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  • Tramming the mill using a rotor question.

    Hello Group.
    I am in the process of setting up my new to me milling machine and have stopped at the local VW service shop and got a couple of brake rotors for tramming. When I was younger I had a VW bug and remembered that it had solid rotors not vented (the holes between the inside and outside) so I picked up one of these and a vented type.
    So, the question is, is one better over the other as to trueness or any other issues I should be considering?
    I will be truing them up on a friend's lathe and cutting the centers out.


    TX
    Mr fixit for the family
    Chris

  • #2
    Skip the rotor completely and tram to the table
    or vise bed. Tee slots are not a problem.
    I don't know why people think a brake rotor
    (or similar thing) is needed to tram.
    In a real machine shop, you might tram the
    head of a manual mill a few times a day
    if you are milling angles and such.
    And you better only take a minute or so
    or the boss thinks you are lacking something.
    Stop listening to people with this brake rotor
    idea. If you suck at indicating, practice it.
    Use a 4 jaw on the lathe and practice using it.
    That also should take a minute or so to get a
    part in less than .0005". Just get in the shop
    and use your tools and practice. Leave the
    brake rotors for the cars.

    --Doozer
    Last edited by Doozer; 04-16-2015, 07:41 PM.
    DZER

    Comment


    • #3
      I use a solid rotor. As for truing, make sure that the table is free from burrs and dirt, and set up an indicator in your mill. If you then carefully rotate the rotor under the indicator, you can see if there are any high or low spots on it. On my (new) rotor, the needle on the indicator barely moved throughout 360 degrees of rotation...using a very sensitive dial test indicator held in a collet.
      David Kaiser
      “You can have peace. Or you can have freedom. Don't ever count on having both at once.”
      ― Robert A. Heinlein

      Comment


      • #4
        If I need to know whether the quill spindle centre is square to the table in the "X and "Y" planes I check the tram.

        If its near enough for the job in hand I use it "as is" and don't adjust the tram at all.

        If it needs tramming I adjust the tram - and if it doesn't it doesn't get adjusted.

        And not all tramming needs to be to an order of accuracy of say +/- 0.0002" (2 "tenths") over say 8" where as +/- 0.002" (or more) over say 8" will do.

        There is no mention so far of checking the mill table for flatness, dents or burrs etc. as after all the mill table top face is just as much a reference plane in the event of tramming as a surface plate is in many other instances.
        Last edited by oldtiffie; 04-16-2015, 09:51 PM.

        Comment


        • #5
          Yes, my point exactly.
          If your "rotor" sits on a bump from a nick on the table,
          it will throw things off, whereas just swiping the table is
          immune to picking up a bump, because it is direct.
          The needle will show the nick or bump, and you can
          either ignore it and still be able to tram the mill, then
          stone it out after.
          I once tried a 6" Timken race to tram a mill, more farting
          around than it was worth. It became evident in 10 seconds
          that it was kinda useless and cumbersome.
          Then there are those tram thingys with two indicators
          permanently mounted to a tee-shaped affair.
          Those are like training wheels on a motorcycle.
          I saw in a video that even Starrett makes one.
          Kind of superfluous in my opinion.


          --Doozer
          Last edited by Doozer; 04-16-2015, 11:22 PM.
          DZER

          Comment


          • #6
            I mount an indicator in/on the spindle and then check readings by sliding a 2" gauge block (on its side) between the stylus and the table. The gauge block helps factor out table imperfections.

            Comment


            • #7
              Big bearing races, brake roitors etc are all fine if that's what works for you. If you're a little bit practiced and know the nod ratio (how many thou to tweak the nod per thousandths of tram error for an 8" circle) you can tram a turret mill in a minute or three.

              I tram directly on the table unless the vice is in the way. Then I use the 3" dimension of a cheap import no-hole 1-2-3 block to space up from the table. My "tramming block" has 15 degree lead belt sanded on it so the indicator doesn't "trip" as it ramps up to the reference surface. I use a version of the Indicol tool for most all tramming and location purposes.

              Practice is the big thing. Otherwise it's over-shoot - crap! Under-shoot - crap!. Snug - move a bit - crap! etc. for a good part of an hour.

              Thing is to pick a way to do things and get really practiced so all your moves are competant and automatic. Sieze on the latest fad then move on to another at the first frustration and you'll never get proficient - but you will get gadget poor.
              Last edited by Forrest Addy; 04-17-2015, 01:08 AM.

