CBN grinding wheels?

Discussion in 'Woodturning Discussion Forum' started by bob sesti, Apr 28, 2012.

  1. robo hippy

    robo hippy

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    I don't understand the part about jigs saving steel because you can control pressure better, and spend less time at the wheel. This is not a matter of one method being better than the other, which in this case would be jig vs. platform/free hand grinding. It is a matter of how well you know what you are doing. The only thing that makes platform sharpening faster is that you do not have to set up a jig. Kind of like 'which holds better, a tenon or a mortice?" Of course the answer is they both work fine, when made properly.

    robo hippy
     
  2. odie

    odie

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    There is a lot of insight and truth to what Robo Hippy is telling us, here......

    The old saying about "there's more than one way to skin a cat" holds true!

    For myself, I did freehand grind, but it's been 20+ years since I have with any regularity. I was never that good at it, but if I had stuck with it, I have no doubt I would have learned to use freehand as well as some of the other turners do.......but........around 1990, or so, I purchased a Wolverine, and have been using it ever since.

    Like Robo indicates......learn to use what you got, and you'll make it work as well as the alternative.

    I will say this, though........ Jigs do make the less experienced turner get results easier than freehand, but freehand will get the same end result with a little perseverance and practice.

    His point about less set-up time is to be considered.......

    ooc
     
  3. Jim Carroll

    Jim Carroll

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    granted jigs take time to set up but so does regrinding because you have not got the correct hold on the tool or the angle was not just right and there is an extra facet there where there should not be.

    For most turners it is basically seconds to put the tool in the jig and know that a couple of wipes later you are back at the lathe . Not having another go because you did not get what you wanted.
     
  4. MichaelMouse

    MichaelMouse

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    As Roy says, the tool is its own jig. Lay it on the wheel and follow. Just like turning, if you think about it. Not to say someone couldn't wreck anything, but grinding a "facet" of any significance beyond optical would take some extra effort.

    I use three-five different gouges in different applications on the average bowl, each of which would require a reset of the jig. Too easy to do it freehand to spend time with a jig.
     
  5. robo hippy

    robo hippy

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    My stance on free hand grinding/sharpening is that you have all the skills you need to do it, and have developed them by turning. ABC: anchor the tool on the tool rest (I use a platform, not really free hand) rub the bevel and cut. You move with your body. Learning this is no more difficult than learning jigs, it is just a mental thing.

    robo hippy
     
  6. Matt Lewis

    Matt Lewis

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    "It is also my opinion that if you could survey the best of the best turners......they ALL would be honing their tools to perfection!"

    Now there is a statement I wouldn't put money on being accurate. Mostly because nobody would ever agree on the so called "best of the best turners."

    Back to the technical discussion...have we considered speed and feed in this equation? Isn't it an incomplete argument one way or the other without consideration of those two items?

    This discussion reminds me of when I bought a really capable/fancy rack stereo over twenty years ago because I wanted the best system I could afford. Later I realized that the system was much more capable than my ears and required far more input from me to tweak it to its full potential. Consequently, I spent a lot of money and lugged the thing around the world for many years and never pushed it to its full potential. Lesson learned is that something smaller and less capable would have done the trick sufficiently and although a "better" more capable system was in my hands I never really needed it. I guess I am trying to say that the "best" of something is really only a useful term if you are comparing like things and like requirements. And I think it only matters if you can detect the difference or care to. Can the folks buying your objects detect the difference and if they can do they care to? Besides, it all ends up being a matter of opinion...just like if a turner is really good or not. Everybody has their favorites I suppose.........
     
    Last edited: May 8, 2012
  7. wnnelson

    wnnelson

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    Honing wastes time?

    At a demonstration by Allan Batty he honed his tools all the time. He kept a slip stone in his apron and constantly used it as he turned. I don't remember him going to the grinder once. If you know his history he was a English trained production turner. He stated that they were taught to sharpen their tools with a grinder once a day at the end of their shifts. The whole next day of turning was done with only using the hone to get a good cutting edge. What do you think is faster, honing for a good edge or going to the grinder? Time was money for him but I'm sure that quality also counted in the finished product. True they did not have the sharpening jigs that are so prevalent today but I think the way they were taught the jigs would have wasted their time not improved their work. So to say that honing is a waste of time is a extreme leap in thinking and definitely not true for all turners.

    PS
    At this time Mr Batty is not doing very well and is very ill. I wish him and his family well.
     
  8. Brian McInturff

    Brian McInturff

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    I'm a believer that honing is a waste of time for removing waste wood down to the finish cut. Then, it depends on how the wood reacts to my finish cut if I hone. So what this boils down to does the removal of the waste wood benefit any from honing. Maybe would be the likely answer. Maybe, if you only use one gouge. Like many others , I use several tools when I'm turning and rarely have to resharpen before I get to the finish cut.

    So, let's go one step further. Does honing speed up the removal of wood? I'd say "MAYBE" but probably not enough for me to notice.

    Disclaimer: finish cuts are excluded.

