Westfield Fasteners Product Specification:

DIN 939 - Engineering Studs with Thread Engagement 1.25 x Thread Diameter

This product guide contains the specification for Double Ended Engineers Studs with a length of engagement equal to 1.25 x thread diameter. They are a stock item available from Westfield Fasteners.

Product Description

Studs are short sections of metal rod threaded at both ends, with a plain shank inbetween. The thread proportion at the 'stud end' varies between standards, but this type, DIN 939, specifies this length at 1.25 x the thread diameter. The stud end is designed to be screwed into a tapped hole, whilst the 'nut end' of the stud is used for securing the mating part with a nut. The thread on the stud end of the part may include a tighter thread tolerance than the thread of the nut end.

A stud as part of an assembly has a couple of advantages over bolts, being helpful in initially locating the components and from there making it easier to apply an accurate amount of torque. Engineering studs are also known as engineers studs and double ended studs to help differentiate them from the fully threaded type.

Scope of the DIN Standard

DIN 939 defines these stud's form, with figure 1 and table 1 below of this specification showing the key dimensions and tolerances for sizes M3 to M52. Non preferred threads are listed in brackets in table 1. Non preferred thread sizes are not generally recommended for new applications.

The nut end of the stud features the usual 6g medium tolerance fit for external metric threaded fasteners. The thread tolerance for the stud end as defined in the standard is either Sk6 or Sn4. Sk6 is a transition fit defined in DIN 13 part 51, and is intended to be tighter than the standard 6g thread fit. An Sn4 fit is effectively a medium tolerance thread fit similar to 6g.

The finished ends of these studs conform to DIN 78 for K type (chamfered) thread ends.

The DIN standard includes metric fine pitch threads, but if these become available they would be covered in a seperate specification.

technical drawing of a stud with a length of engagement equal to about 1.25 x diameter

d		M4	M5	M6	(M7)	M8	M10	M12	(M14)	M16	(M18)
b₁		5	6.5	7.5	9	10	12	15	18	20	22
b₂	1)	14	16	18	20	22	26	30	34	38	42
	2)	20	22	24	26	28	32	36	40	44	48
	3)	-	-	-	-	-	45	49	53	57	61
x₁		1.75	2.0	2.5	2.5	3.2	3.8	4.3	5.0	5.0	6.3
x₂		0.9	1.0	1.25	1.25	1.6	1.9	2.2	2.5	2.5	3.2

d		M20	(M22)	M24	(M27)	M30	(M33)	M36	(M39)	M42	(M45)	M48	(M52)
b₁		25	28	30	35	38	42	45	50	52	58	60	65
b₂	1)	46	50	54	60	66	72	78	84	90	96	102	110
	2)	52	56	60	66	72	78	84	90	96	102	108	116
	3)	65	69	73	79	85	91	97	103	109	115	121	129
x₁		6.3	6.3	7.5	7.5	9.0	9.0	10.0	10.0	11.0	11.0	12.5	12.5
x₂		3.2	3.2	3.8	3.8	4.5	4.5	5.0	5.0	5.5	5.5	6.3	6.3

DIN 939 - Engineering Studs with Thread Engagement 1.25 x Thread Diameter

Figure 1: Engineers Stud to DIN 939

Table 1: Dimensions & Tolerances according to DIN 939 (mm)

Table 1 Continued: Dimensions & Tolerances according to DIN 939 (mm)

Notes, Thread Length b2