Which mirco-bevel/polishing question

D

dieselpusher6262

Joined
Jun 3, 2009
Messages
34
i have a zt300 that i have spent a lot of time on, for anyone thinking of removing the dlc coating with sandpaper its alot of work, days and days) and i gave it a 15 degree bevel, starting from 120 grit to 240,320,400,500,600,1000,1200,1000(missed some scratches)1500,2000,2500,3200,3600,4000,6000,8000,12000. to say the least that to took along time. i had considered removing blade material down to 1/16" for the mirco-bevel, but decided it would be safer and more uniform to create my 15 degree bevel and decided what to do from there. today i took a fine cermaic rod and tried to put the mirco bevel on it and at 20 degree it marked up a decent amount of my polished area. i thought the mirco-bevel was supposed to be nearly unseen. did i use the wrong angles, and since i am thinking i am going to have to repolish my edge i was thinking about taking it down to 10 degrees with a 15-17 mirco-bevel. this was a hard use knife but with all time and energy i put into, along with how much i thinned out the blade i plan on keeping it for an after work carry. also after i polished the edge i stropped it for maybe 2 hours lights with white and bare leather, should i hold of on that until i do the mirco-bevel or is that left realitively coarse compared to 12k abrasive media. thanks for taking the time to read everything
 
could wait started to reprofile at 10.5 degree (couldnt get a good adjustment on my sharpener at 10) anyways i also wanted to ask the guy at the knife shop (which everything else see said was right) told me to after i am all done sharpening and polishing to put my knife (or blade only) in the dishwasher, run it on the highest temp setting and as soon as i turns off take that hot blade and put it in a bowl if ice water there by ht a little. he said the milder heat wont effect anything else but the edge and i should pick up a couple of rockwell points. I have never heard of anything like this, does it work and if it does i would like to use hot water, the oven something where i could monitor the temp. i am guessing a dishwasher could go to 200 degrees, but sure but if anyone knows of this please let me know and what i would need to do it at home. Would dry ice be better to cool the blade. I am just weary of instructions that are so vague. thanks again
 
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no


90% chances he had a good time on you. 10% left he is completely stupid. 200°F is 200°F even at the edge. and 200°F on a dishwasher will do nothing but dulling your edge ... try to get s30v data sheet to see what temperature is advised for tempering. this is the lowest range of T° that will effect the HT (and at this range it will softent the steel) below that it won't do anything even at the very apex of the edge.
 
I'd say that knifeshop guy is, knowingly or unknowingly, full of it. The heat from a dishwasher shouldn't do anything, ice water won't either. Dry ice might, but for $200+, the makers should have done it for you w/ liquid nitrogen.
 
that was my thinking, but maybe i the low heat could just effect the outer most layer of the steel. and i dont think he was joking, i was in there for maybe two hours. pretty much how is when ever i meet someone that shares my anal retensive complusion about getting the edge just prefect, and not for show or display i can not help myself even knowing that it has a hard day ahead. I am learning to imbrace my addiction, and at very least if always have something to do on the weekends. oh one other thing, i was out looking to buy some metal polish and other little things and woodcraft had the paper wheel sharpener, if figure i wouldnt need the grinding wheel but would the paper wheel beable to get things sharper then where i am at with sandpaper. i have some stone but i seem to be drawn to curved blades.
 
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That knifeshop guy is full of it. Completely and utterly ridiculous.
 
i would agree that the knife shop guy is full of it. you can steam clean a blade and not hurt the heat treat. it takes a lot more heat than 212 degrees to do anything to an edge.

as for the paper wheels, look through the paper wheel thread and see how many guys have bought the wheels and liked them. get a set and learn how to use them. i also offer phone help if anyone needs it. check out some of the vids at my website of knives i made and sharpened on the wheels along with some knives sent by members.

here is the link to my paper wheel thread http://www.bladeforums.com/forums/showthread.php?t=578787 check out page 36, post 710 with some good info.
 
