Choosing The Right Boring Bar For Machining Hard Materials

Machining hard materials like tool steel, carbide or fired ceramic whilst maintaining accuracy and structural integrity can be challenging. Without the right boring bar, tool life, surface finish and accuracy can suffer.

If your business machines any of these materials then these issues make for a costly combination leading to wasted time, rework and premature tool replacement due to excessive wear. So how do you choose the right boring bars for the job? Something which repeatedly produces accurate results and enjoys a long tool life?

Why Choosing The Right Boring Bar Is Essential

There’s plenty of choice when it comes to boring bars and manufacturers, and when you’re pricing for a job or a production process it can be tempting to go the for most budget-friendly version. But this could end up costing you more in the long run. Here’s why:

1. Excessive tool wear and breakage – Sub-par tools simply don’t last as long. The upfront cost might be lower, but you will find your machine boring bar wears through far faster when machining hardened materials, or breaks, which leads to an increased replacement rate and unplanned downtime.
2. Poor surface finish – A boring bar not designed for hardened materials will cause vibration and chatter, leading to poor tool life and bad surface finish.
3. Loss of dimensional accuracy – Accuracy is paramount in precision tooling and especially boring. But with a long or improperly specified boring bar deflection becomes a major issue. This can lead to holes which are out of tolerance or not truly round.
4. Higher cutting forces – If the insert geometry and tool material aren’t suited to hardened materials it can lead to increased force on the machine’s spindles and bearings.
5. Reduced productivity - Slower cutting speeds, frequent tool changes, and quality issues all lead to longer cycle times and higher costs.

How To Choose The Right Boring Bar

To make sure you having the right boring bar consider the following:

• Type of material being machined – When you machine hardened materials such as tool steel (up to 72HRC), fired ceramic or glass, thermal resistance and wear resistance become top priorities. You must carefully select the correct cutting tool material, grade or coating to machine each of these materials successfully.

German manufacturer DTS offers CBN (Carbon Boron Nitride) grades, PCD (Polycrystalline Diamond) and even diamond coated boring bars which are well-suited due to their stability at high temperatures and resistance to wear.

• Geometry size – If you’re machining holes under 5mm, tool geometry and stability are critical. Boring bars for small holes are usually slender and as a result, lose rigidity which increases deflection and inaccuracies under cutting forces.

DTS offers brazed boring bars down to Ø0.80 mm (Typ BS) and MiniTools with indexable inserts from Ø3.50 mm. Choosing a tool designed specifically for small diameters helps maintain tolerance, surface finish, tool stability and increases tool life.

• Best Tools For Specific Materials – CBN, a synthetic abrasive material, is optimal for hardened steels while CVD-D and UltraDiamond are preferable for ultra-hard, brittle non-ferrous materials e.g., silicon carbide or fused quartz. By matching to the specific material being machined you limit wear and tear and maximise tool life.
• Ensure your set up matches your boring bar – The result will only be as good as the entire system you operate. A top-notch boring bar can still yield inaccurate results if the rest of the set up isn’t sufficient.

Make sure you choose a precise tool holding system. DTS’s hydraulic chucks or short, rigid clamping adapters help maintain consistent insert positioning and reduce thermal distortion and runout.

• Choose tools which maintain rigidity and have vibration control - Tools with stronger shafts and built-in vibration control, like DTS’s MiniTools, help reduce shaking and bending when working on tiny, detailed parts. This makes the work more accurate and helps the tool last longer.

Need help selecting the right boring bar for your specific application? Contact one of our expert team members for a consultation and tool recommendation today!