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#1
Knife Sharpening / Re: SG-250 Bond Strength - Too...
Last post by Thy Will Be Done - Today at 02:42:18 PMTo be clear, the wheel is grinding virtually always. It's more a matter of how quickly that is important to me considering this is a low-RPM grinder which will never win a speed contest against something like a belt grinder.
I don't believe that many people realize this but a well conditioned surface on a 220 grit stone should literally cut tracks in the knife you are grinding. The only time I can achieve this is using the diamond grading tool. I just re-cut the surface again yesterday and it's back to cutting tracks again.
What does that mean exactly? It means that placing a knife on the moving wheel and not moving the knife laterally will cut deep grooves in the edge immediately which make it difficult to even move the knife laterally again once they are there in the edge. I mean immediately, as in under a second on the wheel.
Again, most people are using these wheels in a glazed and/or loaded state which significantly reduces cutting speed and cutting depth in the steel on a single pass. In general, a bond strength which is too weak is much less of a problem than one that is too strong. Sure, it will waste more abrasive though.
The problem is that the only good way to get the wheel back to cutting as a true 220 grit stone is perhaps a separate issue but the two are indeed linked and many modern steels and edge geometries seem to be a poor choice for this wheel, IMO.
The problem is many knives are ultimately ground very thick and obtuse at the edge, which necessitated lowering the edge angle dramatically, often 2-3x lower than they come factory. This also grows the width of the edge bevel dramatically which is indeed part of the problem as you said.
As the edge bevel width grows, the contact pressures on the wheel fall off dramatically and therefore does not reach the critical pressure of which new abrasive grains will be uncovered by shearing off worn abrasives. So the stone simply loads and glazes rapidly and needs to be recut with the diamonds again.
I don't believe that many people realize this but a well conditioned surface on a 220 grit stone should literally cut tracks in the knife you are grinding. The only time I can achieve this is using the diamond grading tool. I just re-cut the surface again yesterday and it's back to cutting tracks again.
What does that mean exactly? It means that placing a knife on the moving wheel and not moving the knife laterally will cut deep grooves in the edge immediately which make it difficult to even move the knife laterally again once they are there in the edge. I mean immediately, as in under a second on the wheel.
Again, most people are using these wheels in a glazed and/or loaded state which significantly reduces cutting speed and cutting depth in the steel on a single pass. In general, a bond strength which is too weak is much less of a problem than one that is too strong. Sure, it will waste more abrasive though.
The problem is that the only good way to get the wheel back to cutting as a true 220 grit stone is perhaps a separate issue but the two are indeed linked and many modern steels and edge geometries seem to be a poor choice for this wheel, IMO.
The problem is many knives are ultimately ground very thick and obtuse at the edge, which necessitated lowering the edge angle dramatically, often 2-3x lower than they come factory. This also grows the width of the edge bevel dramatically which is indeed part of the problem as you said.
As the edge bevel width grows, the contact pressures on the wheel fall off dramatically and therefore does not reach the critical pressure of which new abrasive grains will be uncovered by shearing off worn abrasives. So the stone simply loads and glazes rapidly and needs to be recut with the diamonds again.
#2
Knife Sharpening / Re: SG-250 Bond Strength - Too...
Last post by Royale - Today at 01:44:27 AMFor context, I sharpen knives and scissors commercially, been doing it for about... 1.5 years, and now on my second SG-250 (already down to 230mm/9" 😭)
I've used my SG-250 to reprofile many cheap-ass soft steel knives, many exotic Japanese steels, all the way up to ZDP-189.
I used to grade my SG-250 coarse quite frequently for it to cut a lot faster? Then I realised very quickly that it doesn't wear down evenly, and any slight change in the diameter (like grading again) would start to create another facet on the bevel (usually at heights 3mm or wider)
I used to think my stone was always glazed, and wasn't operating efficiently. Then I realised that when grinding any secondary bevel height more than 3mm, the progress slows to a crawl (possibly because all downward pressure is now more evenly distributed over a wider area)
In summation, before you start discarding serviceable items, why not try grinding a narrower angle (12-15 DPS) on your harder steel knives to get a better feel of how the SG-250 cuts? I learnt the hard way that the lack of significant tactile feedback during grinding doesn't mean the grindstone wasn't working 🤦🏻�♂️
I've used my SG-250 to reprofile many cheap-ass soft steel knives, many exotic Japanese steels, all the way up to ZDP-189.
I used to grade my SG-250 coarse quite frequently for it to cut a lot faster? Then I realised very quickly that it doesn't wear down evenly, and any slight change in the diameter (like grading again) would start to create another facet on the bevel (usually at heights 3mm or wider)
I used to think my stone was always glazed, and wasn't operating efficiently. Then I realised that when grinding any secondary bevel height more than 3mm, the progress slows to a crawl (possibly because all downward pressure is now more evenly distributed over a wider area)
In summation, before you start discarding serviceable items, why not try grinding a narrower angle (12-15 DPS) on your harder steel knives to get a better feel of how the SG-250 cuts? I learnt the hard way that the lack of significant tactile feedback during grinding doesn't mean the grindstone wasn't working 🤦🏻�♂️
#3
Knife Sharpening / SG-250 - Oil Better Suited Tha...
Last post by Thy Will Be Done - Today at 12:51:44 AMAfter extensive use of this stone with water trough, I'm beginning to think that this stone is much more suited to using something like a thick mineral oil on the cutting surface. That may not even be thick enough because ideally it would not be something that would simply soak into the stone at all. I suppose that is the issue with oil after all and wondering if there is anything similar one could use to both act as a coolant and a friction reducer to limit wear to abrasive much more than water and also keep the edge from losing temper.
