Thread: The Burr

You've pretty much got it. I think it's still sharpening, but it's actually what sharpening is. considering the state of the edge, what needs to be raised, not violating simple things (no tearing off coarse burrs for no reason, and no increasing angles to avoid doing something else that should be done - grinding, of course).

What people think they're doing following a method isn't sharpening if the sharpening isn't getting done.

There's a lot of information in a blade about its use characteristics based on how the burr behaves, too.

"Let burrs be your friends", eh?

When grinding, burrs form by plastic deformation of the material due to the impact of the abrasive particles as they smash into the metal. Any process that grinds, cuts or shears metal forms burrs. Typically, with burrs formed by abrasion, the larger the abrasive particles used, the heavier the burr will be, so they are pretty obvious when your blade comes off the grinder. The usefulness of the burr to me is that a nice even burr shows me I've got two planes meeting, which is the object of the exercise. The size of the burr can also be an indication of the brittleness of the material, you get larger, more tenacious burrs on softer material. It's pretty obvious that shearing off a coarse burr directly is going to leave a very ragged edge, which is why we are told to hone it off on ever-diminishing grits.

When re-honing a blade between grindings, I usually start with a fine diamond to re-form the edge 'til I can feel a tiny, even burr has formed. If I haven't been too slack & put off sharpening much longer than I should, or planing something vicious, that usually takes 30-50 strokes on the diamond stone. What I like to see when I move to my finest stone to create a micro-bevel is a barely visible, fine hair of metal come away off the full width - then I know I've got a really straight, clean edge. It doesn't always happen 'cos I'm too often in a hurry & don't pay enough attention to each step.

Even the finest grits will leave a microscopic burr, which is a problem when micro-machining, but stropping or buffing is enough to remove it sufficiently & create a very satisfactory edge for woodworking purposes.

Then there's the 'working' burrs we deliberately make on scrapers. Yep, burrs are my friends...

Cheers,

Originally Posted by IanW

"Let burrs be your friends", eh?

What I like to see when I move to my finest stone to create a micro-bevel is a barely visible, fine hair of metal come away off the full width - then I know I've got a really straight, clean edge. It doesn't always happen 'cos I'm too often in a hurry & don't pay enough attention to each step.


Cheers,

Hi Ian

Nothing wrong with all your comments , but as I am currently in "burr eccentric mode" if I see a burr "break" even a slither, I start considering if I could changed angle - ie slighter steeper, used a finer grit, or again with the finest grit work the backside and eroding that burr a bit further

The underlying thought is that the edge will on magnification be a tad rugged, if a burr "breaks".

The overall process - ie sharpening approach is the same but the edges produced are just that hair nicer,, when watching that dang burr monomaniacally.


Cheers M

Oh - should add the change in thinking is not exactly out of the blue- was travelling with friends over easter and one friend left his shaver behind- leading to vist to the supermarkets and the usual ideal chatter that this blades have a stupendous markup and lead us poor sods to sacking out a stupid blade why too long. And let not even go into what the pink colour ones cost, no bargains that side of the aisle. Ie the usual.
Will some time after- no while holidaying - I am bad but but not that bad, researched razors - besides confirming the assumption that the supermarket price is overdone, is essentially correct - (now purchasing blades approximately 10% of cost) there was something else, learn’t


There are dudes testing razors and on the standardised test they are getting results of 24 grams. There are few YouTube by “sharpologists” testing blade after strapping But the sharpest I have seen them get a blade to is about 80 grams, on the same test, and usually 100. While no real evidence it does suggest there more to had. There a couple of individual you have tested stropped blades on the internet with a standard string test and large array of person who have done the same test with razors.


So Davids work points to low 30”s to provide enough strength to avoid damage and avoid ragged edges or inclusions such as carbide’s that can initiate fracturing- the blade can sharp, with fracture but the surface is less pristine. Buffing was the suggested method to make provide this edge. But with a suggestion that there is more possibly gain I start looking at changes in approach to see what happens


Lacking any sort of calibrated testing equipment , I have no idea if the new edges produced with a focus on eroding burrs are sharper. I was producing blades the would easily slice hair prior and now. But the woods loving the new approach, slicing timber is noticeably easier. No idea on durability.


The blades after the change in focus now look like something the cat dragged home, the bevel was once all polished, now only a sliver is polished maybe 0.5mmm wide, the rest of the bevel is as rough as guts.


