Using the Tool Height Table(s)
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    Default Using the Tool Height Table(s)

    One of my machines uses a tool holder with a flange that actually is pulled up against the spindle face as it is locked in the spindle. This makes it dead easy to measure tool lengths off the machine with a height gage. I can measure on the machine with an electronic height setter or measure on the surface plate with a height gage and as long as everything is cool they measure within a couple tenths. Good enough for the work I do, and far better than the machine itself is capable of.

    On another machine I never set the tool lengths because they vary beyond the Z travel, and its just faster and easier to crank the table down and then crank it up until the tool zeros my 2" height setter. The machine is always machine (home) set with Z-zero at +2" work offset. Atleast in the G54 offset. I may use other values when using additional work offsets. Its not as fast as a tool table with a bed mill, but its fast enough.

    My main work horses have 24K spindles with until recently ER spindle noses. I had to use the height setter after every tool change. Sometimes quite creatively. Recently I changed one out to an ISO20 spindle. Just being able to push pull the 5 port air valve to swap tools saves me a lot of time already, but I want to start setting up the tool table and using M6 G43 to apply the tool height offset just like I do on the machine in paragraph one.

    However I have a problem. I am having a hard time wrapping my mind around how to measure the tool length off the machine. I am wondering if its even practical. An ISO 20 does have a flange, but as near as I can tell its only purpose is to provide a way to hang the tool in a tool changer. From what I understand the tool is only reference by how firmly it is pulled into the spindle taper. To me that says I can only measure the tool length offset on the machine its being used on. Am I missing something? I guess I could have a physical tool zero instead of using the spindle face, and have an iso 20 ground "socket" I placed on the surface plate to put tools in to measure. Seems to me that would result in different measurements of the same tool just depending on how firmly I set the tool holder in the "fixture" setting on the surface plate.

    This becomes more interesting because I have a second machine I plan to upgrade to the ISO20 quick change spindle. Already have it on hand. Just haven't had an afternoon to spare to make the change. If possible it would be nice to use some of the same tools on both machines. If I could get reliable relative tool lengths off (not in the spindle) of the machines I could just measure once, and plug the value into both machines saving me time.

    I am a one man shop who started out as a hobbyist, and now pretty much run continuously as my primary business. Taking time now to figure out how to save time later is a cumulative gain. Five minutes setting tool lengths might save more time over a year then shaving 20 minutes per part off a 50 piece order.

    I sincerely would like some help, guidance, or confirmation.

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    I ran across this old thread on Practical Machinist:

    fixture to measure tool length Erickson 30 taper

    It gives me the impression that I should be able to turn a fixture for measuring tool height "good enough" even at my modest skill level on the lathe.

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    We shall see how it goes. I turned a measuring fixture on the lathe.

    Well, I made a fixture to hold the tool holders to measure. Now I need to make up a physical tool zero reference tool.

    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 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 and the reference surface on the bottom. 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 tool 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 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 hard 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.

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    Ok, I couldn't help myself. I had to check. I used a writer erase marker on the taper (thinner than bluing), dropped it in the fixture and held it in tight while giving it a span. It wiped off about 90% of the marking. Its not perfect, but its certainly better than I expected.

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    I'm sure you've figured out that the difficulty comes in correlating height on your fixture to height on the machine, as the tools will no doubt sit differently on your fixture than the machine.
    Here's how I've handled it: I touched a gage block off on the bare spindle nose. I called this zero. I then used a Haimer to touch off the same gage block. I put this difference in as the length of the Haimer in my tool table. I then measure the Haimer in my fixture on my surface plate. I subtract the Z-length I put in my tool table. That's my height gage zero for measuring futher tools.

    This can be done with a gage pin in an ER collet chuck if you want to be simple about it. I went with the Haimer because I like Haimers.

    You can check this against other tools, or repeat the process if you want to see how good your correlation is.

