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Reading your answers, I´m starting to be impatient...

In this moments, the Bess Tester PT50 is in Spain´s Customs 
Hopefully it doesn't cost me too much money.

Regards

Josu,

I have read numerous articles about the problems people experience with Spanish customs. Hopefully I am not misquoting but I read some 800-900 thousand parcels from the US and China (main imports from outside the EU) go unclaimed every year due to them getting lost in the system, overbearing bureaucracy, systems that don't work and people just giving up. To me it seems like a 'legalised' shake down to extract every cent due, even when the value of goods is under the duty free threshold.

If there was ever a reason to set up an EU distributor (outside of Spain) for BESS machines and consumables, this would be it.

I feel your pain.

Smurfs

Thanks Ken.

John, I'll know soon enough if I'm asked to fix it again You have a point though. I'd be interested to see how stable the edge is after some use as it was originally 38 degrees included. I used 30 degrees included as that is what Vadim recommends for ceramic knives.

[Step]

Hi all,

I have just completed my first ceramic knife repair and sharpening by following Vadim's procedure described on his web site. I'm pleased how it worked out so thought I'd share my experience and results.

The knife, which belongs to my sister-in-law, is about 8 years old so was showing signs of wear with a broken tip and chipped edge.



She claimed it was still quite sharp so out of curiosity I perfored a BESS test along the edge at the tip, middle and heel before I got started. I'm pleased I did as I recorded 1025, 1165 and 1085 BESS respectively so knew anything I did would be a great improvement 

Firstly I fixed the broken tip.



As I am not a skilled freehand sharpener I chose to undertake this repair on the side of a CBN wheel, edge-leading, using the Tormek SVX-150 scissor plate to provide better support and control. Initially I started the grind with a CBN #400 grit wheel but it was slow going so switched to a CBN #80 which surprisingly was not as aggressive as I expected - ceramic is harder than I realised!

Once the tip had taken shape I reverted back to the #400 to finish off the repair. All in all this repair took around 10 minutes.



Next I repaired the edge to remove the chips using the SVM-45 knife jig and a pivot collar to maintain the curved edge. This was done edge-trailing at 30 degrees per side using the CBN #80 wheel. It took around 10 alternating passes to remove the chips so the process wasn't too slow.

Next, the setting of the new edge at 15 degrees per side, was done edge-trailing with two alternating passes on a CBN #400 and finished off with two alternating passes on a CBN #1000 grit wheel.

The honing was likewise straightforward and followed Vadim's procedure using a progression of finer diamond compounds on slotted paper wheels, except I stopped at 2.5 micron as I had a balance issue with my finest 0.5/0.25 micron paper wheel. 

Here is the final result




Summary of BESS scores

Step	Heel	Middle	Tip
Dull blade	1025	1165	1085
Set Edge #400	960	760	915
Set Edge #1000	595	400	520
Hone 10 micron	325	210	220
Hone 5 micron	165	105	175
Hone 2.5 micron	95	85	80
Hone 0.5/0.25 micron	-	-	-

It's clear from the variations in BESS readings along the edge that I still have work to do on my technique so will buy a knife to practice so more, nevertheless there was convergence so got there in the end!

[In both cases, the distance from the usb to the center of the stone must be the same.]

Hi Ton,

I'd be grateful if you would clarify which angle you are referring to here...

I want to recall the following comment

snip...
With this setting, the distance from the USB to the center of the stone should be the same in both cases to obtain the same grinding angle.
...

Have you tested whether "grinding with the wheel rotation is different to grinding into the wheel"?
In both cases, the distance from the usb to the center of the stone must be the same.

If it is the edge angle then surely the distance from the USB to the center of the stone is immaterial as the relative projection and support bar height distances in each mounting position will ensure the same edge angle is maintained in each case.

That said, I would expect the heel and chord angles to differ where the distance from the usb to the center of the stone are not the same at each mounting position, so is this what you are referring to?
Edit: Struck out as the heel and chord angles will differ only where blade thicknesses differ. Should have thought this through before posting!

Thanks, Andrew

For example, switching over to the honing wheel, which will require me to re-set the USB on that side and try to achieve the same angle.

Or even jumping to another machine...I noticed that wootz has paper wheels in his collection.  I happen to have 8-inch diameter paper wheels (which I have never used) and a spare bench grinder.  I was thinking about setting up a USB mount on that system.

The idea would be to be able to achieve the same grinding (or honing) angle on the second wheel.  I may be chasing diminishing returns, but I don't know that yet.  So many ideas, so little time.