It be interesting to herar other thoughts on “apparent” sharpness difference between razors and stropped plan blades

Martin, have you ever examined disposable razor blades under reasonable magnification? They are a loong way from what I (& doubtless you), would accept on a plane blade or chisel. But they actually work ok because the fine 'saw' teeth grip the hair & help to start the cut. Way back in my early days, I thought being able to shave my arm with a freshly-sharpened blade was proof that it was 'proper sharp', but you can get a blade to shave your arm off a relatively coarse stone, but is nothing like the edge you can get off a very fine water stone. The difference is very noticeable on the planed surface.

There are different 'sharpnesses' suited to different purposes. I always smile when people say "surgically sharp" as an indication of something being really, really sharp. A disposable scalpel blade is even rougher than a disposable razor blade, by a good margin, you don't need a magnifying glass to see the serrations on the ground edges! It actually works better that way, 'cos the 'teeth' left by the grinding catches on tissue & helps the scalpel to cut.

Scissors for cutting cloth are similar. The first time I sharpened a pair of scissors for my other half, I honed those edges up beautifully with a fine stone & handed them back saying "Here, better than new".. They were decidedly NOT, the fabric just slid away from the closing blades. After some head-scratching (& examining the edges on a new pair), I took them back & went over the edges with a coarse stone to produce fine 'teeth', THEN it cut a bit more like new....

The slight tearing of the tissue by a scalpel as it "cuts" doesn't matter for surgery, but if you need to make a very fine, clean slice through soft tissue, you need a very sharp knife. Sharpening a knife to an edge like that is an acquired skill that takes quite a while to master, I can tell you. I always remember a sly dig an old meat inspector once had at me not long after I graduated. We were collecting specimens in an abattoir for a research project, and he was watching me slash off the various bits we needed. When I had finished, he said to me, "I see you are unlikely to cut yourself with that knife, son". Just as I was starting to puff myself up thinking I was being complimented on my knife skills he added, "...but you may cause some nasty bruises". He then picked up a piece of tissue and whipped off a dozen paper-thin slices in a blur & said "That's what a knife should be". It took me a very long time to be able to sharpen a knife that would cut something like that, but I eventually got about 90% of the way.

The sharpest edges I've had to work with were for cutting ultra-thin sections for electron microscopy. These have to be less than a micron thick, and for routine microscopy, they use glass knives, the glass is scored & snapped to produce a clean edge that is an order of magnitude cleaner & sharper than any steel knife can be made.

"Sharp" is such a relative concept....

Cheers

Hi Ian


Nope never put a razor blade under a microscope. Did look why the razor blades are cutting the test threads with lower force- they have for wood working world a very fine bevel 14 degrees or so- which helps for nk but likely us woodworkers would fold those edges.


And thanks richly for the comment on sharpening scissors. In tome past I sharpener scissors on some crude sharpeners and that was that, but recently I was using me honing gear and have been advised I don't know how to sharpen scissors.

< was puzzling on that as the seemed to cut the test fabric just fine, but I think I stubbled in the same trap.




since your know the offical forum Knife sharpening expert looking forward to tips on that too .the 20 degrees bevel - 40 degree overall that kitchen knife are seems pretty blunt to me- and the relatively low hardness stainless does not help either. Was curious at exactly what professional do - even 90% professional is far superior to me.




Coming back the plane blades - I done something that making my blades perform better. Without some sort of measurable test it hard to find decent way describing the change. One thing I have noticed is the jarrah saving look different. More like a softwood shaving than what I expect of Jarrah. Jarrah shaving when thin usually look stringy and break up easily- but the current shavings are more intact.


_ here's a photo of traditional Jarrah shaving from phot pinched pinch from Derek's Cohens website (sorry Derek) - - sort of crumbly and stringy - this I typical but I though Dereks photo would be more credible than mine as reference of typical
VeritasCustomPlanes3_html_m68a0096-2.jpg

and here’s none with the erode burr away approach doing the vertical jump up- nothing special except it is jarrah and the shaving usually collapse. I don’t recall seeing Jarrah hold together this well.
IMG_6452.jpgIMG_6453.jpg

Anyone likely it ll nothing, I haven't actually changed sharpening procedure, only became more attentive to the concept of eroding burr away and keeping away from process that can break burrs.

Cheers M

Disposable razor blades of any decent type are generally polished to a very fine edge. What they're missing is hardness because they're using a base steel like AEB-L or something and leaving it at a temper where it's flexible, and then relying on a coating to both make the apex more slick and to improve the edge.

