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Machining

bitbybit.occt.parts.mechanical.machining cuts the features a part needs to take standard parts: a thread for a screw, a keyway for a key, a groove for a retaining ring, a spline or a knurl, a flat for a set screw. Standard parts explains the standards, units and frames they share.

A cut, or the tool that makes it​

Each feature comes in two forms. keyway cuts a keyway into the shaft you give it and returns a new solid, leaving the one you gave as it was; keywayTool makes the solid a keyway removes, without cutting anything. Subtracting the tool with bitbybit.occt.booleans.difference gives the same result as the cut, so use the tool to cut several bodies at once, to show the material a feature takes away, or to cut through a boolean of your own:

const shaft = await bitbybit.occt.shapes.solid.createCylinder({ radius: 10, height: 60, center: [0, 0, 0], direction: [0, 1, 0] });
const tool = await bitbybit.occt.parts.mechanical.machining.din.keywayTool({ diameter: 20, length: 20, frame: { origin: [0, 30, 0], normal: [0, 1, 0], direction: [1, 0, 0] } });
const cut = await bitbybit.occt.booleans.difference({ shape: shaft, shapes: [tool], keepEdges: false });

A tapped hole​

Here an M8 thread is tapped into a block, its hole drilled through at the tap drill size the thread table gives; in Rete and Blockly, bitbybit.json.getValueOnProp reads the tapDrill out of the table's answer:

Bitbybit Platform

A tapped M8 hole in Rete

rete logoRete
Script Source (rete)
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        "size": "M8",
        "unit": "mm"
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      "inputs": {},
      "position": [
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    "tapDrill": {
      "id": "tapDrill",
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      "position": [
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    },
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      "id": "block",
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      "id": "drilled",
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        "diameter": 1,
        "depth": 0,
        "tipAngle": 0
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      "inputs": {
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        "diameter": {
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              "node": "tapDrill",
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        }
      },
      "position": [
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    },
    "tapped": {
      "id": "tapped",
      "name": "bitbybit.occt.parts.mechanical.machining.iso.thread",
      "customName": "thread",
      "async": true,
      "drawable": true,
      "data": {
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        "size": "M8",
        "length": 12,
        "internal": true,
        "unit": "mm"
      },
      "inputs": {
        "shape": {
          "connections": [
            {
              "node": "drilled",
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    "view": {
      "id": "view",
      "name": "bitbybit.babylon.scene.adjustActiveArcRotateCamera",
      "customName": "adjust active arc rotate camera",
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      "drawable": false,
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An M8 thread has a coarse pitch of 1.25 millimetres and a tap drill of 6.8. The thread's frame sits at the hole's mouth with its normal pointing out of the part, and the thread runs into the part against it.

Threads​

bitbybit.occt.parts.mechanical.machining.iso.thread models an ISO metric thread and bitbybit.occt.parts.mechanical.machining.ansi.thread a Unified inch thread, instead of the plain face a cosmetic thread leaves. On a shank, turned to the thread's nominal diameter, it cuts the outside thread; with internal on, in a hole drilled to the minor diameter, it cuts the thread of a nut. The thread starts at its frame, at a hole's mouth or under a head, and runs length into the part, at most 400 turns of the pitch. iso.thread takes the size's coarse pitch unless pitch names a fine one, and ansi.thread takes series, coarse (UNC) or fine (UNF). threadTool, in both standards, is the 60 degree groove a thread removes, swept along a right-hand helix.

bitbybit.engineering.mechanical.threads.iso.thread gives a metric thread's nominal, pitch and minor diameters, its pitch, the minor diameter of the internal thread and the drill for tapping it: M8 has a pitch of 1.25 and a 6.8 tap drill. bitbybit.engineering.mechanical.threads.ansi.thread does the same for inch threads, 1/4 UNC having 20 threads per inch and a 0.201 inch tap drill; threadsPerInch gives a pitch of its own, a UN thread. The fasteners cut the same thread when modelledThread is on.