#4
Knife Sharpening / SG-250 Bond Strength - Too Str...
Last post by Thy Will Be Done - Today at 12:46:01 AMI've been using this single stone for long enough to have used half its life, it's down to 9" from 10" diameter so I feel well qualified to say this. It glazes too rapidly for anything other than very narrow bevels and/or very soft/simple carbon steels. It is very well suited for that but anything like high alloy or wider bevels and it stalls pretty quickly. I have been using the diamond truing bit to both keep flat and also to recut the surface as I find that the silicon carbide 'stone' they provide will simply not make the wheel cut aggressively enough to use as a grinder doing more than a simple touchup. Changing geometry takes far longer than it should/could in many cases.
So, all that said I'm finally going for another wheel or I'm just going to get rid of everything I have that isn't simple carbon steel. I'm wondering if the SB-250 is a similar proposition in terms of bond strength. I know silicon carbide can be more friable aka crumbles more easily to renew cutting ability. That said, I don't believe the black carbide is much more friable than the aluminum oxide used in the SG-250. So, I'm wondering how well it really works on harder to grind steels or will it glaze similarly? Which will still mean frequent trips to the diamond bit to recut the surface all too often to keep cutting aggression high enough to work at a reasonable pace without having to press excessively hard on the wheel, which I find is not practical as it causes muscle/body issues for me.
So, all that said I'm finally going for another wheel or I'm just going to get rid of everything I have that isn't simple carbon steel. I'm wondering if the SB-250 is a similar proposition in terms of bond strength. I know silicon carbide can be more friable aka crumbles more easily to renew cutting ability. That said, I don't believe the black carbide is much more friable than the aluminum oxide used in the SG-250. So, I'm wondering how well it really works on harder to grind steels or will it glaze similarly? Which will still mean frequent trips to the diamond bit to recut the surface all too often to keep cutting aggression high enough to work at a reasonable pace without having to press excessively hard on the wheel, which I find is not practical as it causes muscle/body issues for me.
#5
General Tormek Questions / Re: Microscope to check burr r...
Last post by RickKrung - Yesterday at 05:00:26 PMQuote from: John_B on May 14, 2026, 09:15:16 PMHere is an interesting video on the family of inexpensive Chinese microscopes. I think he unfairly compares them to a digital camera system and lens that costs several thousand dollars. I own a DSLR with Macro lens and lighting that I can tether to my computer using Adobe software. It works great but it is not practical for a person sharpening multiple knives or trying to run a small business. If you make your money as a content creator it may be a different story.
I like to use a Bausch & Lomb loupe for edge inspection. Cutting a thermal receipt and feeling for resistance changes gives me a pretty good indication if I got the burr removed.
https://www.youtube.com/watch?v=_K8CtSgXREk
That is an interesting video. I'd be interested in hearing why you think it was an unfair comparison. I also own and use a DSLR/macro lens/lighting/tethering/focus stacking in post-processing tools. I agree it is not practical for someone doing "production" sharpening in real time, however, it could be quite useful for that same person examining edges/burrs during a process of figuring out effective deburring methods that would then get up into practice for the production sharpening process. Even, so, I do not anticipate doing this, mainly because I have an adequate alternative, the Kingmas 60X hand microsope. I also think the video reasonably and accurate demonstrates that the cheap USB cameras really do not deliver on their magnification claims.
As mentioned in a prior post (above), way back, I explored high-end ($1000+) USB cameras that would do in-camera focus stacking, but still found them too fiddly and not worth it compared to the 60x hand microscope. I also think the video acknowledges that the cheap USB cameras can be used, up to a point, to examine edges, but the much cheaper hand loupes are a more reasonable method.
#6
Knife Sharpening / Re: Small Knife Holder - Sharp...
Last post by kwakster - Yesterday at 02:05:15 PM #7
General Tormek Questions / Re: Microscope to check burr r...
Last post by John Hancock Sr - Yesterday at 09:51:06 AMI do not check visually. I use the fingernail method which I find more than adequate. Then I use the paper test for a final check.
#8
Knife Sharpening / Re: Small Knife Holder - Sharp...
Last post by John Hancock Sr - Yesterday at 09:48:55 AMI do my pocket knives by hand. It takes practice but I get really good results.
#9
Knife Sharpening / Re: Small Knife Holder - Sharp...
Last post by Thy Will Be Done - May 14, 2026, 09:57:05 PMI should clarify, meaning large daggers, roughly 6-10" blades.
#10
General Tormek Questions / Re: Microscope to check burr r...
Last post by John_B - May 14, 2026, 09:15:16 PMHere is an interesting video on the family of inexpensive Chinese microscopes. I think he unfairly compares them to a digital camera system and lens that costs several thousand dollars. I own a DSLR with Macro lens and lighting that I can tether to my computer using Adobe software. It works great but it is not practical for a person sharpening multiple knives or trying to run a small business. If you make your money as a content creator it may be a different story.
I like to use a Bausch & Lomb loupe for edge inspection. Cutting a thermal receipt and feeling for resistance changes gives me a pretty good indication if I got the burr removed.
https://www.youtube.com/watch?v=_K8CtSgXREk
I like to use a Bausch & Lomb loupe for edge inspection. Cutting a thermal receipt and feeling for resistance changes gives me a pretty good indication if I got the burr removed.
https://www.youtube.com/watch?v=_K8CtSgXREk