de-burring

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de-burring

Postby Brian Williamson » Fri Apr 02, 2010 8:54 am

Over the years I've been on upteen chainsaw courses and every Instructor has told me to deburr after filing. I never did or do and I would maintain that my chains cut as well as anyones.

Similarly, I never deburr my billhooks (and I have a lot) when I sharpen them and, again, I reckon that they cut better than most people's.

When I sharpen knives I do tend to deburr them, but mostly because it's harder to tell if they are sharp with the burr on.

My point is: I've never met an instance where leaving the burr on has damaged the edge, which is what people usaully claim that it does. Has anyone else? Are we merely blindly copying what other people have done before us (in the same way that people cut coppice stools on a slope)?

I have a theory on this (I love theories) - in the days of the barber-surgeons, there were no disposable razors or scalpels; you had to sharpen all your own kit. If you left a burr on the edge you could either leave scraps of metal within a wound or cause secondary cutting with a bit of trailing burr. So you deburred. Then, woodworkers seeking to copy the finest edges also deburred, even when it offered them no advantages.

So, if there is anything to my theory, somewhere between deburring a chainsaw chain (pointless) and deburring a scalpel (worthwhile) lies a point of indecision. Is it worth deburring the finest veneer knives? Spoon carving knives? Hunting knives? Executioners axes?

What do you think, oh knife wielding people?

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Re: de-burring

Postby robin wood » Fri Apr 02, 2010 10:03 am

An edge with a burr looks like a saw under magnification. It is quick and easy to sharpen and cuts but leaves a (relatively) coarse finish. It may be fine for a billhook but no use for a spoon knife. The chainsaw question is very different, the reason for deburring there is that most saw teeth have a hard chrome coating, if after sharpening you have a burr and this gets pulled upwards then when it breaks it can tear into the chrome coating and damage the edge. I don't deburr but I do tap the bur downwards with the wooden handle of the file so that when the first cut is made the burr breaks off downward cleanly rather than tearing the coating.
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Re: de-burring

Postby Brian Williamson » Fri Apr 02, 2010 11:37 am

Ah, you're talking like a chainsaw instructor Robin! They all say that you can tear the chrome coating off, but have you ever knowingly seen it happen? You'll probably answer that no, you haven't, because you always tap the burr down! I worked in mainstream forestry for nearly fifteen years and I've been a coppice worker for the past ten. I've owned numerous saws and an awful lot more chains, but I've never seen it happen. So is it a rural myth? A throw-back to the days of poorer quality chains? Or am I merely short sighted?

As to the burr on knives, the edge is surely going to be as good as the stone that produced the burr. If you're using a really fine stone then you'll get a really fine edge when the burr falls away (or is ripped off by the first piece of wood it comes in contact with), which is basically my point, that leaving the burr on won't damage the edge. You will certainly get a better edge if you continue polishing away with strops and jewellers rouge, though I think you will probably meet the law of diminishing returns very swiftly. My favourite billhook has a wonderfully polished edge, bevel and shoulder, but it has been polished by the thousands of rods that I've cut with it.

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Re: de-burring

Postby robin wood » Fri Apr 02, 2010 11:47 am

Brian Williamson wrote:Ah, you're talking like a chainsaw instructor Robin! They all say that you can tear the chrome coating off, but have you ever knowingly seen it happen? You'll probably answer that no, you haven't, because you always tap the burr down!


Well the answer to that one is yes I have which is why I sometimes tap the burr off, not always. I have seen it happen after a heavy sharpening (say 10 strokes with new file) after hitting something hard with a tooth. Now I would tap the burr off after a heavy sharpen but not bother after a normal 3-5 stroke sharpen. My theory would be that this doesn't make a big enough burr to end up getting peeled back. I look at knife edges with a magnifier and have not done the same with a chainsaw but it might be interesting.
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Re: de-burring

Postby goldsmithexile » Fri Apr 02, 2010 4:52 pm

I had a discusson with Bernie Garland about this, and he knows his stuff. For meat butchery a knife edge with tiny seratins from a steel is ideal. Stropping to a polished finish is unecessary. Meat cutters rarely use a stone, just there steel frequently to maintain an edge. But as Robin sudgested, for a fine polished and burnished finishing cut on carved wood, with no scratches or striation's, the blade needs to be as smooth and burr free as possible, so stropping is ideal for that. I own and use 2 mora hooks. The only time a stone, emory or file has touched them was when they were new and I altered them bevels. In the 2 years(??) since then I have kept them razor+ sharp just with leather stropping, latterly using a tormek on the ouitsides. If your steel is fine and dense, you can knock the wire edge off first hit in a wooden board, an old joiners trick. Consider the old boys with their strickles, they kept there billhooks and sickles sharp with sand and tallow.....I think they created a micro saw edge :D In any case a pansy polished edge would soon get scratched up with grit and crap on the hazel or whatever.....For general axe hewing I seldom go above a filed edge, why bother, the finer cuts come later......
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Re: de-burring

