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IS 7906-8 (1989): Helical compression springs, Part 8:Method of inspection of hot coiled compression springs madefrom circular section bars [TED 21: Spring]

IS 7906 ( Part 8 ) : 1989 ( lhilhled 1991)

Indian Standard

HELICAL COMPRESSION SPRINGS PART 8 METHOD OF INSPECTION OF HOTCOILED COMPRESSION

SPRINGS MADE FROM CIRCULAR SECTION BARS

UDC 621-272’2 : [ 669’14-422’11 ] : 620’1

@ BIS 1989

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

November 1989 Price Group 1

This Indian Standard ( Part S 1 ws adopted by the Bureau of lndian Standards on 10 February 19S9, after- the draft finalized by the Springs Sectional Committee had been approved by the Mcchanicnl Engineering Division Council.

This standard has been prepared to follow a uniform practice of inspection of hot coiled compres- sion springs made from~circular section bar.

This standard is one of a series of standards on helical coiled compression spring. Other standards are as follows:

IS 7906 ( Part 1 ) : 1976 Helical compression springs: Part 1 Design and calculatrons for springs made from circular section wire and bar

IS 7906 ( Part 2 > : 1975 Helical compression springs: Part 2 Specification for cold coiled springs made from circular section wire and bar

IS 7906 ( Part 3 ) : 1975 Helical compression springs: Part 3 Data sheet for specifications for springs made from circular section wire and bar

IS 7906 ( Part 4 > : 1987 Helical compression springs: Part 4 Guide for selection of standard cold coiled springs made from circular section wire and bar

IS 7906 ( Part 5 ) : 1989 Helical compression springs: Part 5 Specification for hot coiled springs made from circular section bars (first revision )

1s 7906 ( Part 6 ) : 1978 Helical compression springs: Part 6 Design and calculation for springs made from rectangular section bar steel

1s 7906 ( Part 7 ) : 1989 Helical compression springs: Part 7 Quality requirements for cylindrical coil compression springs, used mainly as vehicle suspension springs

IS 7906 ( Part 8 ) : 1989

Indian Standard

HELICAL COMPRESSION SPRINGS PART8 METHOD OF INSPECTCON OF HOT COILED COMPRESSJON

SPRINGS MADE FROM CIRCULAR SECTION BARS

1 SCOPE

1.1 This standard ( Part 8 ) recommends the methods to be used for dimensional inspection and testing of hot coiled helical compression springs conforming to IS 7906 ( Part 5 ) : 1989.

1.2 For carrying out certain tests this standard recommends the use of gauges. However, it is to be recommended that for very small quanti- ties the use of suitable gauges may not be eco- nomical. In that case an alternative method -may be agreed between the purchaser and the supplier.

2 REFERENCE

IS No Title

IS 7906 ( Part 5 ) : 1989 Helical compression springs: Part 5 Speci- fication for hot coiled springs made from circular section bars ( first revision )

3 DIMENSIONAL AND GEOMETRICAL TESTS

3.1 Nominal Dimensions

These are marked for reference only in the spring drawing/data sheet and are not to be checked.

3.2 All dimensional tests specified herein shall be carried out after the spring has passed through the complete manufacturing process as specified in IS 7906 ( Part 5 ) : 1989 and the spring drawing. All these tests shall be con- ducted with the spring in the free state, that is unloaded condition.

3.3 Bar Diameter

This cannot be measured accurate!y after the bar has been coiled into spring due to the slight distortion of the bar occurring in this process. An indication of the diameter may be obtained with the use of ball-ended micrometer or vernier caliper.

3.4 Outside Diameter

This cannot be measured directly as no two diametrically opposite points . occur at the bar surface. ‘GO’ ‘NO GO’ system of ring gauges has to he employed to determine whether the sprins will work within the diameter specified. Where the diameter of the spring body is

1

important the minimum gauge length should be 1’25 times the pitch and where the diameter of the end coil is important, the minimum gauge length should be 1’50 times the bar diameter. This method, however, cannot be used for springs having protruding tips.

NOTE - The tolerance specifikd in Table 1 of IS 7906 ( Part 5 ) : 1989 is applicable to only two- end coils. For the active coils these tolerances are not applicable and the spring drawing should specify the minimum diameter of the sleeve/ maximum diameter of them andrel on which the spring works. Hence it may be necessary to make two different gauges - one for the end coils and the second for the active coils. The ring' gauge for active coils will have a larger inside digmeter than the ring gauge for the end coils.

3.5 Inside Diameter

This cannot be measured as no two diametri- cally opposite points occur at the bar surfaee. ‘GO’ ‘NO -GO’ system of plug gauges has to be used to determine whether the spring will work over the diameter specified. Where the dia- meter of the spring body is important, the minimum gauge iength should be 1’25 times the pitch, and where the diameter of the end coil is important the minimum block gauge should be 1’50 times the bar diameter.

3.6 Mean Diameter

This cannot be measured but is a calculated value.

3.7 ‘Qtal Number of Coils

Total number of coils are measured from tip of tine end coil to the other.

3.8 Number of Active Coils

This cannot be measured but can be calculated as explained in 4.4 of IS 7906 ( Part 5 ) ; 1989.

3.9 Squareness

This is applicable to spring with ground ends ( see Fig. I ). Squareness shall be measured by standing the spring on a surface plate against a square and measuring the largest deviation from the top end coil and the square, using feeler gauges. While cva!uating the results, due allow- ances must-be ma.de tn the following:

a>

b)

Error which can arise due to different outside diameters at the two ends and intermediate active coils.

Frror due to width of the top dead coil being less than the bar diameter.

IS 7906 (Part 8 ) f 1989

J

FIG. 1

3.10 Parallelism

This is applicable only to spring with ground ends. This can be measured by one of the two following methods: -

a) The spring is placed on a surface plate and a second plate is lowered parallel to the surface plate on the spring until the first contact is made with any point of upper end coil. The maximum deviation between the upper end coil and the plate is measured with the use of feeler gauges over the ground ‘surface ( see Fig. 2 ).

b) Another method is to check the height of the spring at two diametrically opposite points and note the difference in the two heights. This checking at diametrically opposite points has to be done at a num- ber of places to determine where the maximum difference in height occufs.

A,

3.11 Bow

Bow shall be on a surface

Fro. 3

measuring with feeler gauges, the maximum deviation between any coil and the surface place.

3.12 Free Length

The method of checking free length ~described here is applicable for springs with groynd ends. Before carrying out this test the sprmg should be scragged once as explained in 8.1 of IS 7906 ( Part 5 ) : 1989. This test should pre- ferably be done when static load testing of the spring is bzing dKne so 3s to avoid duplication of testing.

The spring is placed on a surface plate with a straight edge across the top dead coil and the height is measured with 3 scale standing apprqxi- mutely in the centre of the spring and touchmg the straight edge.

4 LOAD TESTING

4.1 Before carrying out these tests the spring shall be scragged 3s explained under 8.1 Static load testing of IS 7906~( Part 5 ) : 1989.

4.2 Load at Length or Length at Load Measurement

Load/Length measurement shall be carrced out between parallel lateral constant plates and with reference to a calibrated load indicating device. The test is effected with the spring in the upright position in the direction of loading. Springs v.hich are liable to buckle shall be tested over or in a guide. The method of testing shall be agreed between the purchaser and the manufac- turer.

4.3 Spring Rate

This test shall bz carried out as explained in 8.2 of 1S 7906 ( Part 5 ) : 1989.

2

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This Indian Standard has been developed from Dot : No. EDC 75 ( 4906 )

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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