When it comes to drilling large-diameter holes—typically 45mm and above—manufacturers often rely on annular cutters due to their cutting speed and portability. However, with the increasing demand for efficiency and cost control in modern machining, a new contender has emerged: the Indexable Core-Stay Drill.
While both tools are designed for similar tasks, the way they function—and the value they offer over time—can be significantly different. In this article, we'll break down the key differences between these two tools and explain why many manufacturers are now switching to Indexable Core-Stay Drills to save both time and money.
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What Are Annular Cutters?

Annular cutters, also known as core drills or hollow drills, are widely used in magnetic drilling machines and manual drilling applications. They cut only the outer edge of a hole, leaving a solid core, which reduces material removal and allows for faster cutting compared to twist drills.
However, once the cutting edges of the annular cutter become dull, the entire cutter needs to be replaced or re-sharpened, which can be both time-consuming and costly.
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What Is an Indexable Core-Stay Drill?

An Indexable Core-Stay Drill is an advanced tool for large-diameter drilling that features replaceable carbide inserts mounted on a durable steel body. Like an annular cutter, it also cuts around the hole's perimeter and leaves a solid core—but with one key advantage:
Only the inserts need to be replaced, not the entire tool.

This indexable design is commonly found in Indexable High Speed Drills, which are used for small to medium-diameter holes. The Core-Stay Drill brings the same insert-based efficiency to large-diameter drilling.
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Why Indexable Core-Stay Drills Save More Time

1.    Quick Insert Replacement

•     Instead of taking the tool out for regrinding or full replacement, users simply swap in new inserts. This reduces machine downtime, especially in high-volume production.

2.    No Tool Recalibration Needed

•     Since the drill body remains in place, recalibration after insert replacement is minimal—saving setup time and keeping operations running smoothly.

3.    Better Chip Control and Heat Dissipation

•     The design of indexable drills typically includes optimized coolant channels and chip evacuation paths, ensuring continuous drilling without clogging or overheating.

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Why It Saves You More Money

1.    Reusable Tool Body

•     The steel body of an indexable core-stay drill can be used for hundreds of cycles. You only invest in inserts, which are far less expensive than full cutters.

2.    Lower Inventory and Maintenance Costs

•     You don't need to keep a large stock of various cutter sizes. One drill body with multiple insert types can cover a range of applications.

3.    Consistent Performance Over Time

•     Unlike re-sharpened annular cutters, which may lose geometry and performance, fresh inserts offer consistent cutting quality every time, ensuring fewer rejected parts and better tool management.

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When Annular Cutters Still Make Sense

To be fair, annular cutters still have their place—especially for portable drilling in the field, quick one-off jobs, and situations where CNC machines aren’t available. Their simplicity and speed make them ideal for construction sites, mobile repairs, and on-site fabrication.
However, in a CNC or industrial production environment, where speed, repeatability, and cost control matter most, Indexable Core-Stay Drills provide unmatched long-term value.
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Conclusion

While both tools are effective for large-diameter drilling, the Indexable Core-Stay Drill clearly wins when it comes to saving time and money. With its replaceable inserts, longer tool life, reduced downtime, and lower operating costs, it’s the logical evolution of large-hole machining.
If you're already using Indexable High Speed Drills, then the Indexable Core-Stay Drill is a natural next step—offering the same cost-saving, high-performance advantages, but for your larger-diameter drilling needs.
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At SHANG TZANG WANG ENTERPRISE CO., LTD., we manufacture both Indexable High Speed Drills and Indexable Core-Stay Drills, giving you reliable and efficient solutions across all hole sizes. Contact us today to discover how our tools can help you streamline your production and lower your tooling costs.