Quick-Change Gundrill — Head-Exchangeable Setup Guide

A contract shop machining 300 mm deep gun-drilled holes in hydraulic components once spent 45 minutes every tool change — removing the gundrill from the spindle, transporting it to the tool crib, brazing a new carbide tip, resetting tool overhang, and re-qualifying the first part. Switching to a head-exchangeable gundrill system cut that cycle to under two minutes per change, eliminated the brazing station entirely, and reduced per-hole cost by 34 %. The shop recovered the tooling premium in under 90 days.

The Problem — Why Conventional Gundrill Changeover Is Expensive ​

Traditional brazed-carbide gundrills are monolithic tools: a solid carbide tip is silver-brazed onto a steel shank. When the tip wears or breaks, the entire tool must be pulled from the machine, the old tip cut off, a new tip brazed, the tool reset to length, and the spindle re‑qualified. This sequence costs 30–60 minutes of machine downtime per event, requires skilled brazing labour, and introduces quality variability from manual resetting.

In high‑volume production — automotive fuel injectors, hydraulic manifold blocks, mould cooling channels — a single operator may change tools 3–5 times per shift. The cumulative downtime directly erodes OEE (Overall Equipment Effectiveness). Head‑changeable gundrill systems were developed to eliminate this waste.

ISCAR CHAMGUN — The Pioneer Quick-Change Gundrill ​

ISCAR's CHAMGUN system introduced the "no‑setup‑time" concept to gundrilling. The key innovation is a mechanical pocket at the tip of the steel shank that accepts pre‑set carbide drill heads. The head is clamped and released using a polyamide plastic key — no wrenches, no torque settings, no brazing.

Technical specifications:

• Diameter range: 9.8–16.19 mm
• Depth capability: up to 30×D
• Hole tolerance: IT7–IT9
• Surface finish: Ra 0.4–1.6 µm
• Head replacements per pocket: ≥ 15
• Head regrinds: up to 10 times (until length < L‑D)

A single CHAMGUN drill body can carry multiple heads with different geometries and chipbreaker profiles, allowing the same tool to cut steel, stainless, cast iron, and aluminium simply by snapping on the appropriate head. The pocket‑to‑tube connection uses a welded design that delivers high torque resistance without brazing.

Each head is pre‑set to the correct diameter (within a 0.2–0.3 mm window per body). The operator changes heads while the shank remains in the spindle — no tool removal, no overhang resetting, no first‑part qualification. Typical change time: 30–90 seconds.

TaeguTec WIN-GUN — Two-Effective-Edge Design ​

TaeguTec's WIN-GUN (designation TCDGN) takes a different approach. Instead of a single cutting edge (as in conventional gundrills), it uses a two‑effective‑edge head design that distributes cutting forces across two symmetrically arranged cutting edges.

Technical specifications:

• Diameter range: 10.0–25.0 mm
• Depth capability: 12×D and higher
• Shank types: Weldon and cylindrical
• Cutting edges: 2‑effective‑edge design
• Feed improvement: 2–5× higher than brazed gundrills
• Head system: standard DRILL‑RUSH compatible

The two‑edge geometry provides better dynamic balance, reduces vibration, and improves chip splitting — each edge produces smaller, more manageable chips than a single‑edge tool operating at the same feed. This translates directly to higher feed rates (2–5× vs. brazed equivalents) without sacrificing hole quality or tool life.

WIN‑GUN heads are compatible with horizontal machining centres, lathes, multitask machines, and dedicated gundrill machines. Coolant delivery is mandatory — either emulsion or oil — and the recommended procedure specifies a 1×D pilot hole followed by uninterrupted feed (no pecking) with maximum coolant flow.

Indexable Insert Gundrills — Protool PG211 and Tungaloy DeepTri-Drill ​

Between head‑exchangeable systems and monolithic brazed tools lies the indexable insert gundrill — a steel body with one or more replaceable carbide inserts and guide pads. These systems trade the quick‑change speed of a head‑exchangeable system for even lower per‑edge cost.

Protool PG211:

• Diameter range: 11.5–40.0 mm
• Drilling length: up to D×250 (5,000 mm maximum)
• Head adjustment: 0.2 mm range
• Tolerance: up to IT7
• Production volume: 1,500 pieces/month

Tungaloy DeepTri‑Drill:

• Diameter range: 8–40 mm
• Depth capability: up to 45×D
• Insert grades: AH9130 PVD (AlCrSiN‑TiAlN coating)
• Three cutting edges per insert

Indexable insert gundrills excel in mid‑volume production where a single head geometry runs for extended periods. The insert is indexed or replaced in under a minute using a standard torque wrench, but the drill body must be retracted from the hole to access the pocket — still faster than brazing, slower than head‑exchangeable.

