Trapezoidal Screw Threads Design and Dimensions

Trapezoidal screw threads are widely used in power transmission applications where high load capacity and efficiency are required. Their geometry provides improved strength and reduced wear compared to standard thread forms.

Trapezoidal screw threads are power transmission threads with a trapezoidal profile designed for high strength, load capacity and efficient motion conversion in mechanical systems.

Relevant Standards

BS 5346:1976 Specification for ISO metric trapezoidal screw threads
ISO 2901:1977 ISO metric trapezoidal screw threads -- Basic profile and maximum material profiles
ISO 2902:1977 ISO metric trapezoidal screw threads -- General plan
ISO 2903:1977 ISO metric trapezoidal screw threads -- Tolerances
ISO 2904:1977 ISO metric trapezoidal screw threads -- Basic dimensions
Din 103-4 ISO Metric Trapezoidal Screw Thread; Nominal Dimensions

Trapezoidal Thread form and geometry to ISO 2904

........Table of Threads to DIN 103-4

Thread Proportions and Design Equations

H1 = 0,5p	H4 = H1 + ac	h3 = H1 + ac
D4 = d + 2ac	Z = H1 /2	D1 = d - 2H1 = d - p
d3 = D - 2h3	d2 = D2= d - 2Z = d - 0,5p	R1max= 0,5 ac  R2max= ac

a_c = ( D₄ - d ) /2

ISO 2904 Trapezoidal Thread Dimensions

All dimensions in milli metres

d	P	d2 =D2	D4	d3	D1		d	P	d2 =D2	D4	d3	D1
mm	mm	mm	mm	mm	mm		mm	mm	mm	mm	mm	mm
8	1,5	7,250	8,300	6,200	6,500		42	3	40,500	42,500	38,500	39,000
9	1,5	8,250	9,300	7,200	7,500		42	7	38,500	43,000	34,000	35,000
9	2	8,000	9,500	9.250	7,000		42	10	37,000	43,000	41,000	32,000
10	1,5	9,250	11,000	2,000	3,000		44	3	42,500	44,500	40,500	41,000
10	2	9,000	10,500	7,500	8,000		44	7	40,500	45,000	36,000	37,000
11	2	10,000	11,500	8,500	9,000		44	12	38,000	45,000	31,000	32,000
11	3	9,500	11,500	7,500	8,000		46	3	44,500	46,500	42,500	43,000
12	2	11,000	12,500	9,500	10,000		46	8	42,000	47,000	37,000	38,000
12	3	10,500	12,500	8,500	9,000		46	12	40,000	47,000	33,000	34,000
14	2	13,000	14,500	11,500	12,000		48	3	46,500	48,500	44,500	45,000
14	3	12,500	14,500	10,500	11,000		48	8	44,000	49,000	39,000	40,000
16	2	15,000	16,500	13,500	14,000		48	12	42,000	49,000	35,000	36,000
16	3	14,500	16,500	12,500	13,000		50	3	48,500	50,500	46,500	47,000
18	2	17,000	18,500	15,500	16,000		50	8	46,000	51,000	41,000	42,000
18	4	16,000	18,500	13,500	14,000		50	12	44,000	51,000	37,000	38,000
20	2	19,000	20,500	17,500	18,000		52	3	50,500	52,500	48,500	49,000
20	4	18,000	20,500	15,500	16,000		52	8	48,000	53,000	43,000	44,000
22	3	20,500	22,500	18,500	19,000		52	12	46,000	53,000	39,000	40,000
22	5	19,500	22,500	16,500	17,000		55	3	53,500	55,500	51,500	52,000
22	8	18,000	23,000	13,000	14,000		55	9	50,500	56,000	45,000	46,000
24	3	22,500	24,500	20,500	21,000		55	14	48,000	57,000	39,000	41,000
24	5	21,500	24,500	18,500	19,000		60	3	58,500	60,500	56,500	57,000
24	8	20,000	25,000	15,000	16,000		60	9	55,500	61,000	50,000	51,000
26	3	24,500	26,500	22,500	23,000		60	14	53,000	62,000	44,000	46,000
26	5	23,500	26,500	20,500	21,000		65	4	63,000	65,500	60,500	61,000
26	8	22,000	27,000	17,000	18,000		65	10	60,000	66,000	54,000	55,000
28	3	26,500	28,500	24,500	25,000		65	16	57,000	67,000	47,000	49,000
28	5	25,500	28,500	22,500	23,000		70	4	68,000	70,500	65,500	66,000
28	8	24,000	29,000	19,000	20,000		70	10	65,000	71,000	59,000	60,000
30	3	28,500	30,500	26,500	27,000		70	16	62,000	72,000	52,000	54,000
30	6	27,000	30,500	23,000	24,000		75	4	73,000	75,500	70,500	71,000
30	10	25,000	31,000	19,000	20,000		75	10	70,000	76,000	64,000	65,000
32	3	30,500	32,500	28,500	29,000		75	16	67,000	77,000	57,000	59,000
32	6	29,000	32,500	25,000	26,000		80	4	78,000	80,500	75,500	76,000
32	10	27,000	33,000	21,000	22,000		80	10	75,000	81,000	69,000	70,000
34	3	32,500	34,500	30,500	31,000		80	16	72,000	82,000	62,000	64,000
34	6	31,000	34,500	27,000	28,000		85	4	83,000	85,500	80,500	81,000
34	10	29,000	35,000	23,000	24,000		85	12	79,000	86,000	72,000	73,000
36	3	34,500	36,500	32,500	33,000		85	18	76,000	87,000	65,000	67,000
36	6	33,000	36,500	29,000	30,000		95	4	93,000	95,500	90,500	91,000
36	10	31,000	37,000	25,000	26,000		95	12	89,000	96,000	82,000	83,000
38	3	36,500	38,500	34,500	35,000		95	18	86,000	97,000	75,000	77,000
38	7	34,500	39,000	30,000	31,000		100	4	98,000	100,500	95,500	96,000
38	10	33,000	39,000	27,000	28,000		100	12	94,000	101,000	87,000	88,000
40	3	38,500	40,500	36,500	37,000		100	20	90,000	102,000	78,000	80,000
40	7	36,500	41,000	32,000	33,000
40	10	35,000	41,000	29,000	30,000

