the Tormek's shaft, mounts square and runs perfectly round, and no lateral wobbling whatsoever.
Weighs 1920 g, i.e. less than half of the stone, runs effortlessly.

The grit is coarser than the stated 600, feels and grinds like ANSI/JIS #300.
They say the boron nitride crystals don't crash as easily as diamonds with use, so I wouldn't expect the grit to settle down much.

The CBN wheel looks fascinating on the Tormek, like a tamed milky way, and gives a clear bell ring when struck with a finger nail, reminiscent of Buddha temples.

Unfortunately, the CBN wheel of this make has grinding surface somewhat saddle-like, concaving from sides to the middle; not much, yet you can see it with a naked eye.
And this is really disappointing, as otherwise the wheel is so good.



On the few knives I have tried so far, the wheel middle part don't even reach the blade; as a result the heel and tip sections of the blade risk overgrinding.
Because of that you cannot really run it dry; you need a water flow to show points of contact with the wheel, and adjust sharpening routine to compensate for that.
Since I read that the boron nitride particles can cause pneumoconiosis when inhaled, I will not run it dry anyway.

As to the CBN grinding ability, I liked how fast it ground the ceramic and Bohler Vanadis-10 (the hardest blades I got at hand).
Better than anything else we use with Tormek.

Comrades, I need help of the collective genius, as I've run out of ideas.
Sharpening a knife on a rotating wheel concaves its middle, and I cannot avoid this no matter what I try.

In the photo below is a brand new knife.
Before sharpening its edge was straight and touched all the way down on a  flat surface.
After sharpening on Tormek, it got a concave in the middle, seen in the photo as a white line of light under the edge.



Having realised that this concaving happened before to other knives as well, I did a controlled sharpening.
Made sure the next knife edge is straight by leveling on a DMT plate.



Trued the stones.
Locked a collar on the knife jig to ensure the edge moves strictly perpendicular to the stone during sharpening (as described in the "Knife jig aid" thread).
Sharpened it on Tormek with our standard sequence of #220 - #1000 grinding wheels, making sure I slide it across the stone continuously, not spending too much time anywhere along the edge. And it got a concave in the middle, seen in the photo as a white line of light shining under the edge.



At least on my kitchen knives I see that repeated sharpening on Tormek deepened the concave.

Unwillingly, I arrive at a conclusion that middle concaving is intrinsic to sharpening knives on a wide rotating wheel  due to the middle part of the knife spending extra time on the wheel.
When we sharpen on bechstones, we minimise that by placing the knife diagonally rather than across the stone.
If the Tormek grindstone width was, let say, half of what it is now, this effect wouldn't be noticeable (but narrow wheel would be worse for chisels).

Can this be helped?

Jeff Farris wrote somewhere in this forum that the Truing Tool prototype didn't have as much play, but as users found the head too tight to move across, more play was added. I can imagine, that when Tormek later introduced the Japanese stone, it would be too costly for them to modify production line for TT-50, even if chipping was reported.

By now I've trued 6 stones (Japanese, SB, SG) using Ionut's approach, and the results are fabulous, minimal grooves and no edge chipping.
Below I detail my truing procedure, where I shamelessly use Ionut's ideas to reduce the Truing Tool play, and even wording, as why should I change a word in what had been said well enough.

- True on a stable non-vibrating base, e.g. for truing I move my Tormek to a different bench that is heavier and more stable than what I use for sharpening.

- Mark the shaft, the washer, and your grindwheels and always mount the stones aligning all these marks to compensate for manufacturing or wear imprecision that may result in non matching edges of your blade; so when you change the stone the grinding surface of the new mounted stone will match the other one in relation to the universal support. Doing so I don't end having to true the stones needlessly as I change them.
(Now and then I refresh the markings.)


- If the grindwheel  hasn't been used today, before truing let your Japanese stone run idle for about 30 min to soak water (SG or SB stone for 10 min).

