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ISO20 Taper Measuring Fixture

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  • ISO20 Taper Measuring Fixture

    I recently upgrade one of my high speed machines to an ISO20 quick change spindle. Just being able to swap tools in seconds by with a push/pull on the 5 port (4 way?) air valve saves me a LOT of time over grabbing a couple wrenches and tacking the old ER spindle nose on the old spindle. I've cut several jobs with it already. I like it so much I already bought another one for the matching sister machine.

    Now comes the issue of measuring tool length and inputting the data into the machine's tool table so (with the correct g-code) all I have to do is swap tool and press start when it comes to a tool change.

    ISO20 tool holders have a collar on them, but I don't know how consistently they are machined relative to the taper from one tool to the next. The tool holders seat on the taper. Not the collar. In order to start measuring the tool lengths and using the tool table on the machine the only thing I could think of was to mount them in the spindle and measure them using a tool height setter. Slow, and tedious, and I can't run the machine while I am doing it of course. I looked around to see if maybe there was a 20 taper measuring fixture available somewhere. The smallest one I could find was a 30 taper.

    I was prepared to measure on the machine if I had to, but I sure didn't want to have to. I run both machines almost all the time when I am in the shop. I asked around. The guys at new:rec.crafts.metalworking were open with ideas. I also asked at Practical Machinist where I half expected some of the less than helpful responses a self taught guy like myself sometimes gets. I didn't get any responses at all. That rather surprised me. However I found this old thread at Practical Machinist that decided me on a course of action.

    I made a fixture to hold the tool holders to measure. Now I need to make up a physical tool zero reference tool. I can't use the spindle nose as tool zero because I don't have a matching reference on the measuring fixture.

    I turned a center in the three jaw. Then I mounted a tool holder between centers. An indicator mounted in a lathe tool holder made it pretty much dead easy to measure rise over run with the saddle. I did a little math, looked at the protractor on the compound, and set it by eye.

    I swept the tool holder with the indicator and the compound. I had to check it three times. The compound isn't all that smooth. I probably should take it apart, stone it, and then put it back together a little tighter than it is. I didn't have to check it three times because it was off. I had to check it three times because it was dead on first try. The needle jumped a bit due to the import quality of the compound, but the average from end to end was nearly perfect. I was using a half though indicator. It was bouncing less than two lines, and settled in the middle when ever I stopped moving.

    Turning the fixture itself was planned to do all important cuts in the first setup. Cut the taper in the top and the reference surface on the bottom with the first setup. Everything else was unimportant. I used a piece of stock that already had a small hole in it big enough for the bottom of the taper and the pull stud. I face it off, turned the taper with the compound, and then made a clearance cut below the planned bottom/base of the fixture.

    I had it mounted pretty close to the chuck. A regular left hand tool wouldn't fit in the space I had available so I used a carbide insert parting tool. I opened up the clearance cut and angled the parting tool slightly away from the chuck. It has side clearance on the insert, but I wanted to make sure I could use it to make a nice clean draw cut out of the slot to square up a ring on the bottom of the fixture. After I was happy I parted it off and turned it around in the chuck.

    With the work piece mounted bottom out I turned a recess in the bottom leaving just a narrow ring around the outside for it to rest on.

    The tool holders set down in the fixture on their taper and don't wobble even a little. If I press them in firmly there is just the tiniest amount of stick when I pull them out. They feel solid in the hole. I don't know if the taper is a match, but as long as its perpendicular to the bottom I think it will be good enough.

    I did everything I know how to do to make the fixture. Tomorrow I'll test it on the surface plate with real tools in the taper. Then I'll make some cuts with them and see what happens.

    I'm not going to blue it and check it. I don't care if its a perfect taper. I just care that the tools seat to a consistent depth and pretty close to perpendicular with the base.

    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  • #2
    Well, I couldn't help myself. I colored up the taper of one of the tool holders with a write erase marker, dropped it in the fixture, and while holding it firmly in place gave it a spin. It removed about 90% of the marker the full length of the taper in the fixture.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.