DTS Drill Head Selection Guide: Brazed vs Indexable for Ejector Drilling

DTS Drill Head Selection Guide

Selecting the right DTS (Double Tube System) drill head is one of the most important decisions in ejector drilling. The drill head determines hole quality, penetration rate, tool life, and cost per hole. This guide covers the two main DTS head types — brazed and indexable — and provides a selection framework based on diameter, material, production volume, and machine capability.

Brazed DTS Drill Heads

Brazed DTS heads have carbide cutting tips brazed onto a steel body. The tips are ground to final geometry and cannot be replaced individually — the entire head must be reground or replaced when the cutting edges wear.

Advantages

Limitations

Application

Brazed DTS heads are best suited for:

• Small diameters (18–30 mm) where indexable inserts won’t fit
• High-precision holes requiring IT7 tolerance or better
• Long production runs where the lower cost per regrind spreads over many holes
• Steel and cast iron — materials with consistent machinability

Indexable DTS Drill Heads

Indexable DTS heads use replaceable carbide inserts mounted in precision pockets on the head body. When the cutting edges wear, the inserts are rotated or replaced on the machine.

Advantages

Limitations

Application

Indexable DTS heads are best suited for:

• Diameters above 25 mm where insert pockets fit
• Multiple materials — switch insert grades between jobs
• Short to medium runs where regrind turnaround would cause downtime
• Titanium, superalloys, hardened materials — best insert grade matched to material

DTS Head Connection Types

All DTS drill heads connect to the boring bar with a threaded connection. The two standard thread types are defined by ISCAR’s identification system:

Always verify the thread type before ordering. The boring bar and drill head must match. Most DTS heads also use a face-seal or O-ring to prevent coolant leakage at the connection.

Insert Geometry Selection

ISCAR categorizes DTS inserts into standard geometry families. The geometry selection depends primarily on the workpiece material group:

Coating Selection

Selection Decision Tree

START: What is your hole diameter?
├── < 25 mm → Brazed head recommended
│   └── EF thread type
├── 25–65 mm → Either brazed or indexable
│   ├── High precision (IT7) → Brazed
│   ├── Multi-material production → Indexable
│   └── Long runs, single material → Brazed (lower edge cost)
└── > 65 mm → Indexable head recommended
    └── IF thread type (larger diameters)

For any diameter:
├── One material, consistent production → Match coating to material
├── Multiple materials → Indexable with interchangeable grades
└── Prototype / low volume → Indexable (no regrind commitment)

Machine Compatibility Check

Before selecting a DTS head, verify that your coolant system can support it:

Summary

Brazed DTS heads offer higher precision and lower cost per edge for dedicated production in steel and cast iron, especially below 25 mm diameter. Indexable DTS heads provide flexibility for multi-material production, easier maintenance, and better performance in difficult materials like titanium and superalloys. Match the head thread type (EF or IF) to your boring bar, select insert geometry by material group, and always verify coolant system capacity before committing to a head size. For parameter recommendations with your chosen head, see the ejector drilling parameters guide. For Venturi system maintenance, see coolant and Venturi system maintenance.