STEEL IMPEX INDIA
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GSTIN 27ADJPJ5621J1ZF · Reference copy · 11 November 2026

STEEL IMPEX INDIA · ENGINEERING REFERENCE

UNC Thread Dimensions | TPI, Pitch & Diameter

Look up nominal UNC bolt threads, threads per inch and dimensional references. Keep thread series, unit system and tolerance-class requirements separate. Select the exact size/class and facing used by the order; keep the stated source units and revision with the values.

Compiled by Steel Impex India · Source review 11 November 2026 · Values match app v1.5.11

Open reference Common questions

UNC/UNRC basic geometry: ASME B1.1-2003 Table 6; UNJ design references: ASME B1.15-1995 · mm · All listed sizes

Published dimensional reference snapshot, retrieved 2026-11-11. Confirm the specified standard edition, tolerances and manufacturer drawing before manufacture or purchase. A missing value remains Not listed.

Metric dimensions are converted from the source inch values; source rounding limits precision.

The 2-1/4 in UNC size is 4.5 TPI, with all dependent dimensions corrected together. Small 0.0001 in differences retain the published B1.1-2003 table values corroborated by Optimas; they are not extra machining precision. The cited older edition is explicit. UNJ is a different root form, not an interchangeable UNC tolerance. Values are basic/design references, not manufacturing limits.

Basic thread geometry is not a tolerance-limit or gauge chart. UNC coarse pitches differ from the 8UN series often specified for larger flange studs. Confirm the actual thread series and class.

UNC bolt threads · dimensions 1–4
Nominal bolt (in)	Basic major diameter	Basic pitch diameter	UNR external minor diameter	UNJ external minor diameter
#1	1.8542 mm	1.5977 mm	1.3818 mm	1.397 mm
#2	2.1844 mm	1.8898 mm	1.6459 mm	1.6612 mm
#3	2.5146 mm	2.1717 mm	1.8821 mm	1.905 mm
#4	2.8448 mm	2.4333 mm	2.0879 mm	2.1133 mm
#5	3.175 mm	2.7635 mm	2.4181 mm	2.4435 mm
#6	3.5052 mm	2.9896 mm	2.5603 mm	2.5883 mm
#8	4.1656 mm	3.65 mm	3.2207 mm	3.2487 mm
#10	4.826 mm	4.1377 mm	3.5662 mm	3.6043 mm
#12	5.4864 mm	4.7981 mm	4.2266 mm	4.2647 mm
0.25	6.35 mm	5.5245 mm	4.8387 mm	4.8819 mm
0.3125	7.9375 mm	7.0206 mm	6.2586 mm	6.3068 mm
0.375	9.525 mm	8.4938 mm	7.6327 mm	7.6911 mm
0.4375	11.1125 mm	9.9339 mm	8.9535 mm	9.017 mm
0.5	12.7 mm	11.43 mm	10.3734 mm	10.4419 mm
0.5625	14.2875 mm	12.9134 mm	11.7678 mm	11.844 mm
0.625	15.875 mm	14.3764 mm	13.1267 mm	13.2105 mm
0.75	19.05 mm	17.399 mm	16.0249 mm	16.1163 mm
0.875	22.225 mm	20.3911 mm	18.8646 mm	18.9662 mm
1	25.4 mm	23.3375 mm	21.6205 mm	21.7348 mm
1.125	28.575 mm	26.2179 mm	24.2545 mm	24.384 mm
1.25	31.75 mm	29.3929 mm	27.4295 mm	27.559 mm
1.375	34.925 mm	32.1742 mm	29.8856 mm	30.0355 mm
1.5	38.1 mm	35.3492 mm	33.0606 mm	33.2105 mm
1.75	44.45 mm	41.1505 mm	38.4023 mm	38.5851 mm
2	50.8 mm	47.1348 mm	44.0766 mm	44.2824 mm
2.25	57.15 mm	53.4848 mm	50.4266 mm	50.6324 mm
2.5	63.5 mm	59.375 mm	55.9384 mm	56.167 mm
2.75	69.85 mm	65.725 mm	62.2884 mm	62.517 mm
3	76.2 mm	72.075 mm	68.6384 mm	68.867 mm
3.25	82.55 mm	78.425 mm	74.9884 mm	75.217 mm
3.5	88.9 mm	84.775 mm	81.3384 mm	81.567 mm
3.75	95.25 mm	91.125 mm	87.6884 mm	87.917 mm
4	101.6 mm	97.475 mm	94.0384 mm	94.267 mm

