# AutoCAD 3D exercise: a bearing block > Model a bearing block in AutoCAD 3D: extrude, unite, then subtract a bore and two bolt holes as cylinders, solved step by step. Practise 3D solids free online. Model this bearing block, in millimetres: a base 100 by 60 with corners of radius 10, 12 thick; a boss of 40 across standing 40 high in the middle; a bore of 20 through the boss and two bolt holes of 10 through the base, 76 apart. The base and the boss are extruded from their outlines and united into one solid; the bore and the holes are cylinders subtracted from it. - **Exercise:** Advanced · Mechanical · 3D solid - **Commands:** [`RECTANG`](https://mellowcad.com/docs/commands/rectang.md), [`CIRCLE`](https://mellowcad.com/docs/commands/circle.md), [`EXTRUDE`](https://mellowcad.com/docs/commands/extrude.md), [`UNION`](https://mellowcad.com/docs/commands/union.md), [`CYLINDER`](https://mellowcad.com/docs/commands/cylinder.md), [`COPY`](https://mellowcad.com/docs/commands/copy.md), [`SUBTRACT`](https://mellowcad.com/docs/commands/subtract.md), [`-VIEW`](https://mellowcad.com/docs/commands.md#-view), [`VSCURRENT`](https://mellowcad.com/docs/commands/vscurrent.md), [`ZOOM`](https://mellowcad.com/docs/commands/zoom.md) - **In the editor:** [Open it with its drawing](/draw?drawing=bearing-block), dimensioned beside where you draw yours ## The drawing The bearing block in plan, 100 by 60, its boss, bore and holes dimensioned. The bearing block as a solid, seen from the south-east in the Conceptual visual style. ## Step by step The engine draws each step and writes its history as you would type it: the prompts in AutoCAD 2027's order, with the same option letters. After a command's first point, a typed point is measured from the last one, as dynamic input measures it, and the history writes it with @; \# measures from the origin. ### 1. Draw the plan On the Outline layer, [`RECTANG`](https://mellowcad.com/docs/commands/rectang.md) with a `Fillet` of `10`, from `0,0` to `100,60`, and a circle at its centre, `50,30`, with a `Diameter` of `40`. 1. Draw the plan ```text Command: RECTANG Specify first corner point or [Chamfer/Elevation/Fillet/Thickness/Width]: F Specify fillet radius for rectangles <0.00>: 10 Specify first corner point or [Chamfer/Elevation/Fillet/Thickness/Width]: 0,0 Specify other corner point or [Area/Dimensions/Rotation]: @100,60 Command: CIRCLE Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: 50,30 Specify radius of circle or [Diameter]: D Specify diameter of circle: 40 ``` ### 2. Extrude the base and the boss [`EXTRUDE`](https://mellowcad.com/docs/commands/extrude.md) the outline `12` high, then the circle `40` high: two solids. 2. Extrude the base and the boss ```text Command: EXTRUDE Current wire frame density: ISOLINES=4, Closed profiles creation mode = Solid Select objects to extrude or [MOde]: 1 found Select objects to extrude or [MOde]: Specify height of extrusion or [Direction/Path/Taper angle/Expression]: 12 Command: EXTRUDE Current wire frame density: ISOLINES=4, Closed profiles creation mode = Solid Select objects to extrude or [MOde]: 1 found Select objects to extrude or [MOde]: Specify height of extrusion or [Direction/Path/Taper angle/Expression] <12.00>: 40 ``` ### 3. Unite them [`UNION`](https://mellowcad.com/docs/commands/union.md): pick both and press Enter. They are one solid. 3. Unite them ```text Command: UNION Select objects: 1 found Select objects: 1 found, 2 total Select objects: ``` ### 4. Draw the cylinders The bore and a bolt hole as cylinders, with [`CYLINDER`](https://mellowcad.com/docs/commands/cylinder.md): the bore at `50,30`, `Diameter` `20` and `40` high; a bolt hole at `12,30`, diameter `10` and `12` high. Then [`COPY`](https://mellowcad.com/docs/commands/copy.md) the hole from `12,30` to `76,0` further on. 4. Draw the cylinders ```text Command: CYLINDER Specify center point of base or [3P/2P/Ttr/Elliptical]: 50,30 Specify base radius or [Diameter]: D Specify diameter: 20 Specify height or [2Point/Axis endpoint] <40.00>: 40 Command: CYLINDER Specify center point of base or [3P/2P/Ttr/Elliptical]: 12,30 Specify base radius or [Diameter] <10.00>: D Specify diameter <20.00>: 10 Specify height or [2Point/Axis endpoint] <40.00>: 12 Command: COPY Select objects: 1 found Select objects: Current settings: Copy mode = Multiple Specify base point or [Displacement] : 12,30 Specify second point or : @76,0 Specify second point or [Exit/Undo] : ``` ### 5. Subtract them [`SUBTRACT`](https://mellowcad.com/docs/commands/subtract.md): pick the block and press Enter, then the three cylinders and Enter. The bore and the holes go through. 5. Subtract them ```text Command: SUBTRACT Select solids, surfaces, and regions to subtract from .. Select objects: 1 found Select objects: Select solids, surfaces, and regions to subtract .. Select objects: 1 found Select objects: 1 found, 2 total Select objects: 1 found, 3 total Select objects: ``` ### 6. Turn the view `-VIEW` and `SEIso`, [`VSCURRENT`](https://mellowcad.com/docs/commands/vscurrent.md) and `Conceptual`, then [`ZOOM`](https://mellowcad.com/docs/commands/zoom.md) `Extents` and 0.8x to frame it. 6. Turn the view ```text Command: -VIEW Enter an option [Orthographic]: SEI Regenerating model. Command: VSCURRENT Enter an option [2dwireframe/Hidden/Conceptual] <2dwireframe>: C Command: ZOOM Specify corner of window, enter a scale factor (nX or nXP), or [All/Extents/Previous/Scale/Window/Object]: E Command: ZOOM Specify corner of window, enter a scale factor (nX or nXP), or [All/Extents/Previous/Scale/Window/Object]: 0.8x ``` ## More exercises - [AutoCAD exercise: a gasket](https://mellowcad.com/docs/exercises/gasket.md): Beginner · Mechanical · 2D - [AutoCAD exercise: an L bracket](https://mellowcad.com/docs/exercises/l-bracket.md): Beginner · Mechanical · 2D - [AutoCAD exercise: stairs in plan](https://mellowcad.com/docs/exercises/stairs.md): Beginner · Architecture · 2D - [AutoCAD practice exercises](https://mellowcad.com/docs/exercises.md)