- Locking down the truing tool on the Universal Support, press the Universal Support downwards over the left post with the adjusting wheel. Don't press left or right of that point. The Universal Support has a bit of play and the only reference point or surface that you can rely on is the adjusting wheel and the base in which the left post is being inserted. The Universal Support play translates on its horizontal bar into up to probably 2-3 degrees in the effective sharpening area. Because of that, if you apply pressure on the extremities you may start out of square from the beginning.
This step is stated in the Tormek Manual, but often overlooked.
Unlike shown in the manual, press with one finger only.


Remember to do the same each time you mount the Universal Support for sharpening.

- To minimise the TT-50 diamond head play, I used 2.5mm wide x 200mm long cable tie (a 150mm long may just suffice as well). You only need to tie it moderately, enough to back up the diamond housing to it's riding platform and to allow you to rotate the knobs.

(The ragged grindwheel edge you can see in this picture is from previous truing done before using the method I describe.)

- Do not rest your hands on the Universal Support or TT-50 while truing - only rotate the truing tool knobs with your fingers with no downwards pressure on them.

- Start from the side with the highest point on the stone. Turn the US adjusting wheel by 1/12 (half a digit) when adjusting the depth of truing.
Having finished the first run across the stone, lower the diamond tip by a quarter of the digit, and run in the opposite direction; you have to run in both directions because of the wear of the diamond tip by the end of the first run you finish somewhat higher.

- The manual suggests for the truing not going slower than 90 seconds, but with this modification I'd say spend at least  90 seconds, I usually spend 2 minutes to move across the stone.
While truing, do not pause and maintain the same speed.

- Lower the Universal Support on the stone to check they are parallel (remember to press over the left post with the adjusting wheel). I just take out the Universal Support with the TT-50 locked on it, and use another Universal Support for this so that I could resume truing if need be.

For declogging & cleaning Japanese stones I use the following (in order of preference):
- a diamond plate  in the Tormek Square Edge jig;
- Nagura stone;
- fine side of the Tormek grading stone, flat only, but never corners, and parallel to the wheel, not accross.

As the diamond plate I use the cheapest plates I could find on eBay; the one in the picture is 1mm thick  and cost me $5 delivered. Had to clamp it together with a plane iron on the top for rigidity.
#80 diamond plate for the #200 stone;
#400 diamond plate for the #800-1000 stone;
#1000 diamond plate for the #4000 stone (SJ).
Make sure the plate contacts the stone by its surface, not the end, and lightly press with fingertips.

The diamond plate is preferred because this method will keep the surface of the stone always parallel with the universal support.
A quote of Ionut's about the diamond plate: "In fact between sharpening when using finer stones I use this method to cleanup and flatten the grinding surface of the stone about 50 times until I will use the TT50 again to make sure the wheel is not out of round."


You will soon discover how much sharper your tools get.

This knife jig aid is not for every knife, but yet for the larger portion of knives, which profile is a normal sweeping curve, like most hunting and cook's knives, sheepsfoot and wharncliffe knives.

For this type of knives, the movement to keep the blade on the stone must be axial to the shaft of the knife jig.
Any shifting other than vertical results in uneven bevel.
I use a 1/2 inch shaft locking collar, locked at 12mm from the jig stop (the flat black plastic part), to ensure the jig slides on the Universal Support perpendicular to the stone, vertically rocking on its axis following the blade taper, and not shifting horizontally (or you may say not shifting laterally or forwards/backwards).

I have it on the jig at all times, and when I sharpen a blade of a different profile, e.g. curved etc, I unlock the collar and slide it away.

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.



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.

[Controlled-Angle Support for Paper Wheels]

2017 Update: We have started manufacturing a Controlled-Angle Support for Paper Wheels - please check our website knifeGrinders.com.au
And below is the story of how it all started over a year ago...

I thought you may find interesting my set-up for honing knives on paper wheels with controlled angle.
I used Tormek parts to bring Tormek precision to paper wheels.
Should I even explain importance of angle control?
As you finish sharpening, the angle the knife attacks the abrasive surface becomes very critical.
1º too steep and you'll be gouging the edge into the abrasive surface dulling the edge.
1º too shallow and you'll be honing on the side of the knife, not the edge, honing and honing to no effect.
A coated blade tosses another challenge to freehand sharpening, and angle control helps maintain clear demarcation along the edge.

