Trapezoidal Lead Screw Size Chart: 110 Sizes from Ø4 to Ø24, Lead, Pitch, Starts, Root Ø and Nut Efficiency

The trapezoidal lead screw size chart below is our own range: 110 sizes from Ø4 to Ø24, each with lead, pitch, number of starts, hand, root diameter, the largest end you can have turned on it, and the efficiency with a plastic or a bronze nut. Every row is made to order from one piece, cut to your length with the ends and the nut you need; tap a row for a price. Sizes above Ø24, up to Ø300, are made to drawing. No drawing needed: a photo with a rule, the measurements in a message, the old part or its part number is enough; we draw it, you approve, we machine. Get a quote →

How to read the chart

EKINSUN LTD is a custom parts manufacturer that makes trapezoidal lead screws and the nuts that run on them to the buyer's drawing, from one piece. Lead is the distance the nut travels in one turn; pitch is the distance from one thread crest to the next; starts is how many separate threads run side by side, and lead equals pitch times starts on every row. Root diameter is the thread measured at the bottom of the groove, which is what the largest end diameter is derived from: a journal cannot be larger than the root. Efficiency is the share of the turning work that becomes pushing work, with a plastic nut and with a bronze nut; under 50 % the screw holds a load when the drive stops, above 50 % the load can drive the screw back. A dash marks a cell that is confirmed on the drawing for that size rather than printed here.

The chart, by nominal diameter

Ø4: 2 sizes, outside Ø 4.2, 4.71

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
4.71	1	1	1	RH	3.29	3	38 %	27 %
4.2	2	1	2	RH	3.2	3	56 %	43 %

Ø5: 4 sizes, outside Ø 4.71, 5.4, 5.71, 6

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
5.4	5	1.25	4	RH	3.6	3	70 %	58 %
5.71	10	2.5	4	RH	4.29	4	76 %	65 %
4.71	15	2.5	6	RH	3.29	3	76 %	64 %
6	20	1.25	16	RH	5	5	77 %	64 %

Ø6: 9 sizes, outside Ø 6, 7.4

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
6	1	1	1	RH	4.58	4	32 %	22 %
6	1.5	1.5	1	RH	4	4	42 %	31 %
6	2	2	1	RH	3.97	3	49 %	37 %
6	3	1.5	2	RH	4.1	4	58 %	46 %
6	5	2.5	2	RH	4.02	4	68 %	56 %
6	9	2.25	4	RH	4.02	4	76 %	64 %
6	10	2.5	4	RH	3.97	3	77 %	66 %
6	18	4.5	4	RH	4.02	4	77 %	64 %
7.4	25	1.25	20	RH	6.3	6	—	—

Ø8: 9 sizes, outside Ø 8, 8.2, 8.6

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
8	1	1	1	LH and RH	7	7	34 %	17 %
8	1.5	1.5	1	RH	6.2	6	42 %	24 %
8	2	2	1	RH	5.5	5	—	—
8	4	2	2	RH	5.5	5	—	—
8.2	10	2.5	4	RH	5.5	5	75 %	62 %
8	12	3	4	RH	5.6	5	77 %	64 %
8.2	15	2.5	6	RH	5.5	5	77 %	66 %
8	24	4	6	RH	5.6	5	76 %	64 %
8.6	30	1.25	24	RH	7.5	7	77 %	64 %

Ø10: 17 sizes, outside Ø 8.9, 9.53, 10, 10.1

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
8.9	1	1	1	RH	—	5	21 %	14 %
10	1.4	1.4	1	RH	—	—	28 %	20 %
9.53	1.5	1.5	1	RH	—	7	29 %	20 %
10	2	2	1	RH	7.5	—	36 %	25 %
10	3	3	1	RH	—	—	47 %	35 %
10	3	1.5	2	RH	—	5	45 %	33 %
9.53	4	2	2	RH	—	7	55 %	42 %
10	5	2.5	2	RH	—	—	59 %	46 %
9.53	6	1.5	4	RH	—	6	61 %	48 %
10	10	2.5	4	RH	—	7	71 %	59 %
10	10	1.25	8	RH	—	7	70 %	58 %
10	12	3	4	RH	—	—	73 %	62 %
10	15	3	5	RH	7.1	7	75 %	64 %
10	20	2.5	8	RH	—	7	77 %	66 %
10	25	2.5	10	RH	—	—	77 %	65 %
9.53	35	1.25	28	RH	—	6	76 %	70 %
10.1	50	5	10	RH	—	—	71 %	55 %

