Much has been written about the uses of a crowned, or cambered or radiused, edge on plane irons. I’m no expert on woodworking technique so I’ll leave those details to others more qualified to discuss how to put a crowned blade to best use. And much, too, has been written about how to create a crowned edge. When hand sharpening a plane blade it is almost easier to add a bit of crown than not to, especially when the honing action is diagonal or side-to-side, as it usually is when free-handing the blade on the stones. The tendency is to apply extra pressure on the corner of the blade that’s leading the way. Back and forth like that and you’ll have worn a bit more blade off of the corners – a crown is born!
Honing guides are useful helpers at the sharpening bench. They can allow you to repeat a specific angle reliably, bear down hard to re-shape an edge (often eliminating the need for a powered grinder), work the tiniest micro-bevel to save time and effort and, yes, they can be employed to add a bit of crown to a blade. Most honing guides will allow some small amount of slop if you add pressure to one corner, then the other as you stroke the blade along the stones. By doing so, you’ll create a curved, crowned edge. Lee Valley even offers an aftermarket camber-roller that replaces the cylindrical roller in their MkII honing guide which makes it easy to tilt the guide as you hone. Rock and roll!
Enter Dave Powell of Powell Manufacturing, the man who started DMT, the diamond abrasives experts. Dave has teamed up with Toshio Odate to make a diamond honing plate that creates a crowned blade automatically (well, not really automatically – you still have to push the blade back and forth on the plate). The plate has a longitudinal semi-cylindrical hollow shape that is 2.5 thousandths of an inch (0.0025”) deep. Honing a blade in the concave channel will put a 2.5 thou crown on the blade.
The Powell Odate Crowning Plates come in four grits: 60 micron (220-grit), 45µ (325-grit), 25µ (600-grit) and 9µ (1200-grit).
After refining your new crowned edge with the 9µ plate, you use Powell’s Odate Dressing Plate, which is convex by 0.0025” to dress a hollow in one side of your 4000- and 8000-grit waterstones (Norton white and gold stones are recommended by Powell.) Now you can continue to refine and polish your crowned edge on the fine stones.
You may have noticed that it’s been a while since my last blog entry. I’ve had a lot going on and am usually reluctant to be this public about my private life but I need to share what follows. I’ll have a new blog post ready in a couple of days and it really will be about sharpening.
I am being treated for prostate cancer (don’t worry, I’ll be fine.) And my mom died (it’s okay, she was ready.)
My cancer was diagnosed very early; I have radioactive seeds implanted in said offending gland and my prognosis is excellent — I’ll be around a good long while. More about me in a bit.
Mom was 88 years old, living by herself in her own home, but trigeminal neuralgia, failing eyesight, weakening kidneys and an overall decline in strength and balance had left her very ready for the next big step. (“It’s been a good life. I’ve had enough.”) She had a hemorrhagic stroke on February 16 and died a couple hours later. Not bad at all. She was a great mom, a good friend, an adventurous world traveler and yoga instructor into her eighties. Her quick, painless passing is a sadness, not a tragedy. My sister, brother and I, along with the rest of her family and friends miss her a lot.
The topic of this Public Service Announcement is Prostate Specific Antigen (both “PSA” – clever, eh? And you thought it was about Pressure Sensitive Adhesives!), a protein produced by the prostate gland that is measurable in the blood of those of us with a prostate. PSA content in the blood tends to rise when the prostate is upset about something, be it an infection, mechanical abuse (bad bicycle seat), or cancer. Ladies, unless you want to know more about all this, please feel free to return to your woodworking blog perusal. Those of you with Y chromosomes who are up-to-date with your blood tests and doctor visits (that’s code for the digital rectal exam which is not nearly as bad as most of us imagine(d)) are likewise dismissed. But if you’re a male “of a certain age” and haven’t been getting your checkups, bend over! It may be primitive and embarrassing, but that and the blood test are the best we’ve got. Be glad someone is willing to do that for you. Do it because someone cares about you. And if you’re afraid of the exam or what you may find out, you’re just being a foolish little girly-man.
Based on my experience I’d heartily recommend a PSA test along with the physical. Do a little research and you’ll find lots of controversy about the reliability of PSA tests: that they produce too many false positives and negatives which lead to unnecessary biopsies or neglected cancers. Well, I’m here to tell you that my annual PSA test and my doctor’s concern have saved me from some very unpleasant eventualities.
