I’ve got several beat up older japanese chisels in need of much grinding–most are terribly skewed, rounded and dinged up.
Just wondering how hot they can get (using a dry slow speed grinder) before they lose their temper…should I dip them in water as soon as I feel a little warmth, or can I wait till I nearly burn off my fingerprints?
My other question is regarding the longevity of japanese chisels with scalloped backs: what can you do when you’ve ground down to the top of the scalloping?…some of these chisels have only 1/16th or less left at the tip of the back before I get into the hollowed-out area, and I haven’t even started grinding. Has anyone dealt with this?
Thanks,
Max
Replies
mad,
If I remember the instructions that came with the Japanese chisels I was given many years ago, you are supposed to keep the flutes at bay by working (stoning) the flat sides periodically, to maintain the area of flat at the tips. The instructions also said something about having a Special Hammer, with which you were supposed to hit the bevelled side of the chisel to Do Something Special to the metal on that side. I remember being put off by the warning that striking the bevel too close to the edge would break the tip off. So I hollow grind the bevel like I do all my western cheisels, and just work the flat side a little heavier than usual when sharpening them.
Using light pressure on the wheel, and dunking the chisels into water as soon as a fingertip resting near the edge feels warm, will prevent drawing their temper. If the edge turns blue, it's gotten too hot.
Regards,
Ray Pine
My other question is regarding the longevity of japanese chisels with scalloped backs: what can you do when you've ground down to the top of the scalloping?...some of these chisels have only 1/16th or less left at the tip of the back before I get into the hollowed-out area, and I haven't even started grinding. Has anyone dealt with this?
Not personally... but I was reading through David Charlesworths books (I forget which volume), and he suggests that when you get to this stage just return to the stones and 'flatten the back' a little further. You'll be wearing into the scallop so it will retreat from the edge a bit.
I wouldn't risk bluing the steel. I dip my chisels in water often, maybe someone will correct me here but I don't think that it harms the grinding process.
Edit: Spelling
Edited 10/30/2006 5:16 pm ET by Buster2000
I think the answer to your question is 350 F. Now that sounds hotter than it is. You can easily get the edge that hot and still have the meatier part not too warm to touch. If you are burining your fingers, your edge is probably overheated. I think that's the question you are asking. The question you SHOULD be asking is how can I grind cool? Another good question is: is a water quench a good idea?
You can grind cool with just about any grinder and stone. I use the world's worst craftsman grinder (30 years old) with the original gray stone. The stone is worn and badly clogged. Cleaning it frequently really helps, but I find the trick is using a very light touch- so light that the stone is just skipping across the steel. For a big job I find this faster than pushing hard, then setting the tool aside to cool. Which brings me to the other question. I think water quenching is a bad idea. If you buy into the idea that the edge is much much hotter than the rest of the chisel, that water quench could be causing problems. Off the top of my head, I recall hearing something about microcracking.
Adam
I use the world's worst craftsman grinder (30 years old) with the original gray stone.
Hi Adam
Is this driven by 'lectricity?! Or do you manage to convince the neighbourhood kids to turn the handle for you? :)
You can grind cool with just about any grinder and stone. I agree. Taken slowly and "using a very light touch" the blade does not heat up much. I do still dunk it in a tin of tepid water every 10-20 seconds to dissipate any heat. Also, I find a 60 grit white Nortons wheel (my grinder is a high speed 6" affair) grinds cooler than the old grey wheel that came with it. Having completed a mini marathon of hollow grinding several chisels and thick plane blades, my mind turned things creative in this regard. If you have been reading the WoodCentral forum you may have come across my post on flattening the backs of blades using a bench disk sander and a heavy magnet for stability. What I noticed was that the blade heated up considerably less than expected, and my interpretation was that the magnet acted as a heat sink. Back to the high speed grinder. My thought is whether it is possible (and even desirable) to create a heat sink out of the tool rest. For example, by adding an absorbant material (I have a brass plate I can use).
