Laser shaft alignment vs dial gauge: when it is worth paying for and what the job must deliver
Headcore
In short
Laser shaft alignment clamps laser measuring units to the motor and driven shafts, measures offset and angularity at the coupling and calculates the shims and moves that line the centrelines up. A dial gauge can reach the same tolerance but adds bracket sag, rounding and hand calculation. Pay for alignment at every installation and repair, and require a signed report.
What is laser shaft alignment?
Laser shaft alignment measures and corrects the misalignment between a driving machine, such as an electric motor, and the machine it drives, such as a pump, so that the shaft centrelines are co-linear when the machine runs under load at its normal operating temperature. That is how the instructions for one laser alignment tool define proper alignment.[2]
In the same tool, each of the two measuring units carries a laser diode and a detector. As the shafts are turned, parallel or angular misalignment moves the laser lines on the detectors, and the tool calculates the vertical correction (shims) and the horizontal correction (moving the machine).[2]
The result is four values at the coupling: offset and angularity, each in the vertical and the horizontal plane. A maker's 2002 shaft alignment handbook recommends stating an alignment this way rather than as raw dial readings or foot positions.[1]
Laser alignment vs dial gauge: what is the difference?
A dial gauge (dial indicator) and a laser differ in the sources of error, the arithmetic and the record the job leaves behind. Both can bring a machine within tolerance, and one motor maker's manual accepts either.[3][4][1]
| Dial gauge | Laser system | |
|---|---|---|
| How it measures | Gauges on brackets and bars read the coupling rim and face as the shafts turn, in rim-and-face, cross-dial or reverse-dial set-ups | Laser and detector units on the shafts (one tool reads at 9, 12 and 3 o'clock) |
| Main sources of error | Bracket sag, 1 mil (0.025 mm) resolution with up to 0.5 mil rounding per reading, sticking needles, play, tilted gauges and axial shaft play | No mechanical fixtures across the coupling, so no bracket sag |
| Corrections | Shim and move worked out by formula, separately for the front and back feet | Calculated by the tool, with live values while the machine is moved |
| Acceptance in that motor manual | Eccentricity of no more than 0.03 mm over a full turn of the shaft | Follow the laser instrument maker's instructions |
| Record | Readings written down by hand | Stored results and a report (one tool's report holds dimensions, results, soft foot, instrument data and space for date and signature) |
| Equipment cost | Lower | Higher, from entry-level to high-end systems |
When is shaft alignment worth paying for?
Shaft alignment is worth paying for whenever a motor and its driven machine are installed, reinstalled or disturbed, and whenever the machine shows the signs of misalignment. One motor maker's manual says the motor "must be correctly aligned and leveled with the driven machine", and that incorrect alignment "may result in bearing damage, generate excessive vibration and even shaft distortion/breakage".[3]
In South Africa, the SABS wrote laser alignment "on installation of new and repaired pumps" into the scope of its October 2025 request for proposals for pump and motor maintenance at all its sites, alongside annual vibration and temperature analysis of critical pumps and motors.[6]
Weigh the price against the parts misalignment damages: the 2002 alignment handbook puts mechanical seals at up to a third of a pump's cost, and notes that most pump makers and repairers recommend replacing the bearings whenever a damaged pump is repaired.[1]
In practice, these are the usual triggers:[3][6][1]
- a new installation, or a machine moved to a new base;[3][6]
- a motor back from a rewind or repair, or a pump back from the workshop;[6][3]
- repeated bearing, seal or coupling failures, coupling bolts working loose, rubber powder inside the coupling guard, or oil leaking at bearing seals;[1]
- a vibration report with high radial and axial readings, or abnormal temperatures on the casings;[1]
- changes to the foundation, baseplate or pipework, which can shift a machine from its aligned position.[1]
What alignment tolerance should you ask for?
