COGSDILL THREAD ROOT ROLLING BURNISHING TOOL

Cogsdill Thread Root Rolling Tools (TRR), also known as cold root rolling, significantly increase the fatigue strength of highly stressed components whilst also producing a superior surface finish.
Together these reduce the chance of corrosion and dramatically extend the life of threaded connections.

ROLLING IN THE DEEP

Cold Root Rolling is an advanced method of roller burnishing that uses controlled pressure to cold-form the material at the root of newly machined or previously cut threads.
This process introduces a compressive residual stress that cancels out the tensile stress that the component is subjected to during use.

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Connection Size	Thread form	Thread root radius (in)	Roller Diameter (in)	Roller Edge Radius (in)	Required Roller Force (lbf)	Required Roller Force (lbf)	Required Roller Force (lbf)	Required Roller Force (kN)
Number (NC) Style					BOX		PIN
NC38	V-0.0038R	0.038	0.787	0.042	2925	13	1800	8
NC40	V-0.0038R	0.038	0.787	0.042	2925	13	1800	8
NC44	V-0.0038R	0.038	0.787	0.042	2700	12	1800	8
NC46	V-0.0038R	0.038	0.787	0.042	2700	12	2025	9
NC50	V-0.0038R	0.038	0.787	0.042	2700	12	2025	9
NC56	V-0.0038R	0.038	0.787	0.042	2700	12	2025	9
NC61	V-0.0038R	0.038	0.787	0.042	2475	11	2025	9
Regular (Reg) Style
3 ¹/₂	V-0.040	0.02	0.787	0.022	1575	7	900	4
4 ¹/₂	V-0.040	0.02	0.787	0.022	1350	6	900	4
5 ¹/₂	V-0.050	0.025	0.787	0.027	1800	8	1350	6
6 ⁵/₈	V-0.050	0.025	0.787	0.027	1800	8	1350	6
7 ⁵/₈	V-0.050	0.025	0.787	0.027	1575	7	1350	6

Typical Speed: 30 RPM
Feed: Same as threading (use thread re-cut cycle)
Interference: Dependent on connection size and type
Nominal Pre Load: 8.33 kN
Deflection Load: 0.155 kN per 0.01mm
Example: NC38 BOX requires 13 kN force Nominal pre load = 8.33kn Therefore extra 4.67 kN force required Interference required = 0.155/4.67 = 0.033 mm

TRR-EX (PIN)

TRR-IN (BOX)

Using a hardened formed HSS roll that matches both the profile and designated radius of the tapered thread, pressure is applied in order to deeply penetrate the root radius, which displaces and deforms the thread material.

The most common reason for failure is fatigue wear at the pipe thread.
This is due to the drill string repeatedly bending when directional drilling – potentially over several kilometres and at angles up to 90 degrees.
The repeated cyclic stress of compression and tension can cause the material to crack and fracture.
As a preventative solution, Cold Root Rolling ensures extended wear life to the pipe thread connection by altering the materials substructure and improving the surface finish to diminish corrosion that occurs in harsh environments.

The rolling force is provided by a pre-loaded spring.
The tool is fed radially into the workpiece by a specified amount depending on the size of the connector being rolled.
The tool is then fed up the threads using the thread re-cut cycle on the machine.
This deforms the root of the thread and introduces the compressive residual stress.