Hi arnman / Steve

I don't know if you are aware but jvh has developed an Excel spreadsheet which does what you want and more and is available via this post https://forum.tormek.com/index.php?topic=3919.msg26587#msg26587. No need to reinvent the wheel (no pun intended)

Even if you are developing your own solution it provides an excellent reference point to check your own results.

Thanks for the clarification Jan.

I don't have a SE-76 but do have the SE-77 so can now determine the 'right' angle. That said if you have already done the calculation and can share it that will save me and others the effort of doing so

Jan,

I'm just curious about the annotated angle of 91.5⁰ in your sketch as I would have just assumed it to be 90.0⁰.
Did you derive this angle mathematically or did you measure it using an AngleCube or such like?

Thanks, Andrew

["muddying the waters further"]

...
calculating the angle of the chord, not the edge angle. Could this be the source of much of the confusion evident in this thread, or am I muddying the waters further?

You are right AND "muddying the waters further"

Or may be not...
So the enhancements that wootz has made to his software is in effect calculating the chord angle using the target grind angle, which means the angle at the edge is more acute. That being the case the finer edge angle goes some way to explaining how wootz is achieving lower BESS scores with the software tweaks, improvements I might add are probably at the expense of edge retention.
...more muddy water?

Dutchman, please would you confirm if I am correct in thinking that the objective of the formula adjustment is to shift the tangent from the bevel edge to the blade center line so that the target angle occurs at the mid-point of the hollow grind, not at the edge?

If so (and if I'm not mistaken) the tangent at the blade mid-point runs parallel to the chord so I guess what your formula is effectively doing is calculating the angle of the chord, not the edge angle. Could this be the source of much of the confusion evident in this thread, or am I muddying the waters further?

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.

Hi Vadim,

Could the angle issue simply be due to the reduction in the jig projection length during grinding, as illustrated in the schema diagram in your initial post? If it is would it not be better to recheck the projection after each grinding step in your sharpening procedure, and if necessary return to the initial projection length using the adjustable stop? Perhaps such a tweak is all that is needed to ensure the target edge angle is always maintained.

Or may be I've missed something and it is not as straightforward as I think 

Andrew

PaGorg, that is really a clever and cost effective solution. Thanks for sharing.

My guess is it will be strong enough but if you find it is not you have the option of mounting the SHF12 Flange Mounts to a 107mmx50mm backing plate and then mount the XB-100 to that plate using the existing 4 holes (or perhaps that's going over the top ).

Apologies for resurrecting an old thread but I found this discussion on uneven bevels extremely informative and I wish to make an observation which I think is relevant which doesn't seem to have been mentioned (although it has possibly been made in another thread I've yet to read  ).

What prompted me was the following post from texaspro...

<snip..>. I already know that my 2.5mm wide blade (Benchmade Mini Griptillian) in the SVM-45 is not the same on both sides. I am trying to figure out why and how to fix it. Unfortunately putting shims in the jig or grinding the jig down as Wootz suggests, is not applicable on 2.5mm wide blades (his method is more for under 2mm or over 3mm, from what I understand).

To be perfectly clear, the problem I am having is an uneven bevel (one side is higher than the other). No matter what I try, the angle is always different on one side as opposed to the other, causing the bevel to be higher on one side.

I can think of two scenarios where uneven bevels could occur with a perfectly centered blade, i.e 2.5mm in thickness. The first would be an uneven number of grinding passes on each side of the blade, and/or the uneven application of pressure during each pass.

It may seem obvious, but having a perfectly centered blade will not guarantee a symmetrical bevel. It also requires that refined human touch!

The problem for me is that shipping costs and customs taxes are higher than price of the product (I´m in Europe).

Josu, another option.

As you live in Europe you could buy THK compound via the home_tool store on ebay. Here's the link https://www.ebay.co.uk/str/thkdiamondtools3.

Shipping is free from Hong Kong and to get started you could buy the 13 bottle bundle containing a wide range of grits, some of which you may not need, so I'd suggest you specify the bottles of each grit you want during checkout. Total cost £43.00. I've ordered from them previously and did not have to pay import duty or VAT (too low value I guess).

Hi Vadim,

I observed similar behaviour when I was grinding the life out of my practice chisel. This was especially noticeable when I changed from a more to less acute edge angle as more of the edge was ground away to arrive at a flat bevel. I found that in the process of grinding the jig projection length was reduced by up to 1 to 2mm, throwing out the desired bevel angle by a similar number of degrees.

In my research I too measured the thickness of the bevel at the heel and modified my projection calculation so that the correct angle was achieved at the moment of burr creation. As a sharpening novice it is pleasing to read someone else with vastly more experience has arrived at the same point with an almost identical solution.

Cheers, Andrew