How To Improve Tapping Efficiency Of Small Holes in Titanium Alloy?

Tapping small holes of M6 and below in titanium alloy  is a key processing procedure. However, titanium alloy features poor thermal conductivity, high chemical activity and susceptibility to work hardening, which easily lead to problems such as tap wear and chipping, tool jamming and breakage, poor chip removal, and low thread precision during processing.

 

 

Extremely poor thermal conductivity, resulting in concentrated cutting heat and high temperature, accelerating tool wear, and the work hardening of the material is much higher than that of ordinary steel;

 

High chemical activity at high temperature, easy to cause chip adhesion and clogging, and small taps are highly prone to seizing and breaking;

Low elastic modulus, causing rebound and shrinkage after thread processing, increasing friction and tapping torque, and leading to tool jamming;

Small chip space in small holes, insufficient cooling, poor rigidity of taps leading to deformation, and the processing difficulty is further intensified in deep blind hole working conditions.

 

 

Taps require high strength, wear resistance and resistance to titanium adhesion. M42 cobalt high-speed steel is preferred for Gr5 processing, and hard alloy for high-precision processing; matched with PVD coatings, chlorine-containing coatings are prohibited.

 

Select tap types as required, adjust edge parameters to reduce friction and chip adhesion, thicken the tap core and reduce the number of flutes for small-size taps to enhance rigidity.

 

Regularly resharpen the cutting edges, keep usage records and replace tools in a timely manner to stabilize processing quality and extend tap service life.

 

 

(1) Reasonable Matching of Cutting Speed and Feed Rate

Due to the poor thermal conductivity and susceptibility to hardening of titanium alloy, the tapping speed must be strictly controlled : the cutting speed decreases successively for α-type, α+β-type (Gr5) and β-type titanium alloys; low speed is adopted for high-speed steel taps, and the speed can be increased appropriately for hard alloy taps. The optimal parameters for Gr5 are a cutting speed of 3–5 m/min and a feed rate of 0.05 mm/r. The feed rate should not be too small to prevent tool wear and high-temperature oxidation of chips; conventionally controlled at 0.1–0.3 mm/r, and adjusted to 0.05–0.1 mm/r for micro-small holes below M2 to balance thread quality and tool safety.

 

(2) Optimization of Bottom Hole Parameters and Processing Technology

The rebound and shrinkage of titanium alloy are much greater than those of ordinary steel, so the bottom hole diameter needs to be appropriately enlarged, and the calculation formulas for cutting threads and extrusion threads should be distinguished to effectively reduce tapping torque. The bottom hole adopts the process of rough drilling + reaming to reduce the surface hardening layer; chamfer the hole edge at 45°, and a hole reaming process can be added for high-precision working conditions to make the tap enter smoothly and improve thread precision.

 

(3) Standardized Tapping Operation Process

Peck tapping is preferred for segmented tool retraction to remove chips and supply cooling, which is suitable for small holes and deep blind holes in titanium alloy; retract the tool regularly for deep blind holes, and reduce the number of tool retractions for through holes to improve efficiency. Machine tapping replaces hand tapping in mass production to ensure stable feed; avoid sudden stops and rapid reversals during processing, and retract the tool slowly after tapping to reduce burrs and tool damage.

 

 

(1) Selection of Adaptable Processing Equipment

Automated equipment such as drilling and tapping centers and CNC lathes are preferred for mass production, with stable rotation speed and feed, which can reduce human errors and improve efficiency. Portable CNC tapping machines are selected for small and complex workpieces; special vibration tapping machines are used for high-precision micro deep holes, with long processing stroke and built-in compensation for higher precision.

The radial runout of the equipment spindle must be ≤0.01 mm to prevent tap bending and wear; torque protection should be equipped to automatically stop the machine in case of overload to prevent tap breakage. Equipment with spindle cooling is preferred for deep blind hole processing to enhance the cooling effect.

 

(2) Optimization of Fixtures and Tapping Chucks

Fixtures require accurate positioning and reliable clamping; multi-station fixtures can be used for small parts to improve productivity; flexible clamping is adopted for thin-walled parts to prevent extrusion deformation. Flexible tapping chucks with overload protection are preferred to compensate for feed deviation and avoid tap damage. Micro-small holes are matched with precision micro chucks to reduce runout and stabilize thread processing quality.

 

As a direct titanium products manufacturer, Ruihang provides raw materials for your precision processing requirements.If you have purchasing plans, please send me a message for inquiry. Email:Sam.Rui@bjrh-titanium.com