# 3D printable 2x4 cross connector: joins two 2x4s on edge crossing like a plus, one stacked on the other (STL, STEP)

> Is there a 3D printable block that holds two 2x4s crossing at 90 degrees, both on edge, without cutting the wood?

- Category: Joinery › 3D-print connectors
- Kind: Hardware
- Basis: 2x4 dressed (dry) size 1-1/2 × 3-1/2 in (38.1 × 88.9 mm) per DOC PS 20 American Softwood Lumber Standard; 1.4 mm sliding clearance is Xem's FDM default for this part.
- Page: https://xemstudio.com/objects/2x4-cross-block-connector/ · JSON: https://xemstudio.com/api/geometry?object=2x4-cross-block-connector · Plain text: https://xemstudio.com/objects/2x4-cross-block-connector/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 55.5 | 55.5 | 90.0 |

**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

- Both boards stand on edge (the 1-1/2 in side is the width). The block slides down over the lower board and the upper board drops into the top slot at 90°, so the stack is about 7 in to the top of the upper board.
- No cutting or notching of the lumber. Add a screw through a wall into each board if the joint must not lift apart.
- Slots are 39.5 mm for a 38.1 mm board. Rough-sawn, wet or swollen 2x4s can run thicker: test-fit one block first.
- Print upright as modelled, 4 or more walls, 20 % or more infill, PETG or ABS outdoors. No supports: the lower slot's 39.5 mm ceiling bridges.

## 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 |
|---|---|---|---|---|
| lower slot | 39.5 mm wide, 40 mm deep | 2x4 on edge (38.1 mm) | slide | all |
| upper slot | 39.5 mm wide, 40 mm deep | 2x4 on edge (38.1 mm) | slide | all |

## Sizes

| feature | size mm | fits |
|---|---|---|
| block | 55.5 × 55.5 × 90 | — |
| lower slot (opens down, along X) | 39.5 wide × 40 deep | 2x4 on edge, 38.1 thick |
| upper slot (opens up, along Y) | 39.5 wide × 40 deep | 2x4 on edge, 38.1 thick |
| walls / web | 8 / 10 | — |
| lead-in chamfer | 1.5 | — |

## Where the files are

- NIST / ALSC: [Voluntary Product Standard PS 20-25, American Softwood Lumber Standard](https://www.nist.gov/document/ps-20-25-final) — web — Publisher's page; dimensions are facts
- American Wood Council: [Weights and Measurement: nominal vs actual lumber sizes](https://awc.org/weights-and-measurement) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/2x4-cross-block-connector/index.json · license: https://xemstudio.com/files/hardware/2x4-cross-block-connector/LICENSE.md

- 2x4-cross-block: [STEP](https://xemstudio.com/files/hardware/2x4-cross-block-connector/2x4-cross-block.step) · [STL](https://xemstudio.com/files/hardware/2x4-cross-block-connector/2x4-cross-block.stl) — 2x4 cross connector: 55.5 × 55.5 × 90 mm block, two 39.5 mm slots 40 mm deep at 90°, one down, one up; prints upright with no supports

## Questions

**What size is a 2x4 really?**

1-1/2 × 3-1/2 in (38.1 × 88.9 mm) dry and dressed. The slots here are 39.5 mm so the 38.1 mm side slides in.

**Do the boards need to be cut or notched?**

No. The block slides over one board and the other drops into the top slot; the wood stays full length.

**Does it work with the boards lying flat?**

No. Both slots fit the 1-1/2 in side, so both boards stand on edge.

**How do I print it without supports?**

Print it upright as modelled. The lower slot's 39.5 mm ceiling bridges on any tuned FDM printer.

**Will it hold if I lift the top board?**

It locates the boards but does not lock them. Drive a screw through a wall into each board if it must not come apart.

## Fits with

- [Dimensional lumber: actual sizes of 1x2 to 6x6, 8 to 16 ft (2x4 = 1-1/2 × 3-1/2 in)](https://xemstudio.com/objects/dimensional-lumber/)
- [Cross lap joint (cross halving)](https://xemstudio.com/objects/cross-lap-joint/)
- [Half lap joint (corner)](https://xemstudio.com/objects/half-lap-joint/)