View Full Version : Measuring T.I.R. method

12-09-2003, 01:13 AM
Hi, in my quest to make believe I'm a HSM, I figured I should check the t.i.r. of my lathe and mill.

I didn't know what to do so I chucked up a piece of old reamer shank that now gets used like a center finder 'cause it seems pretty true......I threw it in the drill chuck and also in the three jaw in the lathe, then put an indicator against it and set it to read in the middle of my "Last word"....I turned each spindle by hand and the needle only moved a thou to either side.

Now would that be two thousandths total?....seems like it would make sense.

I was thinking I should put the indicator against the inside of the mill spindle and check things that way......it's a Grizzly mill/drill with and R-8 spindle.


12-09-2003, 01:20 AM
First I would get myself something a little more dependable like a ground dowel pin or failing that a good automotive wrist pin,these will be more accurate than a reamer shank.

Okay T.I.R.(TOTAL INDICATED RUNOUT)thats what it stands for so yes,+.001>-.001" would be .002" t.i.r.

12-09-2003, 03:58 AM
Measurement of spindle error is best done with a ball because it is much easier to line up. The error you measure with your indicator is the sum of the error in the test artifact, the alignment of the artifact, the indicator error and any errors in stick slip friction and dirt you might have. If you get a master gage ball mounted on a stem that has a roundness of better than 5 millionths and use a little oil on the ball when you run it you will get a fairly good indication of spindle error motion. You need to indicate the radial error and then the axial error. A further test is to measure the radial error close to the spindle and then further out. A comparison of the two indications will give you an idea of the so called "tilt error" or "cone error". Finally there is a technique similar to reversing a square in which you make a measurement of radial error motion relative to a mark on the spindle and then reposition the ball 180 degrees relative to the mark and also move the indicator to the other side of the spindle. This is the ball reversal technique and you then subtract the first measurement data set from the second measurement and this allows you to separate the error in the ball from the spindle error. In this way you absolutely know the roundness of the gage ball and the spindle radial error. This ball reversal method only gets important when you are trying to measure to an accuracy much better than the roundness of the gage ball. Since is relatively inexpensive to get a master ball that is good to a couple millionths it is easy to assume the error in the ball is small and count the indication as all spindle error. This is a short summary of a long story and even this is long. There is an ANSI or ASTM standard for measurement of spindle error that will give you a more detailed explanation and procedure if you get real interested.

12-10-2003, 05:31 AM
If you make parts and they fit together properly - you ARE a HSM - if they look good and you don't get cut to ribbons handling it - pat yourself on the back.

Sometimes I just like to make stuff quick and dirty. othe times I am anal retentive - it depends on how important it is. If it is something you want to show off, take your time and do your very best. But if you are making a tool you only need for twenty minutes and then never again - don't waste time on making it pretty.

Learn first all the tricks of the trade before you sweat the little things - and most important - be safe and have fun learning!

12-10-2003, 11:34 AM
Thanks guys, sometimes it's all a mystery without being able to ask a pro.....I'm so glad I'm able to participate, and learn from you all.


12-11-2003, 02:22 AM
I,am still learning the tricks,and when making a set up I still seem to think of a beter,stronger,faster way to do it as I,am running the setup. In your minds eye to try prove your setups,by exadration ie what if. At times holders MT or collets can be removed and installed 180 deg. beware of them chips under same.

12-12-2003, 06:27 AM
Just remember, we all screw up. I am certainly no exception. I do some real doozies at times. Then I have to remember to pull my head out of my ass for a fresh look at the problem - clumsy me!

Brain farts - I calls them. http://bbs.homeshopmachinist.net//biggrin.gif

You just file them in the "Lesson learned" bin or "scrap" bin as we call it and start over - hopefully not to repeat the same damn mistake (been there, done that, have the t-shirt)