    And where do you stop with honing? 600? 1200? 3000? Diamond paste honing? If you are a honer then why stop at one of these grits? If you really want that sharp, keen edge then why not take it to the limit? Maybe it's because you think it's sharp enough....
     
  9. odie

    odie

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    One thing to consider, here, Brian.......is the less clean the cut, the deeper into the wood the wood fibers will be effected. For a roughing cut, I agree that this doesn't make that much difference, but the closer you get to the final shape, and especially the finish cut, sharpness does make a difference in the quality of surface finish that can be achieved with minimal sanding required.

    Sharpness doesn't mean you can remove more wood.......only the cut will be cleaner. As MM continually points out (.....and, he is absolutely right!), a turner needs to let the tool cut the wood as it wishes to be cut. I know exactly what he means by that, but I suspect there are a few here whom that advice is completely lost on. No matter how sharp the tool is, it can be forced to cut more aggressively, deeper, and faster......but, this should not be the main focus. The focus should be to get the best cleanest cut, no matter at what stage of completion his turning is at the moment. Sharp tools accomplish that objective, but there is much more to it than that. The turner must learn how to best manipulate the tool through the cut, not to mention use of the best tool for that particular cut.

    The exception would be when removing a lot of wood, just to get rid of it......like the bulk of the interior of a bowl. Here, I'm not too worried about the quality of the cut, but more interested in getting rid of the bulk. However, once anywhere near the final shape, the focus returns to getting the best cut. When there is wood to get rid of, I often find myself practicing, practicing, and more practicing getting a fine cut with nice smooth body movement, even though this isn't absolutely necessary in the evolution of any particular bowl. Every piece of wood has it's own characteristics, and lots of practice getting that fine clean cut adds to the knowledge base and skill level.....and this is also good for the soul!



    ooc
     
    Last edited: May 8, 2012
  10. idahohay

    idahohay

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    My contribution to he information overload, and in a way inspired by M.M.

    "A turner needs to let the grinder grind the tool as it wishes to be ground"
     
  11. Thomas Stegall

    Thomas Stegall

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    Brian brings up an excellent point regarding the principle of diminishing returns. At what point do you stop honing and why at that point? It seems that the argument to stop at a given grit could be used to stop at the grinder before honing?

    In reference to production turners I believe their motivation for honing might be to minimize grinding away the tool because they do so much stock removal? Or because in a demo its hard to face the audience and talk to them while you are grinding? Or because a honing stone is easier to travel with when you can't rely on every place to have the same grinding jigs? It is a mistake to think that everything a pro does during the demo is exactly how they do it in their shop.

    In either case I have heard nothing but good feedback about CBN grinding wheels, so I will give them a try, but with their cost, probably won't replace my white stones until they need it. The one thing I am unclear about is the issue of grit on CBN vs. White stones and which CBN grit would be more desirable for routine sharpening (before I hone of course).
     
  12. robo hippy

    robo hippy

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    The CBN wheels from D Way come in two grits, 80, and 180. The one from Acu Grind comes in 200 or 220 grit. When the D Way wheels are new, they are very aggressive, with the 80 grit cutting like 40 grit, and the 180 cutting more like 80 grit. They do break in, and the 180 is closer to standard 180 grit wheels. I haven't seen the Acu Grind yet, and will check them out in San Jose. I have both wheels. I use the 80 on my scrapers as they produce an excellent heavy duty burr for roughing out bowls with. I do sharpen my bottom feeder type gouges on that side as well because the platform is already set to that angle. Some times I sharpen them on the fine wheel as well, and don't notice any real difference in how they cut. So, 80 is more for roughing and shaping, though, not as fast as the belt sander at my saw sharpening service shop. 180 for most others.

    robo hippy
     
  13. odie

    odie

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    If anyone is interested, I see that Woodcraft is now offering an 8" CBN wheel in 120 grit. Here's a link:
    http://www.woodcraft.com/Product/2021136/25960/WoodRiver-Diamond-Grinding-Wheel-8-120grit.aspx

    ================================

    Thomas.....

    Yes, this is a good point about the "diminishing returns" for honing. I think you and Brian are right that it's a valid consideration.....and, there has to be some point where it's not worth it to hone at any finer of grit. I regularly hone my gouges at 600 grit, and that works out well for my purposes. It's been a few years since I started honing with the diamond plates, but my next jump up is to 1200 grit. I did some testing with the 1200 grit, but felt I wasn't getting any better quality of surface cut with that high a grit. Since that initial test, I've stayed with the 600 grit for all gouges. From my perspective, I guess the "diminishing returns" point was at 600 grit. I haven't purchased every grit I can get, so my findings aren't too scientific.........but, the proof is in the surface quality I'm achieving on my bowls. This, I'm feeling satisfied with, so I've stayed with what works for me.........

    ooc
     
  14. TJ Hamilton

    TJ Hamilton

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    Odie, the Woodcraft link goes to a diamond wheel; I thought we established that CBN and Diamond were different? Help!