Ask first for the machine maker's tolerance or your plant's own standard. Where neither exists, the 2002 alignment handbook suggests the values below for short flexible couplings: each value is the maximum deviation from the target, which may itself be offset for thermal growth. Angularity is a gap difference per 100 mm of coupling diameter, so double it for a 200 mm coupling. Acceptable is calculated from an allowable sliding speed in the coupling; excellent from where misalignment starts to show as vibration.[1][5]
| Speed (rpm) | Offset, acceptable | Offset, excellent | Angularity per 100 mm, acceptable | Angularity per 100 mm, excellent |
|---|---|---|---|---|
| 750 | 0.19 mm | 0.09 mm | 0.13 mm | 0.09 mm |
| 1,500 | 0.09 mm | 0.06 mm | 0.07 mm | 0.05 mm |
| 3,000 | 0.06 mm | 0.03 mm | 0.04 mm | 0.03 mm |
| 6,000 | 0.03 mm | 0.02 mm | 0.03 mm | 0.02 mm |
Sources:[1]
What is the procedure for laser shaft alignment?
A laser shaft alignment works from the base up: check the base and feet, correct soft foot, set the thermal targets, measure, correct, measure again and report.[1][2]
Thermal growth is why a hot machine is aligned off-centre when cold. In one tool maker's guide, a motor that rises 4 mils (about 0.1 mm) when hot is set 4 mils lower when cold. The worked example in the 2002 handbook is a pump handling liquid at 300 °F (about 149 °C), its shaft 26 inches (660 mm) above the base, which grows about 0.038 inch (0.97 mm): more than ten times the acceptable offset at 1,500 rpm.[5][1]
In practice, a complete job covers these steps:[1][2]
- inspect the base and bolts, clean and deburr the mounting faces, and check the coupling halves for run-out;[1]
- check soft foot on every foot and correct it before aligning: the 2002 handbook's tolerance table allows 0.06 mm of soft foot at any speed, with no more than three shims under a foot where possible;[1][2]
- take the machine maker's cold alignment targets for thermal growth before starting, and set the coupling gap to the coupling maker's figure;[1][3]
- record the as-found offset and angularity, vertical and horizontal;[1][2]
- shim and move the machine, then measure again until the coupling values are within the agreed tolerance;[2]
- check that pipework is supported but free to move with thermal expansion;[1]
- issue the report, and enter the maximum alignment deviation in the motor's installation report, as one motor manual recommends.[2][3]
Do South African regulations require shaft alignment?
The text of the Driven Machinery Regulations, 2015 does not mention shaft alignment or set a tolerance for it, although the regulations apply to the repair, maintenance, inspection and testing of driven machinery (regulation 2); what they do require is the coupling guard.[7]
Regulation 3(a) requires the user to cause "every shaft, pulley, wheel, gear, sprocket, coupling, collar, clutch, friction drum or similar object to be securely fenced or guarded", unless it is as safe by its position or construction, so a coupling guard removed for the alignment goes back on before the machine runs.[7]
When the motor is switched off or locked out for the work, regulation 7(5) of the Electrical Machinery Regulations, 2011, requires a notice at the switchgear or control gear "switched off or locked out to enable persons to work on electrical machinery or other machinery operated by electricity", warning against reclosing it; regulation 7(6) forbids anyone to act against that warning.[8]
What drives the cost of shaft alignment, and what should the quote itemise?
