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About how much torque should an R8 Drawbar have?

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  • About how much torque should an R8 Drawbar have?

    Gents--there are times when I think I am over tightening a collet or arbor for a R8 Spindle Vertical Mill. About how much "tightening" or torque should it take?

    As always, thanks for sharing your expertise.

  • #2
    I don't have a torque value but they don't have to be all that tight. I snug things up and then give a tug on the wrench to get 1/2" or so of additional movement. I probably tighten drills larger than 3/4" a little tighter.
    Byron Boucher
    Burnet, TX

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    • #3
      I have my air powered draw set at 25 ft.lbs. Checked with a torque wrench.

      Haven't slipped or stuck a collet yet.........

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      • #4
        1/2 turn less than striping the threads, couldn't resist ha ha.

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        • #5
          I put my import mill in lowest gears, snug it down hard with wrist action and then pull it back with my shoulder till the quill starts to turn. I do not use a second wrench in my other hand. So far, after all my dinking around, I've not had a collett spin in the quill nor a bit in the collett. Once they start spinning your on the highway to hell !!
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          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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          • #6
            Its independent to the size of the endmill or tool your using,

            All collets (from the same machine) have the identical leverage ratio (the outside of the collet against the spindle bore taper),

            what this means is this force then gets transferred directly to the cutting tool,


            So --- all you really need for a 1/8" endmill is a mild cinch up since not only is the leverage compounded to such a small surface area (high unit pressures)
            The cutters radius and strength itself has minimal holding requirements

            recommendations;
            Every cutter need's to have its torque adjusted to meet its needs,
            Save the drawbar threads for when you chuck up your 3/4" endmill --- flycutter --- or 5" R8 three jaw chuck....

            This is why (or just one of the reasons actually) I don't own a power drawbar and never will - I like using only what I need --- it also saves collet and spindle bore wear...

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            • #7
              I simply send the bolt home, and then slap the wrench a couple of times with an open hand.

              If the taper is true and seats correctly, it should take virtually 100% of the torque anyway. There should be no real load on the drawbar, other than if you are performing an operation that is trying to pull the tool holder out.




              This is purely my opinion. I am NOT a know-it-all.

              Mark

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              • #8
                Until you can`t tighten it any more,with the supplied wrench.
                Every Mans Work Is A Portrait of Him Self
                http://sites.google.com/site/machinistsite/TWO-BUDDIES
                http://s178.photobucket.com/user/lan...?sort=3&page=1

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                • #9
                  I use the brake on the Webb Mill to hold the spindle from moving when tightening or loosening a collet. I tighten them up until I can feel that the collet has seated nicely. Another inch or so on the wrench and I'm done.

                  To remove, I lock the spindle and use a dead-fall hammer to tap the top of the drawbar. Works for me.

                  I'm also very careful to make sure that there is no grit on the collet before I insert it into the spindle. A wipe with an oily rag will help.

                  .

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                  • #10
                    The Bridgeport Operators Manual, Bridgeport developed the R8 taper....

                    They just might know something about it.

                    http://kneemills.com/index.asp?html=Documentation

                    Clearly states "The drawbar should be tightened with a NORMAL amount of pressure using wrench furnished with machine."
                    Last edited by Bguns; 11-07-2010, 06:35 PM.

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                    • #11
                      Originally posted by Bguns
                      The Bridgeport Operators Manual, Bridgeport developed the R8 taper....

                      They just might know something about it.

                      http://kneemills.com/index.asp?html=Documentation

                      Clearly states "The drawbar should be tightened with a NORMAL amount of pressure using wrench furnished with machine."

                      Well, "a NORMAL amount of pressure". That nails it down, doesn't it? LOL

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                      • #12
                        Originally posted by Bguns
                        The Bridgeport Operators Manual, Bridgeport developed the R8 taper....

                        They just might know something about it.

                        http://kneemills.com/index.asp?html=Documentation

                        Clearly states "The drawbar should be tightened with a NORMAL amount of pressure using wrench furnished with machine."

                        I tried but I can't help myself !

                        Well I guess that settles it, just tighten it a "normal" amount. I'm searching my machinist manual now to see what a "normal" amount is for a person 6' tall and 274 pounds who is out of shape and also a tiny person who works out. When I find it I'll report back and you'll be able to extrapolate how many pounds of torque for your shop!
                        - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                        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.

                        Comment


                        • #13
                          How long is the wrench supplied with BP?
                          Mike
                          WI/IL border, USA

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                          • #14
                            Yup, super manual specifications.

                            But clearly not as tight as you can get it with the wrench...

                            I don't plan on putting a torque wrench on mine.

                            I just use a normal amount of effort on a standard length 3/4 in box wrench.

                            Too tight and a light tap will not break taper loose... That tapping goes right to the $$$ spindle bearings...

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                            • #15
                              Originally posted by MichaelP
                              How long is the wrench supplied with BP?

                              I don't know, haven't ever seen one. I use a 10" long 3/4" combination wrench on my Webb (BP clone). It works very nicely. This is not rocket science.

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