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Cutting gear racks on a vertical mill

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  • Cutting gear racks on a vertical mill

    Has anybody ever cut their own gear racks on a vertical milling machine? The quill travel on my machine is only 3", but the head moves up and down, so with some careful measuring the head could probably be raised/lowered incrementally to cut longer racks. I have a complete set of gear cutters 24DP. and have cut many gears but never a rack. I have purchased lengths of rack (they aren't horribly expensive) but I'm curious as to whether anyone has made their own.---Brian
    Brian Rupnow

  • #2
    I have made a 4' rack but in all honesty it came out a bit rough, I cut 6 teeth them asked a bit of commercial rack as an index by clamping on top and advancing the rack one tooth at a time, it worked but my cutter was not brilliant.
    I toyed with making racks on the lathe, imagine a rack then make it a round bar, ir was actually quite promising, it was easier to make the tool. The pinion was very like a rack worm if that makes sense, internal radius was the bar radius, I was making an arbour press so the rack was the ram at 2" diameter
    If I had a suitable head I'd try the mill again, I need a 90 degree drive or horizontal head.
    Mark

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    • #3
      I've thought about making a right angle head like Chuck Fellows did to convert my vertical mill to a horizontal mill for "one of" projects like racks, but for the work involved, it is far cheaper to buy rack commercially as I need it.
      Brian Rupnow

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      • #4
        A rack tooth form is not an involute. I would make or have made an end mill of the appropriate shape and mill with the vertical head.
        Jim H.

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        • #5
          Jim--On the set of gear cutters I have, the largest cutter goes from 137 teeth to rack. The larger a gear gets in diameter, the less involute there is to the toothform. You are right. However, the gear cutters take that into account. That is why you can't cut all different gear diameters with one cutter.
          Brian Rupnow

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          • #6
            I fully understand that. Take a look at a true gear hob however, it will cut all tooth counts and is not involute form. Take a look in Machinery's Handbook at the basic rack of the full depth involute system. It is straight sided.

            Even if it required a modified shape, it still would be much simpler to produce an end mill of the appropriate form to cut a rack on a vertical milling machine than to modify a vertical milling machine to use an involute cutter to produce what would be an imperfect rack in the end.
            Jim H.

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            • #7
              If nothing else, grind a one fluted cutter (easiest in home scenario) with the proper angle and mill your keyway like you would mill most anything on the machine.

              Just see what material you cut, as for example cold rolled will end up as a banana after cutting the rack.
              Amount of experience is in direct proportion to the value of broken equipment.

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              • #8
                I'm not talking about a keyway. I am talking about a gear rack.---Different thing altogether. I already have a full set of gear cutters. The only limitation on using my largest cutter to make a rack is the limited (3") travel of the quill in my vertical mill.
                Brian Rupnow

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                • #9
                  Originally posted by brian Rupnow View Post
                  Has anybody ever cut their own gear racks on a vertical milling machine? The quill travel on my machine is only 3", but the head moves up and down, so with some careful measuring the head could probably be raised/lowered incrementally to cut longer racks. .....
                  Assuming that your gear cutters are at least larger in diameter than the quill you're still going to run into the size of the head fouling any longer stock that is held in a vertical position.

                  On my present mill the nose of the quill is a bit over 4" in diameter. So the only way I could make a piece of rack that uses the whole 3.5" of travel of the quill would be to make up a LONG arbor. I'm basing this on the fact that the only medium and finer pitch gear cutters I've seen were fairly small. And certainly smaller than my present size mill's quill.
                  Chilliwack BC, Canada

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                  • #10
                    As you describe, on a mill of the style you are using there is need to have a right angle drive on the quill in order to cut a rack of any reasonable length.

                    Even then to get rack length longer than the Y-axis travel limit you need to lay the rack lengthwise along the table and cut on the Y-axis. Downside is that cutting with the Y-axis removes the ability to use the X-axis power feed ... presuming you have one of course.

                    Norman

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                    • #11
                      I never thought of that. My saw arbor is fairly long, but not longer than the stroke of the quill. It looks like I might get be able to get 3" maximum long rack using my vertical mill.
                      [B[/B]
                      Last edited by brian Rupnow; 11-26-2016, 03:27 PM.
                      Brian Rupnow

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                      • #12
                        No power feeds on my mill Norman,--although it does have an awesome travel in the x axis--something like 22".
                        Brian Rupnow

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                        • #13
                          In Post 10, Sir John cuts a rack several feet long in his vertical milling machine using a simple end mill;

                          http://bbs.homeshopmachinist.net/thr...r-Rack-Cutting
                          Jim H.

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                          • #14
                            The trick with the end mill used to cut the rack is that on smaller size pitches the tool would need to spin up pretty high. But it's got the advantage that a suitable cutter can be easily made by a home shop sort.
                            Chilliwack BC, Canada

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                            • #15
                              Sir John knows a heck of a lot more than I ever will about machining. I'm pretty sure I've had my question answered. If I ever need any 24 dp racks, I buy them. that is what I did when I built the advance mechanism for my sawmill.
                              Brian Rupnow

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