Deep drilling
How to use the calculator
Select the tool type (standard / TSC / gun drill), enter the diameter and depth, specify the material, cooling and system rigidity - the calculator will determine the strategy, Peck Q step and recommend a CNC cycle. All parameters are recalculated instantly.
L/D - main parameter: depth to diameter ratio. L/D < 5 - standard drilling; 5–8 — transition zone; > 8 - deep drilling, requiring a separate strategy.
Three deep drilling strategies
Standard (G81).Up to L/D ≈ 3–5 with internal cooling. Continuous cutting, minimal cycle.
Chip-break G73.L/D 3–8 for standard drills, up to L/D 8 for TSC. Short Peck without full output - breaks chips, but does not waste time on full output. The chips should come out of the grooves freely.
Full Peck G83.L/D > 5 for standard without internal cooling, L/D > 10 for any tool. Complete output at each step is chip evacuation and zone cooling. Slow but sure.
Gun drill.Specialized tool for L/D > 10–30. Continuous cutting without Peck - HPC supplies coolant through a bar, chips are evacuated through a single groove. Pilot required before entry.
Why external cooling is not enough for L/D ≥ 5
At a depth of more than 5×D, the flow of external coolant does not physically reach the cutting zone - the pressure dissipates, the liquid does not penetrate into the gap between the chips and the walls of the hole. The chips heat up, sinter in the grooves, and the drill breaks. The solution is through-tool coolant or HPC with a pressure of 20 to 80 bar depending on the diameter.
Frequently Asked Questions
How to choose Peck Q step? Starting point: Q ≈ 0.5×D for standard without TSC, Q ≈ 1.0×D for TSC and chip-break. Adjust according to the type of chips: the chips should come out freely, without compaction in the grooves. For stainless steel and heat-resistant materials, reduce Q by 20–25%.
Is a pilot needed for deep drilling? Mandatory for L/D ≥ 5 and for gun drill at any L/D. The pilot sets the exact direction - with a large L/D, the slip increases along the length of the hole. A 1-2×D depth pilot eliminates the initial drift.
Is it possible to use a standard drill at L/D 10? Technically it is possible, but only with G83 (full output), internal cooling and reduced Q. Without internal coolant at L/D ≥ 8 the risk of failure is high. TSC drill with L/D 8–12 is the optimal choice in terms of performance and reliability.
How to use the coolant calculator
Select the coolant supply method (through-tool / directed / flood / dry), enter the diameter and L/D, specify the type of operation and fluid. The calculator will provide target pressure (bar) and flow (l/min) ranges. Enter the pressure of your pump - the tool will immediately show whether it is enough, on the verge, or whether the equipment needs to be changed.
Why coolant pressure is critical when deep drilling
At L/D ≥ 5, chips occupy most of the groove cross-section. If the pressure and coolant flow are insufficient: the chips become compacted at the bottom, the temperature in the cutting zone rises sharply, and with L/D ≥ 8 the drill breaks without warning.
Through-tool (internal supply) is the only reliable method of cooling at L/D ≥ 8. External flood supply does not physically reach the cutting zone at such a depth - this is not a question of the amount of coolant, but the physics of the flow.
How requirements change with L/D and diameter
The smaller the diameter, the higher the required pressure: for Ø3 mm you need 25–45 bar, for Ø20 mm 10–22 bar is enough. This is explained by the cross-section of the channels - small channels require a larger differential to ensure the required flow rate.
According to L/D: when the depth increases from 8×D to 20×D, the target pressure increases by 20–30%, flow rate by 15–25%. Take this into account when choosing pumping equipment for your machine.
Is it possible to get by with flood at L/D 10? No. When L/D ≥ 8, flood does not evacuate chips from the cutting zone. The only valid replacement is the G83 with full pinout and reduced Vc, but performance drops 3-5 times. The through-tool pays for itself on the first thousand parts.
A 15 bar pump - is it enough for Ø10 mm at L/D 8? At the lower limit it is acceptable (target 15–28 bar). But filter contamination or leaks will lower the actual pressure at the spindle below the minimum. Measure the pressure directly in front of the spindle, not at the pump.
Oil vs. emulsion for deep drilling? Oil requires a little more pressure due to viscosity, but lubricates the edge better - especially for Ti and stainless steel. The emulsion dissipates heat better at high speeds and is easier to maintain. For most operations in steel - 7-8% emulsion.
We supply drills with internal TSC channels. We help you select coolant parameters for the tool and machine.