How Consistent Is The Ring on Taper Tooling

Lets try wording this a little differently:

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.

On 11/7/2019 2:01 PM, snipped-for-privacy@whidbey.com wrote: > Greetings Bob, > There is some variation in the flange location of regular CAT > spindles. But the tool doesn't really draw very far up into the taper > when clamped. Not enough to matter. In order to do so the socket would > need to expand and/or the tool shank would need to shrink quite a bit > and this doesn't happen. So tool setters just use a socket ground to > the tool taper and the tool is set into this socket. This socket is > either set on a tool setting fixture, or is mounted in a tool setting > fixture. And you can get a socket to set on a reference surface like a > surface plate. So you can do exactly this. I wouldn't be surprised if > you can buy one of these sockets from some outfit like MSC. If you > can't then just turn one. > Eric

So from reading that I can't (as I suspected) use the ring as a reference. It also seems that if I want to measure off machine with a fixture, I'll need to also use a physical tool zero mounted in a tool holder as well. Maybe something like a gage pin in a collet chuck tool holder.

The more I think about it though swapping tools between machines while possible might be confusing and lead to crashes. I'd be better off to go ahead and just duplicate tools. Probably need another dozen tool holders eventually to cover the range of commonly used tools.

So you think just setting the tool in a socket fixture will be repeatable enough it just won't matter? I'm not a whizz on the lathe, but I can probably make something that will work.

Could you set up a dial indicator to read the flange in the spindle, then run all your sockets thru and record the variation?

Instead of machining a socket you could cast one.

Clamp two tool holders on opposite ends of a shaft to fixture the lower one exactly upright in the mold.

I have no experience with this but I wonder if you could put each toolholder in your spindle and measure the distance between the ring and some reference surface on the spindle? That would answer your first question. Second, even if they are different, could you measure each toolholder and engrave its offset on the ring? Then you just add that offset to the tool length when you set up a new tool in that holder. Not the "right" way others have posted where you have a socket on your surface plate, but maybe it would be good enough?

Might be an idea but check the characteristics of the alloy being used as not all are dimensionally stable, IIRC some actually shrink slightly after a time to allow for removal and gauging of holes. Also I have Bendalloy and it is recommended to coat the tube internally with oil to prevent sticking to the tube so the release film thickness might be an issue.

I would not want to risk engraving as these are run at 24K RPM. It probably would not fail catastrophically, but it might contribute to long term bearing life. I have considered seeing if I could measure these relative to the spindle, but I'm not sure how I would go about it. I don't think a "stack of shims" would get me there.

Also, most of the low melt alloys I have looked at are pretty soft.

I'm having a hard time finding a measuring fixture for any 20 taper. The smallest I can find is for 30 taper tool holders. It looks like making one really is my only option.

The engraving was just for convenience at setup time so you didn't have to track down the table of offsets for each holder. I was thinking of something like a dial test indicator in a magnetic base attached to the spindle head, so that the DTI arm rested on the top surface of the flange so you could remove and insert holders in the spindle. Zero the DTI on the first one, then the rest of the holders are relative to that one. Put a tool in the first one and measure from tool point to the top of the flange, and then use that plus the DTI reading for another holder to know what to set the tool at in that holder. You will have to either make a fixture with a hole that the taper drops through, with a flat surface so the cutting tool is sticking straight up, and then set that fixture on your surface plate. Or maybe just hold the top of the flange on the edge of your surface plate so part of the flange rests on the plate and the taper portion hangs down, and use your height gauge on the top of the tool to set the height.

If nothing else you could set up the DTI and check a couple of holders to see how reproducible the flange location is. Oh, and manually rotate the spindle to see how square and flat the top of the flange is. I've never seen this done, but you asked for ideas :-).

I ran across this old thread on Practical Machinist:

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.

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.

I wasn't going to test it for fit up since that's not really what its for, but I couldn't help myself. I wiped the taper of my new "tool zero" with write erase marker, and dropped it into the fixture. I held it in firmly and gave it a spin. About 90% of the marker was wiped off.

I love it when that happens. Eric