stopper bolts / external hexagon socket, internal hexagon socket / regular thread / mating surface at the head / steel, stainless steel / yinc Plated / A70, A90 (UST5-25)

Dimensional Drawing

M (Coarse)	Thread pitch	D	B	(C)	H	h	t	t1	m	(L)	B1	SR
3	0.5	3.5	5.5	6.4	2	0.7	1.5	2	1.8	—	—	3.5
4	0.7	5	7	8.1	2.8	1.5		2.2	2.4	2.2	2	5
5	0.8	6	8	9.2	3.5			2.3	3.2	2.8	2.5	6
6	1.0	8	10	11.5	4	2	2	2.6	3.6	3	3	8
8	1.25	10	13	15	5.5			2.8	5	4	4	10
10	1.5	13	17	19.6	7			3.2	6	5	5	13
12	1.75	15	19	21.9	8			3.5	7	—	—	15

Product Specifications

* 1 The operating temperature is a reference value.
The operating temperature of polyacetal/silicon is affected by the adhesive.
* 2 Bright chromate for LUST is being switched to trivalent chromate.
[!] Only the urethane stopper part at the tip is not sold. (Standard products are not available)

Part Number Display Method

Specification Table

Selection Supporting Information

Cautions/prohibitions

Tightening shaft force and fatigue limit when fastening with bolts

• Calculation of the appropriate tightening axial force when tightening bolts should be within the elastic range of up to 70% of the specified capacity for the torque method.
• The fatigue strength of the bolt due to repeated loading should not be over the allowable value.
• The objects tightened should not be caved in on the bolt and nut seating surfaces.
• The objects tightened should not be damaged due to tightening.

The torque method, torque gradient method, angle of rotation method, and elongation measurement method are available as bolt tightening methods, but the torque method is widely used because it is simple and easy to use.

Technical information

Bolt strength

1) When bolt is subjected to tensile load

Pt = σt × As:: (1)
   = πd² σt/4: (2)

Pt: Axial direction tensile load [N]
σb: Yield stress of bolts [N/mm²]
σt: Allowable stress of bolts [N/mm²]
      (σt = σb/safety factor α)
As: Effective sectional area of ​​bolts [mm²]
      As = πd²/4
d: Effective diameter of bolts (root diameter)[m]

(Example) Find the appropriate size for a single hex socket head cap screw to repeatedly (pulsating) receive a tensile load of P = 1,960 N {200 kgf}. (The hex socket head cap screw is made of EN 1.7220 Equiv., 38 to 43HRC, and has a strength class of 12.9.)

(1) From equation
As = Pt/σt = 1,960/219.6 = 8.9 [mm²]
∴It is recommended to find an effective sectional area larger than this from the "Bolt Fatigue Strength" table below and select M5 of 14.2 [mm²].
   In consideration of fatigue strength, select M6 with an allowable load of 2,087 N {213 kgf} from strength class 12.9 in the table.

2) When receiving tensile impact loads, such as stripper bolts, select based on fatigue strength. (Similarly, the stripper bolt that receives a load of 1,960 N {200 kgf} is made of EN 1.7220 Equiv., 33 to 38 HRC, and has a strength class of 10.9.)

According to the table "Fatigue Strength of Bolts" below, when the allowable load for strength class 10.9 is 1,960 N {200 kgf} or more, the M8 is 3,116 [N] {318 [kgf]}. Therefore, MSB10 with a shaft dia. of 10 mm with an M8 threaded section is selected. When the bolt is subjected to shear load, use a dowel pin in combination.

■ Unwin safety factor α based on tensile strength

Material	Static load	Repeated load		Impact load
		Pulsating	Alternating
Steel	3	5	8	12
Cast iron	4	6	10	15
Copper, soft metals	5	5	9	15

Allowable stress = standard strength / safety factor α
Standard strength: Yield stress for ductile materials (fracture stress for brittle materials)

The yield stress of strength class 12.9 is σb = 1,098 [N/mm²] {112 [kgf/mm²] }
Allowable stress σt = σb/safety factor (safety factor 5 from the above table "Unwin Safety Factor α Based on Tensile Strength")
                =1098/5
                = 219.6 [N/mm²] {22.4 [kgf/mm²] }

■Bolt fatigue strength (for screws >> fatigue strength of 2 million cycles)

Nominal of thread	Effective sectional area As mm2	Strength class
		12.9		10.9
		Fatigue strength *	12.9	10.9	10.9
		N/mm2 {kgf/mm2}	N {kgf}	N/mm2 {kgf/mm2}	N {kgf}
M4	8.78	128 {13.1}	1117 {114}	89 {9.1}	774 {79}
M5	14.2	111 {11.3}	1568 {160}	76 {7.8}	1088 {111}
M6	20.1	104 {10.6}	2087 {213}	73 {7.4}	1460 {149}
M8	36.6	87 {8.9}	3195 {326}	85 {8.7}	3116 {318}
M10	58	73 {7.4}	4204 {429}	72 {7.3}	4145 {423}
M12	84.3	66 {6.7}	5537 {565}	64 {6.5}	5370 {548}
M14	115	60 {6.1}	6880 {702}	59 {6}	6762 {690}
M16	157	57 {5.8}	8928 {911}	56 {5.7}	8771 {895}
M20	245	51 {5.2}	12485 {1274}	50 {5.1}	12250 {1250}
M24	353	46 {4.7}	16258 {1659}	46 {4.7}	16258 {1659}

Fatigue strength* is extracted from "Estimated Fatigue Limits for Metric Threads for Machine Screws, Bolts, and Nuts" (Yamamoto) and revised.