Just opening up a little discussion here. What do you think?
View Image
Regards from Perth
Derek
Hi Derek,I did read that thread. Very interesting, I just don't know enough to add anything intelligent. I was led to believe that the heat sink is a better way to cool an overheated high carbon blade.I believe the mechansim is similar to the effect that you can get ice faster if you put warm water in your ice cube trays. I should be able to do that math, remember those equations, but alas.According to Bill Tindall, thre are many better grinders than my old electric grinder and about 300,000 better wheels than mine. I used to put an 8" white wheel on my other electric tool, my Jet wood lathe. That worked okay- in fact, maybe I should rig that up. I'm sharpening up my old addis gouges.adam
Adam, the warm water trick DOES work under lab conditions but isn't worth squat in your GE fridge, so plan ahead for chillen those cocktails. All the best, Pat
Are you saying that if I put ice cube tray number 1 in the lab freezer, and the initial water temp is 70 degrees, and I wait until the water has cooled to 40 degrees and then I put in tray number 2, with an initial temp of 40 degrees, that tray number 1 will freeze before tray number 2? Is there some sort of loss of heat momentum at play?
I was a chemistry major only long enough to flunk calculus.
Thanks all for the advice.
I too use a sandpaper on glass system for honing, which works great for me, but I was basically trying to figure out the most efficient way to remove alot of metal without a wet-grinding system. I've got about 10 chisels to go through, some of which are very skewed. It just seemed so tedious after spending 20 minutes on one chisel, cooling the blade every 5-10 seconds, and achieving mediocre results.
I think Adam was right: I need a lighter touch and a little more patience.
As to the idea of a heat sink: I wonder how effective that would be given that the first area to heat up is the edge of the blade (the part that really counts), and the heat transfers from there...might have to experiment with that one....
Max
I'm glad you are gleaning the sense out of this thread. I think you are on the right track. Obviously if you want to utilize a heat sink, you want a lot of surface contact. So if you can lay that flat chisel back on an iron plate, you're there. I just wanted you to know that quenching can be bad for your tools.Beyond that, I don't think 20 minutes- I've spent an hour, restoring a chisel is too much time. Just be careful not to overheat them. Also know that if you do, the area effected goes beyond the discoloration.Adam
Adam,
Just what are the bad effects of quenching? I'm talking here about a regular dip into room temp water of an edge tool that is being ground, to prevent overheating or drawing temper, not the quenching that takes place during forging of tool steel.
I've never been aware of any ill effects from this, have done it regularly when reshaping or otherwise doing extensive grinding of an edge tool. Always try to use a light touch, and dunk before it gets hot to the touch. I keep a fingertip right up on the edge when grinding, and at the first sensation of warmth, into the water it goes. The tool, not my finger!
I will say that the older I get, the less impatient I become. Used to turn tool steel into spring (blue!) steel at the grinder pretty regularly when I was young and in a hurry. So I use a lighter touch at the wheel nowadays. Normal grinding in the couse of sharpening, I don't heat up the edge enough that it gets above baby-bottle temp.
Regards,
Ray
Slaw, I was a chem major for two years (quant/ qual and all the rest) till I saw all the starving dedicated chemists in the late 60's. I then shifted to a BS Management / A.A.S. Computer science and have done very well.
I tried this at home and my chem friends jumped all over me-what was the ambient temp of your kitchen-how far from the sink to the fridge etc. The bottom line is that it works in small lab controlled samples at the same time. It also works to a not to perceptual degree at home due to the lack of control of the two temps of the samples and the freezer variables -shelf/position/ temp/ recovery rate of the cold source etc. The basic driver here is that the warm water has a higher molecular activity rate and cools faster.