UNC bolt threads · dimensions 5–8
Nominal bolt (in)	UN internal minor diameter	UNJ internal minor diameter	Threads per inch	Pitch
#1	1.4249 mm	1.4681 mm	64 TPI	0.3969 mm
#2	1.6942 mm	1.7424 mm	56 TPI	0.4536 mm
#3	1.9406 mm	1.999 mm	48 TPI	0.5292 mm
#4	2.1565 mm	2.225 mm	40 TPI	0.635 mm
#5	2.4867 mm	2.5552 mm	40 TPI	0.635 mm
#6	2.6467 mm	2.733 mm	32 TPI	0.7937 mm
#8	3.3071 mm	3.3934 mm	32 TPI	0.7937 mm
#10	3.6805 mm	3.7948 mm	24 TPI	1.0583 mm
#12	4.3409 mm	4.4552 mm	24 TPI	1.0583 mm
0.25	4.9759 mm	5.113 mm	20 TPI	1.27 mm
0.3125	6.411 mm	6.5634 mm	18 TPI	1.4111 mm
0.375	7.8054 mm	7.9781 mm	16 TPI	1.5875 mm
0.4375	9.1491 mm	9.3447 mm	14 TPI	1.8143 mm
0.5	10.5842 mm	10.7975 mm	13 TPI	1.9538 mm
0.5625	11.9964 mm	12.225 mm	12 TPI	2.1167 mm
0.625	13.3756 mm	13.6246 mm	11 TPI	2.3091 mm
0.75	16.2992 mm	16.576 mm	10 TPI	2.54 mm
0.875	19.1694 mm	19.4742 mm	9 TPI	2.8222 mm
1	21.9634 mm	22.3063 mm	8 TPI	3.175 mm
1.125	24.6482 mm	25.0393 mm	7 TPI	3.6286 mm
1.25	27.8232 mm	28.2143 mm	7 TPI	3.6286 mm
1.375	30.3428 mm	30.8 mm	6 TPI	4.2333 mm
1.5	33.5178 mm	33.975 mm	6 TPI	4.2333 mm
1.75	38.9509 mm	39.4995 mm	5 TPI	5.08 mm
2	44.6888 mm	45.3009 mm	4.5 TPI	5.6444 mm
2.25	51.0388 mm	51.6509 mm	4.5 TPI	5.6444 mm
2.5	56.6268 mm	57.3126 mm	4 TPI	6.35 mm
2.75	62.9768 mm	63.6626 mm	4 TPI	6.35 mm
3	69.3268 mm	70.0126 mm	4 TPI	6.35 mm
3.25	75.6768 mm	76.3626 mm	4 TPI	6.35 mm
3.5	82.0268 mm	82.7126 mm	4 TPI	6.35 mm
3.75	88.3768 mm	89.0626 mm	4 TPI	6.35 mm
4	94.7268 mm	95.4126 mm	4 TPI	6.35 mm

UNC bolt threads · dimensions 9–11
Nominal bolt (in)	Minor-diameter area	Tensile stress area	Lead angle
#1	1.4064 mm²	1.6968 mm²	4° 31′
#2	2 mm²	2.3871 mm²	4° 22′
#3	2.6193 mm²	3.1419 mm²	4° 26′
#4	3.2 mm²	3.8968 mm²	4° 45′
#5	4.3355 mm²	5.1355 mm²	4° 11′
#6	4.8064 mm²	5.8645 mm²	4° 50′
#8	7.7161 mm²	9.0322 mm²	3° 58′
#10	9.3548 mm²	11.2903 mm²	4° 39′
#12	13.2903 mm²	15.6129 mm²	4° 1′
0.25	17.3548 mm²	20.5161 mm²	4° 11′
0.3125	29.2903 mm²	33.8064 mm²	3° 40′
0.375	43.7418 mm²	49.9999 mm²	3° 24′
0.4375	60.1934 mm²	68.5805 mm²	3° 20′
0.5	81.0966 mm²	91.5482 mm²	3° 7′
0.5625	104.5159 mm²	117.4191 mm²	2° 59′
0.625	130.3223 mm²	145.8062 mm²	2° 56′
0.75	194.8383 mm²	215.4834 mm²	2° 40′
0.875	270.322 mm²	298.0639 mm²	2° 31′
1	355.4832 mm²	390.967 mm²	2° 29′
1.125	447.0959 mm²	492.2571 mm²	2° 31′
1.25	574.1924 mm²	625.16 mm²	2° 15′
1.375	679.9986 mm²	745.1598 mm²	2° 24′
1.5	834.837 mm²	906.4498 mm²	2° 11′
1.75	1122.5784 mm²	1225.804 mm²	2° 15′
2	1483.868 mm²	1612.9 mm²	2° 11′
2.25	1948.3832 mm²	2096.77 mm²	1° 55′
2.5	2399.9952 mm²	2580.64 mm²	1° 57′
2.75	2980.6392 mm²	3180.6388 mm²	1° 46′
3	3625.7992 mm²	3851.6052 mm²	1° 36′
3.25	4335.4752 mm²	4580.636 mm²	1° 29′
3.5	5109.6672 mm²	5374.1828 mm²	1° 22′
3.75	5941.9236 mm²	6232.2456 mm²	1° 16′
4	6845.1476 mm²	7148.3728 mm²	1° 11′

Reference sources

Prepare a bulk enquiry for delivery within India

Include the material grade, standard and edition, complete size, quantity, finish, certificates, required date and delivery PIN code. For valves include body/trim, seats, service fluid, temperature, end connection and actuator. For fasteners include thread, pitch, length, property class and coating.

For a village, small town or large city, give the district, nearest transport depot and unloading arrangements. Stock, suitability, freight and delivery are confirmed for each order.

Prepare your material enquiry Delivery checklist

Common questions

Are every size and class combination available?

No. The charts preserve the published combinations and label manufacturer specials or conflicts. “Not listed” is not a zero dimension and is not permission to interpolate a missing size.

Are inch fasteners interchangeable with converted metric sizes?

No. Converting an inch diameter for display does not change its thread series or fit. Order the specified thread, pitch or TPI, tolerance class, length convention and material.

What should a bulk buyer send for a quotation?

Send the exact standard and edition, grade or class, complete dimensions, quantity, finish, certification and delivery town, district and PIN code. Include the nearest transport depot for village or small-town delivery. Availability, price, freight and delivery are confirmed against your enquiry.

Reference sources and corrections · Toolkit terms. Source scope, units and missing values remain part of every reference. A catalogue listing is not a stock guarantee, approval for substitution or brand affiliation.