NX CAM Essentials for Beginners: Episode 8 — Drilling Cycles & Hole-Making Operations (Updated May 2026) (Updated May 2026)

Here's something most NX CAM tutorials gloss over: drilling cycles and hole-making operations account for 40 to 60 percent of actual machining time on the most common industrial parts — engine blocks, transmission housings, cylinder heads, structural brackets. At Bajaj Auto's Waluj plant (Plot G-137, MIDC Waluj) or Endurance Technologies at E-92, the CNC programmers who know their hole-making operations cold are genuinely more valuable than generalists who can cavity-mill but fumble when it comes to tapping sequences, boring bars or counterbore cycles. The AURIC investment of ₹71,343 crore with 62,405 confirmed jobs at Marathwada's manufacturing cluster means there are more machining centres running hole-making operations in this corridor than ever before. Episode 8 covers everything: spot drilling, peck drilling, reamers, boring, counterbore, countersink, and tapping — the complete hole-making toolkit in Siemens NX CAM, with the practical details that actually matter on the shop floor.

Hole-Making Operations in NX CAM: An Overview of the Full Toolkit

NX CAM's Hole Making operation type covers all hole-making operations in a unified programming environment. The available subtypes are: Drilling (for through and blind holes using standard drill bits); Spot Drilling (for creating a precise starting indentation before the main drill); Peck Drilling (for deep holes where chip evacuation requires periodic retract cycles); Reaming (for finishing holes to tight diameter tolerances after drilling); Boring (for high-precision holes using single-point boring bars); Counterbore (for creating a flat-bottomed recess around a hole for bolt heads); Countersink (for a tapered recess at the hole entrance for flat-head screws); and Tapping (for cutting internal threads using a tap). Each of these subtypes produces a specific canned cycle in the output G-code (G81 for drilling, G83 for peck drilling, G84 for tapping, G85 for reaming and so on) — but you don't need to memorise the G-code numbers because NX handles the mapping. What you need to understand is when to use each cycle and what the key parameters mean.

Spot Drilling and Center Drilling: Starting Every Hole Correctly

Every drilled hole should start with either a spot drill or a centre drill operation. Here's why: a standard drill bit has a flexible tip that will wander when it first touches a flat metal surface — the drill walks sideways before it starts cutting, creating a hole whose centre position is off by 0.1–0.3mm. A spot drill creates a precise conical indentation at the exact target position. The drill tip then seats into this conical guide and starts cutting directly on centre, dramatically improving positional accuracy. In NX CAM, create a Spot Drilling operation first in your operation sequence. Set the depth to approximately 60–70 percent of the drill diameter (enough to guide the main drill but not so deep it creates an oversized chamfer). The spot drill tool diameter should be larger than the main drill — typically 1.5 to 2 times the drill diameter. For position-critical holes (dowel pin holes, precision bearing seats) where positional tolerance is ±0.05mm or tighter, spot drilling is mandatory. At plants like Endurance Technologies and Bajaj Auto, position-critical hole sequences are called out explicitly in the component drawing and the CNC programmer is responsible for including the spot drill step.

NX CAM Operation	G-Code Cycle	Typical Tolerance	Use When
Spot Drilling	G81	Position guide only	Before every drilled hole
Peck Drilling	G83	H12–H13 (±0.1mm)	Depth > 3× drill diameter
Reaming	G85	H7 (±0.018mm)	Bearing seats, dowel pins
Fine Boring	G76	H6 or better	High-precision fits
Rigid Tapping	G84	6H thread tolerance	Internal threaded holes

Peck Drilling and Deep Hole Drilling: Controlling Chip Evacuation

Peck drilling is the cycle you use when the hole depth exceeds approximately three times the drill diameter. The problem with drilling deep holes without pecking is chip evacuation: as the hole gets deeper, chips pack up in the flutes of the drill bit, the cutting edge stops cutting cleanly, and heat builds up rapidly. This leads to broken drills, rough hole surfaces and hole oversizing. Peck drilling solves this by periodically retracting the drill to clear chips. In NX CAM, the key peck drilling parameters are: Peck Depth (how far the drill advances per peck — typically 1 to 2 times the drill diameter for normal materials, 0.5 to 1 times for tough alloys like stainless steel or titanium); Retract Amount (how far back the drill retracts to clear chips — full retract for very deep holes, partial retract for moderate depths); and Feed Rate Reduction Factor for the final peck (most programmers reduce feed by 20–30% for the last peck approaching full depth). For cast iron engine blocks and aluminium transmission cases — the most common materials at Bajaj Waluj and Endurance — standard peck depths of 1 to 1.5 times drill diameter with full retract work reliably.

Reaming and Boring: When You Need Tight Tolerance Holes

Drilled holes have tolerances in the H12–H13 range (IT grade) — typically ±0.1mm or worse on diameter. When you need an H7 tolerance hole (±0.018mm for a 10mm hole), which is what bearing seats, dowel pins and precision bushes require, you need to ream or bore after drilling. Reaming uses a multi-flute reamer tool run at slow feed rate after a drill undersizes the hole by 0.2–0.3mm (leave stock for the reamer). In NX CAM, create a Reaming operation after your drilling operation, select the same hole features, set the spindle speed to roughly half the drilling speed and feed rate to 25–50 percent of drilling feed. Boring with a single-point boring bar gives even tighter tolerances (H6 or better) and is adjustable — the boring bar diameter can be fine-tuned to hit the exact target diameter. NX CAM's Boring operation requires you to specify both the approach and retract moves carefully — boring bars must retract without touching the hole wall, which requires an orient-spindle-then-shift retract move (called a Back Boring or Fine Boring cycle in most controllers). At Skoda VW Shendra and Toyota Kirloskar component plants, fine boring is standard for all bearing seat holes.