I have seen one exception - here it is - a feather artist club blade. these are single edge blades. Feather's DE blades are super refined at the edge (like no visible defects) and are realistically too crisp - they induce razorburn and bleeding for a lot of people because they're snipping the pore skin off that's pushed up by the blade when shaving the hair. A good razor shaves the hair, but can't make a push cut in to the little tab of skin (thus, cut the hair, no razorburn).

here's an astra - apologies, I don't have one undamaged but could bust out a new one and take a picture under the micrscope if someone wants me to.
https://i.imgur.com/hfqPFw4.jpg

Of course, having the scope on hand, I wanted to see how these edges were holding up, and of course they dent. at the very left, you can see a factory part of the edge. the others is starting to develop a roll and a burr. In my opinion, we are given razor blades that don't hold up well because it's not in the interest of a razor maker to make a step-off of this type of edge that will be slightly less sharp but last for months.

here's damage picture 2 - one or two shaves.
https://i.imgur.com/37Awh1o.jpg

I won't harp on edge damage principles - I thought maybe I could figure out a way to modify the apex on these little guys, but they're too flimsy and a little soft. You can't really do it by hand because the angle at the apex is so slight that any pressure creates deflection - they're weak.

here is my own straight razor after honing, testing a stone for someone. It's not a difficult task to go to an oxide and make this look like a mirror, but it serves no practical purpose to do it unless trying to impress someone (I have sent insanely sharp razors to a few people who have told me over and over just how sharp they want a razor to be and I couldn't make it too sharp. I told them the edge would be transient, and they would bleed, they insisted - and so they did).
https://i.imgur.com/ZkqqKoL.jpg

This is at twice the magnification, by the way, of the factory blades above.

at some point, i did a razor on linde A quickly just to see what it would look like:
https://i.imgur.com/t7fAfCK.jpg I think this is a picture of that, but it could be something else with linde. the apex here is destined for failure if it's not rounded on the back side of the picture, but it looks good. An edge in this condition will cause massive razor burn before it starts to deflect, though. Perhaps to the point of a little "weeping" on the face from the pores - red weeping.

here is the same razor as freshly honed with slate above, done previously with a similar stone, but this is after about 200 shaves. You can see that the linen has burnished the bevel and if you look at the apex, it's fattened a little bit.
https://i.imgur.com/wtduVAt.jpg

Whatever scratches were deeper initially on the bevel remain as they're not removed, and they look chaotic, but at the bevel, the apex is modified, this razor severs a hair easily still if you lay it on the edge under its own weight and it doesn't cut skin. It's practically indestructible and when honed this way and taken care of properly, if shaving every day, there is about five minutes of honing per year, 30 seconds of linen once a week and 20 seconds on cordovan shell each day before shaving.

the astra pictures with minor damage were after one or two shaves. This stuff accumulates quickly and when the edge is full of deflections and damage, the razor feels dull. But it's not due to abrasion - if it were abrasion, the razor steel in the other pictures (like file steel, a little cleaner maybe, but not much different) would just be worn to a fat edge.

I have only taken pictures of a few blades, and haven't taken a picture of a feather DE - which I have, I think, and have not used based on reports of sharpness level. Tim zowada had a picture of one once. the machines that hone the very tip of the blade probably have a lot of speed, cooling and a very light touch. the straight razor has the same slight angle, but it has hardness like the upper end of woodworking tools and an array of iron carbides that have toughness that other types of more wear resistant carbides don't, but they also allow the steel to be heat treated without having too much carbon in solution like one might get with a 1% carbon steel. i believe most of the old straight razors are probably about 1.2% carbon, and it's strange to say for most folks, I think, what happens at 0.8% carbon is predictable. What happens with good heat treatment at 1.25% is predictable (high hardness, good toughness). Steel right at 1% or so suffers from too much carbon in solution and not enough of a carbide array to prevent it and you can just about get anything. Three very plain steels that look almost the same on paper behave very differently.

the 13c26 steel or AEB-L or whatever it may be in a given razor is a super small carbide stainless steel that will fold, but it won't break or snap easily. It's a masterfully designed alloy - it can be made cheaply and it's finer - far finer, than any powder metallurgy steel anyone here has gotten their hands on (only CPM-1V might be finer - it costs the moon and nobody here would use it because it's not wear resistant like the higher alloy steels) - it wears longer than A2 and with furnace and liquid nitrogen, can be 62 hardness all day without being brittle. But it won't go into razor blades in that form with a modified apex for two reasons - the blades could be broken by bending them too far, and a blade could shave like "day 3" on a DE blade for at least a month. maybe more, without any coatings.

