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Slot round body: cut a groove or add a ridge all the way round a 3D model

Q: How do I cut an O-ring groove inside a tube?

Select the tube, click Slot round body in the Body card, pick Inside and the Square shape, type the groove's width and depth and its height from the bottom, then click Cut the slot. The groove runs all the way round the inside wall.

Q: What is the difference between a slot and a ridge?

Slot (cut in) cuts the shape into the body's wall; Ridge (add) adds the same shape standing out of the wall. A ridge with a flat top on the outside makes a snap lip that prints without supports.

Q: Can the slot go upright or at an angle?

Yes. Level runs round the body at one height, Upright runs over the top and under the bottom, and At an angle leans it by any angle you type. Cut through at turns it round the body.

Q: Can I draw my own groove shape?

Yes. Click Draw it on the cut: the body is shown cut through in blue, and the shape you draw against one of its walls runs all the way round the body - a dovetail, a half round, anything closed.

An O-ring groove inside a tube, a groove round a box, a snap ridge on a lid - the Slot round body tool runs a shape all the way round a body, along the wall you put it against, whatever that wall's outline. The body is shown cut open so you see exactly what you get, and you can drag the slot up and down with its distances to the top and the bottom. It works on shapes you made and on imported STL files.

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A tube shown cut open with an O-ring groove all the way round its inside wall, outlined in orange

Watch the tutorial

Every option in under three and a half minutes, with subtitles: inside and outside, the shapes, smooth sides, a ridge, drawing your own, a box, upright and at an angle. Watch on YouTube ↗

1Open the tool

The first example is a tube: Tube from Basic shapes, made 40 mm across and 30 mm tall in the Size card.

Select the body and click Slot round body in the Body card (after Thickness).
The body is shown cut open on the side facing you, and a square groove is already there, 2 mm wide and 1.5 mm deep, half way up, on the outside wall. Its shape on the cut is outlined in orange.
Two red dashed lines with labels show how far the slot is from the body's top and bottom.

A 40 mm tube shown cut open with a square groove round its outside, outlined in orange, labels 14 mm to the top and 14 mm to the bottom — The tool opened on a tube: the slot outlined in orange, its distances to the top and the bottom.

The Slot round body panel: Slot or ridge, Direction, Cut through at, Shape tiles, Outside / Inside, Height, Width, Depth, Smooth sloped sides, Draw it on the cut, Show the body cut open, Cut the slot — The panel, top to bottom.

2Outside or inside

Outside puts the slot on the body's outer wall, Inside on its inner wall - inside a tube, a cup or a ring. That is an O-ring groove: here 2.5 mm wide and 1.8 mm deep, all the way round the inside of the tube.

Inside is greyed out where the cut has no inner wall at that height (a solid body), and the slot stays on the outside.

The tube cut open with a square O-ring groove round its inside wall — Inside: an O-ring groove round the inside of the tube.

3Size and height

Width - how tall the groove is along the wall (for the Round shape: its Diameter).
Depth - how far it goes into the wall. For a ridge it is called Height out: how far it stands out.
Height - where it is, in mm up from the body's lowest point. Type it, or slide the bar under it. For an upright or leaning slot this is called Position: where it is across the body.

The panel's last line says how much material the slot removes (or the ridge adds) all the way round, and warns you when a cut would split the body into pieces.

4Drag it along the body

Move the mouse over the orange outline - the cursor turns into a hand - and drag it up or down. While you drag, only the outline and the two distances move; the slot is made again when you let go. It moves in 0.1 mm steps (hold Alt for any position) and stops when it reaches the top or the bottom of the body.

The orange slot outline being dragged up the tube, the red labels showing its new distances to the top and the bottom — Dragging the slot: the distances to the top and the bottom follow the mouse.

5The shapes

The Shape tiles: Square (an O-ring groove), Round, V, Flat top and Flat below - two right triangles against the wall, one flat on top and sloped below, the other the other way round - and Draw (your own shape, below).

A flat-top triangular groove inside the tube — Flat top.

A flat-below triangular groove inside the tube — Flat below.

6Smooth sloped sides

Smooth sloped sides (no steps) is on by default: a V, a round or a drawn slope is made as one smooth slope. Untick it and sloped sides are built from thin steps (0.1 mm when the slot is applied) - the way the tool also works where the body's wall changes along the slot, such as a tapered wall.

