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Thread: Just fell in love with HSS

  1. #1
    Join Date
    Feb 2011
    Location
    South Africa
    Posts
    296

    Default Just fell in love with HSS

    I just finished grinding my first HSS lathe bit and wow can't believe I spend almost 3 years using carbide on my home lathe.
    I was always a bit unsure about the angles and decided to stick to carbide inserts where I know the angles are right.
    Got 2 1/2 x 4 blanks from a local supplier just HSS no cobalt just incase I mess it up.
    The are Kennedy blanks made in England and it turned out pretty well.

    I just thumb sucked the angles and bounced it between my 2 grinding wheels depending on how I had to hold it ( one is green silica and the other white I assume Alu oxide)
    It cuts Alu like butter and even suprised me on hardened 4140.
    Now I just need to firgure out how to put a ring on square shank and I can marry it. (I know I have a problem)
    What type of wheel should I have used for sharpest edge and/or rapid removal?
    If somebody sees something wrong with the tip please give me a headsup I still need to do the other one just want to wait for the judges verdict.
    If you are using violence and it does not work, You are not using enough.

  2. #2
    Join Date
    Jul 2007
    Location
    Europe-Asia border aka somewhere on the Saros
    Posts
    1,790

    Default

    A job well done, especially for a first attempt.

    There are a number of nuances for different materials wrt to clearance angles and rakes. Generally, the harder the material, the lower the angle, and vice versa.

    For roughing, not everyone bothers with the radius on the tip. the tip radius varies depnding on finish and feed per rev from sharp to +/- 1/32" radius or larger for finishing.

    As far as which wheel, the green one for carbide and the white one for HSS. Wheel wear, within reason, is the means by which the wheel sharpens itself - by exposing fresh aggregate.
    Design to 0.0001", measure to 1/32", cut with an axe, grind to fit

  3. #3
    Join Date
    Dec 2009
    Location
    Adelaide, South Australia
    Posts
    498

    Default

    Carbide is certainly over rated for home use, as a lot of the machines used for HSMers are not rigid enough, or have the revs. I have a carbide parting blade that I keep meaning to use but so far I met anything that HSS could not manage...

    I'd suggest getting a diamond hone so that once you are finished grinding you can put a final finish on your tool. Hand grinding of tools can (inadvertently) round the edges a little.

    Michael

  4. #4
    Join Date
    Aug 2009
    Location
    Canada, Bc
    Posts
    7,515

    Default

    Get the angles right? you can't really get the angles wrong!

    Just have some clearance and it will work. Rake is a trade off beween tip strength, free cutting and finish (sometimes). Some materials like copper/brass iirc don't like any rake. Some plastics don't like excessive rake either. Some plastics/woods/aluminum love lots of rake.

  5. #5
    Join Date
    Oct 2002
    Location
    Champaign-Urbana, Illinois
    Posts
    820

    Default

    Quote Originally Posted by Black_Moons
    Get the angles right? you can't really get the angles wrong!
    That's pretty true. Any tool will cut any material for the most part and there's a wide range of angles that will work, so there really isn't any need to fret about getting the angle "correct". If you're going to be cutting lots of brass or aluminum, you might want to grind up some bits for each one (no rake and lots of rake respectively), but otherwise a nice, middle-of-the-road tool with 5-10 degrees on each angle will do most everything.

    Shape is much more important to me. Is the tool going to fit where I need it to fit? The end relief has to be able to clear the live center if I need to machine close to it. If that's not a concern, I just do the same 5-10 degrees there too. You also want to make sure that each face is one smooth grind. Lots of facets on the face make it harder to hone. Use the tool rest and that shouldn't be an issue. Lastly, hone the edges with a sharpening stone, just to smooth out the rather jagged edge left by the grinding wheel. I also put the radius on the tip with the sharpening stone rather than the grinding wheel because it is very easy to get too big a radius with the grinder. You only really need a little radius (1/32" or so at the most) to get a good finish.
    Stuart de Haro

  6. #6
    Join Date
    Aug 2006
    Location
    Taylorsville Ky
    Posts
    5,882

    Default

    The only angles that are important are the relief angles on the leading cutting edge and the front clearance angle.

    The front clearance angle can be 0 but is best at about 5 deg. The reason it can be 0 is the work is round and the top of the cutter is at the center line so the front of the cutter should never rub the work.

    The side of the cutter that is doing the work has to have an angle that gives clearance in relation to the feed that is being used. A fine feed can use a 2 to 4 deg relief but a heavy feed may need 10 deg relief or more.

    The angles you grind on the cutter are dependant on the feed, DOC and material your cutting. There is no exact angle to grind to and experimentation is the best way to learn. Look at the sides and top of the cutter after one pass. Does it look like the cutter is rubbing? Did the chips come off nice or did it seem like the tool was working to hard. Try more relief on the sides and maybe some back rake.

    Experiment to learn.
    It's only ink and paper

  7. #7
    Join Date
    Nov 2010
    Location
    North Western Ontario
    Posts
    78

    Default

    Hi

    Tool bit grinding 101

    http://www.youtube.com/watch?v=hrDr4rYLiAk

    This guy is worth subcribing to. He has posted 100+ videos
    A dedecated teacher who just can't quit.

  8. #8
    Join Date
    Dec 2010
    Location
    Finland
    Posts
    2,709

    Default

    Very nice firs one, congrats Usually when i grind HSS bit I grind a small "channel" just behind the cutting edge on the top of the HSS bit instead of giving it a rake angle. This acts as a chip breaker and in most cases prevents the tool from forming long stringy chips as the chip is forced to curl and this usually breaks it in tiny pieces.

    There is a place for HSS and for me it is shapes that I haven't ground a carbide bit yet or when working with brass/plastic due to not having carbide bits intended for brass or plastic. Quite often I can't use HSS because of machining something hardened (48-58 HRC).

  9. #9
    Join Date
    Oct 2004
    Location
    Toronto
    Posts
    1,464

    Default

    how does it compare to india/taiwan HSS?

  10. #10
    Join Date
    Dec 2009
    Location
    Stevens Point, WI
    Posts
    4,534

    Default

    I bought 5 pounds of hss off ebay when I got my lathe. I have enough hss for a lifetime! It is also nice because there is a wide variety of different types of hss in the bunch to play around with. And it was around $20 for the whole deal shipped.
    Andy

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