# Hex cap screws and heavy hex screws, inch 7/8 to 1-1/2 (ASME B18.2.1): across flats F, head height H, thread length LT

> What are the head size, head height and thread length of a 7/8, 1, 1-1/8, 1-1/4, 1-3/8 or 1-1/2 inch hex cap screw or heavy hex screw?

- Category: Hardware › Fasteners
- Kind: Standard part
- Basis: ASME B18.2.1 tables as printed by M.E. Campbell (cap screws), Boltport (cap screws and heavy hex screws) and Torqbolt (heavy hex values); inches, max / min as printed; 12 envelope files
- Page: https://xemstudio.com/objects/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/ · JSON: https://xemstudio.com/api/geometry?object=hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2 · Plain text: https://xemstudio.com/objects/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 44.0 | 38.1 | 126.3 |

**Exact dimensions.** Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part.

## Notes

- Two head styles share these sizes. A hex cap screw (ASME B18.2.1) has the regular head: 1-5/16 in across flats at 7/8, 1-1/2 at 1, 1-11/16 at 1-1/8, 1-7/8 at 1-1/4, 2-1/16 at 1-3/8, 2-1/4 at 1-1/2. A heavy hex screw has the larger head: F max 1.438, 1.625, 1.812, 2.000, 2.188, 2.375 in. Head height H is the same for both (H max .563, .627, .718, .813, .878, .974 in). The existing page hex-bolts-inch covers 1/4-20 to 3/4-10; this page continues the cap screws and adds the heavy hex style.
- Two independent printings agree on every cap-screw value (M.E. Campbell and Boltport) and on every heavy hex value (Boltport and Torqbolt's table, whose heading says 'hex screws' but whose F, G and H are the heavy hex column). Body diameter E min differs by style: .8660 (cap) against .852 (heavy) at 7/8.
- Thread length LT: M.E. Campbell and Boltport print two columns, for screw lengths 6 in and shorter and over 6 in (the Boltport page does not label the two columns; the reading is the same as M.E. Campbell's for the cap screws). Torqbolt prints a single LT min per size, and it equals the longer-screw column (2.250 at 7/8 to 3.500 at 1-1/2). Cap and heavy hex LT are identical at each size. M.E. Campbell marks LT as a reference value.
- J min is the minimum wrenching height; only Boltport prints it (cap screws only: .378 / .416 / .461 / .530 / .569 / .640 in). Boltport also prints runout and a Y value whose column headings were not clear, so they are not used.
- Threads: UNC 9, 8, 7, 7, 6, 6 and UNF 14, 12, 12, 12, 12, 12 threads per inch for 7/8 to 1-1/2 (see threaded-rod-inch-unc-unf-sizes). Class 2A threads. The files draw the thread as a plain cylinder at the major diameter.
- Files: 12 envelopes, one per size and style. The head is a hexagonal prism at F max and H max, the shank a plain cylinder at E max, 4 in under the head. 4 in is an example length of ours; ASME B18.2.1 lists many standard lengths. No washer face, head chamfer, fillet or thread is drawn, because those are not in the tables read. Not covered: the plain hex bolt (ASME B18.2.1 hex bolt) at 7/8 and up, which has its own head heights (not read here).

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| shank (thread as plain cylinder) | Ø22.225 (7/8), 25.400 (1), 28.575 (1-1/8), 31.750 (1-1/4), 34.925 (1-3/8), 38.100 (1-1/2) mm = E max, the thread major | nut of the same UNC thread: hex-nuts-inch-7-8-to-1-1-2-jam-heavy (hex, jam, heavy hex); clearance holes and tap drills on thread-reference-tap-drills-clearance | designed | hex-cap-screw-* |
| shank (thread as plain cylinder) | same Ø as the cap screw (E max); heavy hex head F max is the larger 1.438 / 1.625 / 1.812 / 2.000 / 2.188 / 2.375 in | heavy hex nut of the same thread (hex-nuts-inch-7-8-to-1-1-2-jam-heavy); heavy hex heads and nuts are paired | designed | heavy-hex-screw-* |