You may enjoy this. My heavy math final for my BS was "A" sheet of paper with one word problem . He gave out the blue books and the paper and said "see you gentlemen next week ". He didn't care who helped you. The next A.M. I collared my buddy from the local Poly Tech college(you know the type-a plastic pocket protector and 32 pens in it) and we gave it two full days . I got a "C" Pretty nasty exam Eh? The class was a combine of higher level algebra/calculus and analytical geometry. Enjoy, Pat
The basic driver here is that the warm water has a higher molecular activity rate and cools faster
Pat: Two ice cube trays: One is room temperature, one is almost boiling. I put them on the counter for a week. Assume equal volumes and everything else is the same. Assume no evaporation. Do I understand you to be saying that if I then try to freeze the two trays of water that are now the same temperature, the one that used to be hot water will freeze sooner?
smslaw
slaw, it's not that complicated. Two trays, one with hot tap water and another with cold tap water. Put them both in the freezer and the hot water one is supposed to freeze first because the warmer water had a higher molecular rate because of the higher temp. Pat
But if that's true, at some point on the way to being frozen, the one that started hotter will be the same temperature as the other one. For an instant at least, both are the same temperature. Then why should the one that used to be hotter end up frozen sooner?
From a quick google search:
"Does hot water freeze faster than cold water? If it does, why? of course hot water takes longer to freeze than cold water. It first needs to be cooled down to the temperature of the cold water and then takes as long as the cold water to freeze.The scientific finding that was misinterpreted and which thus led to the above stated myth is the following:Water that was heated (to a boil) and then cooled off again (!) will freeze *slightly* faster than water that was never heated. This is due to the fact that dissolved gasses were driven out of the water by heating it. In the water that was never heated the dissolved gasses slow the freezing process.This should NOT be memorized as "Heated water freezes faster" (Wrong!) Heated and re-cooled water freezes faster! I hope I could help you here."
Samson,The heat transfer rate is governed by T1-T2. When the delta is higher, the rate is higher, the faster that water is becoming ice. It may be true that in the real world, you can't measure when one becomes ice faster or for other reasons the cold water ice cube tray wins the race to ice. But the story is told to engineering students to teach about the importance of the rate of heat transfer. For us, the story is directly relevant since we could be risking some expensive steel chisels or plane irons by quenching them, achieving HT rates that are too high for the steels we are using. Forget about the dissolved gases and everything else. It may or may not be true. But none of that is relevant. Mike's point was that HT rates do have a sort of momentum, so a quick quench in ice water isn't a solution. I don't recommend quenching tools and I think if the tool is getting hot, stop and or change your grinding technique or equipment. Okay?Adam
Hey, Adam, I was just curious about this tangential issue of warm water freezing faster. I just passed on a quote I found on a reputable looking site aftera quick google search that said it was a myth and explained it as a mischaracterization of another experiment. I appreciate your point about the need to control the speed of heat transfer.
By the way, Arts and Mysteries ain't the same without you.
Oh, and can you ask Calvo for some specifics about the Swiss v. German carving tool issue raised in the other thread in the General forum?
Best,
Sean
Sean,Thanks, but I think Dean did a great job. Its my goal to include other woodworkers. I'm sure folks get tired of the sound off my annoyingly droning voice. And i think its good to get other views on that subject. I wish Arts and Mysteries was around when I was starting out. No way. I'm not asking Calvo about his gouge choice. And I prefer Addis thank you very much!Adam
Edited 11/1/2006 8:54 pm ET by AdamCherubini
Samson, thanks for the clarity in this issue. Will the gas free ice cubes change the taste of my 12 year old Irish whiskey? Please see my response to Slaw and have I been duped by my beloved geeks? Just to maintain the purity of this thread, I never loose the temper of my edges as I use a 1000 grit slow rotating wet stone for planner/jointer and french knives, or major bevel changes to chisels or plane irons. Pat
Slaw, bear with me son, I gave up the chemistry degree in the 60's when I saw all those starvin chemists. What my geek friends (and I love them dearly-it's a natural afliction) tell me, it's like two guys runnin the 50 yard dash but one (the hot one) gets to start 20 yards behind the line in a sprint and the gun goes off as he gets to the line where the other guy gets to start from a standing start. It's supposed to be the advantage of the faster molecular motion of the hot guy that accelerates his cooling. I personnaly don't care just as long as it cools down my fine Irish whisky (not too much ice please) . All the best Paddy
...it's like two guys runnin the 50 yard dash but one (the hot one) gets to start 20 yards behind the line in a sprint and the gun goes off as he gets to the line where the other guy gets to start from a standing start. It's supposed to be the advantage of the faster molecular motion of the hot guy that accelerates his cooling.
