Sharpening Carbide Bits

Discussion in 'General Engine Discussion' started by IronHorse, Apr 21, 2010.

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  1. Apr 21, 2010 #1

    IronHorse

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    I picked up a "green" wheel for my grinder. I want to resharpen some of my Carbide tipped lathe bits. My question is, do you "dip" these type of bits in water like you do for HSS or let them air cool?

    Ironhorse
     
  2. Apr 21, 2010 #2

    tup48

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    Hi Ironhorse;

    When I sharpen my Carbide bits the first thing I do is to grind the under side with a regular wheel and then grind the carbide with the green wheel.

    Yes I always dip the tool in water (not to cold).

    A good rule is to hold the tool close to the end being ground and when your fingers start to get hot it is time to dip in water.

    Richard
     
  3. Apr 21, 2010 #3

    rake60

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    Are you are referring to brazed carbide bits, such as this turning tool and boring bar
    from my tool box?

    [​IMG]

    If that is the case you HAVE to keep them cool!
    Heat from grinding build up quicker than we would expect.
    That heat can become high enough to weaken the brazed bond between the
    carbide and the tool.

    Grind a little and quench it, grind a little and quench it...

    If you are referring to solid carbide tools, grind them until you are happy with
    the result and let them air cool.

    Rick

     
  4. Apr 21, 2010 #4

    Blogwitch

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    IH,

    This is very basic stuff, but a reminder in case anyone doesn't know about it.

    When grinding carbide tools, either by hand or machine, you only ever grind up or down on the cutting faces, NEVER across.

    If you grind or lap across the face, you will find that the carbide will de-laminate and chip very easily when cutting.


    Bogs

    tungsten grinding.jpg
     
  5. Apr 21, 2010 #5

    IronHorse

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    thanks guys for the info.

    IronHorse
     
  6. Oct 24, 2010 #6

    davisdesigns

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  7. Oct 24, 2010 #7

    Brian Rupnow

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    A very timely thread. I bought a green wheel last week to sharpen my carbides, and haven't used it yet.----Brian
     
  8. Oct 25, 2010 #8

    davisdesigns

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    I think just about everything we do now days is bad for us.. The grinding wheel it's self is hazardous to breath, maybe all these years of grinding with an aluminum oxide wheel has given me alzheimer's. I forget things often..
    maybe all these years of grinding with an aluminum oxide wheel has given me alzheimer's. I forget things often.. ;)

    PS sorry about the above post I put it in the for sale section, I was warned…



     
  9. Oct 25, 2010 #9

    Ned Ludd

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    Hi Guys,
    I seem to recall that one should not quench carbide when grinding, for the same reason that you should either use flood cooling or none at all when turning with carbide tools to prevent cracking. Am I wrong, again?
    Ned
     
  10. Oct 25, 2010 #10

    doc1955

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    You are correct you can cause premature failure even if you don't see the cracks in the carbide. The best thing is to cool with just an air gun cracks will form from thermal shock otherwise.
     
  11. Oct 25, 2010 #11

    Mainer

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    FWIW, carbide really ought to be sharpened on a diamond wheel. The green wheels abrade the carbide away but don't actually cut it the way a diamond wheel does.
     
  12. Oct 25, 2010 #12

    doc1955

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  13. Oct 25, 2010 #13

    Brian Rupnow

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    I just sharpened all of my carbides on my new green wheel. Couldn't find my expensive HEPA air mask, so I tied an old T shirt over my nose. I looked a bit like the Lone Ranger, and wondered what the nosy neighbours who can see into my garage were thinking. Of course, this made my glasses fog up instantly, so I not only looked like an outlaw, I stumbled around a bit like Mr. Magoo----You get 10 points if you're old enough to know who Mr. Magoo is/was. My green wheel is 3/4" wide, and so as not to rub a groove in it, I moved the carbide tools back and forth a bit while I was grinding them. I think this is in direct conflict with what somebody posted earlier. All of my carbide tools LOOK sharper now. Of course, I don't know if they will cut anything now, but Hey, they were dull before anyways. They are cheap Chinese carbides, and were only sharpened across the end and on one side (Which I think is normal.) Of course now that I have sharpened 2 adjacent sides, they have one Hellish sharp point where the 2 egdes that were sharpened meet. I'm not shure if I should leave this sharp corner, or endevour to break it a bit----on my green wheel, of course.----Brian
     