Knife shop guy is 100% full of it. Knowingly or not. For a hardness increase to take place in steel, the grain structure must be transformed. Unless the steel is heated to its critical temperature and quenched, this will NOT happen. Critical temperatures for all steels are over 1000 degrees fahrenheit. Period. No ifs, ands, or buts. The only change made by lower temperatures is annealing or tempering, or lowering of the hardness.The only possible exception to this rule might be cryogenic treatment, (and no, an ice water bath is not cryo - liquid nitrogen temperatures at least are necessary for any effect) which some claim can add a few points of hardness on the rockwell C scale. The main benefit of cryo is the refinement of the grain structure into finer crystals, which may or may not help with wear resistance.
 
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I left my izula out in the sun then threw it in the freezer, it rockwelled at 82! :eek:
;)


All kidding aside, he has no clue what he is talking about.
 
eKretz said:
Knife shop guy is 100% full of it. Knowingly or not. For a hardness increase to take place in steel, the grain structure must be transformed. Unless the steel is heated to its critical temperature and quenched, this will NOT happen. Critical temperatures for all steels are over 1000 degrees fahrenheit. Period. No ifs, ands, or buts. The only change made by lower temperatures is annealing or tempering, or lowering of the hardness.The only possible exception to this rule might be cryogenic treatment, (and no, an ice water bath is not cryo - liquid nitrogen temperatures at least are necessary for any effect) which some claim can add a few points of hardness on the rockwell C scale. The main benefit of cryo is the refinement of the grain structure into finer crystals, which may or may not help with wear resistance.
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There have been a few accounts of home freezer treatements increasing hardness, but these seem to be cases where the heat treatment and/or the hardness testing were likely botched in the first place. Admittedly, this is also colder than just ice water. Hardness increases are definately possible with dry ice magnitude temperatures, though LN2 is generally seen as superior. The grain size is unaffected by cryogenic treatment. However some reports of extremely fine carbides forming have been published. This is during tempering of cryogenically treated pieces.
 
with the last post i have some additional questions. first due you benefit from ht'ing because of the heat, or because of the difference in temp from say 1000 degrees to the quench at room tempature. 1000-80=920 degree difference. could the same results be had from 400 degree heat and -520 quence (i have no idea of LN2 making numbers up here) more interested in therory. damm it to each person that replied and especially me2 i hold you accountable for this sprout of a new obession. i can already see what lays ahead as i have 7 tabs open all relating to ht. thanks for info i think i am going to have to go back threw all the old post (there are like 370+ pages) and starting finding answer. anyone have a good place to start to get an understanding of basics and terminology?
 
Try to think in terms of the microscopic structure of the steel. The microstructure (an abbreviation) is what controls the properties. The heat treatment is the path used to reach the desired microstructure.

Heating the steel above the critical temperature changes how the atoms are arranged compared to the normal room temperature arrangement. Cooling the blade quickly results in a different arrangement, even though we are back at room temperature again. Tempering the blade, which is heating it yet again, but to a lower temperature than before, changes the atomic arrangement yet again.

These different atomic arrangements, or microstructures, are the goal. Heat is just the most efficient, and in some cases the only, way to get there. The principle of microstructure controlling properties applies to all metals, but for the sake of simplicity, most people limit these types of discussions to steels used for blades.

The above paragraphs are DRASTIC over simplifications. There are any number of members here who can elaborate on these topics to your hearts content. I suppose I should give credit where credit is due, see below.
Kevin Cashen, Stacey Apelt, Mete, Sunshadow, Ray Benson, Karl Koch, Roman Landes, John Verhoeven, and a host of others I can't remember have all answered my heat treatment related questions with mind numbing (literally) ease. Stacey's basic metallurgy sticky thread gets into more detail and depth over on the Shoptalk Forum.