Keyways​

bitbybit.occt.parts.mechanical.machining.din.keyway cuts a DIN 6885 keyway and bitbybit.occt.parts.mechanical.machining.ansi.keyway an ANSI B17.1 keyseat, sized for a shaft or bore of diameter. Into a shaft it is the round-ended pocket a key sits in, length from end to end; with inHub on, it is the straight keyway cut through a hub's bore. It starts on the axis at the frame's origin, runs length along the normal and faces the frame's direction. keywayTool, in both standards, is the solid it removes. The keys that fit them, and the depths they sit at, are on their own page.

Retaining ring grooves​

bitbybit.occt.parts.mechanical.machining.din.ringGroove cuts the groove of a DIN 471 ring into a shaft or of a DIN 472 ring into a bore, by kind, and bitbybit.occt.parts.mechanical.machining.ansi.ringGroove the groove of an inch tapered ring. The groove starts on the axis at the frame's origin and runs its width along the normal, so a retaining ring given the same frame sits in it. ringGrooveTool, in both standards, is the solid the groove removes.

Splines​

  • bitbybit.occt.parts.mechanical.machining.din.splinedShaft makes a DIN 5480 involute splined shaft, its teeth at 30 degrees, from the referenceDiameter the spline is named by and its module, both in millimetres as the standard names them: W 25x1.25x18 is a reference diameter of 25 and a module of 1.25.
  • bitbybit.occt.parts.mechanical.machining.ansi.splinedShaft makes an ANSI B92.1 splined shaft from its teeth, 6 to 60, and its pitch, such as 16/32, its teeth at 30 degrees with a flat root.
  • splinedHub, in both standards, cuts the matching spline through a hub, and splinedHubTool is the solid it removes. A shaft starts at its frame's origin and runs along the normal, a tooth pointing along the frame's direction.

bitbybit.engineering.mechanical.splines.din.involuteSplineSizes gives a DIN 5480 spline's teeth, profile shift and the shaft's and hub's tip and root diameters: 25 by 1.25 has 18 teeth, the shaft 24.75 across its tips and the hub 22.5 across its own. bitbybit.engineering.mechanical.splines.ansi.involuteSplineSizes gives an ANSI B92.1 spline's pitch diameter, module, and the shaft's and hub's major and minor diameters: 24 teeth of 16/32 have a 1.5 inch pitch diameter.

Knurls​

bitbybit.occt.parts.mechanical.machining.din.knurl knurls a round shaft to DIN 82, its pitch 0.5 to 1.6 millimetres, and bitbybit.occt.parts.mechanical.machining.ansi.knurl to ASME B94.6, by diametralPitch, 64, 96, 128 or 160 teeth to an inch of diameter. pattern is straight, left or right (diagonal) or diamond, where the grooves cross; a diagonal or diamond knurl's grooves twist through at most 1000 degrees along its length, and a diamond on a long knurl is heavy to build. The crests sit on the diameter nearest the one given that the pitch divides into whole teeth. knurlTool, in both standards, is the solid the knurl removes.

bitbybit.engineering.mechanical.knurls.din.knurlSizes works out how many grooves fit, the diameter that makes them divide the circumference evenly, their depth and their angle to the axis: 19.6 millimetres at a pitch of 0.8 takes 77 grooves on 19.608, so turn the shaft to 19.608 before knurling. bitbybit.engineering.mechanical.knurls.ansi.knurlSizes does the same to B94.6: 1/2 inch at 96 DP takes 48 grooves, 0.016 deep.

Flats​

bitbybit.occt.parts.mechanical.machining.flat cuts a flat into a round shaft of diameter, such as the D flat a set screw bears on: everything beyond a plane depth in from the surface, for length along the axis. It starts on the axis at the frame's origin, runs along the normal and faces the frame's direction. bitbybit.occt.parts.mechanical.machining.flatTool is the solid the flat removes.