Ø12: 16 sizes, outside Ø 11.9, 12, 12.2, 12.62, 12.7, 12.8

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
12	2	2	1	RH	9.58	8	31 %	22 %
12.7	2.5	2.5	1	RH	9.73	9	35 %	25 %
12	3	3	1	RH	8.5	8	41 %	30 %
12	4	2	2	RH	9.34	9	47 %	35 %
12	5	2.5	2	RH	8.9	8	53 %	41 %
12	6	3	2	RH	8.5	8	58 %	45 %
12	9	3	3	RH	8.16	8	66 %	54 %
12.62	10	2.5	4	RH	9.19	9	67 %	55 %
12.2	15	3	5	RH	9.2	9	73 %	62 %
12	15	2.5	6	RH	8.7	8	74 %	62 %
12.7	16	3.2	5	RH	9.5	9	73 %	62 %
12	18	3	6	RH	9	9	75 %	64 %
11.9	25	5	5	RH	8	8	77 %	66 %
12	25	2.5	10	RH	9.2	9	77 %	66 %
12	45	3	15	RH	9.6	9	76 %	62 %
12.8	45	1.25	36	RH	11.4	11	76 %	64 %

Ø14: 9 sizes, outside Ø 13.62, 13.9, 14, 14.3

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
14	2	2	1	RH	11.5	11	28 %	19 %
14	3	3	1	LH and RH	10.5	10	37 %	27 %
14	4	4	1	RH	9.5	9	45 %	33 %
14	6	3	2	RH	10.5	10	54 %	41 %
14	8	4	2	RH	9.7	9	61 %	48 %
13.62	10	2.5	4	RH	10.37	10	65 %	53 %
14	12	4	3	RH	9.7	9	68 %	56 %
14.3	18	3	6	RH	11.4	11	73 %	62 %
13.9	30	5	6	RH	10.1	10	77 %	66 %

Ø16: 11 sizes, outside Ø 15.9, 16, 16.5, 17

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
16	2	2	1	RH	13.5	13	25 %	17 %
16	3	3	1	LH and RH	13	13	34 %	24 %
16	4	4	1	RH	11.5	11	41 %	30 %
16	5	2.5	2	RH	12.2	12	46 %	34 %
16	8	4	2	RH	11.5	11	58 %	45 %
16	16	4	4	RH	11.5	11	71 %	59 %
16	16	2.29	7	RH	12.6	12	70 %	58 %
16.5	21	3	7	RH	13.6	13	73 %	62 %
16	25	5	5	RH	11.5	11	76 %	64 %
15.9	35	5	7	RH	12.1	12	77 %	66 %
17	90	5	18	RH	14.3	14	71 %	55 %

Ø18: 9 sizes, outside Ø 17.9, 18, 18.7, 18.8

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
18	2	2	1	RH	15.5	15	23 %	15 %
18	4	4	1	LH and RH	13.5	13	38 %	27 %
18	8	4	2	RH	13.5	13	54 %	42 %
18	16	4	4	RH	14.3	14	68 %	56 %
18	18	4.5	4	RH	14.4	14	70 %	58 %
18.7	24	3	8	RH	15.7	15	73 %	62 %
17.9	40	5	8	RH	14.1	14	77 %	66 %
18	60	6	10	RH	13.9	13	76 %	64 %
18.8	100	5	20	RH	16.2	16	71 %	55 %

Ø20: 8 sizes, outside Ø 20

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
20	2	2	1	RH	17.5	17	21 %	14 %
20	4	4	1	LH and RH	15.5	15	35 %	25 %
20	8	4	2	RH	15.5	15	52 %	39 %
20	12	3	4	RH	15.8	15	61 %	48 %
20	16	4	4	RH	15	15	67 %	55 %
20	18	6	3	RH	13.66	13	69 %	57 %
20	20	4	5	RH	15	15	70 %	59 %
20	45	5	9	RH	16.1	16	77 %	66 %