If you pursue this study, I'd recommend starting with basic material science and metallurgy information. There is a honey pot full of misinformation, superstition, supposition, and in very rare cases, deceit, in knife making heat treatment. Supposition isn't necessarily bad as long as it's presented properly. Asking probing questions will tell you if the source of information knows what's going on or thinks it knows what's going on, and there is a world of difference. Also, keep in mind that research continues in metallurgy, and sometimes no one knows what's going on, though there are always a few peolple with really good guesses.
 
Me2, with respect to grain size/structure, there is a very slight difference in size between austenite and martensite. One of the goals of cryo is to fully transform the retained austenite to martensite, which does have slight effect on density and therefore size of grain...admittedly very slight. This is why steels can change size when heat treated. Perhaps I should have used the term atomic structure instead of grain size.

Diesel, me2's post covered a lot of bases well; as for the temperature question you asked, it isn't the difference in temperature of heating and quenching that drives the process. As I stated, for heat treatment to work, critical temperature MUST be reached. This transforms the grain structure of the steel from austenite to martensite. The steel should be allowed to "soak" at this temperature for a set length of time, depending on thickness and steel type, as well as desired hardness characteristics. If the steel is allowed to cool slowly, the grain structure will transform back, nearly to it's original state. When the steel is quenched from it's critical temperature, it is rapidly cooled, and this has the effect of helping "freeze" the grain structure in a state closer to what it has at the critical temperature. Some austenite is inevitably present after heating and quenching since the steel cannot be instantly cooled; transformation of this "retained austenite" into martensite is one of the goals of cryo treatment.

Edited to add: here is a link for further cryo info:http://www.nitrofreeze.com/cryogenic_tech.html

Also, for further grain size/structure info:http://books.google.com/books?id=am...4kPVMWw&sig=8nnSqtkAshrMki5H99_MAelZrXc&hl=en
(look to about the bottom third area of the page for the grain size/structure info, or read the whole thing, it's relevant)
 
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dieselpusher6262 said:
with the last post i have some additional questions. first due you benefit from ht'ing because of the heat, or because of the difference in temp from say 1000 degrees to the quench at room tempature. 1000-80=920 degree difference. could the same results be had from 400 degree heat and -520 quence (i have no idea of LN2 making numbers up here) more interested in therory. damm it to each person that replied and especially me2 i hold you accountable for this sprout of a new obession. i can already see what lays ahead as i have 7 tabs open all relating to ht. thanks for info i think i am going to have to go back threw all the old post (there are like 370+ pages) and starting finding answer. anyone have a good place to start to get an understanding of basics and terminology?
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there are 2 major steps in heat treating:
1. quenching. this hardens the blade.
2. tempering. this relieves some stress in the blade steel caused by quenching.

every steel based on it's final purpose will have it's own heat treat recipe

don't try to heat treat a blade thats already heat treated. you would just ruin the original heat treat and lose most of the blades performance. before a steel can be heat treated it has to be in it's annealed state (full softened).
 
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eKretz said:
Me2, with respect to grain size/structure, there is a very slight difference in size between austenite and martensite. One of the goals of cryo is to fully transform the retained austenite to martensite, which does have slight effect on density and therefore size of grain...admittedly very slight. This is why steels can change size when heat treated. Perhaps I should have used the term atomic structure instead of grain size.
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Without precisely defining our terms, I can see we could go on for some time and miss each other's meaning. I think what you are referring to by grain size is the size of the unit cell of each individual FCC or BCC unit.

The second article you linked to above is interesting, if a bit dated. Some of the terminology used there is no longer in common use and may cause some confusion if readers go looking to modern sources. I know I read through many a book trying to find troostite and came up empty handed.

For anyone interested in further reading, such as dieselpusher6262, just be aware that there are literally warehouses full of research that was done by various steel companies in the late 1800's and throughout the 1900's. If you have a question, it is very likely someone has found the answer. The trick is knowing where to look. Anyone claiming to be doing something new or revolutionary has a huge burden of proof to show what they are doing really is new and revolutionary.
 