Oh yeah, here's the defective feather artist club blade - I think these are more like the cheap blades a barber would use in a shavette to shave your neck and throw away immediately.
https://i.imgur.com/yqT4cOY.jpg

a feather DE blade would have the underlying perfection in the honing, but the corrosion or uneven coating, whatever it is, would look more like near optical perfection.

Originally Posted by MartinCH

Hi Ian


Nope never put a razor blade under a microscope. Did look why the razor blades are cutting the test threads with lower force- they have for wood working world a very fine bevel 14 degrees or so- which helps for nk but likely us woodworkers would fold those edges.

It's definitely bevel - cutting something is part wedging and part severing. I have the scope pictures and ability to take them, but haven't done much picture taking of razor blades outside of straight razors when confirming the quality of a razor or the fineness of a finishing stone.

straight razors are generally 16 or 17 degrees from what I understand. Since hairs aren't that rigid, the bevel behind the edge doesn't have to be that much stronger, but you can see from the picture I posted above, what linen and leather does to the edge. It looks a little more dull, but it's lacking defects and there is no apex to propagate.

Superficial testing of edges shows potential, but if it's not combined with something (like two weeks' worth of shaving), it can be somewhat misleading. As in, you want to know what the edge will be like in a cycle of use, and that's always missing.

Originally Posted by MartinCH

.....Since your now the offical forum Knife sharpening expert looking forward to tips on that too .the 20 degrees bevel - 40 degree overall that kitchen knife are seems pretty blunt to me- and the relatively low hardness stainless does not help either. Was curious at exactly what professional do - even 90% professional is far superior to me....

Martin, I'd never claim 'expert' status for anything, I'm perfectly happy being Mr. Everidge! I simply learnt how to grind & hone a knife so it would cut tissue the way that old meat-inspector demonstrated. And yes, the 'secret' is a ridiculously low bevel as well as a keen edge. A typical SS knife sharpened like that is a flimsy thing, it's likely to chip badly if it contacts anything hard like bone or a SS table - both occupational hazards for a dissection knife. For everyday use on autopsies I used a knife with a far less acute bevel. Given my years of practice in sharpening woodworking tools, I managed to keep my knives sharper than most of my colleagues seemed to be able to do. Over the years I found a compromise bevel angle that was 'sharp' but didn't lose a chunk the size of a 5c coin if it contacted bone. [And for the record, I did cut myself occasionally, enough to require a couple of stitches on one occasion, so sharp knives are no protection! ]

I keep a steeper bevel on our kitchen knives - most people just don't seem to get it that slicing stuff on metal or ceramic surfaces or chucking them in the dishwasher with the rest of the cutlery doesn't do them much good. Who was the genius that invented glass cutting boards??

Sharpness is certainly as much about edge bevel angles as it is about the perfect edge. We tend to learn what each of our blades will tolerate in terms of bevel angle and find a compromise that balances the lowest angle that gives tolerable durability (at least that's been my approach). The bevel angle is a key factor for the simple reason that a low angle allows the blade to penetrate the material being cut with less force; it's analogous to pulling a load up a shallow vs a steep ramp. You can demonstrate this to anyone's satisfaction by putting blades with either high or low sharpening bevels in a BU plane.

Why I fuss about the fineness of edges is for durability of the edge & the quality of the surface it leaves. I wouldn't get too hung-up about stringy shavings from a plane; certainly they can tell you much about how your plane is performing, if you get strings instead of shavings from wood that doesn't normally "string", you probably have a very gappy blade. But some bits of wood will give stringy shavings no matter how well-prepared a blade is, and hardwoods, especially typical Aussie hardwoods, are more likely to yield stringy shavings than softwoods. But the surface can still look (& feel) fine so I suggest we should pay as much attention to the surfaces we're getting, that's the real object of the exercise after all.

If you want to impress someone by shooting out a perfect, full-width, full-length 1 thou shaving, select your wood as carefully as you prepare your plane. In general, fine-grained softwoods are the better choice, softwoods have longer fibres than hardwoods and hang together better....

Cheers,

Thanks Ian, will look at picking up a short steel cooks knife and sharpen around 15 degrees for LOML. She has long term arthitis, not that anyone can see and I don't think the stainless are great. The larger steel knives I have are to unwieldy for her preference.

Also it may be a curious thing but LOML says the hairdressers only use one or two sharpeners in town to sharpen there scissors as they are the specialist who know how to get them to work.


