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Diagnosing sharpening problems

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Silly_Billy

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I'm hoping for advice about how I can learn to diagnose sharpening problems and ways to improve. I've done a sharpening course and haven't had any problems sharpening until today.

Today I was sharpening my No.4 smoother. It's a Quangsheng plane with a T10 iron, and I love using it. Until today, I have always been able to get it razor sharp (i.e. sharp enough to easily shave hairs). What could I have done wrong today?

  • The blade has been ground to 25 degrees using a 120 diamond stone. (I have little space and no power for a grinder.)
  • I added a bevel at 32 degrees using 1000 diamond stone. It seemed to take considerably longer than usual to reach the point where a burr formed.
  • I removed the burr on a 8000 diamond stone and then added a bevel at 35 degrees. Again, it seemed to take longer than normal for a burr to form. Also, the edge didn't look uniformly polished. I wondered at first if some of the diamonds had worn away on one side, so I flipped around the diamond stone. But I was still left with inconsistency in the polished edge - one side didn't seem to reach the same degree or mirror finish.
  • Finally, I used the ruler trick to add a back bevel with the 8000 diamond stone. When I inspected the edge, it looked like it wasn't straight :shock:
  • For all angle measurements, I used a honing guide.

I was wondering if diamond stones can wear away because I've used them a reasonable amount. However, I am expecting my technique to be the more likely cause of my woes.

Any help or advice would be much appreciated!
 

El Barto

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It sounds as if you need to give it a little tickle on a grinder to bring that 25° bevel. But you don’t have a grinder so maybe go back to your coarse stone, restore to 25° then add your 32° bevel.

It’s possible and quite easy to sharpen an iron out of square. I wouldn’t worry about it but if it bothers you, when you restore your 25° bevel, apply more pressure to one wiser to restore squareness.
 

D_W

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do what you need to to get the 1000 stone's work all the way to the edge end to end and the 8000 stone's work to the edge end to end and front to back. The little cosmetic things (if you're making microbevels that aren't perfectly identical on each side) isn't a big deal if the overall geometry isn't threatened.

If those irons are very hard, once in a while, you can use something like a grinder, coarse paper, etc, and damage the edge a little bit such that it will be fragile until you have honed off some of the damage with the 1k stone. I have seen this exactly twice in 14 years (and I make a lot of tools) - it's usually an issue with tools that need tempering. you have diamonds, so you won't notice an overhard iron like someone using an oilstone might.

At any rate, follow the advice to get the polish all the way to the edge end to end (use a loupe if you have to) and if the edge still continues to chip, try a different iron.

I looked up the t10 spec, and it's almost identical to 1095. 1095 at normal woodworking hardness for chisels and planes is a very tough steel and should tolerate some sharpening abuse. When it's overhard, though, it won't - it'll seemingly grind and then while finishing an edge or with initial use, the edge may crumble.

As I mentioned, I've seen it about twice (one of the tools was japanese, and it's definitely overhard), but I've seen people suspect that the edge is crumbling probably 100 times as often as it actually happens due to harsh sharpening.
 

Bod

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You say your using a Honing Guide, which one?
Some are more reliable than others.

Bod.
 

--Tom--

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What’s the issue you’ve got, that it’s not sharp enough for use or that it’s not straight?

If not sharp enough, you either haven’t hit the apex or you haven’t deburred.

Diamond stones do bed in after a bit of use and slow down, so if you’re sharpening based on number of strokes, or time at each grit then your problem is likely to be not hitting the apex. We’re you sharpening to a burr on each stone?

A useful trick for beginners is to colour the bevel in with permanent marker, and then take one or two strokes on the stone. Looking at the bevel you can clearly see where the metal is being abraded. If you still have marker on the apex you need to do more work on the stone, or increase the angle your sharpening at.

If you’ve definitely hit the apex, you may have a wire edge, with a burr running along it. This will seem sharp but will fold over the edge on use making it seem dull. There are a few ways to deburr, from dragging the edge through some softwood as though it were knife, to stropping on leather.

I think you just didn’t hit the apex though
 

Silly_Billy

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Firstly, many thanks to everyone for all the help and advice.