Postby SeanHellman » Fri Apr 02, 2010 8:50 pm

Good advice so far. Taking the burr off is essential to a good sharp edge, the finer you go with the grits and stropping the better the edge will be. I have seen photographs taken with electron microscopes and have studied my edges under a normal microscope, there is no such thing as a zero radius edge, they are always like a saw with ridges, serrations and even rolled over wire edges. The coarser the grit the edge was sharpened on the worse these serrations are, the less sharp the edge. Coarse serrations may seam sharp at first but through abrasion and friction with wood they wear and break down quickly, finer serration from a stropped deburred edge will wear down slower and stay sharp longer.
With sharpening and how far you go with grit size is always dependent on what you will be using the tool for. As long as the edge works for you, thats fine, but this edge may not be good enough for someone else.
If you have a tools with a burr on and it is used without removing it in a controlled way eg stropping, then this burr will be forced from the edge possibly fracturing some of the edge away itself. This will cause a fine nick which will blunt quickly. A blunter tool will blunt quicker than a really sharp tool.

A sharp edge will catch on the thumb nail. Hold your thumb nail down on a piece of wood and present the edge onto the nail at a few degrees greater than you honed it at. The edge should catch on the nail , if it skips or slides off it is blunt.

goldsmithexile wrote:For meat butchery a knife edge with tiny seratins from a steel is ideal.
I disagree a properly sharpened knife would be superior to one with serrations in.

goldsmithexile wrote:If your steel is fine and dense, you can knock the wire edge off first hit in a wooden board, an old joiners trick
As I have said I think this is bad practise, the wire edge is attached still and so knocking it off can cause a jagged edge, undoing the honing you have just done.
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Re: de-burring

Postby goldsmithexile » Fri Apr 02, 2010 8:57 pm

Well like I said if your steel is fine and dense.....If joiners did that for years, there must be something in it, it worked for them or were they all wrong because they didnt know about veritas kit :lol: I never heard of any joiners stroping edges did you (traditionally I mean, ones who did it all day every day?) As for steeled knives for cutting meat, talk to bernie..... :lol: As far as I can tell no butcher workers in meat factories strop there knife, just a quick few passes of a steel.....
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Re: de-burring

Postby RichardLaw » Fri Apr 02, 2010 9:16 pm

Hum, I have mused on de-burring chains, I was told to knock them on the top with the base of the file handle. That deals with the burr on the top, but leaves the one at the side!
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Re: de-burring

Postby SeanHellman » Fri Apr 02, 2010 9:35 pm

goldsmithexile wrote:As for steeled knives for cutting meat, talk to bernie..... :lol: As far as I can tell no butcher workers in meat factories strop there knife, just a quick few passes of a steel.....


Are you talking about a steel which is smooth and just re alines the edge and straightens the rolled edge, or a steel with groves in which takes a fine amount of metal off the edge like a hone?
A steel is better suited to a butcher than a leather or wood strop, because of the blood and dampness. As Brain said how far do we go and is it worth the effort?

From what I have heard over the years, read and researched, we will always have our own theories and I am sure we will never come to consensus.

I think that the shape of the edge or edge geometry, what angles you hone too, are the most important part of sharpening, give me a 1200grit water stone and I can put an edge on a tool which works fine.
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Re: de-burring

Postby Brian Williamson » Sat Apr 03, 2010 8:29 am

Great stuff guys. I find this kind of thing endlessly fascinating (I hope that you do to!).

There seems to be some consensus here - that the further you go up the grits (or is that down?) the finer the edge will be.

Sean makes a really interesting point in that a finer edge will stay sharp for longer than a less fine one because smaller serrations support themselves better than large ones. Hadn't thought of that one before.

Also some division on the effect of the burr. I think that the presence of a burr merely indicates that the two sides of your bevel are meeting at an edge. It gives little indication of how sharp that edge will be. As you move through the grits the burr will get finer, but does it ever come off of its own accord, or do you always have to physically remove it (either by making the first cut, or by inducing metal fatigue by working it from side to side)? And no one yet has claimed to have personally experienced a knife edge damaged by not deburring. So I remain unconvinced by that effect (interesting to hear Robin's experience with chainsaws though).

As to the word strop, what do you take that to mean? I would use it to define wiping (rolling?) your edge back-and-forth on something (wood, leather, the heel of your hand) to fatigue and remove the burr. This could be with or without any kind of polishing compound and the strop itself would be noticeably softer than the blade. Does anyone use it in a different way?

I read a magazine article once that was describing a japanese tradition of knife making so refined that they used different knives for slicing green and red tomatoes, and that the knife should be so sharp that it would cut through under its own weight with no slicing action neccessary. I decided that it was tosh. Do you reckon that was a justifyable reaction?

Ultimately, I guess, the only accurate guage of sharpness is how well the edge does its job.

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Re: de-burring

Postby goldsmithexile » Sat Apr 03, 2010 9:33 am

LOL the japs also have polishing plane's which are so sharp they will run down an inclined board and take a shaving under there own weight (there plane's are wood, so no weight to them ike an iron western one....maybe its a cultural myth or a zen moment or something :idea: )
Like you say does the edge do its job? Match the apropiate edge to the required job in hand. Why waste time and effort to go to far if its not warranted?
LOL my fire wood splitter works best with a blunt and short 45 degree bevel (put on decades ago by a farmer in normandy......
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Re: de-burring

Postby robin wood » Sat Apr 03, 2010 9:47 am

Brian Williamson wrote:Ultimately, I guess, the only accurate guage of sharpness is how well the edge does its job.
Brian.