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DIN 103 Trapezoidal Thread Standards

Table of trapezoidal thread dimensions to DIN 103-4

Ds	P	E	he	a	b	Ks	hs	Dn	Kn	hn
mm
10	3	8,5	1,25	0,25	0,5	6,5	1,75	10,5	7,5	1,5
12	3	10,5	1,25	0,25	0,5	8,5	1,75	12,5	9,5	1,5
14	4	12	1,75	0,25	0,5	9,5	2,25	14,5	10,5	2
16	4	14	1,75	0,25	0,5	11,5	2,25	16,5	12,5	2
18	4	16	1,75	0,25	0,5	13,5	2,25	18,5	14,5	2
20	4	18	1,75	0,25	0,5	15,5	2,25	20,5	16,5	2
22	5	19,5	2	0,25	0,75	16,5	2,25	22,5	18	2
24	5	21,5	2	0,25	0,75	18,5	2,25	24,5	20	2,25
26	5	23,5	2	0,25	0,75	20,5	2,25	26,5	22	2,25
28	5	25,5	2	0,25	0,75	22,5	2,25	28,5	24	2,25
30	6	27	2,5	0,25	0,75	23,5	3,25	30,5	25	2,75
32	6	29	2,5	0,25	0,75	25,5	3,25	32,5	27	2,75
36	6	33	2,5	0,25	0,75	29,5	3,25	36,5	31	2,75
40	7	36,5	3	0,25	0,75	32,5	3,75	40,5	34	3,25
44	7	40,5	3	0,25	0,75	36,5	3,75	44,5	38	3,25
48	8	44	3,5	0,25	0,75	39,5	4,25	48,5	41	3,75
50	8	46	3,5	0,25	0,75	41,5	4,25	50,5	43	3,75
52	8	48	3,5	0,25	0,75	43,5	4,25	52,5	45	3,75
55	9	50,5	4	0,25	0,75	45,5	4,75	55,5	47	4,25
60	9	55,5	4	0,25	0,75	50,5	4,75	60,5	52	4,25
65	10	60	4,5	0,25	0,75	54,5	5,25	65,5	56	4,75
70	10	65	4,5	0,25	0,75	59,5	5,25	70,5	61	4,75
75	10	70	4,5	0,25	0,75	64,5	5,25	75,5	66	4,75
80	10	75	4,5	0,25	0,75	69,5	5,25	80,5	71	4,75
85	12	79	5,5	0,25	0,75	72,5	6,25	85,5	74	5,75
90	12	84	5,5	0,25	0,75	77,5	6,25	90,5	79	5,75
95	12	89	5,5	0,25	0,75	82,5	6,25	95,5	84	5,75
100	12	94	5,5	0,25	0,75	87,5	6,25	100,5	89	5,75

Applications of Trapezoidal Screw Threads

• Lead screws in machine tools and CNC equipment
• Linear actuators and positioning systems
• Jacks, presses and lifting mechanisms
• Valve actuators and control systems
• Power transmission in heavy machinery

Advantages of Trapezoidal Threads

• High load carrying capacity
• Good efficiency for power transmission
• Stronger than square threads in practical use
• Improved wear resistance and durability
• Easier to manufacture than square threads

Limitations of Trapezoidal Threads

• Lower efficiency than square threads due to flank angle
• Higher friction compared to ball screws
• Wear can occur under continuous high load
• Requires lubrication for optimal performance

Frequently Asked Questions

What are trapezoidal screw threads used for?

They are used for power transmission applications such as lead screws, jacks and linear motion systems.

Why are trapezoidal threads preferred over square threads?

They are easier to manufacture and provide better strength while maintaining good efficiency.

What standards apply to trapezoidal threads?

Common standards include ISO 2901–2904 and DIN 103 for dimensions and tolerances.

Are trapezoidal threads efficient?

They offer good efficiency but are less efficient than ball screws or square threads.

Do trapezoidal threads require lubrication?

Yes, lubrication is recommended to reduce friction and wear during operation.

See Also

• Edge Distances
• Bright Hexagon Screws/Nuts/Washers
• Cap Screws
• Strength,torques and Loads
• Tensile/Yield Strength
• Bolt Head Clearances
• Screw Stress Areas
• Bolt Loading ( Preloading etc )
• Bolted Joints (Shear Loads etc)
• Screw Thread Locking systems
• Studs/ Weldstuds
• Concrete /wood
• Thread dimensions for ISO "medium" class threads 1,6mm to 300mm
• Equations & Tables for Screw Thread Tolerance calculations

Useful Links

1. roton..Information on Trapezoidal Lead screws
2. getotec..Manufacturers technical brochure