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Thread: Heat damage to blades when grinding...

  1. #16
    Join Date
    Feb 2004
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    In the past I have ground A2 blades on a belt sander with 40-60 grit sandpaper.



    One can remove a lot of steel without danger of overheating it - just dunk in water regularly. The belt sander runs cooler than a dry grinder.



    I've done the same on a dry grinder. Again, slow work and use of water regularly. Here is a D2 jack blade I cambered using a 46 grit 3X wheel (I just hate the mess!) ...






    Today the 8" 180 grit CBN wheel arrived. I set it up on the grinder. It replaced the 3X wheel. The guards were removed - the CBN wheel is solid steel and is not going to blow up! Using the Tormek BGM-100 set up I tested it on a 1" Stanley chisel. In no time it created a full hollow that resembled the Tormek hollow (smooth and even) but only took seconds to do. And no heat.

    Regards from Perth

    Derek

  2. #17
    The effort required to ruin an iron or chisel on a dry bench grinder would be monumental and there would be severely burnt digits involved. Sure you might monkey up a portion of blade, but having to grind back more than a 1/16" to 3/32" would be something.

    The hollow bevel you get off of a bench grinder makes honing super fast and efficient and the right bevel angle for any given job prevents any undue damage to your tool. Given the advantage of registering a bevel on two contact points, the front and back of a hollow grind I'd be willing to bet that you use up less tool steel while acquiring sharp rather than having to deal with a flat bevel.

    The bench grinder requires a workable tool rest, an appropriate wheel - grit and friabilty, and balancing. A good jig to hold your tool isn't a bad thing either. Once you have the machine sorted you simply need to take the time and develop the skills to use the tool. These forums are full of guys who haven't, won't, or can't effectively sharpen tools on a bench grinder. What is missing? In my opinion: patience and perseverance.

    Set up your grinder while its turned off. Get the tool rest angle right and make sure that only the tiniest bit of steel is going to be removed in a pass. When you have run the tool over this setting until no more steel is removed simply give the tool rest a tap with your knuckle and go at it again until your hollow bevel is ready for honing. It takes time to develop the deft touch that allows you to walk up to this machine and get a good result with little fuss but it is by no means a black art. With time you will not even give the process a second thought.

    The bench grinder is grat for metal working cutters as well as wood!

  3. #18
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    So total grinder newbie question here, (I currently grind on stones or my Viel, the red sander/grinder from LV) when you grind on a wheel, how close to the edge do you get? Especially if you are grinding a new edge on a tool that has chipped, or is damaged?
    Paul

  4. #19
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    Pardon my cutting across your question Paul. Thanks Derek, I've seen your stuff on setting up a belt sander for tool grinding - and confirmed it with a test… It was in large part what informed the decision to think in that direction.

    Then I got sidetracked into building a grinder based on a disc sander which works just fine with a honing guide - I was attracted by the prospect of the nice flat disc. It sorted out some plane blades for me - but it definitely has quite a high heating tendency. Changing the self adhesive discs is a bit of a PIA also - although not bad if a heat gun is used to soften up the bond first. Notwithstanding what I said about setting up the belt sander another option might be to reduce the rpm on the disc - about 1/2 speed would place it with most tool grinding systems...
    Last edited by ian maybury; 10-23-2014 at 2:03 PM.

  5. #20
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    Quote Originally Posted by Chris Fournier View Post
    It takes time to develop the deft touch that allows you to walk up to this machine and get a good result with little fuss but it is by no means a black art. With time you will not even give the process a second thought.
    This may be the hardest part to understand and accept by those new to sharpening. The biggest impediment to learning to sharpen may be the fear of causing damage.

    When my sharpening teeth were cut, a few of my blades did turn blue at the tip. The bright side of this is the metal is softer, it hones away easier.

    To all the beginners, it is a process easier learned by experience than by reading or being told about it. What is even more amazing is no matter how sharp my skills can make an edge, I find there are still more things to discover about sharpening.

    Most recently a thought struck me while using one of my pocket knives to shave a stick. This knife was given to me years ago and mostly sat in a drawer. It is kind of big for my everyday use and only has a single blade. Recently the knife was sharpened for the purpose of easily cutting rope. It was able to push through a rope and make a clean cut with little effort. When whittling the stick, it was a little difficult to get a good slice right handed, but it worked well left handed. There wasn't a bevel on one side of the blade and the bevel looked to have been made with a grinder on the other side. The bevel appeared to have been made by someone holding the handle of the knife to the right of the grinding wheel. This would be natural for someone who is right handed at the grinder. Slowly but surely I have been erasing the damage done in the past and making it work better whittling with either hand.