In practice, the cost differs with the work around the measurement, so an alignment quote is comparable only when it itemises each of these:[1][2]
- the number of couplings: a train with a gearbox is two alignments, the gearbox to the driven machine and the motor to the gearbox;[1]
- preparation: the 2002 alignment handbook recommends 2 to 4 mm of shims under the feet of both machines at installation, so a machine can later be lowered, and jack bolts or a puller for horizontal moves instead of a hammer;[1]
- soft foot correction, from shims to tapered shims or, at worst, machining the feet flat;[1]
- thermal growth targets, taken from the machine maker or calculated, and any hot check;[1]
- isolation, the switchgear notice and removing and refitting the coupling guard, and who does each;[8][7]
- the report and the instrument's calibration certificate (one laser tool maker supplies its tool's certificate with 2 years' validity).[2]
What to put in your request
- Each machine train: driver and driven machine (for example motor, gearbox, pump), power in kW, speed in rpm, and the coupling type, make and size, with spacer length if there is one.[1][5]
- Reason for the alignment: new installation, reinstallation after a rewind or workshop repair, or repeated bearing, seal or coupling failures, with the latest vibration report attached.[6][1]
- Tolerance: the machine maker's figure or the plant's own standard; failing both, a named published table and the column to use (acceptable or excellent).[1][5]
- Operating temperature of each machine and the machine maker's cold alignment targets, so thermal growth is set before measuring.[1][5]
- A soft foot check on every foot before aligning, with the readings in the report, and who supplies the precut shims.[1][2]
- As-found and as-left readings: vertical and horizontal offset and angularity at the coupling, against the stated tolerance.[1][2]
- A report with machine name, dimensions, results, soft foot readings, instrument serial number, technician's name, date and signature, plus the instrument's calibration certificate.[2][1]
- Who isolates and locks out the motor, posts the notice at the switchgear, removes and refits the coupling guard, and provides lifting for the motor.[8][7][1]
- Price per machine train, with preparation, soft foot correction and thermal targets on separate lines.[1]
Questions buyers ask
What are the four types of shaft misalignment?
Measured at the coupling, misalignment comes out as four values: offset and angularity, each in the vertical and the horizontal plane. Offset or parallel misalignment means the shafts are parallel but not in line; angular means they meet at an angle; a machine can have a combination of both. Soft foot is a separate fault, a foot not sitting flat, which distorts the readings and is corrected first.[4][1]
Doesn't a flexible coupling take up misalignment?
Only within limits, and at a cost. The 2002 alignment handbook notes that flexible couplings are typically designed to take 400 mils (about 10 mm) or more of radial offset, but the reaction forces they create load the shafts, bearings and seals. A tool maker's guide adds that coupling tolerances are often looser than machine tolerances, so align to the machine's tolerance. Rigid couplings have no tolerance for misalignment and are aligned as accurately as possible.[1][5]
How often should shaft alignment be checked?
Periodically, at an interval set in your maintenance plan: one motor maker's manual says the coupling alignment "must be checked periodically" without setting an interval. Recheck also after changes in foundation or baseplate supports or in piping forces, which the 2002 alignment handbook lists among the causes of a machine's position changing.[3][1]
Is a dial gauge alignment good enough?
It can be. Dial gauges give accurate readings, though they are more complicated to use, and one motor maker's manual allows at most 0.03 mm of eccentricity over a full turn of the shaft when aligning with dial gauges. Ask for the same as-found and as-left values against a stated tolerance from a dial gauge job as from a laser job.[3][4][1]
Sources
- PRUFTECHNIK LTD (distributed in the US by LUDECA), A Practical Guide to Shaft Alignment, edition 4, 2002.
- SKF, SKF TKSA 31 & TKSA 41: instructions for use, February 2025.
- WEG, Installation, operation and maintenance manual of electric motors (code 50033244, revision 31), February 2023.
- Engineering News (article supplied by SKF), Laser alignment solves the problem of shaft misalignment quickly and easily, 8 July 2016.
- Fluke, Shaft Alignment Tolerances: What They Are, Why They Matter, and How To Achieve Alignment Within Tolerance, April 2026.
- South African Bureau of Standards (SABS), on the National Treasury eTender portal, RFP 201845: appointment of a service provider for repairs, maintenance and replacement of pumps and motors for all SABS sites for 36 months, 16 October 2025.
- Department of Labour (Government Gazette 38905), Driven Machinery Regulations, 2015 (GN R. 540), 24 June 2015.
- Department of Labour (Government Gazette 34154), Electrical Machinery Regulations, 2011 (GN R.250), 25 March 2011.