Thread: How Sharp is Sharp Enough?

Originally Posted by Luke Maddux

In performance, my plane blades are easy to push, perform fantastically with regard to tearout, and make that pssssst sound we all love. My chisels leave a great finish and are easy to push and control while paring and chopping.

Reckon that's all that counts Luke.

Originally Posted by Luke Maddux

I can get a 3000 grit and a 6000 grit diamond stone. That would be a little over AU$500. It's a lot of money,

Yep, not just a lot of money but a waste of money IMO.

There may be some benefit in then finishing on a 12k Shapton pro after the 1200 plate. There's not not much mess from it because it only requires a spritz of water to work, and it will give a bright polish. It's the only waterstone I have now. As it's only used for about 5-10 strokes it stays flat for a reasonable time.

Perhaps you recall that I'm a diamond paste on cast iron blocks kinda guy. The Shapton 12k will set you back about $100 or something, but that's way less than $500. However, two syringes of 3k and 8k diamond paste are about $20 each, and a CI or mild steel block is about $40 (I think?).

For a fairly significant wire I drag the back of the bevel slightly on a piece of MDF, and raise the blade to vertical as I do so. Then push down slightly and the wire pops off. For finer wires produced by the paste regime I use (1200, 3k, 8k, 14k) I find the wire disappears by the time I've finished. For the last few strokes of 8k and 14k I only do a push stroke. None of this 40 strokes stuff either - usually 10-20 (a stroke being up and back).

If the blades are sharp that is all that really matters

Personally I think you are spending too much time on each step, especially steps 4 and 5 -- the stropping
in part that reflects the big jump in grit size between each step.

BUT, it's all a compromise, more stones is more $$ for some time saving at each step of the process.


IF (and only IF) you want to add a finer stone between steps 3 and 4, you should look at the Spydeco ceramic stones (medium, fine or Ultra fine).
Derek uses a medium and Ultra fine stone, and I have an Ultra Fine (purchased over 20 years ago) which I use dry for touching up an edge while working.
The spydercos can also be used with a little soapy water, a light machine oil, or keroscene -- I've tried all 3, but dry is most convenient for touching up an edge

To quote Derek -- http://www.inthewoodshop.com/Woodwor...ningSetUp.html

The [medium and Ultra Fine] Spydercos are hard and retain their flatness like oilstones, but are worked dry. Spyderco do not say what the grits are, but they are reputed to be 1500-2000 and 6000-8000, respectively (it would not surprise me if the Ultra Fine is about 10000 as it leaves a mirror finish). The Syderco are expected to be the ceramic version of an oilstone.

So, the Spyderco Fine would presumably sit at around 4000-5000 grit. Link to the Spyderco Ultra Fine stone Spyderco Bench Stone (Ultra Fine)

Derek goes on to say

... the Medium Spyderco, ... raises a very fine microbevel in about 8 strokes. On a PM-Vll blade it is so small that one must look carefully to see it. Five strokes on a Ultra Fine Spyderco, and I could call it done.
A few strokes on either Veritas green compound on planed hardwood or, my preference, the 0.5 micron diamond mesh (from LV), and the blade is very, very sharp.

No water. No mess. I can focus on the important part of woodworking - working the wood.

Derek also reported

After purchase, both the Medium and Ultra Fine Spyderco stones needed flattening - not a lot, but this needed to be done before putting them to use

Each required about 15 minutes combined on coarse (250 grit) and fine (600) Eze-lap diamond stones.Derek also reported

This was also my experience

I just kept backing up and backing up, fewer strokes on any grit. Kept testing the edges in the wood that I expected to carve. Mind you, a banged-up gouge will take far longer to fix.
But I have learned that with reasonable care, I can do about 1/2 the work that I was taught to do for edges which cut very smoothly in soft woods.
That means a half dozen passes on 1500 and hone with green on a hard card stock strop.

Hi Luke

Further to Ian's quotes from my website, I might offer you the following ..

I was cutting dovetails in some really interlocked and brittle Jarrah over the weekend. Much of the time I can stop at an Ultra Fine Spyderco (6-8000 grit) for plane and chisel blades, and the edge is sufficient for the task. For this task, however, I stropped (about 3 strokes each side of the bevel using green compound on hardwood). The edge was significantly sharper and cut the wood fibres very cleanly (where as before it struggled on the UF).