The problem is your don't start timing when he crosses the start line you start timing when he's 20 yards back. So even though runner one starts from a standstill, he has a 20 yard advantage. When runner two reaches the start line, runner one will be going the same speed but will be 20 yards down the track. Even if runner two has a faster acceleration time he still has to make up 20 yards.
This is the same thing with ice. I don't know about "molecular momentum", but regardless the water temp still has to cool to a lower temperature before it freezes.
This is one of those science run amok myths. There are elements of truth but it boils down to cold ice freezes quicker.
My suggestion is to keep a stock of ice on hand for your whisky... then you don;t have to wait for either!
Damn...reminds me of my differential equations final:1) A moth is spiraling into a candle in a clockwise motion. At T0, the moth is at a radii of R, has an angular momentum of w (sorry no greek letters here, that's supposed to be an omega). Assuming the moth does not alter it's flight, at what delta T does the moth burst into flames.I hated that professor.Jim"There are two spiritual dangers in not owning a farm. One is the danger of supposing that breakfast comes from the grocery, and the other is that heat comes from the furnace." - Aldo Leopold
I have a beautiful 14" Japanese dovetail chisel (beveled sides) where the scallop did NOT move back under hard pressure an the waterstone. I then tried the trick of hammering lightly on the bevel with the back against a wood block After 20 minutes of light tapping, I could see no change. So, of course, I began to hammer just a little bit harder...with predictable results. I now have a hammered chisel, but the edge is chipped and there is a 1/4" crack on the other side of the edge. Oh, and the scallop still runs into the edge!
The message here is: If you're going to try the hammer technique, be careful. It can get away from you quickly. I'll hold onto the chisel until I run across the right "sensei" who can show me how to do it properly. It was an expensive lesson!
Regards,
Ron
Find an Immigrant Eupoean who used a Scyth during his summer holidays for cash. I got this as advice and a demo from my neighbour Franco Foppoli - a nothern Italian who used to catch the train to Switserland each summer for the hay cutting. He is a professional fitter and very competent with tools.
The modern scyths are thin and high-carbon steel. The sharpening technique involves a fairly coarse carborundum stone at regular intervals during use. During the evenings these guys would set up a smal anvil and peening hammer and peen the edge back for about 1/4". Apparently this had two effects - it made it thinner and therefore better cutting/sharpening during the day, but also it work-hardened the edge for edge retention. If you have a look at these, most of the blade is not hardened - just the edge.
