Description of parameters for extension springs with english hooks
Physical parameters
d (wire diameter): This parameter describes the diameter of wire used as material for spring.
De (external diameter): External diameter of a spring concerns both hooks and coils. Tolerance for this parameter is (+-)2%(indicative).
H (Hole): This is minimum diameter of hole in which spring can work. Tolerance for this parameter is (+-)2%(indicative).
Ln (Maximum length):
Maximum acceptable extension length for a spring. It is also the
maximum extension for static applications. Tolerance for this parameter
is (+-)15%(indicative).
Fn (Maximal force):
Maximal acceptable force which can operate on a spring. It is also the
maximum force for static applications. Tolerance for this parameter is
(+-)15%(indicative).
L0 (free length): Free length is measured in spring's free state. Tolerance for this parameter is (+-)2%(indicative).
Nr of coils: This is a total number of coils in a spring - in the picture above it is equal to six.
R (Spring rate):
This parameter determines spring's resistance, while it is working. It
is measured in 1 DaN/mm = 10 N/mm. Tolerance for this parameter is
(+-)15%(indicative).
L1 & F1 (length under charge F): The charge F1 at length L1 can be calculated using the equation : F1 = Fn - R(Ln-L1). Equation derived from the previous for calculating L1 = Ln - (Fn-F1)/R.
Hooks: Extension springs with English hooks have both hooks closed forming a ring. Both hooks lie in the same plane.
Tolerances
maximal force: Tolerance for the maximal force is (+-)15%(indicative).
maximal length: Tolerance for the maximal length is (+-)15%(indicative).
Spring rate: Tolerance for the spring rate is (+-)15%(indicative).
Description of parameters for extension springs with german hooks
Physical parameters
d (wire diameter): This parameter describes the diameter of wire used as material for spring.
De (external diameter): External diameter of a spring concerns both hooks and coils. Tolerance for this parameter is (+-)2%(indicative).
H (Hole): This is minimum diameter of hole in which spring can work. Tolerance for this parameter is (+-)2%(indicative).
Ln (Maximum length):
Maximum acceptable extension length for a spring. It is also the
maximum extension for static applications. Tolerance for this parameter
is (+-)15%(indicative).
Fn (Maximal force):
Maximal acceptable force which can operate on a spring. It is also the
maximum force for static applications. Tolerance for this parameter is
(+-)15%(indicative).
L0 (free length): Free length is measured in spring's free state. Tolerance for this parameter is (+-)2%(indicative).
Nr of coils: This is a total number of coils in a spring - in the picture above it is equal to six.
R (Spring rate):
This parameter determines spring's resistance, while it is working. It
is measured in 1 DaN/mm = 10 N/mm. Tolerance for this parameter is
(+-)15%(indicative).
L1 & F1 (length under charge F): The charge F1 at length L1 can be calculated using the equation : F1 = Fn - R(Ln-L1). Equation derived from the previous for calculating L1 = Ln - (Fn-F1)/R.
Hooks:
Extension springs with german hooks are produced in two versions: with
hook positions of 0 degrees and 90 degrees as shown in the picture
above.
Tolerances
maximal force: Tolerance for the maximal force is (+-)15%(indicative).
maximal length: Tolerance for the maximal length is (+-)15%(indicative).
Spring rate: Tolerance for the spring rate is (+-)15%(indicative).
Wire Types: :
music wire: a high carbon steel for high stress applications
harddrawn MB: a carbon steel for low stresses and low cost
oil tempered wire: a carbon steel for wire forms and torsion springs
stainless steel: types 302 and 316 for high stresses in larger wire sizes
chrome vanadium: an alloy wire for high stresses in larger wire sizes
phosphor bronze: for electrical applications
brass: for applications requiring water resistance
Technical Details 