I’m concerned about three issues.
  1. I have previously sharpened until l got a burr, but this time I struggled to sharpen enough for a burr to form. (I know about burr removal.)
  2. I struggled to get a mirror polish from edge to edge of the microbevel. I had always found it straightforward to get a mirrored microbevel until yesterday.
  3. It looks like the edge has crumbled. However, D_W is way more experienced than me, and I’ve listened to his advice that edge crumbling is very rare.

Also, I’m wondering if I used my 120 stone effectively to establish the primary bevel properly. I think a grinder would save me time and hassle, but I’m reluctant to spend money when my technique could be the issue. And I might have to use a bench grinder in the kitchen!

Bod":2r3dcvs0 said:
You say your using a Honing Guide, which one?
Some are more reliable than others.
Thanks Bod, it's a Veritas Mk.2 honing guide.
 

bridger

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odd that a blade that has been successfully sharpened many times before is failing on the same stones. is there anything else you're doing differently? honing fluid? as far as the diamond stones aging out, try sharpening something else with them, see if the problem persists with a different tool. I bet it won't, but I'm mystified about what IS going on. if it was a bad spot in the steel I'd expect it to show up at one spot on the edge first, not the full width all at once, and you'd have seen it coming from flattening the back.

maybe try grinding past your ruler trick back bevel and sharpening without it. hone the burr off with your finest stone after each grit, flat on the back of the blade.


I acquired a hand crank grinder a while back. for light bevel setting and things like sharpening drill bits it has advantages over a powered grinder in terms of control and heat generated. it's also smaller, quieter, clamps to the edge of a table or bench and requires no electricity. it's a bit of a search to find an old one in good shape but worth the hunt. I had to fabricate a tool rest for mine.
 

Silly_Billy

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Thanks. I think I'm going to try again from scratch, going from with a new 25 degree primary bevel, and see what happens.

bridger":5dfga27r said:
I acquired a hand crank grinder a while back.
Many thanks, I hadn't thought about a hand crank grinder but will now look for one.
 

Silly_Billy

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D_W":16boikzv said:
I looked up the t10 spec, and it's almost identical to 1095. 1095 at normal woodworking hardness for chisels and planes is a very tough steel and should tolerate some sharpening abuse.
I like T10 more than A2, but I know steel choice is very much personal preference.

Matthew at Workshop Heaven wrote a bit about Quangsheng T10 irons: Quangsheng are the only volume iron handplane manufacturer to use water hardening carbon steel for their cutting irons. Water hardening steels are usually associated with tools from Japan, they are purer than the oil or air hardening varieties. From a metalworking perspective T10 steel is less predictable to work with than O1 for example, but it can be tempered harder without losing it's toughness and it takes a supremely fine edge.
 

woodbloke66

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Silly_Billy":3s22rcjm said:
I think I'm going to try again from scratch, going from with a new 25 degree primary bevel, and see what happens.
That's what I would do do, but you don't need to grind right back to the edge. If you have a read through the following blurb that I penned some years ago:

https://knowledge.axminstertools.com/th ... -red-line/

...a red felt tip pen will allow you to get incredibly close to the edge without actually grinding into it and that's the point at which you stop. Then hone at 30deg using the honing guide of your choice; the Veritas is fool proof and pretty hard to beat. Finish off with the 'ruler trick' and strop if required - Rob
 

D_W

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Silly_Billy":15rvebdj said:
D_W":15rvebdj said:
I looked up the t10 spec, and it's almost identical to 1095. 1095 at normal woodworking hardness for chisels and planes is a very tough steel and should tolerate some sharpening abuse.
I like T10 more than A2, but I know steel choice is very much personal preference.

Matthew at Workshop Heaven wrote a bit about Quangsheng T10 irons: Quangsheng are the only volume iron handplane manufacturer to use water hardening carbon steel for their cutting irons. Water hardening steels are usually associated with tools from Japan, they are purer than the oil or air hardening varieties. From a metalworking perspective T10 steel is less predictable to work with than O1 for example, but it can be tempered harder without losing it's toughness and it takes a supremely fine edge.
I may have said something earlier about wire edges, but plain steels above a certain hardness range definitely do better releasing wire edges - which is strange given their toughness reputation - that's shown to be practical in terms of what's best for chisels - generally the plainest steels - and what tolerates a razor strop despite a final angle of 16-18 degrees (straight razors) - same thing, carbon steel excels. Even O1 makes a very mediocre razor once you've had a good vintage razor in hand.