dave
Ron,it's not normal practice to tap-out the cutting steel on Japanese laminated chisels, unlike the planes. With the planes, the wedged profile of the blade is critical to the fit of the blade to the dai (wooden block), so flatting the back to move the hollow lower will upset the fit. The blade will become too loose and will need shimming as a result. The strategy is to tap-out therefore, the cutting steel using a pointed hardened hammer, taping on the bevel around the 1/3 of the way down, never close to or directly upon the cutting steel ("ha-ga-ne").With chisels, the profile of the tool is not influencing fit to a jigged holder like the plane, thus the strategy is to go back to the coarse stone (~1000 grit) and take some material off the front third of the chisel back. This will move the hollow down. If you are using a coarse stone and the hollow doesn't seem to be moving down, then either your stone is not cutting well for some reason (either clogged or not suited to the steel you are trying to flatten), or the steel has been hardened too much and is simply hard to sharpen. This is a manufacturing defect, though vastly preferable to not getting the edge hard enough. The really good blades sharpen easily and retain their edge well, I might add.It is critical for good results that your coarse stone be as flat as possible when working the back of the chisel.Well, i'm sure the foregoing is fairly obvious to you now, and you have a cracked chisel sitting there. Sounds pretty bad, but they can usually be saved, so long as there are no cracks running inward to the body of the chisel, you can re-establish the bevel by combination of grinding back, tapping out, and taking matrial off the bottom until the hollow is re-established. Yep, you may well have to tap-out a bit. Otherwise, if you purely take steel off the bottom to re-establish the hollow, you end up having the grim task of trying to remove lots of very hard cutting steel. Tapping a bit downward will mean less work on the back to see the hollow again. If you want to tackle it again, drop me a line and I'll share some tips for how to do that without damaging the tool.
I sharpen my chisels by hand on an 18" square of 3/4 granite, with a cheap honing jig. I use varying grits of sandpaper up to 1200 grit. This sounds tedious but it isn't. Once you have a chisel sharp, it's easy to touch up the edge as needed with just a few strokes. I have an old waterwheel grinder that I use to get old chisels that have been abused back into shape before going to the sandpaper to put a scary sharp edge on them. This way there is no fear of losing temper.
I read recently that Japanese chisels/plane blades should not be holow ground. As the sharp edge is brittle, it needs the backing of the iron. Hollow grinding tends to remove that support.
I've switched to the scary sharp system, it leaves an amazing edge in almost no time, and there is no heat build-up to worry about.
Regarding the hollow back, I believe you used to be able to send the items to the Japan Woodworker store and they would re-establish the edge for you.
Matt
It's true, though.
Has to do with the rapid cooling change of the surface causing the water to freeze faster. In the case of the water in the freezer, one factor is the dryness of the air.
Warm exhaust exiting a tailpipe may freeze when the air temerature is above the freezing level. It cools so quickly it freezes.
This applies to people in desert climates who make ice in shallow pans even thought the mean air temperature doesn't drop below the 50F range. This effect is night sky radiation.
Seeing how this has been done in deserts by nomadic peoples for countless centuries, maybe it is new age. <g>
Mike
How water freezing faster is one of the first myths debunked in any thermodynamics class. It's one of those myths that keeps perpetuation due to 'scientific' home tests.
Hot water freezes faster in your home freezer because it can lose more than 25% of it volume to evaporation. Smaller volume, quicker cooling. I suppose if you want tiny ice cubes you could do it this way... or you could just add the less volume of cold water and get them quicker.
Water in gas for from your exhast converts to liquid water when it leave the tail pipe. Same as when you breath out.
There are also pressure variations, water freezes at 0 degrees celsius at standard pressure. Ever felt the compressor after is charges or discharges.
I've never read about the nomads...
Anyway, I don't think Derek was saying that the magnetic field was acting as a heat sink, rather that the magnet (as in the metal) itself was acting as a heat sink. Derek correct me if I am wrong...
Metod,
The ice cube thing, like the danger to the chisel or teh ice in the desert is all about the RATE of heat transfer. What Mike and I were trying to tell you is:
You want to control the heat transfer RATE- not just the final temperature, when you quench your steel. This is the reason for the names of tool steels A-2, O-1, W-1 etc. I think you want a lower HT rate and a constant one. I'm fairly certain a heat sink is a safer way to cool a chisel. An anvil or heavy iron vise or something is ideal, especially if the two parts can touch (tranferring heat through conduction as well as convention, and radiation).
Quenching an edge could cause problems based on how you do it. This is one of those things the old timers did and eveybody thinks is fine. But the old timers almost always used W-1 steel, steel designed for the high heat transfer rates associated with water quenches. They also didn't pay $75 for a chisel!