    A few times at the Farmers Market a man named Dean has talked to me. He has done sharpening professionally. Hope to get together with him when we both have a little time this winter so he can share some of his knowledge.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  6. #21
    Join Date
    Dec 2006
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    Corcoran, MN
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    372
    [QUOTE=Chris Fournier;2325123]

    The bench grinder requires a workable tool rest, an appropriate wheel - grit and friabilty, and balancing. A good jig to hold your tool isn't a bad thing either. Once you have the machine sorted you simply need to take the time and develop the skills to use the tool. These forums are full of guys who haven't, won't, or can't effectively sharpen tools on a bench grinder. What is missing? In my opinion: patience and perseverance.

    Set up your grinder while its turned off. Get the tool rest angle right and make sure that only the tiniest bit of steel is going to be removed in a pass. When you have run the tool over this setting until no more steel is removed simply give the tool rest a tap with your knuckle and go at it again until your hollow bevel is ready for honing. It takes time to develop the deft touch that allows you to walk up to this machine and get a good result with little fuss but it is by no means a black art. With time you will not even give the process a second thought.

    Chris, I'm sure you're right and I like your explanation. My requirements have been met by my present set up so I don't think adding a grinder and tool rest etc. would improve my results, given my limited goals. Maybe in the future.

  7. #22

    Right over the edge

    Quote Originally Posted by paul cottingham View Post
    So total grinder newbie question here, (I currently grind on stones or my Viel, the red sander/grinder from LV) when you grind on a wheel, how close to the edge do you get? Especially if you are grinding a new edge on a tool that has chipped, or is damaged?
    I grind a brand new edge so effectively I grind over the edge! I realise that this may seem impossible to a person starting out but with the right touch it is easy as pie. As I mentioned, you won't wreck a tool with grinding mistakes, you'll simply use more steel than you really need to. When I say deft, I mean light and by light I maen feather light. The challenge is to understand how light is right.

    HSS is a treat because you can blue it up as you please and it won't degrade the steel but our typical chisel and plane blades ain't HSS and blue is bad! Honestly if you are really watching what you are doing, straw, yellow, brown are all coming up before blue, purple and black!

  8. #23
    I'd agree with the edge comment, too - I grind mine pretty much off, but try to stop short of making a large wire edge. It doesn't present a burning problem, there's not much metal removal going on with a typical refresh grind.

  9. #24
    Join Date
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    It has taken me quite a while and a great deal of reading to figure out that my experience with the Tormek is not actually atypical. It is very slow, it wasn't something I was doing wrong. No amount of dressing the stone fixes the problem for very long. The other thing that I am a little surprised to learn, but should not be, is the belt grinder is potentially the fastest "conventional" route. Again this information corresponds to my personal experience. I have achieved my fastest results with the belt sander. I have found, much like David and others have explained concerning bench grinders and friable wheels, the heat can be managed if one pays close attention.

    I am concerned with the dust created by a friable grinder wheel or belt though. I have had a number of bouts with allergic reactions in the last two years which give me reason to be paranoid of air borne metals & dust and skin contact with fine metal particles. The only real solution I see for me is the CBN wheel Derek mentions just receiving above. I understand that these wheels do not pollute the air nearly as much as friable grinders. I am also reading that these wheels can be wet down to further reduce and consolidate the refuse. Running one of those wheels on a Tormek seems like the "perfect" solution to me. Derek posted a link to a company in AU that apparently sells a CBN wheel that fits a Tormek. I am in contact with them trying to find out how crazy the shipping cost will be. I keep thinking that some company in the US should carry the same wheel but thus far I have not been able to find one.

    Apparently Derek bought a 8" CBN wheel for his bench grinder instead of a 10" wheel for his Tormek. I am guessing his motivation was partly financial. I also think Derek may want to leave the regular wheel on his Tormek for bevel touch ups. I do not have a bench grinder at the moment. I am trying to figure out whether I am better off buying a new grinder and 6-8" CBN wheel or ordering the 10" wheel from AU. My guess is the two options will cost about the same if I don't go with an expensive grinder. I do not recall anyone commenting on brands/models of grinders which seems a little odd considering how much has been posted about people using grinders. From posted pictures it looks like just about everyone uses a different brand/model.

    I have read about a CBN wheel with a rounded edge, which may be the reason Derek went with a grinder mountable wheel instead of a Tormek wheel? I am still researching, but I think the Tormek wheel in AU is the regular version of the wheel. I sharpen quite a few large green wood tools with curved, often hollow ground, blades so a curved grinding surface may be important to me. I also think the wheel speed of a Tormek is slower which may reduce the effectivness of a CBN wheel.

    It is starting to look like a new grinder and CBN wheel are in my future. I know this is not the most financially conservative approach. Considering how much I have paid Dermatologists... and the amount of time and money I have spent researching and exploring options I am good spending the money if I am confident I have finally found a REAL solution to grinding bevels.