BTA and Ejector Quick-Change Systems — UNISIG UNI-50BTA ​

Quick‑change technology is not limited to gundrills. BTA and ejector drilling systems have their own changeover challenges: swapping between BTA and gundrill tooling on a dual‑purpose machine traditionally required dismantling the pressure head, changing coolant seals, and re‑aligning the guide bushing — a process taking several hours.

UNISIG's UNI‑50BTA machine solves this with a revolutionary pressure head design that allows tool change without dismantling:

Specifications:

• Diameter range: 8–65 mm (both BTA and gundrill)
• Depth ratio: 100:1 or greater
• Max depth: up to 3,000 mm (modular lengths)
• Changeover time: as low as 10 minutes (vs. 2–4 hours traditional)
• Features: counter‑rotation, preloaded ballscrews, zero‑endplay spindles

The UNI‑50BTA enables a single machine to drill BTA or gundrill tooling in the same setup — even on the same part — without secondary operations. For contract shops that run both gundrill and BTA work, this dual‑system capability eliminates the capital cost of a second machine while maintaining changeover times under 15 minutes.

Replaceable BTA drill heads (botek range, Ø7.76–500 mm) use threaded connections — single‑start or quadruple‑start threads — for quick head exchange on the drill tube. Indexable insert BTA heads (from Ø15 mm upward) allow insert changes without removing the head from the tube, and above Ø25 mm the cutting diameter can be adjusted for wear compensation.

Exchangeable-Head Drills for Shallow to Moderate Depths ​

The exchangeable‑head concept extends beyond deep hole drilling into conventional drilling depths (3×D–8×D), where similar changeover economics apply.

Walter Drion·tec D5150:

• Diameter range: 9.0–17.99 mm
• Depths: 3×D, 5×D, 8×D
• Screwless clamping: heads exchanged directly in the machine
• Patented axial pull‑out protection
• No pilot hole required

DrillMeister system:

• Diameter range: 6.0–9.9 mm
• Depths: 1.5×D, 3×D, 5×D, 8×D
• Self‑clamping: small torque for head mounting/removal
• No re‑adjustment of tool overhang

These systems are particularly cost‑effective on multi‑spindle machines and CNC lathes with driven tooling, where tool change access is restricted and every minute of changeover time multiplies across spindles.

Economic Analysis — When Does Quick-Change Pay? ​

The decision to adopt head‑exchangeable gundrills depends on changeover frequency, labour cost, and required utilisation. The breakeven point can be estimated as:

Breakeven volume = (System premium) ÷ (Savings per change)

At a system premium of $2,500 over a conventional gundrill, the breakeven occurs at approximately 67 changes — roughly three months of production in a typical two‑shift operation running two tool changes per shift.

Additional hidden savings include:

• Elimination of brazing station and skilled labour
• Reduced work‑in‑progress from shorter changeover queues
• Consistent first‑part quality (no overhang resetting)
• Lower inventory — one shank body serves multiple head diameters

Application Areas and Industry Adoption ​

Head‑changeable deep hole drilling systems have found their strongest adoption in industries where changeover frequency is highest and downtime cost is most acute.

Automotive:

• Fuel injector bodies (4–8 mm holes, 15–25×D)
• Transmission valve bodies (multiple diameters per part)
• Diesel common‑rail fuel rails
• Typical changeover: 3–5× per shift → 10–15 min saved per event

Mould and die:

• Cooling channel drilling in injection moulds (8–16 mm, 20–30×D)
• Ejector pin holes (multiple diameters on one mould plate)
• Contoured deep holes requiring multiple tool geometries

Hydraulics and pneumatics:

• Spool valve bodies (multiple port diameters, cross‑holes)
• Manifold blocks (high hole count, mixed diameters)
• Cylinder tubes (through‑holes, stepped bores)

Aerospace:

• Landing gear components (large diameters, expensive materials)
• Hydraulic actuators (precision tolerances, zero defect policy)
• Structural components (deep holes in titanium and superalloys)

Selection Criteria — Choosing the Right System ​

Selecting among head‑exchangeable, indexable insert, and brazed gundrill systems requires evaluating five factors:

Choose head‑exchangeable when you change diameters or geometries more than twice per shift and depth is under 30×D.

Choose indexable insert when you run the same diameter for extended periods at depths up to 45×D and want the lowest per‑edge cost.

Choose brazed carbide when you need diameters under 8 mm, depths beyond 45×D, or custom flute geometries.