Adam
This sounds like a job for Mythbusters! I can't buy water freezing in desert when the air temp is only 50 or so. Unless you have an extraordinary micro climate where the air temp around the water dips to at least 32 F, you are not going to freeze water. Or were my science teachers all wrong? Tom
A few years ago I called the National Weather Service here in Texas to ask a question: How does frost form on the roofs of houses when the air temperature does not dip below 32 F (or 0 C). The answer I got made sense--micro climates form on the roofs when the temperature dips close to, but not to or below freezing point. The air movement over the roof with circulation underneath allows a micro climate to form and dip the temperature below freezing, thus forming ice crystals. It's not magic or voodoo, just the law! Thanks for noticing the emperor has no clothes! Tom
Metod,
Don't try to confuse me with facts, I know what I think!
Ray
Metod
<<We can't be far away, when some political candidate starts promising new physical laws or to find some existing ones unconstitutional - satisfying whatever lobbying groups.>>
Wow...lucky us: we can continue the Lysenko-isation of science in America!
Tschüß!
Mit freundlichen holzbearbeitungischen Grüßen aus dem Land der Rio Grande!!
James
Metod,
I thought a myth was an unmarried female moth.
Ray
Metod,
Growing up in a communist country (even one -- Jugoslavia -- that was relatively liberal, at least in some respects, in comparison to, say, the DDR or USSR) undoubtedly gives you a unique perspective on liberty and freedom that most Americans do not possess. I suspect that you have first-hand experience of the dangers of ideology "winning" the clash between truth and ideology.
For my part, I am a perpetual student of history, particularly that of 20th century Europe. My area of specialisation -- if you want it call it that -- is Germany and the Soviet Union, WW II, and the governments and militaries of each of those countries. I am, by no means an "expert" on any of these subjects, but I do have a fairly wide-ranging and in-depth knowledge.
Combined with 26 years in uniform -- a fair portion of that in Germany during the Cold War -- and the opportunity to visit some rather interesting places -- like Panmunjom, on the North/South Korean border (a really scary place, BTW); the inter-German border; divided Berlin (along with a ride in the duty train through East Germany); and several of the National-Socialist concentration camps, including Dachau, Bergen-Belsen, Sachsenhausen, and both main Auschwitz camps -- I suspect that my perspective on liberty and freedom is a bit different that that of most Americans, as well.
Unfortunately, I see many parallels in American society to features of the totalitarianism seen in the Germany, Eastern Europe, and Soviet Union of the past. Things such as speech codes on college campuses; so-called hate crimes (if you murder someone because of race, religion, political stance, sexual orientation, etc., does it make them any more or any less dead than if you murdered them for their wallet or purse or because they saw you commit a crime, etc.?); resorting to name-calling, personal attack, and denunciation when one cannot logically answer or rebut a debating point; use of ideology as a substitute for real thought; imposition of increasingly more stringent and redundant laws on areas of life that -- in reality -- probably don't need any laws governing them at all; increasingly intrusive collection and (indiscriminate) distribution of information on people's finances, spending habits, reading and movie tastes, internet usage, health, etc. You have, no doubt, observed the same kinds of things.
Science, amongst many other areas, has become politicised to the point that there are areas of science that appear to be (at least somewhat) stifled be cause science and ideology don't match up. Climate change and its cause(s), stem cell research, and evolution are just a couple of the areas that immediately come to mind.
So, I think that we all need to pay close attention to what the politicians are saying and be very choosy in whom we elect to offices of public power and responsibility. A mindless backlash against the current crop is just as counter-productive as re-electing the worst ones back into office.....
Q.: What's the definition of "Honest Politician"?
A.: One who stays bought.
"Any society that would give up a little liberty to gain a little security will deserve neither and lose both." (Ben Franklin)
Yours in the defense of Liberty....
Tschüß!
Mit freundlichen holzbearbeitungischen Grüßen aus dem Land der Rio Grande!!
James
Edited 11/2/2006 2:17 pm by pzgren
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