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Re: [taigtools] turning endmill holders on a mill

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  • Vlad Krupin
    ... Thanks for that piece of advice, Jeff. I think I did that. Quoting from my previous email, I ...aligned the cutting point with the center of the drilled
    Message 1 of 4 , Mar 3 7:04 PM
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      On 3/3/06, Jeff Demand <jdemand@...> wrote:
      >
      > Vlad,
      >
      > My experience with using a mill for lathe type work so far has been
      > limited to thought games; still trying to make an adapter to fit taig
      > stuff to my unimat, an exercise which has escalated to the 'no prisoners'
      > stage. What DID strike me from your post was
      > " is about perpendicular to the tangent of the surface being cut..." Could
      > it be that you are not boring 'on centre'. Maybe try to set the boring
      > cutter tip to also be in line with the centre of the drilled hole. (dial
      > test indicator, +/- .001" is critical)


      Thanks for that piece of advice, Jeff. I think I did that. Quoting from my
      previous email, I "...aligned the cutting point with the center of the
      drilled hole..." I think I must've not phrased it very well, but I think
      this is exactly what you are suggesting. I did not dial that in, just
      eyeballed it because I found that having boring bars dead-on-center is not
      absolutely critical when I use them on my mill, especially for larger holes.


      I think I'll play with that some more. It does seem that the carbide boring
      bar was more rubbing than cutting, so I am thinking about grinding a HSS
      boring bit with a fairly aggressive positive rake and making that very
      sharp. Maybe it'll start cutting more than rubbing...

      Thanks again for all suggestions.

      Vlad


      Jeff
      >
      > *********** REPLY SEPARATOR ***********
      >
      > On 3/3/2006 at 11:58 AM Vlad Krupin wrote:
      >
      > >Since I just asked for some insight about my not-very-cocentric end mill
      > >holders, I figured I'd ask another question that stems from that. I know
      > >that some people (Tom Benedict?) have successfully used mill as a lathe.
      > I
      > >tried to do that yesterday, and failed miserably.
      > >
      > >Since I could not make a cocentric 3/8" end mill holder on the lathe, I
      > >tried drill it to .330" on the lathe, and then finish by boring it out to
      > >size (.373") on the mill. I mounted a boring bar vertically in the
      > >toolmaker's screwless vise, aligned the cutting point with the center of
      > >the
      > >drilled hole, made sure the angle or the 'top' surface of the carbide bit
      > >is
      > >about perpendicular to the tangent of the surface being cut, just like I
      > do
      > >on my lathe. Then I advanced one axis by 0.005" so the boring bar should,
      > >in
      > >theory, enlarge the hole by about 0.01", and took a cut. LOTS of chatter.
      > >Hmmm... maybe I miscalculated and took too deep a cut. Let's try that
      > >again.
      > >Advance by another 0.005, take another cut - same result. Some of the
      > >inside
      > >surface looks almost glazed, some - as if it has been gnawed by mice;
      > >chatter marks in some places. Ok, maybe the feed is too slow. Increase
      > the
      > >feed a little, add some cutting oil, take another cut - same result. We
      > are
      > >getting pretty close to final tolerance here... Oh, well, forget the
      > 3/8",
      > >we'll make this into a 1/2" holder. I want to figure out what's wrong.
      > >Maybe
      > >the feed is still too slow. Increased the feed a bunch, so the shavings
      > >should be about 0.003" thick. LOTS of chatter again. The surface does not
      > >look 'rubbed' anymore, but still very rough. Hmmm... maybe RPM is too
      > >slow... Carbide cuts faster than HSS, right? So, I doubled the RPM,
      > >adjusted
      > >the feed accordingly. Same result. Just out of curiosity, I tried taking
      > a
      > >0.01" deep cut. Horrible sound, smoke all over the place from the burning
      > >cutting oil, the endmill holder got really hot. Not good.
      > >
      > >Argh! I can cut the same steel with the same boring bar on my lathe with
      > no
      > >problems! In fact, it cuts like butter, and does not even get too hot to
      > >touch. My mill is relatively well-adjusted - the gibs are tight, the nuts
      > >are tight, the leadscrew bearings are tight - everything is as tight as I
      > >could get without having too much friction. There is less than 0.002"
      > >backlash on either X or Y.
      > >
      > >So, am I doing something wrong, or does the mill just 'flex' too much
      > >compared to the lathe?
      > >
      > >Vlad
      > >
      > >--
      > >Vlad's shop
      > >http://www.krupin.net/serendipity/index.php?/categories/2-metalworking
      > >
      > >
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      > >
      > >
      > >
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      > >
      > >Let the chips fly!
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      --
      Vlad's shop
      http://www.krupin.net/serendipity/index.php?/categories/2-metalworking


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