              Comment


              • #8
                It should be understood that when "tramming" a quill spindle centre to the mill table that both the mill table ("knee" mill or vertical head on a vertical mill) as well as the quill itself should be clamped.

                You might be surprised how the tram will lose adjustment when the quill clamp is loosened and re-tightening and the same for the vertical dove-tail clamps - so be warned and be careful.

                Same applies to tail-stock quills.

                Comment


                • #9
                  Originally posted by Doozer View Post
                  Skip the rotor completely and tram to the table
                  or vise bed. Tee slots are not a problem.
                  I don't know why people think a brake rotor
                  (or similar thing) is needed to tram.
                  In a real machine shop, you might tram the
                  head of a manual mill a few times a day
                  if you are milling angles and such.
                  And you better only take a minute or so
                  or the boss thinks you are lacking something.
                  Stop listening to people with this brake rotor
                  idea. If you suck at indicating, practice it.
                  Use a 4 jaw on the lathe and practice using it.
                  That also should take a minute or so to get a
                  part in less than .0005". Just get in the shop
                  and use your tools and practice. Leave the
                  brake rotors for the cars.

                  --Doozer
                  I must agree, what your doing by using a rotor is adding another variable, what you want to know is not the relationship with the brake rotor and table, it's the spindle and table, so just measure that.
                  Mark

                  Comment


                  • #10
                    I use the top of the rotary base for my vise (i.e. without the vise), if I want a uniform surface. Sometimes I just use the table. A brake rotor will work. Whatever you're comfortable with. After all, it's YOUR shop! Do what you please.
                    ----------
                    Try to make a living, not a killing. -- Utah Phillips
                    Don't believe everything you know. -- Bumper sticker
                    Everybody is ignorant, only on different subjects. -- Will Rogers
                    There are lots of people who mistake their imagination for their memory. - Josh Billings
                    Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                    Don't own anything you have to feed or paint. - Hood River Blackie

                    Comment


                    • #11
                      Clamp a piece of aluminum in your vise. Take a cut along the top. Look at the marks made by the end mill. Determine which side is low and adjust the mill head accordingly. Repeat as needed until you have both the leading and trailing cuts showing on the surface. At this point you may or may not be perfectly square to the table surface but you are square to the travel. Should be the same thing, no?

                      Comment


                      • #12
                        Originally posted by Doozer View Post
                        Skip the rotor completely and tram to the table
                        or vise bed. ...

                        --Doozer
                        ^^ This!

                        I've never understood the need for a rotor.

                        Edit: For what it's worth, most lathes will cut a very slight cup when facing material. Even our rebuilt HLV at work cuts a very slight cup; about 0.0002" difference across a 2" radius. To get a good tram with a faced disc, you need to make sure the disc is centered on the spindle before starting.

                        If you use a rotor, you have to make sure the table is clean and nick free. Then you need to center the disc under the spindle. Then you tram.

                        I prefer my single step method: tram.
                        Last edited by Fasttrack; 04-17-2015, 12:07 PM.

                        Comment


                        • #13
                          I do what John does, with an ordinary end mill, better yet a flycutter. I also bought a "training wheel" device from Enco on sale. It works quite well for a quake check. Bob.

                          Comment


                          • #14
                            There is way too much emphasis on the need for super accuracy in setting up the tram when the real need of the accuracy of a tram for the job in hand may be somewhat (considerably) less.

                            Assuming for the moment that super high tramming is necessary it is a little unfortunate that any vertical face cut with the side of an end milling cutter will only be truly vertical to the horizontal trammed face if and only if there is no conical run-out of the milling cutter.

                            In the event of a conical run-out the vertical faces will be somewhat like (but less than) those on a dove-tail - on an "outside" vertical face the end of ther end milling cutter will describe and arc (and diameter) that is wider than that at the collet.

                            In short, and "outside" face will have a deeper cut than at the collet.

                            And an "inside" cut (as in a slot) the end milling cutter will also have a deeper cut than at the collet.

                            If that is the case, neither vertical will be square to the trammed (horizontal i.e. mill table) surface.

                            A similar situation arises in the cutter centre is running true but the helical (vertical) cutter edges are not true/parallel but are in fact conical.

                            So - I don't worry too much (or in many cases) or at all as I only need a tram to suit the job in hand.

                            Comment


                            • #15
                              Skip the brake rotor, just another piece of crap.

                              Use 1-2-3 blocks on the table to allow a free sweep from one side to the other. Heck, lay your vise parallels on the table, they are well matched. (you can always mike them)

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