Holes look simple and are not. A single part can carry plain holes, counterbores, countersinks, precision holes and threaded holes, some of them through each other. RockCAM recognises all of them from the 3D model, and this page is where you change what it decided.
A part with several hole types highlighted — plain hole, counterbore, countersink, precision hole and threaded hole.
Further hole examples, including broken holes, stacked counterbores and intersecting holes.
RockCAM sorts holes into three families and handles each one in its own way:
- Precision holes — holes with a tolerance on the diameter.
- Threaded holes — holes that will be tapped.
- Plain holes — everything else, with no tolerance and no thread.
Any of the three may also have a counterbore or countersink, and that has to be machined too.
The general route down a hole is: spot, drill, mill the counterbore or countersink, ream where called for, finish the head, then finish the wall, ream it or tap it.
The hole machining method settings page where the route for each hole type is set.
How RockCAM recognises precision and threaded holes #
A 3D model carries no annotations, so RockCAM cannot read a note that says “tap M6”. It reads the diameter, and looks it up in a table.
If the diameter matches a threaded hole in the table, it is treated as threaded. If it matches a precision hole, it is treated as precision. Anything else is a plain hole.
That lookup is a guess, and sometimes it is wrong. To control it you have three options: edit the table, disable a row, or mark the hole with a colour.
The threaded hole table #
The threaded hole table with a row per thread size.
The default table covers M3 to M12, including the tools RockCAM uses for each. You can add rows and change the existing ones.
| Column | Meaning |
|---|---|
| Label | An identifier only. Write whatever is clear to you |
| Enabled | Whether this row is used. On means the size is recognised; off means it is not |
| Tap diameter | The tap RockCAM uses when it identifies this thread |
| Thread mill diameter | The thread mill RockCAM uses when it identifies this thread |
| Hole diameter | The diameter RockCAM uses to recognise the thread |
| Tolerance | How far the drawn diameter may deviate. A hole drawn at 5.05 mm can still be read as M6 |
| Chamfer C | A separate chamfer for the mouth of a threaded hole, which is usually different from a normal chamfer. It applies when the mouth has a sharp edge; a drawn chamfer face is followed exactly |
The precision hole table #
The precision hole table with a row per hole size.
The columns work the same way, with two differences.
| Column | Meaning |
|---|---|
| Label | An identifier only |
| Enabled | Whether this row is used |
| Reamer diameter | The reamer used, which is also the nominal hole diameter |
| Part allowance | The part allowance set on the reaming operation |
| Tolerance | How far the drawn diameter may deviate |
| Blank allowance | What the previous step leaves behind. If the previous step was drilling, the drill is one blank allowance smaller than the reamer; if it was hole milling, the milling leaves this much. Set it high enough not to break the reamer |
Case: a 5 mm hole could be a precision hole or a thread #
It can be either, and the tables cannot tell. Turn the 5 mm precision hole row off so the diameter is no longer read as a precision hole, then mark those holes by colour instead.
The precision hole table with the 5 mm row switched off and the colour-marking rule set.
With that in place, paint the wall of each precision hole in the chosen colour. The colour is configurable.
Case: a special hole that is not in the table #
Add it to the table first. RockCAM always looks the tool up in the table, whether the row is enabled or not. Make sure the diameter exists as a row and that a suitable tool is attached to it; only then will RockCAM machine the hole.
Case: it got it wrong #
The quickest route is often to let it run, look at the result, and correct the operations that are wrong. Editing the tables is worth it when the same mistake keeps coming back.
Choosing the machining method for precision holes #
A precision hole can be milled, reamed, or simply drilled to size. RockCAM ships with methods you can change.
The precision hole method table, read from the top down.
The table has three columns and is read top to bottom: when the hole diameter meets a condition, that method is used. The first row whose condition matches wins.
In the example below, holes over 6 mm are spotted, drilled, rough-milled and finish-milled; smaller holes are spotted, drilled and reamed. The break-point is 6 mm.
A precision hole machined spot, drill, ream after RockCAM read it from the table.
Threaded, counterbored and countersunk holes #
These use the same table format as precision holes, with the same top-down rule.
Spot drilling and drilling settings #
The spot drilling and drilling settings, with the depth and threshold fields.
Three values are worth understanding.
- Maximum spot depth. The deepest RockCAM will spot. It scales the spot down for smaller holes, so it never spots through.
- Drill floor allowance. For blind holes only. Adjusts the final drill depth —
-0.2drills 0.2 mm deeper than the model. - Hole-milling threshold. Above this diameter the hole is a large hole: RockCAM drills it with a smaller drill first, then rough-mills it. Below the threshold, a plain hole is drilled straight through with a drill of the same diameter.
The maximum spot depth field.
The drill floor allowance field.
The hole-milling threshold field.