## Sizes

| style | size (in) | UNC / UNF TPI | E body dia max / min | F across flats max / min | G across corners max / min | H head height max / min | J wrenching height min (cap only) | LT thread length, L ≤ 6 in | LT thread length, L > 6 in | file: F max / H max (mm) |
|---|---|---|---|---|---|---|---|---|---|---|
| hex cap screw | 7/8 | 9 / 14 | .8750 / .8660 | 1.312 / 1.285 | 1.516 / 1.465 | .563 / .531 | .378 | 2.000 | 2.250 | 33.32 / 14.3 |
| hex cap screw | 1 | 8 / 12 | 1.0000 / .9900 | 1.500 / 1.469 | 1.732 / 1.675 | .627 / .591 | .416 | 2.250 | 2.500 | 38.1 / 15.93 |
| hex cap screw | 1-1/8 | 7 / 12 | 1.1250 / 1.1140 | 1.688 / 1.631 | 1.949 / 1.859 | .718 / .658 | .461 | 2.500 | 2.750 | 42.88 / 18.24 |
| hex cap screw | 1-1/4 | 7 / 12 | 1.2500 / 1.2390 | 1.875 / 1.812 | 2.165 / 2.066 | .813 / .749 | .530 | 2.750 | 3.000 | 47.62 / 20.65 |
| hex cap screw | 1-3/8 | 6 / 12 | 1.3750 / 1.3630 | 2.062 / 1.994 | 2.382 / 2.273 | .878 / .810 | .569 | 3.000 | 3.250 | 52.37 / 22.3 |
| hex cap screw | 1-1/2 | 6 / 12 | 1.5000 / 1.4880 | 2.250 / 2.175 | 2.598 / 2.480 | .974 / .902 | .640 | 3.250 | 3.500 | 57.15 / 24.74 |
| heavy hex screw | 7/8 | 9 / 14 | .8750 / .852 | 1.438 / 1.394 | 1.660 / 1.589 | .563 / .531 | – | 2.000 | 2.250 | 36.53 / 14.3 |
| heavy hex screw | 1 | 8 / 12 | 1.0000 / .976 | 1.625 / 1.575 | 1.876 / 1.796 | .627 / .591 | – | 2.250 | 2.500 | 41.27 / 15.93 |
| heavy hex screw | 1-1/8 | 7 / 12 | 1.1250 / 1.098 | 1.812 / 1.756 | 2.093 / 2.002 | .718 / .658 | – | 2.500 | 2.750 | 46.02 / 18.24 |
| heavy hex screw | 1-1/4 | 7 / 12 | 1.2500 / 1.223 | 2.000 / 1.938 | 2.309 / 2.209 | .813 / .749 | – | 2.750 | 3.000 | 50.8 / 20.65 |
| heavy hex screw | 1-3/8 | 6 / 12 | 1.3750 / 1.345 | 2.188 / 2.119 | 2.526 / 2.416 | .878 / .810 | – | 3.000 | 3.250 | 55.58 / 22.3 |
| heavy hex screw | 1-1/2 | 6 / 12 | 1.5000 / 1.470 | 2.375 / 2.300 | 2.742 / 2.622 | .974 / .902 | – | 3.250 | 3.500 | 60.32 / 24.74 |

