Hydraulic valve bodies are some of the most demanding components I have worked on in the industrial sector. The bores need to be straight, round, and smooth. The valve spool fits inside the bore with a clearance measured in microns. If the bore is off, the valve leaks or sticks. I have drilled valve bodies for mobile and industrial hydraulic systems. The principles are the same regardless of the valve size. ...
Some of the most demanding deep hole drilling jobs involve drilling a small-diameter hole through several meters of steel with near-perfect straightness. The classic application is gun barrel drilling — the process that gun drilling is named after. Defense applications remain the most stringent driver of long tube drilling standards today, from rifle barrels to artillery components and missile guidance housings. The challenge is straightness. A 5mm hole through 2 meters of steel at a 100:1 L/D ratio needs to be straight to within a few hundredths of a millimeter per meter. If the hole drifts, the wall thickness changes, and the part is scrap. For defense-grade components, the stakes are even higher because barrel straightness directly affects projectile accuracy. ...
Pump components are a regular source of deep hole drilling work. Gear pumps, piston pumps, and centrifugal pumps all have components that need precise bores. The work ranges from small precision holes in pump housings to large bores in pump shafts. I have worked on components for hydraulic pumps and centrifugal pumps. Each type has its own requirements. Here is how the common pump component categories break down in my experience: ...