At any rate, the reputation for keenness is probably related to ease of getting rid of the wire edge. I have no idea how the economics work out, but Rob Lee mentioned to me that the business owner hat Rob prefers V11 as it's far more stable than O1 (it is, I've hardened the same alloy), and O1 is more stable than 1095 (or T1). I guess the cost of labor is low enough in the east that they can afford to spend time and labor dealing with warpage.

A2 was touted as being better wear-wise (it is a little, I tested that), but it doesn't like some stones (washitas) and isn't quite as tough. From what I can tell as an amateur maker, the balance of the reason for it is favorability with hardening - far less follow-up work than O1. The first person I've heard of using it (retrospective, by date used, is George Wilson here in the US - slipping plane irons to coopers as he'd experimented with alloyed steels and liked it vs. the lower carbon plain steel that the blacksmiths made. When Lie Nielsen was having trouble with W1 steel, he suggested it to them and they said "no" at the time :) They tried to resolve their issues with W1 by hardening only part of the iron (the first inch or so), supposing that most users would never get there.

V11 is what A2 should be, but given only one choice across the shop, I'd still have plainer steels (increased wear resistance in V11 doesn't seem to play out as well - subjectively - in rough wood as it does smoothing. In smoothing, it's supreme)

All that said, steel that gets rid of its wire edge early is dreamy to work with on the stones and if it gets you to the stones more often, you'll be better for it in the long run.
 

Silly_Billy

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I think my original iron must be jinxed :?:

I started sharpening it from scratch. I reground the primary bevel to 25 degrees but using the 'red line' advice from woodbloke66. However, I struggled to get a burr :x . I'm still baffled what I'm doing wrong.

To see if I was simply having a lousy sharpening day, I tried with another iron. Out came the O1 iron from my low angle block, and I got it sharp enough to shave.

While I can sharpen, I'm wondering how to improve. Is it merely endless practice? I know the basics and can get my blades sharp enough, but how can I up my sharpening game?
 

D_W

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Lack of a burr can be due to massively overhard steel or very poor quality steel. Make sure the edge catches on your fingernail at least so you know you've gotten back to it. There's a short period of time where it looks like the flat is gone but it isn't yet. You can even get some wire edge before you're through it.
 

Silly_Billy

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Many thanks D W.

Also, I'm wondering how how different sharpening stone materials impact the final edge. Many of the experts (e.g. David C) seem to use waterstones rather than diamond stones. I've made my choice and already invested in diamond stones, and finances dictate that's what I'll stick with. However, I can't help being curious whether different types of stone would leave a different edge.

I wonder too if different types of sharpening stone suit different steels.
 

D_W

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This is a complex and contentious question, but the practical take away from it isn't that contentious. If you go fine enough, it doesn't matter what the abrasive is - use what pleases you. Fine diamonds and fine alumina do a nice job. What's fine? 1 micron diamonds in a vial - I tested edge life 1, 2.5 and 5 microns last year vs. arkansas stones in O1 (when I tested V11). I didn't test V11 because in clean wood, it lasts too long.

diamonds on metal and wood look cosmetically different under the microscope, but the edge durability is about the same.

It's important to know that refinement beyond a certain grit only needs to happen at the very edge (e.g., if you stop with a 1200 grit diamond plate, only the very last bit of the edge needs to be in contact with the 1 micron diamonds - polishing a wide bevel with a fine abrasive generally results in incomplete sharpening).

If you're getting good results, it's not necessary to follow my advice on the 1 micron diamonds unless you're doing a lot of work (they'll end up saving you effort by extending edge life).
 

D_W

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by the way, you can always match something up to its historical mate (an old ward iron to a washita or charn finisher), but it's not really necessary. Some of the steels that are alloyed, I've found to be particular (A2 and washitas don't get along at all - I wish I could post some of this stuff permanently somewhere), but they all work OK with synthetic abrasives.

The advantage of using diamonds as you're doing is that most of the ugliness of highly alloyed tools will never materialize under your fingers (you won't notice it). None of them have anything that diamonds don't cut - they just get cut a little slower by diamonds, but that's it.
 
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