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    Quote Originally Posted by burdickjp View Post
    I'm sure you've figured out that the difficulty comes in correlating height on your fixture to height on the machine, as the tools will no doubt sit differently on your fixture than the machine.
    Here's how I've handled it: I touched a gage block off on the bare spindle nose. I called this zero. I then used a Haimer to touch off the same gage block. I put this difference in as the length of the Haimer in my tool table. I then measure the Haimer in my fixture on my surface plate. I subtract the Z-length I put in my tool table. That's my height gage zero for measuring futher tools.

    This can be done with a gage pin in an ER collet chuck if you want to be simple about it. I went with the Haimer because I like Haimers.

    You can check this against other tools, or repeat the process if you want to see how good your correlation is.
    I went with the simplest solution. For now I am going to use a physical tool zero. Drop it in the fixture. Zero the height gage on it. Start measuring tools. If I want to measure tools on the machine I can put tool zero in the spindle, and zero to the height setter first. I may never need to do that. My goal was to be able to quickly measure tools OFF the machine.

    Using a gage pin was a great idea. In fact its almost exactly what I did for tool zero except I used a broken 1/8 shank 1/32 ball mill backwards in the collet. I left it with what I think is less stick out than any tool I am likely to use.

    I tested it in the fixture several times. Dropped it in, set it in, pressed it in hard, rotated it, and rotated the fixture. As near as I can see variation was less than 2 tenths. Since using a height gage is a little bit about "feel" that's hard to 100% quantify for sure. As long as its consistently better than 5 tenths its probably "good enough."

    I have been thinking about moving my granite plate into the machine room were temperature will be more stable. That's a bit of a chore though.

    Of course if I ever loose track of tool zero I'll have to remeasure the lengths of every tool.

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    If you measure from the spindle nose to the length of tool zero then all of your tool measurements can be offset by this and should prevent catastrophe if you lose tool zero.

    You can even check the measurement of another tool to be sure that you're thinking correctly.

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    Atleast that's the way I think it will all work.

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    Quote Originally Posted by burdickjp View Post
    If you measure from the spindle nose to the length of tool zero then all of your tool measurements can be offset by this and should prevent catastrophe if you lose tool zero.

    You can even check the measurement of another tool to be sure that you're thinking correctly.
    That is true, but then I have to do the math every time I measure a tool. Its a good thought. I guess I'll have to decide if I want to take a little more time every time I measure a tool or take some more time all at once when I inevitably lose tool zero. LOL.

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    Quote Originally Posted by Bob La Londe View Post
    then I have to do the math every time I measure a tool.
    I don't think you do.

    touch off of a gage block with the spindle nose. Touch off of your gage pin. The difference in Z is the tool length of your tool zero. Write it down.

    Take your tool zero to your offline fixture. Zero your height gage on your granite. Measure the height of your tool zero. Subtract the tool length you measured on your machine. This is the reference height for all the tool length measurements you'll be making in the future.

    Make a gage block stack that height, or face a rod to that height. Now in the future when you set up a tool you drop it in your offline fixture, you zero your height gage on your reference height and then you measure the tool. Whatever you measure is what you put directly into your offset table.

    If you're lucky you can face your offline fixture to the correct length or add a pin to it or something like that so that you can zero off of that and then measure your tool length.

    Does that make sense?

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    Quote Originally Posted by burdickjp View Post
    I don't think you do.

    touch off of a gage block with the spindle nose. Touch off of your gage pin. The difference in Z is the tool length of your tool zero. Write it down.

    Take your tool zero to your offline fixture. Zero your height gage on your granite. Measure the height of your tool zero. Subtract the tool length you measured on your machine. This is the reference height for all the tool length measurements you'll be making in the future.

    Make a gage block stack that height, or face a rod to that height. Now in the future when you set up a tool you drop it in your offline fixture, you zero your height gage on your reference height and then you measure the tool. Whatever you measure is what you put directly into your offset table.

    If you're lucky you can face your offline fixture to the correct length or add a pin to it or something like that so that you can zero off of that and then measure your tool length.