    Tom, in D'Ville, confused.
     
  15. Brian McInturff

    Brian McInturff

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    I think 600 would be the choice of those that hone. I have a 1200 plate and think it "can" provide a little sharper edge but not worth the time. I have some diamond paste that goes to I think 4,000 or 8,000 that is packed up with some of my old flat work days. Never tried it with turning tools though, again not worth my time. The whole premise of my last post was to get across the fact that the reason that those that don't hone is because they found the results off the grinder was sufficient. And like wise those that religiously hone do so because that's what they feel works for them. Neither one is right or wrong and for anyone to state that one doesn't want a sharper tool(or however it was worded) didn't take into account that unless they hone theirs to the infinite grit then theirs isn't as sharp either. We all find what we are comfortable with and what gives us the best result we are comfortable with. I'd venture to say that no one could tell a piece off the lathe was turned with a tool honed or just from a grind. Tool control and presentation has a lot more to do with it.

    This has been a very interesting thread.
     
  16. Brian McInturff

    Brian McInturff

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    T.J.
    CBN wheels are a lot different than Diamond wheels. I didn't look back through the older posts in this thread but The differences have been posted, probably by Robo Hippy. He seems to have the best knowledge and explanation of the 2.
     
  17. odie

    odie

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    TJ.......

    My mistake........yes, you are correct..... there is a difference.

    I ran a search and found the CBN to be a synthetic substance slightly less hard than diamond.

    Here's that link......scroll down to see the difference between CBN and diamond.

    http://www.riegger-diamant.com/grundlagen/aufbau-schleifscheibe.php
     
    Last edited: May 8, 2012
  18. Matt Lewis

    Matt Lewis

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    Not sure I understand how the CBN wheels can go from one grit to another by "breaking in" as you can't change the fundamental properties of the material just by grinding to my knowledge. Isn't that the point of a grit specification? Help me understand. I have attached a primer on CBN wheels. The important points are the grit equivalence chart and recommended surface speed per minute on page 35.

    Regards,

    Matt
     

    Attached Files:

    Last edited: May 8, 2012
  19. Ian Robertson

    Ian Robertson

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    I have 3 CBN wheels, 2 from D-way and one Optigrind.

    The 2 (80 & 180#) from D-way are 8" wheels mounted on a normal (2850 RPM) speed grinder, and a 6" (80#) Optigrind mounted on a slow speed grinder (1440 RPM).

    I have had them for just over 6 months to see if they outlast white wheels. So far they are still performing as good as new. They have to last longer than 12 months to be a viable economic proposition.

    For over 20 years I have freehand sharpened and then honed my skews because that is what I was taught to do but about 15 years ago I found that it was quicker to skip it as the finish off the wheel was sufficently sharp to do the job.

    Gouges I have always polished the flutes on them but rarely honed after grinding unless it was soft timber that suffered tear out.

    About 12 months ago we did a test on honing v's grinder sharpening and found that it is not worth the extra 10 seconds turning time you gain. The results are on another Forum.

    In nearly all cases you are sanding the job anyway to remove to remove burnishing from the bevel. Polishers don't like burnishing because the finish won't key in.

    I now use jigs to sharpen most of my tools for a very good reason.

    The CBN wheels particularly on the low speed grinder have little or very few sparks so it very hard to tell where the edge is and whether you have "full" bevel shape.

    On the point of Diamond v CBN this might help:

    As some raised the point of production turners only sharpening once a day then honing the rest of the day it is a matter of logistics.

    In some of those works there may have been upwards of 20 turners working. There was generally only 1 grinder for the whole place. Could you imagine the queue at the grinder? Much easier and quicker to hone.

    Timber was green and generally the imported exotics like mahogany etc were soft, much easier on tools so hence less sharpening.

    In the final melt down it is what works for you and the quality of the product you produce.
     
  20. KellyDunn

    KellyDunn

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    This is for Thomas and Brian, This subject seems to be important as it has really gotten large. The largess means things are getting repeated as its a long thread to read each post. It would seem the grinding wheels are a real hit with those that have them. So much so that when my white wheels wear down I will shell out the bucks for these. Then the thread got off on honing. in a yes or no way. Allan Batty and Alan Lacer are I think the only two turners I have seen who hone constantly. Allan Batty even uses a leather strop. The strop is a hand version of when I say I put compound on a pulley belt after hitting a tool with Alan Lacers 500 grit diamond hone and get a real sharp edge. But I am a production full time turner. I only do that when I need a very fine cut. And make no mistake, honing and polishing that edge will give you a fine fine surface. But it last a few seconds. Those few seconds are what I want at the moment for a given wood and cut. Straight off a 120 grit wheel and I tend to be a happy camper. For me when I hone and polish it alters the bevel. Its subtle but I have thousands of hours standing at the lathe. That slight difference I can feel. It actually changes the cutting contact surface. For me depending on the cut I am making it can be a distraction. If so I walk to the grinder and take the honing and polish right off. But I did use the polished grind to do what was needed.
     

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