Page 53 - machining_titanium_05_2019

Selecting A Drill

Selecting a suitable drill is based on the necessary design configuration, cutting geometry, and
cutting material of a tool. Hole diameter, accuracy, and required cutting length define the drill
configuration, while a the geometry and the cutting material are defined by the workpiece material. DRILLING TITANIUM
Fig. 34, which is based on Tables 31-34, shows the application area of ISCAR’s drill families
intended for machining titanium, in coordinates “drill diameter-drill cutting length” in simplified form.

Central drilling: carbide vs. HSS
High-speed steel (HSS) reversible center drill bits are the most popular tools for center drilling.
The bits are simple, always available for purchase, and feature low prices. This may raise the
question: “Does the MM ECS replaceable solid carbide head offer a real alternative to the
bits?”. A seemingly obvious answer may be not so evident, especially in cases of machining
difficult-to-cut material (like titanium). The carbide head ensures noticeable increases in
cutting speed and feed, resulting in higher productivity and reduced machining costs. In
addition, the tool life of the head is much longer. Therefore, the correct answer requires brief
economical calculations, which will show the actual situation for every specific case.

Cutting
Length

12xd

10xd
8xd

4xd
2xd

Diameter d,
3 6 12 20 32 60 mm
(.112) (.500) (.750) (1.250) (2.344) (inch)

Fig. 34 Application range of ISCAR’s drilling line (standard delivery)

To select the most suitable ISCAR drill for machining titanium,
note the general recommendations below:

 SUMOCHAM drills are the first-choice products and should be used wherever possible.
IC908 is the preferred carbide grade.
MULTI-MASTER tools are most recommended for spot drilling.

Coolant
Coolant supply is a vital factor in drilling titanium. Liquid coolant is not only preferable
but is essential. Although wet cooling by flooding under low pressure is still common,
tool body-through (inner) coolant supply ensures high performance. Advanced drills
(both solid and assembled) feature inner coolant channels for delivering coolant
through the drill body, and such drills should be used whenever possible.
Recommended minimal coolant pressure is 12 bars (174 psi). Higher values will improve the
results. Normally, the pressure range is 12…70 bars (174…1015 psi). Higher range values relate to
machining with high pressure coolant (HPC) supply, and they require separate consideration.

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