FEELER GAUGES - THICKNESS GAUGES & ACCURACY

 Feeler Gauges or Thickness Gauges

This instrument is mainly designed  for gauging (measuring) the width of the narrow gaps. Its range is mainly the standard specify the 0.03 mm  to 1 mm. Each leaf are marked with its thickness and also each leaf is detachable, if user is required.

Commonly seen blades sets are given below

Serial No.	No of Blades in a set	Thickness of blades in mm
1	10	0.05 to 0.20 in steps of 0.05
		0.30 to 0.08 in steps of 0.10
2	13	0.05 to 0.30 in steps of 0.05
		0.40 to 1.00 in steps of 0.10
3	13	0.03 to 0.10 in steps of 0.01, and 0.15,0.20, 0.30, 0.40 and 0.50
4	20	0.05 to 1.00 in steps of 0.05

Specification of Material of the blade

The material is suitable  to made the blade is stainless steel shall be hardened and tempered to a hardness of not less than 400 HV and not more than 600 HV

Master Equipment Used to to calibrate the Feeler gauge

• High Precision micrometer
• Universal length measuring machine

Environmental Condition to calibrate the the thickness gauges

As per the ISO 17025:2017 guide line the dimensional instrument should calibrate  in this  temperature and Humidity range.

 Temperature : 20± 1°C 

 Humidity  : 50± 10% RH

Maintenance

The protection from the corrosion  and protection from the climatic condition the blade should be coated with like petroleum jelly or other anticorrosive  substances.

ACCURACY OR TOLERANCE OR ACCEPTANCE CRITERIAL FEELER GAUGE

ACCURACY OR TOLERANCE

 

Nominal Thickness of Blade	Permissible Departure from the Nominal Thickness	Permissible Variation in Thickness of blade
0.03 up to and including 0.04	±0.004 mm	0.004
Above 0.04 up to and including 0.35	±0.005 mm	0.005
Above 0.35 up to and including 0.65	±0.008 mm	0.008
Above 0.65 up to and including 1.00	±0.010 mm	0.010

HOW TO FIND THE ACCURACY AND TOLERANCE OF FEELER GAUGE 

The table is an example

Nominal Thickness	Permissible Departure from the Nominal Thickness	Lower Limit	Upper Limit
0.03	±0.004 mm	0.026	0.034
0.05	±0.005 mm	0.045	0.055
0.5	±0.008 mm	0.492	0.508
0.09	±0.010 mm	0.84	0.86

Here the nominal value (thickness of the blade ) it is measured by the Master instruments like digital micrometer of universal length measuring. The master value is  in between the lower limit and upper limit the instrument is with in the tolerance.

Formula to find the Lower Limit & Upper limit of Permissible error or accuracy

Lower Limit = Nominal Thickness-Permissible departure from the Nominal Thickness

Upper Limit = Nominal Thickness + Permissible departure from the Nominal Thickness

 

The calibrated value is in the between these upper and lower limit the instrument is accepted other wise the instrument is out of accuracy. The  Customer  can decide wheatear the instrument  can be used or not.