January 29, 2014
Converting Laser Alignment System Readings to Rim and Face Dial Readings
By Michael Keohane
VibrAlign released the free Laser-Dials App to aid laser system users who need/want to convert their laser shaft alignment system results to rim and face dial indicator readings. You can also use the App to convert dial indicator readings to laser readings. Most are interested in converting laser results to dials so that is what we will do here.
Proper laser and dial indicator shaft alignment methods lead to the same end result. Confusion typically occurs when dial indicator rim readings T.I.R. (total indicator reading) and Face (Gap) readings are compared to actual offset and angularity results as shown by the laser alignment system.
Setting the stage:
1 – All readings are in mils where 1.0 mil = .001” and 0.1 mil = .0001”. Example 10.5 mils = 0.0105”.
2 – The proper rim and face dial indicator mount (set up) is selected by pressing the “Mount” icon at the bottom of the Laser-Dial App. Also, select the correct face dial indicator orientation with the “Face“ icon.
3 – The face (gap) dial indicator reading represents the angularity as a slope (rise over run) when you divide the face or gap difference (top to bottom or side to side) by the swing of the face dial. For purposes of this discussion we will assume the face dial is indicating almost to the O.D. of the coupling so the swing would be the coupling diameter. This example will be for a 6 inch coupling diameter.
4 – The rim dial indicator reading is TIR. The true offset of the shafts is ½ of TIR.
5 – Rim and Face Alignment Tolerances are specified as 3 mils (thousandths) face and 3 mils (thousandths) rim. These are entered into the laser system’s built in tolerance table as .5 mils/1” Angular Tolerance (3 mils ÷ 6 inches) and 1.5 mils Offset Tolerance (3 mils TIR ÷ 2).
6 – The Validity Rule, for both the Rim and the Face dial readings, must be satisfied (top + bottom reading = side + side reading).
7 – Modern lasers typically display the angularity as mils/inch so there is no need to input a coupling diameter unless you are looking specifically for a gap value.
Initial results showing a machine misaligned
The top left photo shows the initial laser system results with a Vertical Angularity of -2.1 mils/1” and an Offset of -9.9 mils. The Horizontal Angularity is -7.8 mils/1” with an Offset of -7.9 mils.
The bottom left photo is the same initial results however the Vertical and Horizontal Angularity is shown as a Gap difference on the O.D. of the 6” diameter coupling. In this case -12.4 mil/6” and -46.9/6”
The top right photo is the Rim and Face Dial Indicator Mount (setup) from the Laser-Dials App. with the Vertical & Horizontal Angle and Offset laser results entered into their respective boxes.
The lower right photo are the dial results, as you can see the 12 to 6 o’clock face reading (in green) shows that there is a 12.6 mil gap difference top to bottom over 6 inches. Therefore 12.6 mils/6” = 2.1 mils/1”.
The 9 to 3 o’clock face reading (in green) indicates a 46.8 mil gap across 6 inches (-17.1 – 29.7) = -46.8 mils. Therefore -46.8 mils/6” = -7.8 mils/1”
The 12 to 6 o’clock rim reading (in red) of -19.8 mils is T.I.R. so -19.8 ÷ 2 = -9.9 mils offset as shown on the laser. From 9 to 3 there is a 15.8 mil T.I.R. difference (-17.8-(-2.0) = -15.8 therefore -15.8 mils ÷ 2 = -7.9 mils offset.
Final results showing a machine in alignment
The final laser system results show the Vertical and Horizontal Alignment to be in tolerance and once entered into the Laser-Dials App. the Rim and Face Dial Indicator values are better than the specific tolerances of 3 mil face and 3 mil rim.
VibrAlign Laser-Dials App available free on iTunes or Google Play
How to Convert Dial Indicator Specs from the VibrAlign Alignment blog:
Dial Indicator basics video (TIR, Validity Rule & TPS) on the VibrAlign you tube channel:
Laser alignment technology is used for precision measurements. In order for measurements to be accurate, the technology needs to be used properly. This is a great outline of how to properly use the app.
My question to Mr. Michael Keohane,
If we have do alignment with laser device that is mean the readings (values) is real right, not as dial gauge readings TIR (Total indicator Reading) so the true offset of the shafts is ½ of TIR , should be divided by 2 to get a real values. by otherwords the shaft alignment tolerance (table) is real or TIR values ?
Abdullah, Thanks for you comment. You are correct the laser values are the actual (real) values. The tolerance table is also the actual or real maximum allowed offset and angular values. The laser tolerance table is not TIR. I hope this helps.
Sir, I’m sorry I have two quesions (important for me)
Q1) Acaully we CAT engine (7.5 MW) I have doing it alignment with the alternator (sleeve bearing), but the manufacurer told us the in the cold alignment the alignment value shoud be : vertical offest 0.5 to 1.0 mm and horizontal offest 3.0 mm +/- 0.25mm ….. therefore we follow thier istructions exactly, but the result was the cold web deflection of the engine out of its range, OK , then after that we have re-align the engine but not according to manufacurer tolerance, so the cold web deflection as good and acceptable, really we confused.. how we explain that? what the more important web deflection range or coupling tolerance rang? ………………………………..
Q2) are there any fixed rules or thumb of rules … when you do alignment of sleeve/jouranl bearing reagarding to its clearance and how we know it?
thank very much for your time,
Abdullah – Both the web deflection tolerances and alignment (coupling) tolerances are important.
From your previous comment I am assuming you are using a laser alignment system and not dial indicators. If this is correct then you need to verify with Catepillar if the cold offset alignment values they are giving you are the actual offset values or TIR dial indicator values.
If they are dial indicator TIR values then cut the cold offset values in half to use in your laser system and I would think this will solve the issue.
If Cat confirms these are the actual offset values they want you to use and they cause the web deflection values to be out of tolerance then I would consult with Cat regarding this issue.
Yes Mr. Brad , they informed us that the vaues is real (acual), really we are very confused and spaitlly when we pushed the alternator to side as they recommend. but when we consider half of those valuse the web deflection become good.
by the way we have use fexture laser XA
thanking you again
Brad , in case I heave a laser reading and want to convert it into dial gauges reading , I totally agree with all your steps except RIM reading on 3 o’clock
laser alignment is giving the difference between 9 o’clock and 3 o’clock but not the finite reading , right?
The laser will show you the true offset in the horizontal or vertical planes. It is the equivalent of zeroing the dial at 12 and reading the TIR at 6 (divide by 2 to get offset) and then also zeroing at 9 and reading the TIR at 3 (divide by 2 to get the offset). The dials app will show you the dial values (Finite reading) that you would see by zeroing at only 12. Hope this helps.
If the reading in axial aligment 3’o clock is -0.014″ at 6’0 clock is +0.12″ and 9’0clock is + 0.012″ then what will be the position of motor…