Tapping and Thread Milling in NX CAM: Producing Internal Threads

Tapping is the most unforgiving hole-making operation in CNC machining — if something goes wrong, you typically end up with a broken tap inside your part, which is extremely difficult to remove and often scraps the workpiece. The critical parameter in NX CAM tapping is the feed rate, which must equal the spindle speed (RPM) multiplied by the thread pitch: Feed (mm/min) = RPM × Pitch (mm/rev). For an M10×1.5 tap at 200 RPM, the feed must be exactly 200 × 1.5 = 300 mm/min. If your machine controller synchronises the spindle and feed automatically (rigid tapping, available on most modern Fanuc and Siemens 840D machines), NX CAM sets this up correctly with the G84 rigid tapping cycle. If your machine uses floating tap holders (older equipment), the feed rate must be set manually and the holder compensates for small discrepancies. In NX CAM, always verify the tapping feed calculation in the Tool Path Information panel before generating G-code. Thread milling is an alternative to tapping for difficult materials (hardened steel, titanium) — it uses a thread mill tool in a helical interpolation path and is safer because a broken thread mill doesn't get stuck in the part.

NX CAM's Hole Making Feature: Auto-Recognition and Batch Programming

NX CAM's Hole Making Feature Recognition is one of the most useful productivity tools in the software for parts with many holes — engine blocks with 50-plus holes, structural brackets with 20-plus fastener holes. Enable Feature-Based Machining in the Manufacturing Navigator and NX will automatically scan your part model, identify all hole features (diameters, depths, types — counterbore, countersink, through, blind), and group them by type. You then assign operations to feature groups rather than selecting individual holes one by one. A 50-hole part that would take 2 hours to program manually can be processed in 20–30 minutes with Feature Recognition. The key caution: always verify that Feature Recognition has correctly identified all holes and their depths — complex parts with intersecting features sometimes confuse the recognition algorithm. Check the Feature View in the Manufacturing Navigator and compare against the drawing before generating tool paths. At Bajaj Auto and Endurance, large parts with many holes are always programmed with Feature Recognition as standard practice to reduce programming time and errors.

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FAQs

What is the difference between drilling and reaming in CNC machining?

Drilling creates the hole using a two-flute drill bit — it's fast but produces relatively rough hole surfaces (Ra 1.6–6.3 microns) and tolerances in the H12–H13 IT grade range (typically ±0.1mm or more on diameter). Reaming uses a multi-flute reamer run at low speed and feed after a drill undersizes the hole by 0.2–0.3mm. Reaming produces smooth hole surfaces (Ra 0.4–1.6 microns) and tight tolerances (H7, ±0.018mm for a 10mm hole). Use reaming whenever the drawing specifies an H7 or tighter tolerance on a hole — bearing seats, precision dowel pin holes, and bushing bores all typically require reaming after drilling.

Why is peck drilling used for deep holes in NX CAM?

Deep holes — deeper than about three times the drill diameter — accumulate chips in the flutes faster than the drill can clear them during continuous cutting. The packed chips cause excessive heat, tool wear, drill breakage and rough, oversized holes. Peck drilling solves this by periodically retracting the drill out of the hole to clear chips, then re-entering for the next depth increment. The peck depth (how far the drill advances per peck) is typically 1–2 times the drill diameter. In NX CAM, set this in the Cycle Parameters section of the Peck Drilling operation. Most Fanuc and Siemens 840D controllers support peck drilling via the G83 canned cycle.

How do I set the correct feed rate for tapping in NX CAM?

The feed rate for tapping must exactly equal the spindle speed multiplied by the thread pitch: Feed (mm/min) = RPM × Pitch (mm/rev). For an M12×1.75 thread tapped at 150 RPM, the feed must be 150 × 1.75 = 262.5 mm/min. In NX CAM, when you select Tapping as the operation subtype and specify the thread pitch in the tool data, the software automatically calculates and sets the correct feed rate. Always verify this calculation in the Tool Path Information panel. For rigid tapping (recommended for modern machines), the G84 canned cycle synchronises spindle and feed automatically — but the values you specify in NX must still be correct.

What is Feature Recognition in NX CAM and how does it speed up programming?

Feature Recognition (Feature-Based Machining) in NX CAM automatically scans your 3D part model and identifies all hole features — drilling, counterbore, countersink, threaded holes — including their diameters, depths and types. Instead of manually selecting each hole when creating an operation, you assign operations to feature groups (all M8 threaded holes, all 10mm through holes) and NX generates tool paths for the entire group at once. For parts with 20-plus holes, this can reduce programming time from 2–3 hours to 20–30 minutes. Enable it in Manufacturing Navigator → Feature View. Always verify the recognised features against the engineering drawing before generating G-code, as complex geometry can occasionally confuse the recognition algorithm.