How much pressure when sharpening?
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- This topic has 7 replies, 6 voices, and was last updated 7 years ago by Larry Geib.
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I’m seeking some clarification here–not necessarily because I’m having difficulty sharpening any tools, but because I see variant opinions on the matter and am not sure which is correct. Then again, as sharp as I think my tools are, I don’t feel like I consistently get a noticeable burr on the edge so maybe I’m not quite doing it right?
There are plenty of diamond stone discussion threads throughout here as well as concerns that the stones are wearing out too fast or what have you. I’ve read comments that there really shouldn’t be much pressure applied when sharpening however in recently re-watching one of Paul’s plane iron sharpening videos, I noticed that he used quite a bit of downward pressure while sharpening–going so far as to explain how his grip on the iron while sharpening enabled him to really put a lot of force on the iron while sharpening–which led me to conclude that plenty of downward force is not only necessary, but it also shouldn’t be the main cause of diamond stones getting worn out (if Paul has been using his for years and using that level of force when sharpening then there must be something else causing people to think their stones are worn out).
On the other hand, when watching Joseph sharpen a gouge, it looked like he barely applied much pressure at all and that it was more about rolling the full curvature of the gouge across the stones to ensure that the entire edge gets sharpened. But again, it didn’t look like he was using much pressure.
So what does everyone say here? Is there an authoritative, definitive answer on the right technique? Should the amount of pressure vary depending on what tool (plane iron, chisel, gouge) is being sharpened? Or should one be consistent across sharpenings, regardless of tool/blade?
Check out the 6 minute mark here when Paul discusses the grip for holding the iron for sharpening. “It’s very difficult to get the kind of pressure you want to abrade this steel…”
https://woodworkingmasterclasses.com/2016/11/bench-plane-sharpening-setting/So are we being overly concerned that we are wearing out our diamond plates when that might actually mean we inadvertently use incorrect sharpening techniques resulting in inferior results?
8 April 2017 at 2:44 pm #310944I think, the posture is about optimizing body strength, not maximizing it. With the wrong technique, you need more effort to get the same pressure. Anyway, there is a minimal pressure required to start the abrasion at all, and if you stick to that, you will get exactly the same sharpness as with maximum pressure, it only takes much longer. So, basically do it the way that suits you best. And rest assured: good diamond plates will last longer than bad ones.
Dieter
I’ve seen my fair share of videos on sharpening by experts like Paul and others, and no one has ever suggested I should bring massive force to bear when sharpening.
My impression of Paul’s comment referenced by the OP was that one’s choice of posture and grip on the blade when sharpening freehand were important because of their relationship to a successful result. I think the OP is mis-interpreting what Paul said. As noted by the OP, Paul said, ““It’s very difficult to get the kind of pressure you want to abrade this steel” — difficult to get the kind of pressure you want, not difficult to get the amount of pressure you want.
Controlled pressure, consistent pressure, properly directed pressure, not millions of tons of crushing force.
Just my 2 cents
- This reply was modified 7 years ago by Edmund.
No–I think I’m being mis-interpreted. I don’t mean to suggest I want to press down as hard as I can. What I am getting at is that I have read comments within this board that would suggest barely pressing down at all for fear of damaging the surface of the diamond plate whereas in Paul’s sharpening video above, it is clear (not just from his comments but also from looking at his hands while he sharpens–he’s not “white knuckled” but clearly pressing down with a good bit of force) that there is a fair amount of pressure applied to the iron when sharpening.
To be clear, I don’t believe I suggested/said “massive amount of force” but that appears to be how my question was interpreted. It is to seek clarification–perhaps comfort–that there is no reason to fear damaging your diamond stones by applying pressure when sharpening correctly.
8 April 2017 at 8:40 pm #310950I don’t think pressure is a factor . CONTROLLED pressure is necessary. A light pressure takes more strokes a heavy pressure takes less strikes ,
It’s what ever you can control. And the stones wear,or smooth whatever you call it at a given rate. When they quit giving the result you want then you need to decide wheather to replace them or not. They are not an end all but are a consumeable. ,they wear out
The more you do with them the more they wear.
They do stay flat, more so than rock stones,but they still wear out eventually.
I just sharpen on them put them back til needed then haul them out again,if they get something built up on them I clean them otherwise spray em use them and wipe them dry and get back to cutting wood
Mine are two years old , smoother in the middle by a little and still raise a burr .thats what they need to do for me.
My pressure is heavier than my daughter in laws sharpening but both of us raise the burr.Ah — thanks for the clarification, David B. In that case, I apologize for my mis-interpretation!
As far as pressure ruining diamond stones, in the short term at least, I’d say anything is possible if we are unfortunate enough to reach the wrong inflection point of ridiculous force / poorly-manufactured stones, but if we agree on reasonable sharpening technique and quality stones, it just doesn’t strike me as a realistic possibility.
Diamonds are created from more massive pressure than any human could exert, so we aren’t going to harm them. A chunk of steel or aluminum that thick, resting on a flat surface, is also beyond our ability to deform through direct pressure — with that much force you’d be bending your blade, too. The only remaining element is the bonding process of diamonds to metal. I don’t know about other names, but at least for DMT, the diamonds are electroplated into the metal, so separating the two takes us back to ridiculous force (by sharpening standards) or poor manufacture, at least in the short term.
Over years, sure, eventually everything breaks down, but as far as being afraid to use proper sharpening force I’d say that is not a reasonable fear to have, at least with quality stones. If you have bought quality stones, and they no longer sharpen after owning them for just a short time, I’d suspect clogging before anything else, such as poor manufacture, although that’s always possible. The DMT owner’s guide mentions cleaning the stones periodically, and especially for the finer stones, many sharpening gurus use very low-viscocity fluids (like lapping fluids, or Paul’s windshield cleaner) because the film thickness on many oils is thicker than the height of the diamonds from the surface of the finer stones, so it’s possible to block your blade from accessing the cutting points of the diamonds simply by one’s choice of lubricant / swarf removal agent.
As for the discrepancy in force you noticed between Joseph and Paul, I might suggest a number of possibilities: one, the amount of sharpening desired could have been very different…Paul might have had a somewhat dull iron needing a lot of sharpening, and wanted it done quickly whereas Joseph might have just been touching up a reasonably sharp edge. Two, that they might have been on different “grit” stones. Three, more metal might want for more pressure to get the job done in the same time frame, Paul with a large plane iron and Joseph with a small gouge. Four, the cleanliness of the stones. If I’ve just cleaned my stones, they cut much more readily than after many uses, and they’re clogging up. Probably many more possibilities I’ve missed.
22 April 2017 at 4:55 pm #311370Diamond stones do go through a break-in period where they are coarser than their final state. Some larger grit may be present, or some diamond chips stick out more than others until the plate levels out. With pressure, you can actually break those chips up.
Additionally, the very start of the use cycle involves removing some of the nickel plating that encapsulates the diamonds.After a bit the stones will feel finer than when you bought them. They aren’t worn out, just settled into their true grit.
My experience is that people try to use too fine a plate at the start of the sharpening routine, especially if they are flattening the backs of plane irons. Lapping the backs should start at coarse or even extra coarse plates. If you think sharpening is taking too long, drop back a grit. The higher grits shouldn’t take more than a minute or two with each plate. And with plane irons, you can cheat a bit with the ruler trick.
Anyway, that’s how I approach sharpening with diamond plates. Once you get your routine down, I’ve found diamonds are way quicker and more trouble free than stones.
- This reply was modified 7 years ago by Larry Geib.
- This reply was modified 7 years ago by Larry Geib.
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