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  • #31
    I made a similar insert holder from a stub arbor that fits the spindle (MT3), and I thought about the one cutting edge of the insert touching the wall of the pocket. What I did was go the extra step and relieved a bit more of the metal so that the insert touched the side of the wall at a point somewhat below the cutting edge. Not hard to do, and I feel better about it anyway, knowing that the insert is tightly placed on the holder and no cutting edge is taking any pressure, except the one that's supposed to be cutting. Obviously you'd do this before marking and drilling for the mounting bolt.

    Oh yeah, I made one mistake with the insert mounting bolt- I left it too long and it stuck out the side of the holder. I drove the flycutter a little too close to one of the hold down clamps one day, and found out the hard way that if you destroy the threads on the exposed part, it isn't going to be easy to remove the bolt.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #32
      Originally posted by darryl
      What I did was go the extra step and relieved a bit more of the metal so that the insert touched the side of the wall at a point somewhat below the cutting edge.
      (Dope slaps self) Thanks for that!

      I suppose one could tilt the bolt in an angle vise set to the insert face angle for an even better, full contact fit.
      Last edited by DICKEYBIRD; 06-24-2010, 08:41 AM.
      Milton

      "Accuracy is the sum total of your compensating mistakes."

      "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

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      • #33
        Grade 8 IS "cheese metal"....... they are not really that hard, comparatively. Too hard and they'd be brittle.

        But why go so slow? 5000 rpm is 0.0002" depth of cut per tooth. It seems you could, and probably should, feed faster with the insert.

        They are not razor sharp, and it may be spending a lot of time "rubbing" instead of actually cutting, even though at 5000rpm you don't see that.
        1601

        Keep eye on ball.
        Hashim Khan

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        • #34
          Originally posted by J Tiers
          Grade 8 IS "cheese metal"....... they are not really that hard, comparatively. Too hard and they'd be brittle.

          But why go so slow? 5000 rpm is 0.0002" depth of cut per tooth. It seems you could, and probably should, feed faster with the insert.

          They are not razor sharp, and it may be spending a lot of time "rubbing" instead of actually cutting, even though at 5000rpm you don't see that.

          I have an excuse. My big Webb tops out at 4,200 rpm....but your theory is good.

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          • #35
            Originally posted by hojpoj
            Before things go off on the 'endmill in a chuck' tangent.....................................
            You dont have many post GrassHopper but you must have been doing your homework on this forum!! Very astute observation!
            - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
            Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

            It is true, there is nothing free about freedom, don't be so quick to give it away.

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            • #36
              What I did was go the extra step and relieved a bit more of the metal so that the insert touched the side of the wall at a point somewhat below the cutting edge.
              Excellent suggestion and easy to implement. I didn't show that part because I was trying to keep the number of steps to an absolute minimum.

              That's my story and I will die with it.
              Free software for calculating bolt circles and similar: Click Here

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              • #37
                I love the captions "Ignore" "oops"
                This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
                Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
                Plastic Operators Dot Com

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                • #38
                  Originally posted by J Tiers
                  Grade 8 IS "cheese metal"....... they are not really that hard, comparatively.
                  In my experience, most tooling is not made from particularly hard steel, even the high priced stuff. Grab one of your most expensive non-chinese or indian pieces of tooling and draw a file edge on an inconspicuous spot on it and you'll see what I mean.

                  Paul T.

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                  • #39
                    the bolt was a handy hulk of iron the right shape and size....but the type of steel is maybe a bit of a red herring? one might maybe the tougher steel in the bolt resists deformation/wear where they insert is in contact but that seems a stretch especially in a home shop with one carrying operator. I would think any hunk of steel would perform as well
                    .

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                    • #40
                      The only problem with low grade steel is the 4-40 threads don't hold up. I use 4-40 grade 11 (or whatever ) countersunk cap screws to hold most inserts like these and they can be tightened enough to strip the threads pretty quick in a grade three bolt and even a grade 5. Other than that there is no other reason to use grade 8 material.
                      Free software for calculating bolt circles and similar: Click Here

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                      • #41
                        Originally posted by Evan
                        The only problem with low grade steel is the 4-40 threads don't hold up.
                        good point
                        .

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                        • #42
                          Originally posted by PaulT
                          In my experience, most tooling is not made from particularly hard steel, even the high priced stuff. Grab one of your most expensive non-chinese or indian pieces of tooling and draw a file edge on an inconspicuous spot on it and you'll see what I mean.

                          Paul T.
                          I have some Dorian insert tooling and it is "reasonably" hard......

                          I agree very hard is not needed, but that is off-topic.

                          The point is that grade 8 is not usually so hard that one should be concerned about cutting it. if it IS that hard, there may actually be a problem with it, it may be off-spec for strength.

                          Originally posted by bnm109
                          I have an excuse. My big Webb tops out at 4,200 rpm....but your theory is good.
                          The speed is fine, it's the FEED I was questioning.

                          My question to Evan was why so slow a feed that the cut per tooth was in the tenths, with carbide inserts? Inserts are not usually good at "dusting off tenths".

                          I would expect a couple-three turns just rubbing, and then a cut, then 2 or 3 more just rubbing, then a cut, etc, etc.

                          Is there some question about the tool that suggests the tiny cut, or is it just "what happened"?

                          He could have increased the feed, or slowed the speed. Either could easily increase the cut per tooth to 0.001 or so which is more in the usual range (and 5 times what he had).
                          1601

                          Keep eye on ball.
                          Hashim Khan

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                          • #43
                            My question to Evan was why so slow a feed that the cut per tooth was in the tenths, with carbide inserts? Inserts are not usually good at "dusting off tenths".
                            I missed that you asked me a question.

                            The feed was slow to maximize the finish regularity although if you look I also ran a pass at only 500 rpm and 5 ipm which shows no discernable difference.

                            On the 6061 piece I ran 3 passes back and forth with no change in depth of cut to eliminate, as much as possible, any irregularity from machine vibration. There isn't much vibration with my machine since I am using a 24 volt DC 3 phase brushless motor with closed loop speed control as the main drive motor.

                            These particular inserts are very sharp and will cut regardless of the light chip load. They are high positive rake but are also very fragile compared to standard neutral rake inserts.
                            Free software for calculating bolt circles and similar: Click Here

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                            • #44
                              Originally posted by J Tiers
                              I have some Dorian insert tooling and it is "reasonably" hard.......
                              I would suspect its probably case hardened in the seat area, if you think about it there's no reason to do any more than case hardening on most tooling. But as I stated earlier, its still surprising how much high end tooling is not made from a particularly hard steel or even has case hardening.

                              Paul T.

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                              • #45
                                Evan,

                                Have you tried this tool on mild steel?
                                Mike N

                                Occasional maker of swarf.

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