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26816Re: [GrizHFMinimill] How would I machine a flat-bottomed hole with a boring head?

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  • John Lindo
    Oct 24, 2013
      When you have bored out to the diameter you require,use a boring tool with a flat 90 
      ground on the end,and then incrementally move out the tool to the same depth.
      Unless you have a DRO on the quill,you would want to use a some form of Z axis travel stop.
      I don't recommend you use the Z axis travel even with a DRO because you will need to 
      wind down the head against a resistance of the gib locks.You could end up with a backlash 
      problem,and if you are unlucky the head could come crashing down onto the ledge you are machining.
      Not popular in the US,but the Weiss mill has a DRO measuring the quill movement and a graduated dial that measures the Z axis travel.
      see link showing the DRO next to the fine feed knob.
      Also see boring head with facing facility.it's on my Xmas list.
      I used a Wohlaupter from Germany 25 years ago,when I was Jig Boring, just brilliant.
      Ideal for internal circlip grooves as well.
      see other link
      These tools from Arc are manufactured in China,but the price is 60%  less than
      the German made models,and ideal for the hobbyist.Again Quality versus your wife's purse.

      John
      Spain





      On Thursday, October 24, 2013 1:56 PM, "clevinski@..." <clevinski@...> wrote:
       
      Hi, All,

      Several people have recommended that I buy a boring head for my mini-mill.  I'm trying to visualize how I would use it, and come up with this question, which I'm sure you experienced machinists have resolved thousands of times.

      I understand how one would use a boring head in the mill if making a through-hole in a something.  But what I don’t understand is how you would make a blind hole, or a hole with a lip at the bottom?  If you did this on the lathe, you would, as a last step, “face” the bottom of the hole or lip to make it flat.  But that doesn’t seem possible with a boring head.
       
      I could imagine doing this with a rotary table, using an end mill to machine the flat bottom surface, but only if the hole were shallow enough that the end mill could reach it.
       
      How is this operation typically done?

      Thanks,
      Charlie
      NJ, USA


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