  14. Oct 25, 2010 #14

    Blogwitch

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  15. Oct 26, 2010 #15

    doc1955

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    Thanks Bogs for the link!!
    They do look to be a good source for diamond wheels ans mounted points.
    Plus I see polishing paste looks also to be a good deal. have you tried any of their other products?
     
  16. Oct 26, 2010 #16

    Blogwitch

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    Certainly have.

    Two and four flute endmills both HSS and carbide. Impregnated polishing discs, diamond covered lapping plates, loc line hoses, cheapo scribers, plastic display boxes, ali backing plates, carbide glas and tile drills, etc etc etc. In fact anything that takes my fancy.

    Because the prices are so low, everyone expects the quality to be low as well. OK, some of the bits aren't up to top quality manufacturers standards, but everything I have bought has been good value for money, some in fact, I just don't know how they could make them for the price. But everything carries out the job I intended for them, and some even greatly exceed my expectations.

    Bogs
     
  17. Oct 26, 2010 #17

    doc1955

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    Thanks for the info Bogs!
    I'll give them a try.
     
  18. Oct 26, 2010 #18

    spuddevans

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    I have to agree with Bogs, I have had a few orders from Richon, and have been very impressed with them. I have got a good number of endmills from them and they have all been good. I got a 1/4" roughing endmill and it just eats steel like it is butter, great for hogging out material.

    Great place and reasonable and quick postage ( considering where its coming from )


    Tim
     
  19. Mar 19, 2011 #19

    Captain Jerry

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    Meet my new best friend.

    [​IMG]

    I read this post a few days ago and put it to use today. I needed to turn a groove in a 1/4" stainless steel shaft. The tool may have been dull or high on the center and next I know, the tool rubbed and the SS rod hardened. Even after I resharpened the tool, it wouldn't cut. I needed a really sharp carbide grooving bit and I don't have one. I remembered this post so I dug through the never used stuff and came up with a package of small diamond wheels and an arbor that was less than $10 at Harbor Freight.

    A used and worn V shaped brazed carbide bit was the starting point and in just a few minutes I had my Carbide grooving bit. I held the wheel in a cheap keyless chuck mounted in the lathe to keep my fingers away from the big chuck jaws. At medium lathe speeds and holding the bit in my fingers, it was surprisingly easy to shape the carbide tip to what I needed. Because of the speed and small diameter of the wheel, there was no heat build up and the resulting edge was polished and razor sharp.

    [​IMG]


    When I attacked the SS shaft with it, I increased the lathe RPM about double. Little SS chips rolled of smoothly.

    I was so impressed with the result, I spent the afternoon getting re acquainted with my carbide tools, even those that I never liked. Cheap brazed tools have a poor edge, a ragged finish, and a questionable shape. Its amazing what a difference a few minutes with this little wheel can produce. I had become convinced that "sharp" and "carbide" could not be used in the same sentence. All that is changed. Sharp! carbide is my new best friend. Its even possible to form a small radius at the tip for improved finish.

    [​IMG]

    I dug my old Unimat SL100 out of the drawer and pressed it into use. Variable speed and good bearings and a good true running chuck have turned it into a full time diamond honing machine. I didn't get any pictures of the Unimat setup but There are lots of ways that you could mount and use this little wheel. It doesn't need the high speed of a die grinder or a Dremel.

    Jerry

     
  20. Mar 19, 2011 #20

    Lew Hartswick

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    I don't understand the term, "diamond CBN" To me that is sort of like saying "wooden plastic" the term CBN means "Cubic Boron Nitride" and doesn't have anything to do
    with diamond. ??????
    Or is it another one of those "Chinglish" translations?
    ...lew...
     

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