This is indeed the one we should all remember. Now on British Blades forum sharpening is the one issue that will cause an unpleasant scrap so it is nice to see that we can discuss it openly here without folk feeling they are being told they are wrong.

There will never be consensus because we all work different ways and all choose to put different amounts of time in. My friend Hannes worked with Japanese temple builders and they spent 1 hour of every 8 hour day sharpening. To me that went too far but then it does save a great deal of time when a heavy razor sharp tool can waste wood quickly whilst leaving a wonderful finish.

To answer Brain's burr question's generally the burr becomes thinner and finer as you go down the grits, it will normally come away on its own without stropping if you go down to fine enough grits (my finest stone is a Shapton 16,000) or if you use a strop such as leather stuck on a board. Strops can be just leather or I use them loaded with autosol metal polish. Polishing greatly improves the finish of any tool, particularly as the last stage after going down through progressively finer grits. As Sean rightly points out it is effectively making much finer serrations which shares the wear more evenly, big serations all the wear hits the tips and they soon blunt. If you break the burr away artificially by whatever method you are leaving behind an edge a little like the torn edge of a piece of paper. I am not saying this is wrong, our old time carpenters used a sharpening method that worked for them, Japanese carpenters use a method that works for them, each to their own. We all need to choose how much time we want to put into how good an edge. It is pointless spending 2 hours creating the perfect edge on a tool that gets rough use on dirty wood, or if you are the sort of person that likes to keep their tools without sheaths in big bag together, in that case a quick and dirty sharpening method would suit you better.

A quick comment on butcher's steels and Bernie's sharpening. Most steels are not removing metal and most butchers/kitchen knives do not stop cutting because they are blunt but because the edge has rolled. If you have a very fine edge in a straight line then it easily flips one side or the other like an umbrella turning inside out. The steel realigns the edge and gets it cutting again. Steels do vary, some are mildly abrasive and remove a little metal, others are simply for realigning the edge. Bernie uses a shrade old timer hone steel, which is a fairly coarse abrasive, to put a secondary micro bevel on his knives. It is a good method of sharpening for general purpose knives and is the way a mora clipper comes when new but not so good for a dedicated woodworking tool.
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Re: de-burring

Postby Brian Williamson » Sat Apr 03, 2010 6:10 pm

Wow, Robin, there's a new thought for me. Edges so fine that you constantly have to re-align them. That sounds rather counter productive? Is it because an edge optimised for meat turns over when it hits a bit of bone? Or are some butchers just over enthusiastic?

I do find the same kind of thing with my billhooks. occasionally I'll hit something so hard that it turns the edge. if I simply sharpened it away it would leave a little depression in the blade. usually I find that i can push most of it back into line with the back of another billhook.

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Re: de-burring

Postby SeanHellman » Sat Apr 03, 2010 6:28 pm

Brian Williamson wrote:Wow, Robin, there's a new thought for me. Edges so fine that you constantly have to re-align them. That sounds rather counter productive? Is it because an edge optimised for meat turns over when it hits a bit of bone? Or are some butchers just over enthusiastic?

I do find the same kind of thing with my billhooks. occasionally I'll hit something so hard that it turns the edge. if I simply sharpened it away it would leave a little depression in the blade. usually I find that i can push most of it back into line with the back of another billhook.

Brian.


Bone is a very hard material and can easily roll an edge. I have damaged my my edges from time to time, actually it is often when I lend a tool and do not say it can only be used for finishing cuts and not rough cutting, the edge rolls and as you say Brian if it is sharpened then you have a depression or blunt nick in the blade. I often push these rolled edges back with my burnisher or anything harder than my knife steel and then resharpen.
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Re: de-burring

Postby robin wood » Sun Apr 04, 2010 8:40 am

Brian Williamson wrote:Wow, Robin, there's a new thought for me. Edges so fine that you constantly have to re-align them. That sounds rather counter productive? Is it because an edge optimised for meat turns over when it hits a bit of bone? Or are some butchers just over enthusiastic?

I do find the same kind of thing with my billhooks. occasionally I'll hit something so hard that it turns the edge. if I simply sharpened it away it would leave a little depression in the blade. usually I find that i can push most of it back into line with the back of another billhook.

Brian.


That is exactly what happens all the time with kitchen knives on a miniature scale and what your steel is for. Have a look with a good strong magnifier. If you look at a kitchen knife it is full flat ground from maybe 1-2mm at the back down to nothing at the edge over 2cm depth. If zero ground with no secondary bevel this would give an edge at around 5-10 degrees where a razor is typically 12 degrees. So your kitchen/butchers knife wears a tiny secondary at around 20-25 degrees but the very thin steel just back from the secondary is prone to rolling and flipping side to side hence the steel to keep it realigned.
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