In other words, there is indeed much to gain when going higher in grit .... but choose your battles.

Regards from Perth

Derek

I'm in your camp Luke. I have a lot of fancy sharpening gear and I now pretty much follow the same sharpening system as you. The difference is I power strop but that only saves a little bit of time. I still hand strop (more to maintain the edge) if I'm working on the bench as the paddle is righ there but I'm not seeing the need to go higher and spend more time on the finer stones anymore.

For me, DMT extra fine or a King 6000 waterstone is sharp enough. I finish on a 12000 Shapton because I like shiny things, but I don't believe for a second that it makes a meaningful difference to the blade's performance - at least, not for the work I do.

Originally Posted by derekcohen

I was cutting dovetails in some really interlocked and brittle Jarrah over the weekend. Much of the time I can stop at an Ultra Fine Spyderco (6-8000 grit) for plane and chisel blades, and the edge is sufficient for the task. For this task, however, I stropped (about 3 strokes each side of the bevel using green compound on hardwood). The edge was significantly sharper and cut the wood fibres very cleanly (where as before it struggled on the UF).

In other words, there is indeed much to gain when going higher in grit .... but choose your battles.

Regards from Perth

Derek

Hi Derek,

Thanks for the input. It's good to hear a genuine anecdote about how sharpening to one degree was insufficient but further honing improved performance.

I'm curious, however... If your stropping session was only three strokes on either side of the bevel, why not just do it every time? This seems like such a negligible amount of extra work?

Based on what a few others have said, it sounds like the only thing I would be achieving by including a 3000 and 6000 grit diamond stone would be fewer stropping strokes and a shinier bevel. Given that my charged, leather strop is only worth about $5, I feel like it's worth the extra strokes to save a few hundred. I'll use that on some more tools... to sharpen!

Cheers,
Luke

Luke, the green compound has returned to the regime! It is that significant. I must also note that I prefer it on a 1/4" thick, 8" x 3" slice of flat (planed) Jarrah. Use any hardwood you prefer. This does not dub the edges as leather will.

Re-sharpening is ideally an efficient and speedy affair. It is important to (1) develop a method that suits you, (2) practice it until it is second-nature, and (3) choose your sharpening gear to suit the blades you use. Recognise the limitations of the media you have, that is, harder and more abrasive-resistant modern steels need modern media. It takes extra time to hone some modern steels (such as A2, D2, and PM-V11) on less capable media (such as oil stones, sand paper, and older waterstones).

Try not to equate high grit media (e.g. 12000) with "sharper". Instead, it is more helpful to think of it as "smoother". You get a smoother edge the higher you go. A smoother edge penetrates wood fibres with less resistance than a less smooth edge.

Sharpen more frequently. It is less work than when the edge is truly dull/rounded.

Always feel a wire edge.

My sharpening involves freehanding 3-4 strokes on a worn 600 grit Eze-lap or 1000 grit Pro Shapton, 3-4 strokes on a Medium Spyderco, 3-4 strokes on a Ultra Fine Spyderco, and 3-4 strokes on green compound. This takes about 30 seconds.

Regards from Perth

Derek

Washita for american and english tools, suita for japanese. On the rare situation where a little more is warranted, burnish the very edge with a piece of jasper and strop.

Strop is bare clean leather, and i use it for everything.

Natural stones respond a lot to how you use them, so what I consider good on a washita is not what someone will get with a soft arkansas out of the box. It's hair shaving sharp, but not something you'd shave with on a straight razor.

Same with the suita. Plenty sharp for finish work on wood, but would be a bit lacking on a straight razor edge (most stones are, including most synthetics).

Through Lee Valley, I bought a copy of Leonard Lee's book: "The Complete Guide To Sharpening." (ISBN 1-56158-067-8)
Pages 32 & 33 are 15 scanning electron microscope pictures of chisels sharpened on various stones (prepared by the National Research Council of Canada).
Those high magnification images made me rethink and evaluate everything that I was doing to sustain the edges on wood carving tools.
Looks like beyond a certain point, the atomic structure of steel will defeat efforts to approach a "theoretical" edge.

