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Re: [SherlineCNC] Rack Shaped Gear cutters.......................

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  • Robert Betz
    Hi Marcus, I am ordering from MSC, for the straight cut, a 3/8 shank, 1/4 diameter, 4 flute, double cobalt end mill. For the tapers, a 3/8 shank, 7 Degree
    Message 1 of 22 , Aug 31, 2003
      Hi Marcus,
       
      I am ordering from MSC, for the straight cut, a 3/8" shank, 1/4" diameter, 4 flute, double cobalt end mill.  For the tapers, a 3/8" shank, 7 Degree taper, 1/8" small end diameter, 3/4" cut, square end, single end cobalt end mill.  And, I am ordering 1/4" X 1/4" X 18" lengths of Starrett Oil Hardening Ground AISI Type O1 tool steel.  BTW, it was indicated in a catalog that O1 is known as Silver Steel in England.
       
      Marcus, I really appreciate the time you have taken, especially over this holiday weekend,  to detail all of this gear cutting information from your knowledge and experience.  It has been invaluable to me and probably to many others in the group.  I really believe I've got enough info for now, and now I need to develop my own experience.
       
      Thanks much,
       
      Bob Betz
       
      ----- Original Message -----
      Sent: Sunday, August 31, 2003 6:56 PM
      Subject: Re: [SherlineCNC] Rack Shaped Gear cutters.......................

      Hi Bob:
          M42 cobalt should be just fine.
      The cobalt is added to the HSS to improve toughness and wear resistance.
      Most tools with cobalt in them have about 5%.
      Occasionally you can get them with 10% for harsh applications, but these tools are harder to grind so they're more expensive.
      The reason I recommend a small tip diameter is that you'll want to use this cutter for a lot of different kinds of formtools.
      If your profile happens to have a small radius concavity somewhere along its length, you won't be able to profile around it if the tip radius of your taper cutter is bigger than the radius of the concavity on your formtool profile.
      I make mine often down to 0.016" to 0.018" at the tip for some of the fancy shapes I get into.
      You won't need the ball end...a flat tip willl be fine for this application.
      The heavier cutter will certainly be a lot stronger, but it will be more limited in its usefulness.
      Cheers
       
      Marcus
      ----- Original Message -----
      Sent: Sunday, August 31, 2003 10:33 AM
      Subject: Re: [SherlineCNC] Rack Shaped Gear cutters.......................

      Hello Marcus,
       
      The Cobalt displayed in the catalog states that it is M-42 Cobalt.  I don't see anything that refers to a percent cobalt.  Also, they distinguish between Cobalt and HSS or is it understood that Cobalt is also HSS? 
       
      Just out of curiosity, why the small 1/8" or less tip diameter?  The smaller tips were mostly 1/4" shanks especially when I specified a short (1/2" cutting length).  I was looking at a 3/8" shank and 1/4" tip diameter for strength.  For no reason I selected a flat tip over a ball tip.  However, I plan to follow explicitly your recommendations.  As you can see my ignorance of the subject is profound.
       
      Thanks again Marcus,
       
      Bob Betz
       
      ----- Original Message -----
      Sent: Sunday, August 31, 2003 8:48 AM
      Subject: Re: [SherlineCNC] Rack Shaped Gear cutters.......................

      Hi Bob:
          On a big rigid machine I'd say carbide because of its hardness...but carbide is quite brittle and will crumble if it's allowed to chatter in the cut.
      I'm not a real fan of carbide in a Sherline although lots of people do use it reasonably successfully.
      My choice for this application would be a 7 degree 5% or 10% cobalt HSS cutter.
      Make sure you get one that has a reasonably small tip diameter...1/8" or less would be ideal.
      It should also have the shortest flutes you can get.
      Use it as a finishing cutter only.
      You'll want to rough out your blank as close as possible with a regular, parallel sided endmill.
      Lube the tip of your tapered cutter with a few drops of Rapid Tap, and you're good to go.
      Cheers
       
      Marcus 
      ----- Original Message -----
      Sent: Sunday, August 31, 2003 12:25 AM
      Subject: Re: [SherlineCNC] Rack Shaped Gear cutters.......................

      Hi Shorty, Marcus & All,
       
      Thanks, I was just looking at the listing at MSC.  
       
      What degree taper should I get for cutting the sides of the gear cutter tool, 5, 7, or other degree?  I want a cutter that will last me without having to sharpen frequently.  In what order of quality or hardness does the following rank:
       
      Carbide
      Cobalt
      HSS
       
      Also, not considering price, which material would be the best choice for my cutting the 0-1 tool steel?
       
      Bob
       

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    • Marcus and Eva
      Hi Bob: You re very welcome. Good luck with it, and don t be shy about trying some other alternatives and maybe making some mistakes. It s all part of the
      Message 2 of 22 , Sep 1, 2003
        Hi Bob:
            You're very welcome.
        Good luck with it, and don't be shy about trying some other alternatives and maybe making some mistakes.
        It's all part of the turf!!!
        Cheers
         
        Marcus
        ----- Original Message -----
        Sent: Sunday, August 31, 2003 10:39 PM
        Subject: Re: [SherlineCNC] Rack Shaped Gear cutters.......................

        Hi Marcus,
         
        I am ordering from MSC, for the straight cut, a 3/8" shank, 1/4" diameter, 4 flute, double cobalt end mill.  For the tapers, a 3/8" shank, 7 Degree taper, 1/8" small end diameter, 3/4" cut, square end, single end cobalt end mill.  And, I am ordering 1/4" X 1/4" X 18" lengths of Starrett Oil Hardening Ground AISI Type O1 tool steel.  BTW, it was indicated in a catalog that O1 is known as Silver Steel in England.
         
        Marcus, I really appreciate the time you have taken, especially over this holiday weekend,  to detail all of this gear cutting information from your knowledge and experience.  It has been invaluable to me and probably to many others in the group.  I really believe I've got enough info for now, and now I need to develop my own experience.
         
        Thanks much,
         
        Bob Betz
         
         
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