Ø22: 11 sizes, outside Ø 21.54, 22, 22.23

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
22	3	3	1	RH	18.5	18	27 %	18 %
22	4	4	1	RH	17.3	17	33 %	23 %
22	5	5	1	LH and RH	16.5	16	39 %	28 %
21.54	6	2	3	RH	19.63	19	41 %	30 %
22	8	4	2	RH	17.5	17	—	—
22	10	5	2	RH	16.5	16	55 %	43 %
22.23	10	2.5	4	RH	18.82	18	54 %	41 %
22.23	16	4	4	RH	18.82	18	64 %	51 %
22	20	4	5	RH	18.3	18	68 %	56 %
22.23	24	4	6	RH	18.82	18	71 %	59 %
22	50	5	10	RH	18.1	18	77 %	66 %

Ø24: 5 sizes, outside Ø 24, 24.3

Outside Ø (mm)	Lead (mm/turn)	Pitch (mm)	Starts	Hand	Root Ø (mm)	Largest end Ø (mm)	Efficiency, plastic nut	Efficiency, bronze nut
24	3	3	1	RH	20.5	20	25 %	17 %
24	5	5	1	RH	18.5	18	36 %	26 %
24	10	5	2	RH	18.5	18	—	—
24.3	40	5	8	RH	19.8	19	76 %	66 %
24	55	5	11	RH	20.1	20	—	—

Lead, pitch and starts: the three numbers that must match the nut

A nut runs on a screw only when all three agree. Ø10 × 10 exists twice in the chart, as a four-start screw with a 2.5 mm pitch and as an eight-start screw with a 1.25 mm pitch; the nut of one does not run on the other. When you order from the old screw, count the thread starts at the end face and measure ten crests with a rule: crests give the pitch, starts times pitch gives the lead, and the chart row follows. The thread identification guide shows the measuring.

Written as	Outside Ø	Lead	Pitch	Starts	Chart row
Tr10×2	10	2	2	1	Ø10 × 2
Tr10×4P2	10	4	2	2	Ø10 × 4, two starts
Tr10×10P2.5	10	10	2.5	4	Ø10 × 10, four starts
Tr10×10P1.25	10	10	1.25	8	Ø10 × 10, eight starts
Tr20×4LH	20	4	4	1	Ø20 × 4, left-hand
Tr18×100P5	18	100	5	20	Ø18 × 100, twenty starts

Root diameter and the largest end you can have

The bearing journal, the keyed drive end with its keyway to DIN 6885, and the end thread are all turned below the thread, so their diameter is capped by the root of the thread. The chart column gives that cap for every size. If the drawing needs a bigger journal than the cap, the answer is the next size up, not a thinner thread: a 12 mm bearing seat needs at least the Ø18 group at 4 mm lead, where the cap is 13 mm.

Size	Root Ø	Largest end Ø	Fits a bearing bore of
Ø8 × 1.5 (P1.5)	6.2	6	6 mm, h6 on the journal
Ø10 × 2 (P2)	7.5	8	8 mm, h6 on the journal
Ø12 × 3 (P3)	8.5	8	8 mm, h6 on the journal
Ø14 × 4 (P4)	9.5	9	9 mm, h6 on the journal
Ø16 × 4 (P4)	11.5	11	11 mm, h6 on the journal
Ø18 × 4 (P4) LH	13.5	13	13 mm, h6 on the journal
Ø20 × 4 (P4) LH	15.5	15	15 mm, h6 on the journal
Ø22 × 5 (P5) LH	16.5	16	16 mm, h6 on the journal
Ø24 × 5 (P5)	18.5	18	18 mm, h6 on the journal

Efficiency: plastic nut against bronze nut, and the 50 % line

Two columns, because the nut material sets the friction. The plastic nut runs at a higher efficiency on every row, which is why plastic nuts are chosen for light, fast, quiet travel and bronze for load and life. The 50 % line is the practical one: a screw and nut under it hold position when the motor stops, which is what a lifting or clamping screw needs; a pair above it back-drives, which is what a fast return or a hand-turned slide wants, with a brake if the load must not run away.

Size	Plastic nut	Bronze nut	Holds a load?
Ø12 × 2 (P2)	31 %	22 %	Both hold
Ø12 × 3 (P3)	41 %	30 %	Both hold
Ø12 × 5 (P2.5, 2 starts)	53 %	41 %	Bronze holds, plastic may back-drive
Ø12 × 9 (P3, 3 starts)	66 %	54 %	Both back-drive
Ø12.2 × 15 (P3, 5 starts)	73 %	62 %	Both back-drive
Ø11.9 × 25 (P5, 5 starts)	77 %	66 %	Both back-drive
Ø12 × 45 (P3, 15 starts)	76 %	62 %	Both back-drive

Left-hand sizes

Six sizes in the range are made left-hand as well as right-hand: Ø8 × 1 (P1), Ø14 × 3 (P3), Ø16 × 3 (P3), Ø18 × 4 (P4), Ø20 × 4 (P4), Ø22 × 5 (P5). A left-hand screw is used where a right-hand one would unscrew itself, on counter-rotating shafts and on the second half of a screw that moves two carriages toward each other. Other sizes are made left-hand to order; write LH after the callout and say whether the nut is left-hand as well.

