Pi Tape Ltd
Dean Court, Upper Dean,
Huntingdon, PE28 0NL, UK.
Tel: +44 (0)1234 708882
e-mail: sales@pitape.co.uk
http: www.pitape.co.uk
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Standard Tapes Resolution and accuracy specification for standard tapes. Use and maintenance details. How Pi Tape provide indentification and calibration compliance with BS EN ISO 9001.

For anyone who needs to measure diameters accurately, a precision vernier periphery tape is an essential piece of equipment. Designed to convert the circumferential measurement into accurate diameter readings with a resolution of 0.01mm/0.001".

Easy to use, the tape is wrapped around the outside of any cylindrical component and the vernier reading gives the average true diameter, with just one reading, to ± 0.03 mm /0.001" accuracy on all diameters up to 3600 mm /144".

The vernier periphery tape is graduated to provide a direct reading of the diameter by converting the circumferential measurement into the diameter value. The tapes, which are designed to measure directly the outside diameter of cylindrical components, are manufactured from 1095 clockspring steel with a coefficient of linear expansion of only 0.0000114/°C. This ensures consistent and accurate use over a range of temperatures. The ground steel surface is waxed and the graduations machined through the wax before being acid etched. Since the graduations and numerals are etched into the steel they can never wear off. Maintenance of tapes is minimal, but to avoid rusting tapes should be cleaned and lightly oiled after use using an oil moistened cloth. Tapes are supplied in a circular can and they should be put back into the can after cleaning and oiling for storage.

  • All tapes are individually serial numbered.
  • They are calibrated under 2.25 kg tension at 20° C
  • A Certificate of calibration is issued free with each tape.
  • Calibration in accordance with ANSI/NCSL Z540-1-1994;
    ISO/IEC 17025, ISO 10012-1, MIL-STD 45662A & 10CFR, part 21. All standards are certified traceable to National Institute of Standards & Technology (NIST)
  • Re-calibration for BS EN ISO 9001 requirements
  • Standard width is 12.7 mm (1/2") overall, which gives the width of both guage member and vernier = 6.35 mm (¼").
  • Standard tape thickness = 0.25 mm (0.010")
  • Standard metric sizes from 28 mm to 3,600 mm diameter, ex-stock.
  • Larger metric sizes 3,600 mm to 15,000 mm diameter to order.
  • Standard Imperial Sizes from 0.75" to 144" diameter ex-stock.
  • Larger Imperial sizes over 144" up to 600" diameter to order
 
  The minimum diameter that can be measured is 28mm - on a metric tape and 0.75" on an imperial tape. This is due to the longer length of the vernier section that is required to obtain the resolution of 0.01 mm on a metric tape compared to the shorter vernier length required to obtain the resolution.
   
 
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Blue Easy-Read Tapes Designed for use in poor ambient light conditions where reading the graduations on standard tapes becomes difficult. The easy-read version is manufactured on a 'blue' steel with the acid etched graduations and numerals being filled with a white pigment. The blue background with white graduations and numerals makes reading the tape much easier, hence an easy-read tape.
   
 
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White Easy-Read Tapes Recently introduced in reponse to requests from the plastic pipe industry is the new White Easy-Read Tape. This tape has a plasticised white coating with black lines and numerals printed on the background. The tape cannot be used in an environment where solvents are present which would soften or melt the plastic coating
   
 
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Stainless Steel Tapes Manufactured using 716 ground stainless steel strip. The manufacturing process is the same as for standard tapes. Stainless steel tapes are recommended for use in any corrosive atmosphere where rusting could be a problem They are not recommended for diameters above 108 inch / 2700 mm due to the camber which is inherent in long stainless steel strips.
 