I tried both 8" and 10" paper wheels, getting pretty similar result.
But as I sharpen knives on 10" Tormek, I get somewhat better results finishing on 10" paper wheel as better matching the profile of the T7 grindstone.
With both 8" and 10" wheel a single slow pass across the wheel on each side of the knife invariably delivers hair splitting edge, but as I switched from 8" to 10" I started getting hair popping sharpness, ie as the hair touches the edge, the severed part jumps away.


The wooden support heght is 20 cm.
I used parts are from the Tormek Bench Grinder Mounting Set BGM-100, but they are also sold individually as Horizontal Base for the Universal Support XB-100 and Univeral Support with Micro Adjust US-105.


Distance AB is 13cm for 10" paper wheel, and 8cm for 8" paper wheel.

I realised that even if the paper wheel is true out of the box, I have to true it for actual setup to ensure the wheel surface is parallel to the support.
The stone was trued with the Tormek Stone Grader and the Tool Rest as shown, first coarse side, then fine.


Clamped the knife in the Tormek Knife Jig SVM-45, and set the angle with AngleMaster (select 8" or 10" wheel size depending on what paper wheel you use).
Marker method works as well.
Angle is changed by elevating/lowering the support, fine tuned with the support micro-adjust wheel.


I use 0.25 micron diamond paste, but the white rouge that comes with the paper wheels, or green rouge work as well, except for the hardest steels. I selected the diamond paste because  it covers all range of knife steels, including harder high-end, and once rubbed into the wheel, you cannot change to a different compound on the same wheel because of contamination.
A single slow pass across the wheel on each side of the knife, with light pressure just enough to maintain continuous contact of the blade with the wheel.
Don't forget safety glasses.


Just one pass, and that Chef's knife whittles hair. The hair in he photo is my younger son's, he's blond - I mention this because blonds have thinnest hairs of all. Human hair cuticle is about 0.3 micron thick, and to whittle the hair, the edge must be thinner than that to get between the cuticles - this 0.25 micron paste really does the job.


With these two - Tormek and paper wheels, my multiyear search for getting a perfect sharp knife edge fast is over. Can't wish any better.

Tormek accessories used:
Bench Grinder Mounting Set (BGM-100)
AngleMaster (WM-200)
Tool Rest (SVD-100)
Knife Jig SVM-45

[second jig]

This is to solve annoying bevel asymmetry.
Jig #1 - up to 3mm thick knives.
Jig #2 - for 3-4mm thick knives.
Jig #3 - for 4-5mm thick knives.
Jig #4 - for 5-7mm thick knives.

For centering knives in the jig I use blades from a Feeler Gauge with 1cm wide blades as shims, as explained below.



Tormek Knife Jig SVM-45 has 1.1mm spacing from the centreline of the handle to the bottom of the knife clamp (the static part of the clamp) - thanking Jan for the exact figure.
Ideal for 2.2mm knives, but well acceptable for 2-3mm thick as well.
Knives thinner than 2.2mm will get the top bevel higher, whereas knives thicker than 2.2mm will get the base bevel higher; the further from the ideal 2.2mm thickness, the more noticeable is the bevels asymmetry.

For knives 2mm and thinner I use shims.
Measure thickness of the knife at the clamping spot, and divide by 2 - you get spacing to the centreline of the knife.
Difference between 1.1mm and halved blade thickness is filled with a shim.
Shim is placed on the bottom jaw (the static part of the clamp).

Example
Knife thickness 1.7mm, divided by 2 = 0.85mm.
1.1mm - 0.85mm = 0.25mm shim.

Obviously, for knives thicker than 2.2mm you cannot put shims in the standard SVM-45 - for them I use second jig where I ground away 0.5mm from the static clamp.
Spacing from the centreline of the handle to the bottom of this jig is 1.1mm + 0.5mm = 1.6mm
Ideal for 3.2mm knives, but well acceptable for 3-4mm thick as well.