  10. #25
    Quote Originally Posted by Derek Cohen View Post
    (enabling people with little will power...)


    Derek, you're an enabler. I just ordered an 80 grit wheel from a different seller. I'd assume that d-way tools is selling a wheel that someone else makes, but don't know for sure. The wheel I ordered looks a little different - the radius is similar, but it doesn't have a bushing (the bore hole is 1/2 inch on a 6 inch wheel).

    The only reservation I have about CBN wheels is they warn you not to use them on softer metals (anyone who has stripped diamonds off of a nickel plate diamond hone will know why). I'm not sure how it will hold up with laminated irons, but it will make a good pairing with the pink wheel (which wears sort of fast..but not too bad I guess, and I have no cheap source for another one when mine wears out).

  11. #26
    Join Date
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    David, you really do not need anyone to "enable" you to purchase sharpening equipment!

    The 80 grit is indicated for heavy work. From what I could determine, the 180 grit is nearly as fast and provides a smoother finish. I am very impressed with this wheel so far, and well get the 80 grit for heavier work.

    I got mine from D-way in the USA. I liked their presentation and reputation, and Dave Schweitzer answered all my emails promptly and thoroughly. You can find a few of his videos on Youtube. Plus the wheel they sell is 1 1/2" wide compared with the 1" wheel sold locally. I went for the radius edge as I thought it may be more useful, not only for lathe chisels (as they demonstrate), but also for entering and exiting on straight edges. Possibly for hollow blades as well.

    David assured me that the CBN wheel will grind all hard steels. With regard laminated blades where there is soft steel, he mentioned that a grind on hard steel will remove any loading, if this occurs.

    Installing the wheel is a simple affair. D-way sell a beautifully machined bushing that slipped over the 5/8" arbor on my half-speed grinder. This has a 1 h.p. motor, so is powerful enough to easily push this heavy wheel. It is so well balanced, however, that I imagine a less powerful machine just needs a manual spin (which I do anyway) to start it along.

    I have not yet tuned it up - just slapped on the wheel and bolted back the tool rest. Still, I could not resist grinding a beater chisel.





    Grinding the hollow was quick, and there was minimal heat at the edge. This is the hollow on a 1" Stanley yellow handle chisel ..



    The microbevel after a Ultra Fine Spyderco is too small to see, however it proved its sharpness on Radiarta Pine end grain ..



    Regards from Perth

    Derek
    Last edited by Derek Cohen; 10-24-2014 at 11:35 AM.

  12. #27
    I'm sure the 180 is plenty good for grinding bevels. I ordered the 80 grit because a seller offered me a cheap deal as I'd made an offer on a wheel on ebay but he sold it before responding to my offer.

    I usually touch up turning tools with a diamond hone and sharpen them on a belt grinder, otherwise I'd have wanted a finer wheel too, to do turning tools.

    It'll be interesting to see if it's cooler than the pink wheel (the pink wheel is fantastically cool for a wheel that doesn't release much grit).

  13. #28
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    I love this thread, very helpful! Woodworking=>Sharpening=>grinding bevels in my experience. After what seems like FOREVER I actually think I have the solution. Sure once we have a good bevel we can sharpen in a hurry, but first we have to have a good bevel, not getting around that as far as I can see.

    So I called Dave and ordered a 1/4" radius 8" CBN wheel, and I don't even own a bench grinder, yet. Just so everyone is aware Dave does make a CBN wheel for the Tormek. His Blog/Web site does not reflect everything he has. He sells 10" wheels, which are not listed. He also says some people have used 8" wheels on Tormeks. Dave offered that the slower wheel speed would make the Tormek slower grinding even with a CBN wheel. Dave likes Jet 8" grinders and he has a Delta variable speed that he has used for 8 years. All Dave's wheels come with a 1" hole. He sells bushings to adapt any grinder to the 1" arbor.

    Dave mentioned that Robo Hippy/Reed Graves a SMC member makes and sells a tool holding rig that works well with CBN wheels and grinders.
    Last edited by Mike Holbrook; 10-24-2014 at 7:16 PM.

  14. #29
    I'd stick with a dry grinder, too. I don't know if he was explicitly saying any such thing, but low speed and high pressure is hard on grinding surfaces.

    Good grinding frees you up to use anything to sharpen without worrying about how fast a particular stone cuts - that's a nice thing.

  15. Quote Originally Posted by Kees Heiden View Post
    It's probably inevitable that you overheat a narrow part of the edge on the grinder. All those sparks indicate pretty high temperatures. But that's one reason why we continue on a whetstone. You remove that overheated layer quick enough. I don't find that I loose hardness, not even in the white steel Japanese chisels.

    Those sparks indicate heat being REMOVED from the blade. It's the heat that remains that is the issue

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