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  • Broaching Question

    Installing a powerfeed on my Rockwell mill. Had to make an adapter/extension on right hand end of x- leadscrew since mill has 9/16 dia leadscrew end and powerfeed is set up for 5/8. I'm using the woodruff key that is already in the leadscrew end and plan to broach internal keyway (1/8") in adaptor.
    Question: The 1/8'' broach has about 4'' of teeth in order to make full depth cut. I'm basically trying to broach no more than 1.5'' in a blind hole. Am I going to need additional shims to reach proper depth since the full length of the broach can't be engaged?? Or are there shorter broaches out there?

    I hope I've explained this clearly. I may have to resort to using a modified slotter via the Logan or mill, having done this in the past but not completely satisfied with the results.

    Broach set is made by Dumont.

    Thanks
    I bury my work

  • #2
    I have an idea broaches don't like blind holes much. I can't really picture what you're doing, but I think I'd try to arrange things to have a through hole for the broach...even if that involved then blocking off the hole later, somehow.

    If you're adapting a 5/8" hole to a 9/16" shaft, can you just use a 1/32" shim?
    ----------
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    • #3
      Broaches are only for through holes.

      I adapted a B'port powerfeed to my Rockwell milling machine and just tapped the sleeve for a setscrew in the keyway. It has worked for about four years at this point.
      Jim H.

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      • #4
        woodruff key

        What if you make a bushing that fits on the 9/16 dia and has a 5/8 od .
        Now take bushing and make a 1/8 slot thru the wall with an end mill over where the woodruff key exists.
        Now all you have to do is make a 1/8 round disc the size of woodruff key
        and cut it down to where it extends thru bushing the correct height.

        Making the bushing and a taller then normal woodruff key seems easier than
        broaching it.
        Jim

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        • #5
          there's a couple of ways to make a blind internal keyway, no way the broach will work as each tooth has progressive depth of cut. you can key a blind hole by using the lathe or mill as slotter, nothing rotating, just a tool plunged in and out with a couple of thou advanced per stroke. cross drill a hole at the end of the blind key way - it needs clearance there. the other, easy way imo, would be to make an insert that gets brazed into a blind, flat bottom bored hole in the work. broach a keyway in a through hole in in the insert then brazed into a bored hole and you've got a blind keyway
          in Toronto Ontario - where are you?

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          • #6
            I cut a keyway in a blind hole using the quil feed on the mill, the tool I made by drilling a cross hole in a peice of half inch round near the end and putting a set screw agenst the short tool bit inserted in the hole. To line up the cutter I scribed a center line on the pully then eye balled the cutter to center, taking vary fine cuts untell I got the proper depth. I have done this several times with great results.

            Jon

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            • #7
              Broaching Blind Holes

              Broaching Blind holes is no problem if you're using Slater Rotary Broaching Tools. You can easily create squares and hexagons in milder materials, at shallow depths.

              However, one peculiar limitation of rotary broaching is that it cannot create a single keyway due to uneven pressure on the broach, thus chipping the broach. The typical solution is to create a hole with 4 keyways, etc.

              There are some other limitations, learn more at rotarybroaching.com

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