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Keyway Cutting

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  • Keyway Cutting

    I am attempting to cut a keyway in a drive wheel I am building for a belt sander, the keyway is 3/16" a couple inches long, the shaft is 5/8 "
    I bought a 1/2" boring bar. it has a 45deg and 90 deg square 3/16 holes
    I have tried both without much success, either the bar flexes or not much happens? I am using a 13x40 Lathe, the wheel is Aluminum so obviously my tool is not sharpened correctly I have tried several grinds, there again with not much sucess.
    What angle should I be shooting for in either the 90 or 45 holes? I am only trying to take at the most a 0.02 cut? Using the carriage, I did shorten up the bar so that just enough is sticking out of the holder to make it through the pulley.
    Any insight at all to this would be appreciated.
    Obviously I am a newby.
    Thanks in advance

  • #2
    I suspect you're trying to take too big a cut, especially if you're trying to cut the full 3/16" width all at once. Grind the toolbit down to maybe 1/16" wide, or even less, and try about a 0.005" deep cut. It will take a while to do the whole keyway, so have patience.
    Try to make a living, not a killing. -- Utah Phillips
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    • #3
      You need to grind a very sharp bit with plenty of relief. Look for a continous curly chip to form on each stroke. You should be taking more like .001-.002" DOC 's rather than .02". That's just to much IMHO and the bar will spring away.
      The method is sound and you can cut excellent keyways. As good as with a broach. But be patient and take light cuts and keep the bit sharp.
      Here is a .032 x .032" keyway I cut in .125" steel round using my mill. You won't need quite the radical clearances as I used on this bit , but this is the type of cutting action you'll be looking for. Click the bottom pic to view a short video.


      Last edited by S_J_H; 06-21-2008, 06:22 PM.


      • #4

        I just did this today for the first time. I'm giving new life to an old snowblower and had to cut a 3/16" keyway in a cast iron pulley in the process. I used pretty much your same setup. I cut a 1/2" lenght off a 3/16" lathe bit and used the 90 degree hole on the boring bar. I left the stock 45ish degree on the end of the lathe bit and just ground maybe 10 degrees relief on each side. I put the whole thing in my 11" Rockwell lathe and locked the spindle. I cut the full 3/16" width--cutting oil helps too. Took a good 15min to get'r done as the best cutting depth was about .003/stroke. If you need pics, I can put some up later. Sidegrinder


        • #5
          I'm a rank amerature but have done it sucessfully. Whe you get that last 0.001" of the end of the cutter sharp it starts working great. I grind on a 150 wheel and carefully lay a diamond hone on the surface I just made on the wheel and give it a few strokes. When you get past that, it'll quickly tell you the depth of cut. One thou, OK. 1 1/2 thou OK. 2 thou - UGG, I can't push this thing. Good luck.


          • #6
            Keyway cutting success

            Thank you guys, you saved me once again!
            Once I ground some relief into my cutter things smoothed right out!
            I did also narrow the cuttter up some.
            Now it makes some really neat little chips and did not take all that long to do.
            Thanks again.


            • #7
              Just mount the wheel on the shaft and drill a 3/16" hole in the "joint" and then drive in a tight fitting round pin. Quick and dirty and if you're afraid it'll back out, grab the Loc-tite tube.