Boss
Screw posts inside a 3D-printed case, at sketch points, with a pilot hole, a hole for a heat-set insert or a clearance hole for the screw, and fins.
- Boss AdvancedPart Studio toolbar
| SchoolCAD | Onshape | Fusion | SOLIDWORKS |
|---|---|---|---|
| Boss | – | Boss | Mounting Boss |
A boss is a round post for a screw: the posts inside a 3D-printed case that a circuit board or a lid screws onto. Put a point in a sketch where each boss goes, and SchoolCAD grows a boss from the part under it, with the right hole for the screw and, if you like, fins round it to stiffen it. It works like Mounting Boss in SOLIDWORKS and Boss in Fusion.
Boss is in the Advanced tool set. In Standard, find it with Search tools (` or Alt+C), or switch to Advanced at the end of the toolbar.
How to use it#
- Make the part first, such as a box hollowed out with Shell.
- Start a sketch on the floor of the box (click the face, then Sketch), or on a plane above it, and put a Point where each boss goes (a circle's centre works too). Dimension the points from the edges, or to match the holes of your circuit board.
- Click Boss. Choose the Boss type and the screw Size.
- Set the Height, check the preview and click ✓.
Boss type#
| Type | What it is for |
|---|---|
| Head | The screw goes through this boss and the part (a clearance hole), with its head on the far side, in a counterbore or countersink. Use it on a lid: the screw goes into a Thread or Insert boss on the base. (SOLIDWORKS: Head) |
| Thread | A pilot hole that a self-tapping screw cuts its own thread in: the simplest way to screw into a 3D print. (SOLIDWORKS: Thread · Fusion: Threaded side) |
| Insert | A hole for a heat-set threaded insert, pressed in with a soldering iron. Then a machine screw (M3, say) can go in and out many times. |
| Blank | A post with no hole: a stand-off or a locating pin. |
Options#
| Option | What it does |
|---|---|
| Sketch (Position) | The sketch with the points. Each point, or circle centre, gets a boss. |
| End type (Direction) | Blind: the boss is as tall as the Height, from the part's surface. Up to sketch plane: the boss goes from the part up to the sketch, so sketch on the plane where the board or the lid sits. |
| ⇅ (Opposite direction) | Grows the boss the other way. SchoolCAD looks for the part both ways, so you only need it when both ways find a part. |
| Size | The screw size, M2 to M5. It sets the hole, the insert's hole and the boss's diameter for you. |
| Diameter | The boss's outside diameter. Keep the wall round the hole at least 1.6 mm thick (four lines of a 0.4 mm nozzle). |
| Height | How tall the boss is, from the part's surface. |
| Draft | Tapers the outside of the boss, in degrees, as moulded parts need. Leave it at 0 for 3D printing. |
| Fillet | Rounds the corner where the boss meets the part, so it is less likely to snap off. |
| Hole diameter, Hole depth | The hole in the boss. A Thread or Insert hole goes down to the part unless you set its depth. |
| Screw head, Head diameter, Head depth | For a Head boss: a Counterbore for a socket head (cap) screw, a Countersink for a countersunk screw (90°), or None. |
| Number of fins | Fins round the boss stiffen a tall boss. Fin length is how far they reach out, Fin height how high they go up the boss (three quarters of it, unless you set it), Fin width how thick they are, and Fin angle turns them. |
| Merge scope | Merge with all ticked: each boss joins the part under its point. Untick it, then tick the parts that get bosses. |
Sizes it uses#
| Screw | Pilot hole (Thread) | Clearance hole (Head) | Insert hole and length | Boss Ø (Thread, Insert) |
|---|---|---|---|---|
| M2 | 1.6 | 2.4 | 3.2, 4 mm insert | 5, 6.5 |
| M2.5 | 2.1 | 2.9 | 3.6, 5.7 mm insert | 6, 7 |
| M3 | 2.5 | 3.4 | 4.0, 5.7 mm insert | 7, 8 |
| M4 | 3.3 | 4.5 | 5.6, 8.1 mm insert | 9, 10 |
| M5 | 4.2 | 5.5 | 6.4, 9.5 mm insert | 11, 11.5 |
The insert sizes are for common standard heat-set inserts. Check the instructions for yours, and change the Hole diameter and Hole depth to match. An insert's hole is 1 mm deeper than the insert, so the plastic it pushes down has somewhere to go.
Tips#
- Print a test piece with one boss first: printers make holes a little small, so a pilot hole may need 0.1 or 0.2 mm more.
- For a lid, make Head bosses on the lid and Thread or Insert bosses on the base, at the same points (use the same sketch, or Mirror it).
- Fins and a fillet make a tall boss much stronger. A Rib from the boss to the wall stiffens it even more.
If it does not work#
- A boss grows from a part. The point must be on a face of the part, or above the part with nothing in between. If the boss grows the wrong way, click ⇅.
- The boss's wall round its hole is thin. Make the Diameter bigger, or choose a smaller screw.
- The boss is shorter than its insert's hole. Make it taller, or the hole goes on into the part under it.