Materials: screw and nut

Material	Where it is used	Note
Bearing steel 100Cr6 (GCr15, SAE 52100)	Standard screw material for every size in the Ø4 to Ø24 range	Machine tools, semiconductor equipment, instruments, conveyors
Stainless steel 304 (1.4301)	Screws in wet, washdown, food and lab equipment	On request; the screw with the plastic nut in the photos
Carbon steel C45 (1.0503)	General machinery and large screws to drawing	On request
Aluminium 6061	Light hand-feed and instrument screws where weight matters more than wear	With a bronze or plastic nut
Bronze CuSn12 nut	Load, heat and long machine-tool duty	The bronze column of the chart
Plastic nut (POM)	Quiet, self-lubricating, light load, higher efficiency	The plastic column; anti-backlash version with a spring

Price, lead time, delivery for a size off this chart

There is no list price for a lead screw made to your length and ends; a single piece starts from €25 and is quoted within 12 hours from the callout: outside diameter, lead, pitch, starts, hand, length, the ends, and whether a nut goes with it. One to a few dozen pieces ship in 5 working days, 50 to 500 in 15 working days, delivered DDP to your door with duties in the quote. The first piece is the sample; repeat orders run to the same drawing, and 500-piece and 1,000-piece runs are priced lower per piece. The screw is bearing steel unless the order says stainless 304 or carbon steel C45; the nut is bronze unless the order says plastic; the grades go on the drawing.

Where the chart stops

What you need	In the catalogue?	What to do
Plain Tr bar in an ISO 2904 size, single start	Yes	Buy it there, or ask us, we may have the size
A chart size cut to length with the ends machined	No	Made to order from the row
A size between two rows, say Ø10 with a 7 mm lead	No	Made to drawing; ask before designing around it
A chart size in stainless	Rare	304 to order
Ø60 to Ø300	No	Made to drawing, multi-start included
The nut for a chart size	Rare	Made to the row; see the nut page

Related lead screw pages

Frequently asked

What does a row of the chart mean?

Outside diameter as produced, lead in millimetres per turn, pitch, number of starts, hand, the root diameter of the thread, the largest diameter an end can be turned to below the thread, and the efficiency of the screw with a plastic nut and with a bronze nut. Lead equals pitch times starts on every row; a dash means the value is confirmed on the drawing for that size.

Is Ø10 × 2 the same as Tr10×2?

Yes. The chart lists our sizes by outside diameter and lead; Tr10×2 is the ISO 2904 way of writing the single-start row with a 2 mm lead, and Tr10×4P2 is the two-start row with a 4 mm lead and a 2 mm pitch. Standard Tr sizes in the range are made to ISO 2903 class 7e on the pitch diameter.

Why do 9.53 and 12.7 appear in a metric chart?

They are 3/8 in and 1/2 in blanks that carry a metric lead; 22.23 is 7/8 in. They sit in the Ø10, Ø12 and Ø22 groups because that is the nut size they pair with. The figure on the drawing is the one that counts.

What does the largest end diameter tell me?

It is the biggest plain journal that can be turned on the end of that screw, at or a little below the root of the thread. A Ø16 × 4 screw takes an 11 mm journal, a Ø20 × 4 screw a 15 mm one; a bearing seat of 12 mm on a Ø16 screw needs a Ø17 or Ø18 size instead.

Which sizes hold a load without back-driving?

The rows with an efficiency under 50 % with the nut you use. A Ø12 × 3 screw with a bronze nut is at 30 % and holds; the same screw with a plastic nut is at 41 % and holds; a Ø12 × 9 three-start screw is at 66 % and 54 % and the load can turn it back, so it needs a brake or a self-locking drive.

How do I get a price for one size on this chart?

Tap the row, then the WhatsApp or form button that appears; the size goes into the message. Add length, the ends and whether a nut goes with it, and the quote comes back within 12 hours, from €25 for a single screw.