Many customers ask us the same question:

“Can one machine perform both deep hole drilling and deep hole honing?”

At first glance, this idea sounds reasonable. If one machine could drill the hole and then finish the hole, it may seem to save space, reduce investment and simplify production.

However, in real deep hole machining, drilling and honing are two very different processes. For long deep holes, especially hydraulic cylinder tubes, they are usually completed by two dedicated machines.

Image 01: Deep hole drilling machine / workshop photo

First, Drilling and Honing Do Different Jobs

Deep hole drilling is used to create the hole. The drill removes a large amount of metal and forms the basic internal bore.

Deep hole honing is used after the hole already exists. Its purpose is to improve diameter accuracy, roundness, straightness and surface finish.

Deep Hole Drilling: A Rough Machining Process

A deep hole drilling machine works like a powerful cutting system. The tool rotates and continuously moves forward into the workpiece.

The main goal is to remove material efficiently and evacuate chips from a long, narrow hole. This requires strong cutting force, rigid machine structure and high-pressure coolant.

• Creates the hole from solid material
• Removes large amounts of metal
• Requires high cutting force
• Uses gun drilling or BTA drilling tools
• Needs high-pressure coolant for chip removal

Deep Hole Honing: A Precision Finishing Process

Deep hole honing is completely different. The hole has already been drilled or bored. The honing machine only removes a very small amount of material.

The honing head rotates and moves back and forth inside the bore. This reciprocating movement creates a cross-hatch surface, which is very important for hydraulic cylinder sealing performance.

Image 02: Deep hole honing process / hydraulic cylinder bore

• Finishes an existing bore
• Improves bore accuracy
• Improves surface roughness
• Uses expanding honing stones
• Requires clean honing oil and fine filtration

Why One Machine Is Usually Not Practical

To combine drilling and honing into one machine, the equipment would need two different tooling systems, two coolant systems, different motion controls and different accuracy structures.

A drilling machine is designed for power and chip removal. A honing machine is designed for precision and surface quality. These two design goals are not the same.

If a machine is forced to combine both processes, the cost may become close to buying two separate machines. Tool changing, oil cleaning and machine adjustment can also reduce production efficiency.

Typical Process for Hydraulic Cylinder Manufacturing

In hydraulic cylinder production, the machining process is usually arranged step by step to ensure stable quality.

Image 03: Hydraulic cylinder deep hole machining process

What About Combination Machines?

Some special-purpose machines can combine several operations for short holes or small parts. For example, certain compressor cylinders or automotive parts may use customized compound machines.

But for long deep holes commonly used in hydraulic cylinders, oilfield equipment, engineering machinery and aerospace components, separate machines are still more practical and reliable.

Final Conclusion

Although combining drilling and honing into one machine sounds attractive, the reality is that these two processes require different machine structures, tool systems, coolant systems and accuracy requirements.

For most long deep hole applications, using dedicated machines for each process provides better productivity, quality and long-term reliability.

FAQ

Can drilling and honing be done at the same time?

No. Drilling and honing have different tool movements, machine structures and machining purposes.

Is there a machine that combines drilling and honing?

Some special machines exist for short holes, but they are generally not suitable for long deep holes.

Which process comes first?

Drilling or boring must be completed first. Honing is the final finishing process.

Why do hydraulic cylinder manufacturers use separate machines?

Because separate machines provide better stability, accuracy, surface finish and production efficiency.