Installation and Training Considerations ​

Switching to head‑changeable gundrills requires adjustments beyond the tooling itself:

Machine compatibility:

• Adequate coolant pressure and flow (most head‑changeable systems require 80–150 bar through‑coolant)
• Spindle‑to‑workpiece alignment must be maintained — the drill body stays in place during head changes, so alignment is preserved
• Guide bushings (if used) must match the drill body diameter, not the head diameter

Process adjustments:

• Pilot hole procedure — most head‑changeable systems require a 1×D pilot hole (same as conventional gundrills)
• Feed and speed optimisation — two‑edge designs may allow 2–5× higher feed than single‑edge, but the optimal parameters depend on material and head geometry
• Coolant filtration — chip size and shape differ from brazed tools; verify that filtration and chip‑handling systems can manage the new chip profile

Operator training:

• Head change procedure (plastic key or torque wrench) — 30 minutes of training is typically sufficient
• Head recognition — operators must identify correct head geometry for the material being cut
• Wear monitoring — understanding when to index vs. replace vs. regrind

Troubleshooting Common Issues ​

Future Trends in Quick-Change Deep Hole Drilling ​

Several developments are shaping the next generation of head‑changeable systems:

Robotic tool‑head change — Patented systems (e.g. US20180290250) use multi‑axis robots to pick tool heads from a magazine and attach them to the drill tube, reducing manual intervention and enabling lights‑out operation.

Smart heads with embedded sensors — Instrumented drill heads that transmit cutting force, temperature, and vibration data via RFID or wireless link, enabling predictive tool‑life management and automatic head selection based on real‑time process data.

Larger diameter ranges — As head‑exchangeable technology matures, manufacturers are extending the diameter envelope. Current R&D targets include heads up to 50 mm for gundrill and 200 mm for BTA exchangeable systems.

Hybrid shank systems — Combined head‑exchangeable and indexable insert designs that give the operator the choice of snapping on a pre‑set head (fast change) or replacing an insert (lowest cost) on the same drill body, depending on production requirements.

Frequently Asked Questions ​

1. How long does a head change take with the CHAMGUN system? 30–90 seconds. The shank remains in the spindle; the operator uses the polyamide plastic key to release the worn head and snap in the new one. No tool removal, no overhang resetting.

2. Can head‑changeable gundrills achieve the same straightness as brazed gundrills? Yes. Because the drill shank stays in the spindle between changes, alignment is preserved. Hole straightness depends primarily on the guide bushing and machine condition, not the head‑to‑shank interface. Typical straightness: 0.05–0.15 mm per 100 mm depth.

3. How many times can a CHAMGUN drill body be used before replacement? Each pocket is rated for at least 15 head replacements. After 15+ changes, inspect the pocket for wear; if the head no longer seats firmly, replace the drill body.

4. What is the cost difference between a head‑exchangeable gundrill and a brazed gundrill? The initial purchase price is 30–50 % higher for the head‑exchangeable body. However, per‑edge cost over the life of the tool is comparable or lower when factoring in the elimination of brazing labour and reduced machine downtime.

5. Do I need special coolant or filtration for head‑exchangeable gundrills? Standard emulsion or oil is acceptable. Filtration should handle the chip size produced by the specific head geometry — two‑edge designs produce shorter, more broken chips than single‑edge tools.

6. Which industries benefit most from head‑changeable deep hole drilling? Any industry with frequent tool changes — automotive (fuel injection, transmission), mould and die (cooling channels), hydraulics (manifold blocks), and aerospace (landing gear, actuators).

7. Can I use head‑exchangeable systems on my existing CNC lathe or machining centre? If the machine has adequate through‑spindle coolant pressure (80–150 bar) and a suitable toolholder interface (Weldon or cylindrical shank), head‑exchangeable gundrills can be used on standard CNC equipment. No dedicated gundrill machine is required.

8. What is the maximum depth‑to‑diameter ratio for current head‑exchangeable gundrills? ISCAR CHAMGUN reaches 30×D, TaeguTec WIN‑GUN is rated for 12×D and higher. For depths beyond 30×D, indexable insert or brazed gundrills remain the standard solution.

9. How does the two‑edge WIN‑GUN design affect chip evacuation? Two‑edge cutting produces smaller, more fragmented chips than a single‑edge tool at the same feed per revolution. This improves chip flow through the flute and reduces the risk of chip packing in deep holes.

10. Is a pilot hole required for head‑changeable gundrills? Yes. The standard procedure calls for a 1×D pilot hole using a short drill of the same diameter, identical to the pilot requirement for brazed gundrills.

Summary ​

Head‑changeable deep hole drilling systems represent a significant evolution in gundrill and BTA tooling technology, addressing the highest‑cost element of deep hole drilling in production environments: tool change downtime.

ISCAR CHAMGUN and TaeguTec WIN‑GUN lead the gundrill quick‑change segment, while UNISIG UNI‑50BTA delivers the same philosophy to BTA/gundrill dual‑system machines. The economic case is strongest in high‑change‑frequency environments, where the system premium is recovered in 60–90 days through reduced downtime and eliminated brazing labour. As diameters increase, robotic automation matures, and smart heads enter production, head‑changeable technology will continue to displace brazed gundrills across the manufacturing landscape.