Third jig with 1mm ground off the static clamp.
Spacing from the centreline of the handle to the bottom of this jig is 1.1mm + 1mm = 2.1mm
Ideal for 4.2mm knives, but well acceptable for 4-5mm thick as well.

Example
Knife thickness 3.9mm, divided by 2 = 1.95mm.
2.1mm - 1.95mm = 0.15mm shim.

Fourth jig is adapted Triton Long Knife Jig with 3mm ground off the static clamp. Triton jig has no offset.
Spacing from the centerline of the handle to the bottom of this jig is 3mm.
Ideal for knives 6mm thick at the spine, but can be used for 5-7mm thick as well.

Shim is always placed on the bottom/stationary jaw.

I sharpen daggers freehand, because they present a clamping problem with all guided sharpeners I know: Tormek, Lansky, DMT Aligner blade guide, and Razor-Edge guide. I don't have Wicked Edge, but their forum reads similar - the convex blade makes it difficult clamping a dagger.
Even when I thought I managed to fasten the blade in the jig, as I started sharpening, it crept out.

For a good minute I stared at the flat space by the ricasso... but dismissed the idea.   

Then I guessed that placing narrow shims on the sides of the dagger, narrower than the clamp depth, may extend contact area and improve the grip somehow...
Tormek knife jig depth is 12mm.
I used two 10mm wide feelers as shims.
And to my surprise it worked! The dagger sits in the jig like welded.

A few photos taken when bevelling the dagger.

Hi guys,

The Japanese Sun Tiger 800 grit grinding wheel has become available as of today from this German seller:
http://www.fine-tools.com/Tormek.html

Note that Japanese grit JIS #800 corresponds to US ANSI #600, and European FEPA #1200, i.e. is somewhat finer than 'finely' graded Tormek #1000.
The main advantage of using a dedicated 800 grit stone over graded Tormek standard SG is that you do not have to grade finer grit from the original 220 grit, and hard grading can untrue the wheel and get the corners out of square (the latter mostly frustrates knife sharpeners).

In 2009 Ionut had said all I could possibly say on this topic, so I just refer to his original post, a fragment of which I quote below:
http://forum.tormek.com/index.php?topic=897.0;nowap

"... the so called 1000 grit in my opinion is far from it. If you compare the scratch patterns between the Tormek wheel graded at 1000 and an actual 1000 stone there is a huge difference, and if you add a magnifier glass everything gets amplified. I've tried hardly to grade the stone to get closer results to the real 1000 I pressed the grader so hard I stalled the motor and the best thing I've done when pressing so hard and for long time was to untrue my wheel.
Using a 4000 Japanese stone the Tormek version SG250 for a secondary micro bevel improved a lot the amount of time the edge remained sharp, but I still was not where I wanted.
I got an aftermarket 800 Japanese stone and now I am tempted to change my occupation from "wooder" to "sharpener". All my bevels now are looking as they were before and the big difference is the edge stays as when I was using the manual version to sharpen my tools.

... with this settings all my search for getting always a perfect sharp edge VERY FAST, is over.
Ionut"

[RESULTS]

Hypothetical assumption voiced on this forum was that sharpening towards the tip should use a combination of lifting and forward pivoting to maintain the contact with the stone at the same line.
It seemed logical because the belly upward curvature positions the knife tip closer to the support as compared to the heel, and shorter distance to the support increases the grinding angle and narrows the bevel; pivoting forward was assumed to compensate for that.

Practical trials showed this assumption was wrong, moreover, thicker long knives with little belly curvature require pivoting the tip towards yourself/support, i.e. opposite to the hypothetical assumption.

I used 3 knives:
Thin & long knife - 19cm Global chef knife 1.8mm thick at the heel and tapered to 0.6mm at the tip.
Thick & short knife - 9cm Linder knife 4mm thick at the heel and tapered to 1mm at the tip.
Thick & long knife - 18cm custom camping knife 4mm thick at the heel and tapered to 1mm at the tip.




Knives were mounted in the jig as shown by Jan in
http://forum.tormek.com/index.php?topic=2562.15

This is a clever approach to avoid jig position effect on the bevel described in the Tormek Handbook p.53.