Getting into more detail: first let me say that I’m 58 years old and in excellent health: good diet, proper weight, regular exercise, haven’t smoked tobacco in 35 years and quite moderate in all other things, no family history of cancer at all. Last July my routine blood-work showed that my PSA jumped from 2.87 to 4.31 in one year. Not a high number but the rapid rise was cause for concern. We tried antibiotics, hoping it was just prostatitis but finally last January decided on a biopsy that came back positive for cancer. Mine was caught so early that it was undetectable otherwise, even invisible to ultrasound. The earlier the catch the better the prognosis for survival and an early diagnosis makes one a better candidate for radioactive seed implantation, the current best treatment option (an opinion shared by many). The other treatments are external beam radiation (every day for eight weeks or so with a risk of unpleasant side effects), or surgical removal of the prostate (up to six weeks recovery with considerable risk of side effects.)
As far as I’m concerned, the seeds are the best of the bad. The implant surgery is a one-hour, out-patient procedure that left me with a sore butt for a week or so. I have 137 tiny titanium cylinders containing palladium-103 in my prostate that were inserted with 38 needles through my perineum. (I bought a Geiger-counter on eBay and sure enough, I am radioactive. You should hear that thing crackle!) The radiation irritation came on a week or two later making it hurt to pee. I’ve bitched and complained about this irritation for almost a month now, but I remind myself often that the discomfort is the effect of killing cancer. And, the discomfort I’m experiencing as I cure my cancer is nothing compared to what so many other cancer patients have to go through. Palladium-103 has a 17 day half-life so I’m already at about 25% of the original dose. I’m five weeks post-op right now and feeling better every day. Bottom line, I got lucky.
I’ve been reluctant to “come out” about this publicly. I’m not the most public person and wasn’t sure it was right to post my personal cancer story in my sharpening blog. But a friend whose advice I respect and seek said that I should post my story because so many of my readers are in the target age-group and that most of them would never read such a thing anywhere else. As I’ve been informing my friends about my condition I am dumbfounded by how many men, roughly my age have never had their prostates checked. To them and any of you who are in the same camp I say get over it! If you are of a certain age, floating on that river in Egypt and don’t go to the doctor in the next week, let me put it this way: You like living? You like sex? Peeing on demand? Get thee to a doctor! The life you save may very well, quite literally, be your own.
Okay. I’m done preaching. The next post will be in a day or two and it really will be about sharpening (Odate Crowning Plates, in fact.) But if any of you have questions or concerns that you think my experience can help with, you can find my contact info at hocktools.com and I’ll do my best to answer whatever questions you may have. I seem to have abandoned all modesty in the last few months so don’t be shy about asking personal questions about my condition or my treatment or what I’ve learned along the way. I am here for you, brothers.
“…a dull blade is a good thing because it means two things. 1. You are working the wood and not just fondling the forgings. 2. You get to sharpen it, which makes you a better sharpener.”
This from The Schwarz’s latest blog entry (though “latest” is probably already superseded by Mr. Blog-prolific).
I know this is a bit lazy on my part — simply pointing to another’s post. But when someone writes something that I think belongs in a sharpening blog, I want to share it with the wider sharpening audience that may not have seen the original. Chris’s blog entries are always interesting and entertaining (and he generates a lot of them!) I use Google Reader to keep up with all three of his, and a few others. Use the above link to read his entire post and stay tuned — he’s certain to have another interesting tidbit posted before lunch.
It is common knowledge that skewing a plane reduces the blade’s effective angle of attack in relationship to the wood. If that’s not common knowledge for you, think about it this way, if you walk straight up a ramp, you are walking up its “pitch” angle. If you walk diagonally up the ramp, you are traveling at a shallower angle. It’s farther, walking up diagonally, but easier.
When a plane blade is pushed straight ahead into the wood, the shaving follows the pitch of the blade. When you skew the plane, the shaving follows the longer, but shallower diagonal path up the blade. This fact can come in handy if you are planing, for example, end grain and need to shear the fibers at a lower angle of attack to get the best finish. This lower angle of attack comes with the same bevel and relief angles on the blade. If you honed a low-angle plane to match the skewed angle you may need to grind the blade to a thin, fragile edge.