This theoretical edge discussion exists in the world of razors, too. I'm not sure what the real answer to it is other than to know that once you get past a certain point, a shaving edge is very transient. For example, if you use iron oxide which is a tenth of a micron and cuts very smoothly, you can get a straight razor that will really cut off every little bump on your face, but the durability of the edge isn't so great. I'd suspect it can't hold the sharpness for too long at that level.

If you, instead, use a natural stone and strop the edge to an order of sharpness less, but one that easily severs hairs, the edge can be maintained at that level with a strop and linen for half a year or a year (and the shave is more comfortable and just as close). When working up an edge with iron oxide or tenth micron diamonds, etc, the hair shaving is no easier, and the strop won't keep the edge quality the same for very many shaves. I'm not sure that the edge is technically sharper with the diamonds, it may just have microtoothing that will catch on skin bumps and remove them. Who knows? There is definitely an upper limit to sharpness, especially at a functional level.

One of the nice things about using washita and a strop for tools is the edge quality is durable and very constant until clearance loss is the issue.

Originally Posted by derekcohen

Luke, the green compound has returned to the regime! It is that significant. I must also note that I prefer it on a 1/4" thick, 8" x 3" slice of flat (planed) Jarrah. Use any hardwood you prefer. This does not dub the edges as leather will.

Re-sharpening is ideally an efficient and speedy affair. It is important to (1) develop a method that suits you, (2) practice it until it is second-nature, and (3) choose your sharpening gear to suit the blades you use. Recognise the limitations of the media you have, that is, harder and more abrasive-resistant modern steels need modern media. It takes extra time to hone some modern steels (such as A2, D2, and PM-V11) on less capable media (such as oil stones, sand paper, and older waterstones).

Try not to equate high grit media (e.g. 12000) with "sharper". Instead, it is more helpful to think of it as "smoother". You get a smoother edge the higher you go. A smoother edge penetrates wood fibres with less resistance than a less smooth edge.

Sharpen more frequently. It is less work than when the edge is truly dull/rounded.

Always feel a wire edge.

My sharpening involves freehanding 3-4 strokes on a worn 600 grit Eze-lap or 1000 grit Pro Shapton, 3-4 strokes on a Medium Spyderco, 3-4 strokes on a Ultra Fine Spyderco, and 3-4 strokes on green compound. This takes about 30 seconds.

Regards from Perth

Derek

Reading this with some interest as I too continue on my sharpening journey. I notice in Derek's thread, "always feel a wire edge".

As I sharpen my plane irons and chisels, I can repeatedly work on the courser grits until I feel the burr. I tend to use this as the signal to lap the back of the blade to remove that burr, and then move up to the higher grit.

BUT ... On the higher grits I can never feel a burr !

in the past, I have used wet and dry / PSA combination on a granite block. Anything above 1200 grit and I don't feel any burr.

Recently I invested in a set of Sigma Power ceramic 1000/6000/13000 stones.

On the higher grits, I do feel a difference with my finger tips on the edge when its sharp ... But rarely if ever do I think I feel the burr.

Thoughts ?

I have a Lansky sharpener for knives and I've recently taken to viewing the edge under a cheap 60x microscope/loupe thingy. What I thought was sharp previously shows up as a serated edge bread knife under the microscope. I initially did it out of curiosity but now use the microscope in between each grit to ensure I have a consistent scratch pattern and that the scratches from the previous grit have been removed. When I get back into the shed I intend to do a similar thing with chisels and plane blades. I've found that the edge appears to be sharper but more importantly stays sharp much longer. Of course it may just be wishful thinking and my brain is making these observations to justify the extra work
To answer your question Glenn, I think the burr is there but fingers aren't sensitive enough to feel it. Have a look with a microscope. I think you'll be surprised at what you see on your 'sharp' edge. On the higher grits I often see the remains of the wire edge hanging on to a section that needs a bit more work.

Originally Posted by Glenn.Visca

BUT ... On the higher grits I can never feel a burr !

I use my fingernails to see if it catches on the burr by sliding a fingernail along the back of the iron off the edge. (freshly cut fingernail work the best). on the course grits, the burr will stop my fingernail dead in its tracks. on the finer grits, the burr is just a bump in the road but it can be felt.