All knives were sharpened to included angle of 30 degrees by pulling across the stone WITHOUT pivoting, only lifting the handle of the knife as taper tells to maintain contact with the stone.
To help myself maintain the same blade position as the knife is pulled across the stone, I used Ken's idea of a laser to mark the initial line of contact, "LOC" in Elden's (kb0rvo) terms, as they discussed in http://forum.tormek.com/index.php?topic=2562.15

The same steps for all 3 knives:
- mark the bevel;
- set the 15 degree angle at the heel by manually rotating the wheel and checking the marking;
- sharpen from heel to the tip WITHOUT pivoting.







RESULTS

Thin & long chef knife - uniform bevel along the edge of 1.3mm.
Thick & short knife - uniform bevel along the edge of 2mm.
Thick & long camping knife - widening bevel, from 1.5mm at the heel to 1.8mm at the tip.







For these knives no pivoting was needed, even for the last knife the difference was practically negligible.

The only explanation I can think of is contrary effect of taper and upward curvature:
Because of the taper contact with the stone extends and bevel widens.
However, the belly upward curvature brings the tip towards the support, increasing the grinding angle and thus compensating for the taper.

Note that curvature of the thin & long chef, and thick & long camping knife used in the trial is comparable.
And note the bevel widening towards the tip of the thick long knife, though slightly (by 0.3mm).

Following the same logic, a thick and long knife with little upward curvature, sharpened without pivoting, will have even wider bevel to the tip. Sashimi knives and pig stickers are good examples of such knives.

And true, look at the bevel widening to the tip in the next picture, also sharpened without pivoting; now there is almost 1mm difference between the heel and the tip.


To produce a uniform bevel along the edge of this sashimi knife, I had to pivot the tip over 1 cm towards the support/myself.

CONCLUSION

Regular kitchen knives, as well as thicker but short knives do not require pivoting; lifting on the handle as taper tells is all you have to do.

Thick, long & narrow knives that are tapered towards the tip > 2mm, and have little upward curvature, require combination of lifting on the handle, and pivoting the tip towards yourself.
As a rough guide, you move the tip towards yourself about the same distance as the knife lifts over the edge of the stone, sort of translating the vertical movement into horizontal shift.

Knives with false edge require extra backward pivoting to increase grinding angle towards the tip (otherwise you'll grind it off).
With double edged knives and daggers, where you have to make two edges meet at the middle of the tip, as your grinding nears the tip, pivot the blade tip towards yourself , and stop grinding as the water flow reaches the very tip.

[Frontal Vertical Base]

2018 Update: We have started manufacturing a Frontal Vertical Base for honing and grinding away from the wheel - please check our website knifeGrinders.com.au
And below is the story of how it all started in 2016...

Being so grateful to this forum for heaps of helpful hints, I just want to pay back sharing my honing attachment.
I gave up on freehand stropping long ago, because no matter what technique I tried, I dulled the edge. I admit it is entirely operator error, but alas not everyone is born with freehand talent.

Thanks to two M12 x 120mm bolts, a piece of 35mm wood, and parts from the BGM-100 kit, I can now strop under a set angle.
4-6 slow passes across the wheel on alternate sides of the blade with very light pressure delivers hair splitting edge.
Pictures are self-explanatory.









Flipped to the right, accommodates cleavers thanks to farther distance to the stone compared to the standard support.

Recently started using the Long Knife Jig SVM-140, and noticed that bevel on one side gets always wider than on the other.
Trying to understand what's happening, having turned it over to the second side checked the angle again with the AngleMaster, and was surprised to see the angle is not the same.
The problem is with both kitchen knives and thicker hunting ones.
Now to obtain the same bevel on both sides, I have to adjust the angle every time I flip over the jig.

The only explanation I have is the way they manufacture the jig does not center the clamp right.
Have never had this issue with the regular Knife Jig SVM-45.

Has anyone had similar problem? My jig is of newer design (without locking screw on the stop).
Am thinking of grinding inner surface of one of the clamps to compensate for the asymmetry, but decided to check with you guys first.