6.2 Manufacturing accuracy and limit deviation of cold rolled cylindrical spiral tension springs

Table 12-2-336

Project	Spring manufacturing accuracy and limit deviation
When specifying the length, the limit deviation △ P/N of load P (when the accuracy level of the effective circle is bigger than 3)	± [initial tension] ×α+ (Load at specified length – initial tension) × β]
	Accuracy Level		1	2	3
	α		0.10	0.15	0.20
	β		0.05	0.10	0.15
	Effective coils n		≥3~10		＞10
Limit deviation of spring stiffness P ‘△ P’/N	Accuracy Level	1	±0.05P’		±0.04P’
		2	±0.10P’		±0.08P’
		3	±0.15P’		±0.12P’
	Winding ratio C		≥4~8	＞8~15	＞15~22
Limit deviation of spring outer diameter D2 or inner diameter D1 Limit deviation /mm	Accuracy Level	1	±0.01D Min ±0.15	±0.015D Min ±0.2	±0.02D Min ±0.4
		2	±0.015D Min ±0.2	±0.02D Min ±0.3	±0.03D Min ±0.5
		3	±0.025D Min ±0.4	±0.03D Min ±0.5	±0.04D Min ±0.6
	Winding ratio C		≥4~8	＞8~15	＞15~22
Spring free height △H0 Limit deviation /mm（For springs without initial tension, the deviation shall be determined by both the supply and demand parties）	Accuracy Level	1	±0.01H0 Min ±0.2	±0.015H0 Min ±0.5	±0.02H0 Min ±0.6
		2	±0.02H0 Min ±0.5	±0.03H0 Min ±0.7	±0.08H0 Min ±0.8
		3	±0.03H0 Min ±0.6	±0.04H0 Min ±0.8	±0.06H0 Min ±1
Tolerance of the relative angle between the two shackles of the spring △ /（°）	Spring pitch diameter D/mm ≤10 ＞10~25 ＞25~55 ＞55	angle tolerance △ /（°） 40 30 20 15
The positional tolerance between the central plane of the hook ring and the spring axis is △ (suitable for half hook ring, circular ring, and pressure center circular hook ring, and the positional tolerance of other hook rings shall be agreed upon by both parties)	Spring pitch diameter D/mm ＞3~6 ＞6~10 ＞10~18 ＞18~30 ＞30~50 ＞50~120	angle tolerance △ /（°） 0.5 1 1.5 2 2.5 3
Spring hook and loop length and its limit deviation/mm	Hook and loop length h/mm ≤15 ＞15~30 ＞30~50 ＞50	Limit deviation/mm ±1 ±2 ±3 ±4