Cutting-Fluid

Coolant selection determines tool life, surface finish, and hole quality in deep hole drilling more than any other process parameter. The right coolant makes the difference between a 500-hole tool life and a 2000-hole tool life in the same material. Here is what I use and why. Coolant Types Overview Three coolant types cover almost all deep hole drilling applications. Each has trade-offs in performance, cost, and maintenance. Type Lubricity Cooling Cost per Liter Filtration Requirement Best Application Neat oil Excellent Good $3 - $8 10 - 20 μm Gun drilling, BTA, demanding finishes Emulsion (oil-water) Good Excellent $0.50 - $1.50 20 - 50 μm General deep hole drilling Synthetic Moderate Excellent $1 - $3 20 - 50 μm High-speed work, aluminum Oil-Based Coolants Oil-based coolants provide the best lubrication for gun drilling. I use neat cutting oil for all critical gun drilling and BTA jobs. The oil film between the guide pads and the bore wall reduces friction by 30-50% compared to water-based coolants. ...

I have watched more than one shop chase tool breakage for a week only to discover the coolant was running at half the recommended concentration. Coolant concentration is the kind of variable that does not announce itself. It drifts slowly, a tenth of a point at a time, until one day nothing works right anymore. Here is how I measure it, what the numbers should be, and what to do when they are wrong. ...