Still considering why the blades are a hair sharper than prior to grinding up the Norris the slightly adapting procedure. There is another possibility. The blade was ground down with 80 grit cubitron which is very fast. And only the tip of the blade was polished. What may be happening with this course to fine grit jump it it easy to see that fine grit has reached the valley of the 80 grit. If I used intermediate grits it possible the some valleys of are not polished out as that is more challenging to spot- plus I altered pitch for the fine grit as it is slow, and concentrated that time on a narrow strip just wide enough to see it reach the base of the valley. This does not make a pretty bevel.

IMG_6455.jpg

Its ugly but it works.

Cheers M

Hi All

Found another reason why my edges may be a tad finer. Wood by Wright was demonstrating a blade sharping guide, but one thing about this guide is it can run parallel with the edge. https://www.youtube.com/watch?v=ucXLF7fY44o In this demonstration 2 pictures where shown - the tip of blade sharpened on course grit normal to tip and one parallel. The parallel edge was noticeably finer and had considerably less bur. On theabbreviated sharpening the grind in normal but the hone is parallel- figured right angle would be faster for honing away the course scratches.

Anyone have thoughts on parallel sharpening?\

Cheers M

sometimes you'll need to do it to shape something the way you want, and it works with heavy sharpening to create less camber, but I've tried it and don't generally manage to ever do it.

It won't make a difference at the end of the process.

the point of all of James Wright's videos and everyone else on youtube working the algorithm (which is practically everyone now that you'll be presented with) is to farm you. The video is a contrivance to try to figure out some way to get you to buy the guide so he can make money.

My view - anything that focuses on using a guide after you're an absolute beginner is just material selling. As in, convincing you you need another guide. But freehand sharpening will dominate it if good grinding is understood and leaving the edge (not grinding it off) is understood.

Raising the burr is simply a good way to know you've removed the damaged steel at the apex, rather than just thinning the edge and getting close.

The trouble with burrs is that removing them is a royal pain in the rear. That floppy burr is probably the #1 cause of early edge failure on otherwise quality tools.

The big thing for me has been producing sharp but durable edges. I can make a hair whittling edge that rolls or chips the first time it sees work, and that's useless. I feel like a quality edge ought to stand up to the work.

Of course, the first part of this is assumes that the steel is of adequate quality and properly heat treated. In commercial razors, this is mostly a given. In kitchen knives, not so much. The cheap ones might not even be normalized after blanking and grinding. Woodworking edge tools seem to be all over the map in both categories.

My own observation is that we sometimes obsess about the angle numbers and the precision of the jigs, and whittling hairs, but we sort of gloss over the fact that the edge fails as soon as it hits wood.

Two things get messy there... Rob Cosman's comparison between the Woodcraft socket chisel and Narex's Richter, and Fine woodworking's chisel usage instructional video. In the first, Rob jig preps both chisels, then gives them one good whack into hard maple, and it wipes out the edges on both so badly that they're useless for anything. In the second, the guy has carefully prepped Japanese chisels, and chops such infinitesimally thin slivers that one wonders why mankind invented chisels. The fellow's comment was that the "problem" people have with chisels is that they try to chop too aggressively, and damage the edges, and that they weren't designed for this.

I am fairly certain that workers of old wouldn't have accepted that, as their job relied on getting actual work out of their tools, and that meant they had to figure out how to sharpen them so they would hold up. Sure, no doubt they had one or two kept extra sharp and reserved for making perfect, show-face cuts, but still.

Originally Posted by truckjohn

I am fairly certain that workers of old wouldn't have accepted that, as their job relied on getting actual work out of their tools, and that meant they had to figure out how to sharpen them so they would hold up. Sure, no doubt they had one or two kept extra sharp and reserved for making perfect, show-face cuts, but still.

Hi John

I was missing a bit on why my edges need up slightly sharper. Had a failing antique expensive blade and ground down 15mm of steel looking to get past the area the blade was chipping. in that process I abreaviated ny sharping process - essentially dropped intermedie grits - Jumped from 80 grit to 2 micron diamond dust just on the tip. But somehow in doing this my edges ended up a tad sharper. I was flummoxed,. Put some theories up in this thread on why happened, but none of the have really flown. For my part I keep to the abbreviated process. that makes for an ugly bevel, but the sharper trumps all !! . Even if I don't understand what happened. I using the same tools.

As for the old timers that most certainly abused and worked hard their chisels - that what there so many firmer chisels around, intended for steel bevels and hard abuse. Paring chisels delicate design. The handles are style and designed with a "don't hit me" look. Both the handle and the tip would not withstand. But they are rarer. in practical terms my set only has a couple of decade paring chisels - most the abused chisel manage to do the job af=perhaps after a quick touch up..


Cheers M