Success Stories: Hydril

“Hydril saves over 50 hours per unit by thread milling!”

A case history in cost savings, Hydril is a Premier manufacturer of a variety of outstanding products for petroleum drilling and production, especially for high pressure and severe service applications. The particular product to be thread milled was a 4130 forged steel ram body with a Brinnell hardness of 217Bhn that must withstand 1500psi in hostile environments. The quality of every aspect in this product cannot be compromised due to the ramifications of a failure of any of Hydril Product.

The challenge was to thread mill 57 holes, 3.5 inches in diameter with an 8UN-2B thread 4 inches deep. At the time, this was being done with a high speed steel tin coated thread hob helically interpolated on a Giddings and Lewis series 450 horizontal boring mill. The elapsed time to perform the job was 1 hour and 40 minutes.

As you might guess with the close tolerances and the critical nature of hte application the idea of changing the method and tooling was not welcomed readily by those intimately familiar with the process. But with the promise of better quality thread due to improved tool life and the superior product quality built into the tool, Don Fortune and Gary Hutchinson of Hydril's Maufacturing Engineering Staff had no choice but to investigate the performance of Advent's replaceable thread mill and our claims therin.

The tool selected by Hydril's team was a 12 insert, 2.750 diameter CAT 50 tapered thread mill with a gage length of 8" and through the spindle coolant. The inserts selceted were a tin coated micrograin carbide with 6 degrees rake and straight relief for free cutting and long life. The choice was made easier by the fact that this was a standard tool and in stock.  The holes were drilled to 3.125 x 5.45 deep. The machine was programmed to take three passes to achieve full depth of the thread form. The first two passes were run at 250 SFM, 347 RPM and .04 IPT feed after a 180 degree ramp into the cut at at 71IPM. The final pass was run at 300 SFM 416 RPM and a feed of .078 IPT.

The Result:

Each hole was threaded in 9.8 minutes as opposed to the 90 minutes it took with the HSS hobbing mill, at a cost saving of over $4,000 per unit.

At the end of the test period, the inserts had cut the equivalent of 2268 linear feet without any appreciable wear. The thread mill was supplied by Advent Tool and Manufacturing who are the exclusive manufacturers of a full line of carbide tip, solid carbide and insertable crebide thread mills. They will assist you in selecting the proper tool for your specific application and provide the technical expertise for programming the helical interpolation on your NC machines.

Roy Miller, Hydril