FunctionWhat it does
ansi.keywayCuts an ANSI B17.1 keyseat into a shaft or through a hub, as keywayTool places it.
ansi.keywayToolMakes the solid an ANSI B17.1 keyseat removes: the round-ended pocket milled into a shaft, or the straight keyseat cut through a hub's bore, sized for the diameter.
ansi.knurlKnurls a round shaft, as knurlTool places the knurl.
ansi.knurlToolMakes the solid an ASME B94.6 knurl removes from a round shaft: diametral pitch teeth at the standard's depth, straight, diagonal at 30 degrees or crossing in a raised diamond.
ansi.ringGrooveCuts the groove of an inch tapered retaining ring into a shaft or a bore, as ringGrooveTool places it; parts.mechanical.retainingRings.ansi.retainingRing at the same frame sits in it.
ansi.ringGrooveToolMakes the solid the groove of an inch tapered retaining ring removes from a shaft or a bore: as wide as the groove, down to its diameter.
ansi.splinedHubCuts an ANSI B92.1 spline through a hub, as splinedHubTool places it.
ansi.splinedHubToolMakes the solid an ANSI B92.1 hub spline removes: the shaft's flanks, with the hub's tip and root diameters, so the shaft of the same size slides into the cut.
ansi.splinedShaftMakes an ANSI B92.1 involute splined shaft: its teeth at 30 degrees with a flat root, sized from the number of teeth and the pitch, length long.
ansi.threadModels a Unified inch thread on a shank or in a hole, as threadTool places it, instead of the cosmetic thread parts.mechanical.fasteners.ansi draws.
ansi.threadToolMakes the solid a Unified inch thread removes: the 60 degree groove swept along a right-hand helix.
din.keywayCuts a DIN 6885 keyway into a shaft or through a hub, as keywayTool places it.
din.keywayToolMakes the solid a DIN 6885 keyway removes: the round-ended pocket milled into a shaft, or the straight keyway cut through a hub's bore, sized for the diameter.
din.knurlKnurls a round shaft, as knurlTool places the knurl.
din.knurlToolMakes the solid a DIN 82 knurl removes from a round shaft: 90 degree grooves half the pitch deep, straight, helical at 30 degrees or crossing in a raised diamond.
din.ringGrooveCuts the groove of a DIN 471 or DIN 472 retaining ring into a shaft or a bore, as ringGrooveTool places it; parts.mechanical.retainingRings.din.retainingRing at the same frame sits in it.
din.ringGrooveToolMakes the solid the groove of a DIN 471 or DIN 472 retaining ring removes from a shaft or a bore: as wide as the groove, down to its diameter.
din.splinedHubCuts a DIN 5480 spline through a hub, as splinedHubTool places it.
din.splinedHubToolMakes the solid a DIN 5480 hub spline removes: the shaft's flanks, with the hub's tip and root diameters, so the shaft of the same size slides into the cut.
din.splinedShaftMakes a DIN 5480 involute splined shaft: its teeth at 30 degrees, sized from the reference diameter and the module, length long.
flatCuts a flat into a round shaft, as flatTool places it, such as the D flat a set screw bears on.
flatToolMakes the solid a flat on a round shaft removes: everything beyond a plane depth in from the surface, along length.
iso.threadModels an ISO metric thread on a shank or in a hole, as threadTool places it, instead of the cosmetic thread parts.mechanical.fasteners.iso draws.
iso.threadToolMakes the solid an ISO metric thread removes: the 60 degree groove swept along a right-hand helix.
FunctionWhat it does
ansi.sizesLists the Unified inch thread sizes the tables hold, from #0 to 1 inch.
ansi.threadGives a Unified inch thread by its size and series: the nominal, pitch and minor diameters, the pitch, the internal thread's minor diameter and the drill for tapping it.
iso.sizesLists the ISO metric thread sizes the tables hold, from M1.6 to M24.
iso.threadGives an ISO metric thread by its size: the nominal, pitch and minor diameters, the pitch, the internal thread's minor diameter and the drill for tapping it.
FunctionWhat it does
ansi.involuteSplineSizesWorks out an ANSI B92.1 involute spline from its teeth and pitch: its pitch diameter and module, and the major and minor diameters of the shaft and the hub.
din.involuteSplineSizesWorks out a DIN 5480 involute spline from its reference diameter and module: its teeth, profile shift, and the shaft's and the hub's tip and root diameters.
FunctionWhat it does
ansi.knurlSizesWorks out a diametral pitch knurl's grooves on a cylinder: how many, the diameter they track on, how deep B94.6 presses them and their angle to the axis.
din.knurlSizesWorks out a knurl's grooves on a cylinder: how many fit at the pitch, the diameter that makes them divide it evenly, their depth and their angle to the axis.