The Taylor Hobson UKAS laboratory is the only UK laboratory accredited for the calibration of reference standards for Roundness and Surface Finish. Other laboratories have accreditation to measure these quantities, but their traceability is generally derived from a standard that has been calibrated by the Taylor Hobson Laboratory. Consequently, their quoted uncertainties of measurement are higher.

The Taylor Hobson UKAS laboratory was successfully audited against the new international standard ISO 17025 in February 2002.

Category 0 Accreditation
The permanent laboratory is based at the company headquarters in Leicester, and operates under Category 0 UKAS Accreditation. The laboratory is accredited for calibration of such items as Roundness and Surface standards, Autocollimators and Clinometers, Angle and Length standards.

Category 1 Accreditation
The laboratory also has Category 1 Accreditation for which on-site calibration and measurement facilities are available for the Taylor Hobson product range and also verification of the geometric accuracies for other machine tools and measurement systems. The uncertainties quoted for Category 1 calibrations are dependent upon the actual environment, which would be monitored prior to and for the duration of the on-site calibration.

Category 0 Accreditation

As well as calibrating the reference standards that are to be sent to customers with a new instrument, we also offer calibration of used items. This way, you can actually improve measuring capability by quantifying the errors in reference standards. These errors can then be taken into account and reduce your uncertainty of measurement.

UKAS (NAMAS) Accredited Capability

• Roundness
• Straightness
• Surface Texture
• Diameter and Length
• Polygons and Prisms
• Autocollimators
• Clinometers and Levels
• Telescopes
  

Roundess

The glass hemisphere is a high precision standard used to both calibrate and evaluate the performance of roundness measuring instruments.

By using exclusive measuring techniques, the UKAS (NAMAS) laboratory calibrates the hemisphere to a resolution of 1 nanometre, with an uncertainty of measurement of 5 nanometres.

The resulting certificate includes a polar plot of the profile of the measured plane, which allows the user to accurately ascertain any departures from roundness by comparing the calibrated plot against that obtained on their Talyrond system.



Straightness

Assessment of the accuracy of a straightness and cylindricity measuring instrument can be verified by means of a precision cylinder, which will have been calibrated using a mechanical reversal technique such that the pure error in the straightness of the cylinder is plotted . The result obtained on the users system can then be compared the calibrated profile on the UKAS (NAMAS) certificate.

For more details, contact Pat Kilbane on +44 (0) 116 246 3104 or e-mail calibration@taylor-hobson.com

Surface Texture

The UKAS (NAMAS) laboratory is able to measure all of the parameters associated with surface texture, including German and French derivatives.

Roughness standards are calibrated to an uncertainty of Ra which is the lowest currently available from any laboratory accredited by UKAS.

A tungsten carbide sphere is used to calibrate the Form Talysurf Series range of instruments. It's radius, roundness/sphericity and surface texture are each calibrated to provide a high precision multi-purpose standard.

The ball may be used to calibrate the instrument, or as a "confidence gauge", to ensure its accuracy is maintained.



Diameter and Length

The laboratory is currently accredited for the calibration of spheres, plugs, rings, and length bars. Temperature corrected measuring techniques are used in conjunction with sophisticated control software to achieve uncertainties down to ± 0.5mm.



Polygons and Prisms

The basic methods employed for angle measurement are either the accurate division of a circle, by using a high precision index table, or the generation of a known angle by means of a precision sine bar (angle generator) or indexing head (rotary table) .

The precision index table is used in conjunction with an autocollimator for the calibration of a polygon. Any errors found in the polygon are tabulated on the UKAS (NAMAS) certificate. By taking these errors into account during its use, a higher accuracy of measurement can be achieved.

Autocollimators

A small angle generator jointly designed by Taylor Hobson and NPL is used in conjunction with traceably calibrated gauge blocks for the calibration of an autocollimator. Both progressive and periodic errors are measured and certified. Knowledge of these errors enables more precise use of the instrument by the operator.



Clinometers and Levels

Block levels, clinometers and electronic levels are calibrated by use of sophisticated sine lever techniques. For example, a Talyvel 4 electronic level is calibrated using a Taylor Hobson small angle generator. The user benefits from the ability to compensate for known errors when using the instrument.

Telescopes

The line of sight and displacement errors of a Micro Alignment Telescope are assessed by viewing into fixed focus and variable focus collimators . Deviations are recorded on the UKAS (NAMAS) certificate, providing the means for more accurate measurement. Micrometer and focussing accuracies are also verified using traceably calibrated scales and artifacts.

Category 1 Accreditation

In addition to its range of accredited calibrations made within the permanent laboratory, Taylor Hobson also has category 1 Accreditation, which allows its approved operators to undertake calibration and/or verification of larger items or instruments on the customer's premises. The uncertainties for these types of calibrations are environment dependent, and therefore the environment is monitored for the duration of the calibration and also the equipment stabilisation period.

Accreditation covers calibration of such items as:

• Taylor Hobson Instruments
• Roundness Measuring Instruments
• Length Measuring Instruments