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« on: January 14, 2020, 09:53:51 am »
Morning Folks (well it is in England anyway).
Despite the title, this is a serious question.
My trusty black friend, the SB250 has finally run out of diameter and has reached the stage where I have to remove the honing wheel for anything long. I've just had a frenzy of knife sharpening and that was the final nail in the proverbial coffin. it's still OK for gouges for turning because they're largely ground from up above in the elliptical jig and dont foul on the honing wheel. But as for anything else, particularly chefs knives, alas, too small. I think it was down to about 190 from memory so really has served me well and I think I bought it in 2015 so its pushing 5 years.
So I've done a round robin to see whats new because I have been a little distracted of late and not been on the tools anywhere near as much as I would have liked. All comes of that pesky distraction - having to work for a living. Boo. Hiss.
Whats popped out of my research is of course the advent of the "girls best friend" diamonds! They weren't really a thing last time I looked, now it seems, they really are.
Now I dont take the replacement of my SB250 lightly because it's been a versatile friend, primarily to my wood turning which has become the dominant form of my woodworking but also to the outlying fray of other edge tools I have need to sharpen. That includes all the usual suspects ie scissors, kitchen knives, plane irons and chisels and the odd set of secateurs (felco of course). So the replacement has to be every bit as "game" as it's redundant original.
They're also, a fair sized investment for a consumable so the value must be there.
I could of course simply replace the SB with another but that would be to betray the opportunity that innovation brings and that doesn't sit well with me.
So, I dont have the knowledge to make this decision on my own. I thought, who/where should I turn to for expert advice and guidance and of course, add to that, warmth, friendship and camaraderie.....and of course......I visited my local tool shop! No....stop it.....I came here. Didn't give it a seconds thought. I knew you guys would know the answer.
What I haven't done is trawl through umpteen posts on here to "mine" the answer and for that I apologise. But perhaps a good enough starting point to engage your very useful minds is to say that my current thinking is to opt for the 1200 grit very fine diamond wheel. My understanding is it's never going to need dressing (so that's one in the eye for the SB....no more need to worry about gouges furrowing the stone, requiring endless redressing with the truing tool). Allied to the last, it will never lose it's shape and therefore will remain geometrically accurate to the universal tool rest?
Those seem to me to be the fundamental differences between this medium and a friable one like the grey or black stones. in short, it never changes shape through the action of grinding. Is this absolutely 100% true for HSS turning gouges with, swept back wings and quite pointy tips like 3/8" bowl gouges? I ask this because those suckers really really really do grind quite the trench in the SB over a relatively short space of time. So not just the diamonds themselves (which I appreciate are about the hardest substance known to man) but the underlying wheel itself would have to phenomenally resistant to avoid this happening in the future. Are we certain this is the case? Do we have precedent from any wood turners that use HSS gouges in the elliptical grinding jig? This is definitely my greatest concern because I guess once, it's dented in any way, it's more or less useless since you cant dress or true it.
The other can be packaged in the general versatility category i.e. I do need this to perform widely once we're beyond high speed steel turning tools. So my next priority would be the global knives in my kitchen. I'm a reasonably accomplished chef and not only cook for my family on a daily basis but have wont to throw the odd dinner party where I will prepare more esoteric dishes of the moment. This is a chore if the knives are blunt and a joy if sharp. So this application is also really important. Add to that the usual cornucopia of other assorted tools including scissors and my needs are met.
The grit question is the next big one then. 9 times out of 10 I'll be coming to the Tormek with a known edge and therefore only require sharpening, not shaping. Is my thinking correct on this...…..the friable stones, when graded with the fine side of the stone grader, end up at 1000 grit right? The finest diamond stone is 1200 grit? So by buying the 1200 grit, I'm more or less just polishing the existing bevel?
The fundamental question for me, with respect to grit size is......will the 1200 be just a bit too fine and leave me grinding for ages if I dont set the angle accurately enough? is it forgiving enough to remove enough metal to still give an edge if I'm out by a degree or three?
I'm not big on fiddling and messing so I dont want to waste my life having to be uber careful setting the jigs all the time. On the other hand, I dont want a medium so course that the edge isn't fine enough. it's this balance between setup time and edge quality that's got me agonising between the 600 and the 1200 grit diamond stone choices. I'm pretty clear I dont want the course one though as that seems to be more in the "ding removal" camp.
So that's my dilemma folks, that's what I would humbly ask that you bring your excellent minds to bear on and help me make the decision. it boils down to this I think:
Should I replace the SB 250 with an SB250 or the 600 or the 1200 grit diamond stone? But more importantly, why?
Your input, as always, is appreciated.
All the best
Rob
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