## Where the files are

- M.E. Campbell (distributor): [Hex Head Cap Screws spec (ASME B18.2.1): E, F, G, H, LT for lengths <= 6 in and > 6 in](https://www.mecampbell.com/media/pdf/Hex_Head_Cap_Screws_spec.pdf) — web — Publisher's page; dimensions are facts
- Boltport (mirror host as read): [ASME B18.2.1 hex cap screws: E, F, G, H, J, LT, Y, runout, 1/4 to 3 in](https://www.boltport.com.ferrobend.com/standards/asme-b18.2.1/hex-cap-screws) — web — Publisher's page; dimensions are facts
- Boltport (mirror host as read): [ASME B18.2.1 heavy hex screws: E, F, G, H, LT, 3/8 to 6 in](https://www.boltport.com.ferrobend.com/standards/asme-b18.2.1/heavy-hex-screws) — web — Publisher's page; dimensions are facts
- Torqbolt: [ASME B18.2.1 screws table (heading says hex screws; the values are the heavy hex column): E, F basic / max / min, G, H basic / max / min, LT min](https://torqbolt.com/asme-b18-2-1-heavy-hex-screws-dimensions-standards-specifications) — web — Publisher's page; dimensions are facts
- ASME: [ASME B18.2.1 Square, hex, heavy hex, askew head bolts and hex, heavy hex, hex flange, lobed head and lag screws (inch)](https://www.asme.org/codes-standards/find-codes-standards/b18-2-1-square-hex-heavy-hex-askew-head-bolts-hex-heavy-hex-hex-flange-lobed-head-lag-screws-inch-series) — web — ASME; dimensions are facts
- Torqbolt: [ASME B18.31.3 threaded rods: nominal diameters and UNC / UNF threads per inch, #4 to 5 in](https://torqbolt.com/asme-b18-31-3-threaded-rods-dimensions-standards-specifications) — web — Publisher's page; dimensions are facts

## Free STEP/STL (12 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/index.json

- hex-cap-screw-7-8-9x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-7-8-9x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-7-8-9x4in.stl) — hex cap screw 7/8-9 UNC envelope: hex head 1.312 in across flats x .563 in high (F max, H max), plain shank Ø.8750 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 2.000 in (L ≤ 6 in)
- hex-cap-screw-1-8x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-8x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-8x4in.stl) — hex cap screw 1-8 UNC envelope: hex head 1.500 in across flats x .627 in high (F max, H max), plain shank Ø1.0000 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 2.250 in (L ≤ 6 in)
- hex-cap-screw-1-1-8-7x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-1-8-7x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-1-8-7x4in.stl) — hex cap screw 1-1/8-7 UNC envelope: hex head 1.688 in across flats x .718 in high (F max, H max), plain shank Ø1.1250 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 2.500 in (L ≤ 6 in)
- hex-cap-screw-1-1-4-7x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-1-4-7x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-1-4-7x4in.stl) — hex cap screw 1-1/4-7 UNC envelope: hex head 1.875 in across flats x .813 in high (F max, H max), plain shank Ø1.2500 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 2.750 in (L ≤ 6 in)
- hex-cap-screw-1-3-8-6x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-3-8-6x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-3-8-6x4in.stl) — hex cap screw 1-3/8-6 UNC envelope: hex head 2.062 in across flats x .878 in high (F max, H max), plain shank Ø1.3750 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 3.000 in (L ≤ 6 in)
- hex-cap-screw-1-1-2-6x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-1-2-6x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/hex-cap-screw-1-1-2-6x4in.stl) — hex cap screw 1-1/2-6 UNC envelope: hex head 2.250 in across flats x .974 in high (F max, H max), plain shank Ø1.5000 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 3.250 in (L ≤ 6 in)
- heavy-hex-screw-7-8-9x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-7-8-9x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-7-8-9x4in.stl) — heavy hex screw 7/8-9 UNC envelope: hex head 1.438 in across flats x .563 in high (F max, H max), plain shank Ø.8750 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 2.000 in (L ≤ 6 in)
- heavy-hex-screw-1-8x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-8x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-8x4in.stl) — heavy hex screw 1-8 UNC envelope: hex head 1.625 in across flats x .627 in high (F max, H max), plain shank Ø1.0000 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 2.250 in (L ≤ 6 in)
- heavy-hex-screw-1-1-8-7x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-1-8-7x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-1-8-7x4in.stl) — heavy hex screw 1-1/8-7 UNC envelope: hex head 1.812 in across flats x .718 in high (F max, H max), plain shank Ø1.1250 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 2.500 in (L ≤ 6 in)
- heavy-hex-screw-1-1-4-7x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-1-4-7x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-1-4-7x4in.stl) — heavy hex screw 1-1/4-7 UNC envelope: hex head 2.000 in across flats x .813 in high (F max, H max), plain shank Ø1.2500 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 2.750 in (L ≤ 6 in)
- heavy-hex-screw-1-3-8-6x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-3-8-6x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-3-8-6x4in.stl) — heavy hex screw 1-3/8-6 UNC envelope: hex head 2.188 in across flats x .878 in high (F max, H max), plain shank Ø1.3750 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 3.000 in (L ≤ 6 in)
- heavy-hex-screw-1-1-2-6x4in: [STEP](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-1-2-6x4in.step) · [STL](https://xemstudio.com/files/hardware/hex-cap-screws-heavy-hex-screws-inch-7-8-to-1-1-2/heavy-hex-screw-1-1-2-6x4in.stl) — heavy hex screw 1-1/2-6 UNC envelope: hex head 2.375 in across flats x .974 in high (F max, H max), plain shank Ø1.5000 in (major diameter, thread not drawn), 4 in under the head (example length, Xem choice); published thread length LT 3.250 in (L ≤ 6 in)