    Does that make sense?
    Yes. It adds a little level of keeping things straight to start with though. Facing off the fixture to the exact length would make the most sense if I was using this for just one machine, but I have a second ISO20 spindle I will be installing in a second machine. They both came from the same *manufacturer, but... Yeah I could write down the offset somewhere. Maybe on a slip of paper I put in the box with tool zero and the fixture, so I can lose them all at once. LOL. Actually making a separate gage block to the exact length to zero from to be stored with the other parts would also work, but its starts to get a bit complicated to keep track of everything. Those extra things may get done later. I want to keep it simple for now. Atleast until I get my tool list in the machine to match the tool list I use for it in my CAM software.

    Measuring off machine isn't really that hard though. Using a **noteboard it goes pretty fast. I use about 20 tools regularly on each of those machines. I imagine I could measure all of them in 20-30 minutes if I had to. Using a little extra care for ***1/32 and smaller ones of course.


    * These ISO20 24K spindles cost enough I'll probably have them rebuilt rather than replace them when they wear out. Over time spindle wear could be an issue. I hope the spindle tapers are hardened and ground, but I don't know for sure how wear resistant they are. Over two or three years probably nothing noticeable, but I do not know for sure.

    ** I have a few little white boards in the shop about the size of a piece of paper. I use them in lieu of a notebook when I am working on a "cut to fit," "good enough," project or using information with short term relevance. This means I don't wind up with stacks and stacks of old notebooks full of long irrelevant data.

    *** I use ball nose end mills as small as 0.026" regularly and have had projects where I needed to deep slot with long reach mills that size. A long reach .026 ball mill is so fragile it will break if you give it an angry look. Those I might measure on the machine because a height setter is spring loaded and has give were as a height gage does not.

    Notes: The one machine I am using premeasured tools on already I do not use for anything smaller than 1/16" mills and drills currently. In my world 1/16 inch mills are pretty tough. In fact they are so tough for what I do with them that it always amazes me when I do something stupid on my bigger mill and snap off a 1/2 inch mill and destroy a part. My mind just boggles. LOL.

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    Cut my first job today using tool tables and premeasured tools on the machine I installed the ISO20 spindle in. Would have cut it sooner, but I had some tool change macro issues. At first it wasn't updating the tool number DRO. I think my custom tool change macro I'd written previous missed a command that updated the DRO. Then I decided to try somebody else's fancier tool change macro. Includes a prompt with a pop up that shows the tool number and tool description from the tool table. Very nice. The problem was it kept running the old macro even after I over wrote it. I spent two hours chasing my tail and then I realized I was updating the macro in the wrong machine profile. LOL. It was late when I finally got it all going so I waited until today to run a job on it. I made a few edits to the macro to suite my own needs and it was very nice.

    The little tool fixture with my improvised tool #0 works great as near as I can tell. Cut depth on everything I can measure is dead on. Well as good as the machine is capable of anyway. Thanks for the feedback.

    Now to do the same upgrade on the next machine.

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    Following along.
    I bought a new in box 18” height gauge from a member here, for the sole purpose of performing this tool length measuring task.
    My machine is Cat40, so stuff is easy to find, I got a $50 bench fixture to use on my surface plate. I need to machine/ massage the base flat and then do some repeatability testing of the fixture. I may have to massage the fixture’s taper too.

    I was going have a master tool zero, but then came to the same conclusion as JP?? above- as long as you write down the difference(delta) between the surface plate tool zero and the machine measurement you can recreate it on the surface plate. The delta can really be any number (within the limits of your tool holders/end mills) , consistency is the key.

    Thread is perfect timing ,I just got the order of tool holders for my new to me machine in yesterday

    Keith



    Sent from my iPhone using Tapatalk Pro

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    Sent from my iPhone using Tapatalk Pro

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    Very nice. I wish I had not had to make my own fixture for tool measuring. On the other hand it gave me a lot of confidence in my ability to measure a taper between centers and then cut a matching taper on the lathe.

    The ISO20 tool holders tighten with two wrenches, so they do not need a fixture for tightening on a tool.


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