I recently spent too much time trying to understand the relationship between the skew angle and the resultant effective pitch angle when John Whelan came to my rescue. I found an excerpt from his book: The Wooden Plane: Its History, Form, and Function at Nichael Cramer’s website: http://homepages.sover.net/~nichael/nlc-wood/index.html. The passage is worth reading but the part I needed was this: “…the sine of the effective pitch is the product of the sine of the actual pitch and the cosine of the skew angle.” This sounded to me way more complicated than it needs to be so I cut angles off a couple of rear blocks from our plane kits and started measuring and doing the trig.
Turns out he’s right, of course. To save you some time I did a bit of Excel work and came up with a chart to show the effective angle of a the following pitches and skews:
Skew angle –>
A common pitch plane (blade bedded bevel down at 45°, like your trusty #4, etc.), skewed 30° will attack the wood at an effective angle of 37.8°. If you skew the same plane 45°, it will cut the wood as would an edge at 30°.
I find this sort of research interesting and hope you do as well. I’m sure there are aspects of this study that I haven’t thought of and would appreciate your comments and additions.
And I think I showed some restraint in the literary application of the skew/screw pun for the title. I thought of a lot of others…
While I believe every shop should have a dedicate sharpening station, some are too small and must timeshare precious surface space with other tasks and tools, and some woodworkers don’t always work from their home base shop and could make good use of a traveling sharpening kit.
Abraham Anapolsky, one of the metallurgical collaborators that vetted the steel chapter in my book volunteered to shoot some scanning electron microscope (SEM) images of blades that Konrad Sauer sharpened with his 15,000-grit Shapton waterstone and his ultra-fine natural Japanese waterstone. If you haven’t read the first part of this story go here to get up to speed or what follows won’t make much sense.
Abraham writes: “I finished the data collection, and I have a few ideas I am working on especially about what makes a hard sharp edge (based on some analysis of the edge composition), but I am not finished thinking about everything. However, I do have an answer as to why the two blades look different. If you notice, in the images of the blade honed with the natural waterstone, the surface looks like crumpled paper, the higher mag picture shows this is due to random short scratches. The Shapton images on the other hand have large areas that are smooth and the scratches are all of a specific orientation. Both samples show a range of large scratches (~0.25um wide) that are continuous and very visible; I imagine that these are the remnants of the original grinding, or you used the same coarse stone on both of them. The random short scratches are consistent with a surface moving over an abrasive that is free to move (i.e. a slurry) whereas the specific direction scratches are consistent with a surface moving over a fixed abrasive. Note also that the edge on the natural-stone images has regular fine rounded serrations, whereas the Shapton edge shows no regular serration, but kind of random straight sections. Also, the Shapton edge is much thinner than the natural waterstone edge.”
Double-click on the images to see them larger.
The earlier entry suggested that the softer abrasive of the waterstone was selectively removing the softer steel around the carbides more readily than the carbides themselves, creating the matte surface. This new input suggests that the loose nature of the waterstone’s slurry is (also) contributing to the random, matte surface quality. The Shapton’s grit grains are better anchored in the stone surface which allows them to shear a straight groove in the steel, carbides and all, thus creating the flatter surface.
Mystery solved? I think so. Let me know what you think.
By the way, in Konrad’s defense I need to repeat something from my book (page 213):
I recently mentioned to Chris Schwarz, editor of Popular Woodworking Magazine, something about using a simple, USB, toy microscope to look at edges before and after sharpening. His reply was, “I got to play with one of those gizmos and it was very… humbling.” I know what he means. Magnifying a sharpened edge can spotlight a dismaying array of results. Even an edge that you are certain is as sharp as any living being could make it, one that passes all the sharpness tests and performs beautifully, will show scratches, nicks and abject irregularities that you’d swear couldn’t possibly be there. It’s not for the insecure. If Chris’s experience with the toy microscope was… humbling, mine with the SEM was undoubtedly… more so.
So, don’t worry Konrad. Those edges you sharpened may look nasty at 3000x but I, for one, know how sharp they really are.
My thanks to Konrad for asking the interesting question and providing the samples for the SEM, and to Harrelson, Gary and Abraham for offering interesting answers.
Linda and I will be attending the upcoming Lie-Nielsen Hand Tool Events at Cerritos College in Norwalk, CA on Friday and Saturday, January 29 (12-6) and 30 (10-5) and the following weekend, February 5 & 6, same hours) at the Crucible in Oakland, CA. I’ll have blades and plane kits to show, a couple of demo planes to show off (even one of Jim Krenov’s) as well as books to sign.
We’ve attended a few of these events in the past and find them very rewarding. They’re casual, friendly and fun. Make some time to come by and say hi. I hope to see you there.