## Questions

**What size wrench for a 7/8 hex cap screw?**

1-5/16 in across flats for a regular hex cap screw head (F max 1.312 in); a heavy hex screw head is 1-7/16 in (F max 1.438 in).

**What size wrench for a 1 inch hex bolt head?**

1-1/2 in across flats for a cap screw (F max 1.500 in) and 1-5/8 in for a heavy hex screw (F max 1.625 in).

**How long is the thread on a 1 inch hex cap screw?**

LT 2.250 in for screws up to 6 in long and 2.500 in for longer ones, as printed by M.E. Campbell and Boltport.

## Fits with

- [Hex bolts, inch: 1/4-20 to 3/4-10 (ASME B18.2.1)](https://xemstudio.com/objects/hex-bolts-inch/)
- [Hex nuts, inch: #4-40 to 3/4-10 (ASME B18.2.2)](https://xemstudio.com/objects/hex-nuts-inch/)
- [Hex nuts, hex jam nuts and heavy hex nuts, inch 7/8 to 1-1/2 (ASME B18.2.2): across flats, thickness, UNC / UNF](https://xemstudio.com/objects/hex-nuts-inch-7-8-to-1-1-2-jam-heavy/)
- [Flat washers, inch: SAE and USS, 1/4 to 3/4 in (ASME B18.21.1 Type A)](https://xemstudio.com/objects/flat-washers-inch/)
- [Structural flat washers ASTM F436 (round, hardened): inside and outside diameter, thickness, 1/2 to 1 in](https://xemstudio.com/objects/structural-washers-astm-f436/)
- [Nord-Lock wedge-locking washers NL3 to NL130: inner and outer diameter, thickness, enlarged-OD (sp) pairs, two tables compared](https://xemstudio.com/objects/nord-lock-wedge-locking-washers/)
- [Hex lag screws, 1/4 to 1/2 in (ASME B18.2.1): shank, head width and height, pilot holes + envelope models](https://xemstudio.com/objects/lag-screws-hex-inch/)
- [Threaded rod, inch: #4 to 4 in, UNC and UNF threads per inch, major diameter in inches and mm, standard lengths](https://xemstudio.com/objects/threaded-rod-inch-unc-unf-sizes/)
- [Thread size reference: UNC / UNF and ISO metric coarse / fine — major, minor and pitch diameter, tap drill, clearance hole (close, normal, loose)](https://xemstudio.com/objects/thread-reference-tap-drills-clearance/)
- [Plain washers, inch Type B (narrow, regular, wide): #0 to 3 in ID, OD, thickness + 12 washer files](https://xemstudio.com/objects/plain-washers-inch-type-b/)