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jimnolimit, i am a little confussed i always read about people re ht'ing there blades, normally it is on certain higher end steels (like s110v or someothers that i cant remember the name). how is any finished blade able to be reheat treated if it is already in a hardened state. once again i may be missing something but once steel is hardened it can not be taken back to an annealed state. Question way beneath the level of conversation but when ht'ed is the entire blade effected or is just the outer part. i am "assuming" because of the extreme heat the entire blade would be. also unless i am mis understanding something, ht'ing cryo etc arent exactly understood, or at least not completely, or is more of a fact of how many different steels there are and the way that they react?
 
dieselpusher6262 said:
jimnolimit, i am a little confussed i always read about people re ht'ing there blades, normally it is on certain higher end steels (like s110v or someothers that i cant remember the name). how is any finished blade able to be reheat treated if it is already in a hardened state. once again i may be missing something but once steel is hardened it can not be taken back to an annealed state. Question way beneath the level of conversation but when ht'ed is the entire blade effected or is just the outer part. i am "assuming" because of the extreme heat the entire blade would be. also unless i am mis understanding something, ht'ing cryo etc arent exactly understood, or at least not completely, or is more of a fact of how many different steels there are and the way that they react?
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people who have their blades re-heat treated usually send them out (unless they are a knife maker). before a blade is re-heat treated it first has to be annealed (brought to it's fully softened state). any heat hardened blade can be anneal. adding heat (usually between 400-900 degrees) for any set period of time to a blade that has already been hardened will just add another tempering. tempering relieves stress created by the initial hardening (quenching). a fully quenched blade is very hard and will easily crack or snap, the tempering slightly softens the steel to toughen it up. cryo treatments are the most beneficial right after the quenching process (before the tempering).

what it comes down to is you're not going to perform some magic kitchen steel-processing to make your blade's edge harder. based on that recommendation, the guy at the knife shop doesn't know anything about heat treating steel or metallurgy.
 
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dieselpusher6262 said:
jimnolimit, i am a little confussed i always read about people re ht'ing there blades, normally it is on certain higher end steels (like s110v or someothers that i cant remember the name). Some people like to have their production blades in various high end steels rehardened by a custom maker or custom heat treater to try to improve the properties.

how is any finished blade able to be reheat treated if it is already in a hardened state. once again i may be missing something but once steel is hardened it can not be taken back to an annealed state. As it turns out, steel can actually be rehardened. The various changes that happen in steel are reversible, given enough heat and some time. It is the same concept as being able to freeze and thaw water repeatedly. If a maker botches the heat treatment of a blade, he/she can usually save the blade by rehardening it. As with most things, there is a right way and a wrong way to do it, but it can be done.

Question way beneath the level of conversation but when ht'ed is the entire blade effected or is just the outer part. i am "assuming" because of the extreme heat the entire blade would be. Yes, the entire blade is affected, not just the outer part. There are heat treatments that affect just the outer surface of the pieces being treated, but they are not normally done to knives. Various gun parts, gears, axles, and bearings can have a hardened outer layer, while the interior is basically left annealed.

also unless i am mis understanding something, ht'ing cryo etc arent exactly understood, or at least not completely, or is more of a fact of how many different steels there are and the way that they react? Both are correct. Cryogenic treatment of steels is relatively new and some aspects are not completely understood. Heat treating in general is understood pretty well, though research continues into better ways to do it. There is always someone looking to squeeze that last little bit of water from the stone.

Each steel type will react differently to different heat treatments. In the most general sense, if you heat a blade steel past a certain point, quench the steel, then temper it at a certain temperature, you will get a good blade. The differences lie in the specific temperatures, how fast does the quench cool the steel, and how high is the strength, hardness, and other properties when you're done.
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See my responses above in bold. Please don't feel like anyone is trying to talk above you. Most anyone here will be happy to answer any question you have if they can. If you have specific questions for a project of your own or need clarification of anything discussed so far, just ask. 20 years ago, I thought you could make a good knife from steel found at Home Depot. Good thing I asked someone before trying. That part about different steels reacting different ways will get ya if you're not careful.
 
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