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Internal Diameter Tapes Available in either the standard, easy-read or stainless steel versions. The tapes are manufactured and graduated allowing for two factors. Firstly that the thickness of the tape will be on the inside of the circumference, secondly that the tape will not be under tension. An Internal Diameter tape thus reads the true internal diameter directly. A Standard Outside Diameter Tape can be used to measure internal diameters by adding twice the tape thickness to the reading taken with an outside diameter tape, although the accuracy is slightly impaired. It is therefore recommended that Internal Diameter Tapes are used for measuring internal diameters accurately. When measuring large internal diameters, pieces of masking tape can be used to hold the tape in a proper parallel position.
   
 
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Narrow/Wider Width Tapes As an alternative to a main body width of 1/2 inch (12.70 mm) from which all standard tapes are manufactured, there are two narrower and two wider widths available. Remember the standard tape is reduced to 1/4 inch (6.53mm) at either end to ensure that the tape is parallel to the component for measurement. When taking a reading the vernier section 1/4 inch wide (6.35mm) and the gauge member 1/4 inch wide (6.35 mm) lie along side each other so the overall width becomes 1/2 inch (12.70 mm).

The alternative narrower widths available for both metric & imperial size tapes are:
3/8 inch (9.53 mm) main body width, with 3/16 inch (4.77 mm) vernier / gauge members and for imperial size tapes only:
1/4 inch (6.35 mm) main body width, with 1/8 inch (3.18 mm) vernier gauge members. Narrow width tapes are most useful when measuring the diameters of grooves, when the width of the groove will not accept a standard width tape. Also for measuring the diameters of small lands or steps where the overall width is limited.

The alternative wider widths available for both metric & imperial size tapes are:
3/4 inch (19.05 mm) main body width, with 3/8 inch (9.53 mm) vernier / gauge members or, 1 inch (25.40 mm) main body width, with 1/2 inch (12.70mm) vernier / gauge members.

Wider width tapes are used on rubber covered rollers, or other soft/thin walled parts, where the pressure imparted by a standard width tape would distort the component and lead to an error in the diameter being measured.
 
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Special Thickness Tapes Used as an alternative to the standard thickness of 0.010 inch (0.25 mm), tapes can be manufactured in either 0.007 inch (0.18 mm) or 0.005 inch (0.13 mm). Thinner tapes are more vulnerable to damage and so should only be specified when absolutely necessary. They are not available in the easy-read versions. Their main use is to reduce the pressure and distortion on soft / thin walled parts, where it is not -practical to use a wider width tape
   
 
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Go/NoGo Inspection Tapes Used in production or inspection areas, this tape differs from the standard tapes in that no actual measurement is obtained. There is no vernier scale only a 'Zero' line, and on the gauge member a set of tolerance lines. The tolerances lines are for the minimum and maximum diameters, and if required the nominal diameter, for a particular component. The tape is used to separate the parts into three categories, oversize, undersize and within limits. A tape can have just one set of tolerance lines or a number of sets dependent upon the type of component being inspected. The minimum diameter distance between any two tolerance lines is 0.004 inch (0.10 mm). It is not possible to etch lines closer together than this on a tape.
 
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Extended Range Tapes For practical engineering reasons tapes are manufactured to cover a nominal range of diameter measurement of 12 inches or 300 mm. Tapes having too large a capacity are very vulnerable to damage during use - remember, when measuring the smallest diameter there is some 39 inches /1 metre of extra tape, hanging loose, not being used. If damage occurs to this section the tape will probably have to be scrapped. The larger the range the more vulnerable the tape becomes to getting damaged. Since the major cost in any tape is not the steel but the cost of etching the graduations and numerals there is no significant cost saving in requesting an extended range tape. If 2 or 3 standard range tapes are purchased to cover a total range, they are not only less vulnerable to damage, but it is also cheaper to replace one of them rather than having to replace an extended range tape.
   
Intermediate Range Tapes Tapes can be manufactured to cover any range required to suit a particular component. They are not a stock item and are made to order. On the Standard Size diameters up to 144 inch /3600 mm, they are slightly more expensive due to the one of cost off the set-up. However on the Large Size diameters since all these sizes are made to order, there is no additional cost, and the price is pro-rata.
 
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