MACHFEAT draws the machined features that fill a mechanical detail, at any diameter, depth and rotation: drilled, tapped, counterbore, countersink, a tapped hole in plan, and a dowel pin with chamfered ends. FINISHMARK places the surface roughness symbol, which AutoCAD has never had a native equivalent for.
What MachineFeature does
Three layers are created on first use and left alone afterwards: MACHFEAT-OBJECT for the cut outline, MACHFEAT-HIDDEN for thread envelopes in HIDDEN linetype, and MACHFEAT-CENTRE for hole centrelines in CENTER linetype.
How to use it
- Load the routine with
APPLOAD, or put it on your support file search path. - Type
MACHFEAT. - Choose the feature type.
- Give the diameter, depth and rotation, and pick the position.
- Type
FINISHMARKto place a surface roughness symbol.
How it works
The drill point is not decoration. The cone at the bottom of a drilled hole is where the drill actually stops, and a detail that omits it or draws it flat will be queried by whoever machines the part.
It is drawn at a 120° included angle, the conventional approximation of the 118° standard twist drill point and the one every drawing office uses. That gives the point a height of radius × tan 30°, which is why the slant length works out as radius ÷ cos 30° — one constant, 0.866025, used in three of the six features.
Depth is measured to the full diameter, not to the tip. That is how a drilled depth is specified and inspected. The point is then added below it.
The tap drill is 84% of the thread outside diameter, which is about right for a coarse thread across the common sizes. The thread envelope is drawn over it in hidden line, stopping one sixteenth short of the drill depth — threads never run to the bottom of a hole, because the tap has a lead.
Notes and limits
- Depth is to the full diameter, with the point below it. Specify it the way it is inspected.
- The tap drill is a coarse-thread approximation. For a fine thread, check it against a tapping drill chart.
- The three layers are created once and not touched again, so your linetypes survive.
- One undo group per feature.
Download and details
| Name | MachineFeature — machined hole features in section, at any size |
| Download | MachineFeature.lsp — 20.9 KB, plain AutoLISP source. Downloads directly; no zip to unpack. |
| Type | AutoCAD AutoLISP routine |
| Commands | FINISHMARK, MACHFEAT |
| Requires | nothing beyond a CAD platform with AutoLISP. |
| Source size | 20.9 KB, 487 lines |
| Error handling | Yes — a *error* handler restores every system variable it changed, on cancel as well as on error. |
| Undo | The whole operation is wrapped in a single undo group, so one U reverses all of it. |
| Compatibility | AutoCAD (any release with AutoLISP), BricsCAD, ZWCAD, GstarCAD, ProgeCAD and other IntelliCAD-based platforms. AutoCAD LT needs a LISP enabler. No .NET, no ObjectARX, no installer. |
| Author | YZ, August 2026 |
| Licence | Free to use, supplied “as is” with no warranty. |
References
- ISO metric tap and die chart — drill sizes and pitches for tapped holes
- Standard hole and slot sizes — AISC nominal hole dimensions
- SCREWTHREAD LISP — drawing the thread itself
- More free AutoLISP routines on this site
- Wisey’s Steel Shapes — free structural steel section drawing program