A V-groove made of thin steps — Off: thin steps.

The same V-groove with smooth sloped sides — On: smooth slopes.

7Slot or ridge

At the top of the panel: Slot (cut in) cuts the shape into the wall, Ridge (add) adds the same shape standing out of it. A Flat top ridge on the outside is a snap lip: its flat top holds a lid or a ring, and its slope underneath prints without supports.

A flat-top ridge 1.2 mm high standing out all the way round the outside of the tube — A flat-top ridge on the outside: a snap lip.

8Draw your own shape

Click Draw it on the cut… (or the Draw tile). The body is shown cut through in blue - draw a closed shape against one of its walls with the sketch tools (polyline, arcs, circles, rectangles, rounded corners…). Points snap to the cut's corners and to the 1 mm grid. The editor starts from the shape you were using, so you can also just change it. Use it and the shape runs all the way round the body along that wall - here a dovetail groove inside the tube.

The Draw the slot on the cut editor: the tube's wall cut through in blue and a dovetail shape drawn into the inside wall — The cut in blue, a dovetail drawn into the inside wall.

The drawn dovetail groove running all the way round the inside of the tube — The drawn shape all the way round.

A drawn slot is dragged in the view like the others; Change the drawing… opens it again.

9See the whole body

Untick Show the body cut open to see the whole body with the slot in it; tick it again to look inside.

The tube shown whole with the groove visible only from outside — Show the body cut open: off.

10Level, upright or at an angle

The second example is a box, 50 × 30 × 20 mm. A slot round it follows its outline, corners and all:

A box shown cut open with a square groove all the way round its outside — A groove round a box.

Level - round the body at one height.
Upright - round the body over the top and under the bottom.
At an angle - leaning by the Angle you type (−89 to 89°).
Cut through at - turns the cut, and with it an upright or leaning slot, round the body: type an angle or pick 0°, 45°, 90° or 135°.

An upright groove running over the top and under the bottom of the box — Upright.

The upright groove turned 90 degrees round the box — Upright, cut through at 90°.

A groove leaning at 30 degrees round the box — At an angle: 30°.

The Direction card with At an angle picked, the Angle field at 30 and the Cut through at chips — Direction, Angle and Cut through at.

11Apply it

Click Cut the slot (or Add the ridge). The body is changed in one step - Ctrl+Z / ⌘Z undoes it - and its colours are kept. Cancel (or Esc) leaves the body as it was.

The finished tube beside the box with a round groove leaning at 30 degrees all the way round it — Applied: the box with its leaning round groove, beside the tube (its dovetail groove is inside).

12Good to know

The slot follows the wall it is drawn against, at every height of the slot - it works on round, square and drawn outlines, and on imported STL files.
For an O-ring, make the groove a little narrower than the cord is thick, and its depth about 75-80 % of the cord.
A groove cut too deep into a thin wall would split the body: the panel warns you before you apply it.
Printed lying flat, a flat-top ridge's slope underneath needs no supports; a flat-below ridge is the one to print upside down.

Questions

How do I cut an O-ring groove inside a tube?

Select the tube, click Slot round body in the Body card, pick Inside and the Square shape, type the groove's width and depth and its height from the bottom, then click Cut the slot. The groove runs all the way round the inside wall.

Does it work on shapes that are not round?

Yes. The slot follows the wall it is drawn against, whatever its outline: a box, a hexagon, a heart, a drawn shape or an imported STL.

What is the difference between a slot and a ridge?

Slot (cut in) cuts the shape into the body's wall; Ridge (add) adds the same shape standing out of the wall. A ridge with a flat top on the outside makes a snap lip that prints without supports.

Can the slot go upright or at an angle?

Yes. Level runs round the body at one height, Upright runs over the top and under the bottom, and At an angle leans it by any angle you type. Cut through at turns it round the body.

Can I draw my own groove shape?

Yes. Click Draw it on the cut: the body is shown cut through in blue, and the shape you draw against one of its walls runs all the way round the body - a dovetail, a half round, anything closed.

A groove all the way round, in one click

Open the app, add a shape or import an STL, and click Slot round body in the Body card.

Open 3DPrintCAD

Also see: Basic shapes and body tools, Push / pull face tool, Hole pattern tool, Sketch tool and Box generator.