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Thread mills save a combination concept.

Thread mills save a combination concept Case-history report tells how threading tools for tough oil-field parts saved a switch to single-machine operation.

Short tool line and poor metal cutting were serious problems when a manufacturer of high-pressure valves first tried to combine the work of three separate lathes into one threadmilling process.

Fortunately, a switch to a lowercost tooling system solved the problems for Hydro-Seal Valve Co Inc, Kilgore, TX. And, they gained more benefits. The company is actually machining superior threads and getting 12-times longer tool life.

"To be honest with you, the job couldn't have been done without the new tooling," says Michael D Dickey, shop production manager. "I was getting ready to scrap the whole operation and go back to the old method using three lathes."

The firm manufactures a variety of valves and related products that control the flow of air, gas, and fluids up to 10,000 psi. Located in the heart of the East Texas oil field, Hydro-Seal serves the energy industry worldwide in a variety of applications. Their products are used in oil-field drilling and maintenance, refining, processing, and distribution.


"I was using a variety of standard high-speed-steel thread mills," Dickey says. "They would not allow us any life whatsoever, and they never gave us any warning before we had tool failure. I'm talking at least $300 worth of broken-in-half tools. And I was getting only three to four parts per tool.

"The quality of the work wasn't acceptable, and the job really never did get off the ground. My boss wasn't very pleased about it, either. We were into machining and processes for 100,000 parts plus, and there was no return coming back at all. We had dead parts and tools."


Dickey took his problems to Carboloy Inc, PO Box 330237, Detroit, MI 482323. The firm suggested Snap-Tap(R) tooling supplied by Seco Tools AB. These thread mills use multi-tooth, carbide, indexable inserts in fixed pockets, ensuring concentricity. Dickey was able to buy a toolholder and several inserts for about the same price as one HSS thread mill.

"With the new thread mills, we consistently get 60 good parts per insert instead of four unacceptable parts as before," Dickey says. "Being able to flip the inserts over and use two sides gives us additional mileage. Also, the tools run at 1625 rpm, compared to the previous 300 rpm, which was all the high-speed steel would tolerate."

The Snap-Tap thread-milling process produces full-profile threads in a single feed revolution, and permits cutting close to shoulders or hole bottoms. It also provides good chip control. The same setup used for thread milling may be used for other operations, ensuring exact location and thread alignment. The cutter body handles right-hand, left-hand, internal, and external threading.

The process

At Hydro-Seal, tooling runs in a Kearney & Trecker MM180 HMC horizontal machining center, which has a 20" x 20" x 20" workspace. The workpiece is a body for a safety-relief valve, and it has three threaded ends. The part is a casting and can be either 1030 steel or 316 stainless. To ensure a reliable supply, Dickey orders castings of both materials from two independent foundries.

First, the operator manually loads each casting onto the HMC's 360-degree indexable table. He applies uncoated P30 and S25M grades of carbide to the 1030 steel castings, and uncoated K20 and HX grades to the 316 stainless.

Next, the inlet is given a standard 2", 11 1/2-pitch ID NPT thread. When these tapered pipe threads have been machined, the workpiece is indexed again, and the tool is changed.

Finally, the third leg of the casting gets a 3", 12-pitch UN ID thread to accommodate a bonnet that contains the valve's activating mechanism.

Because the thread mill produces an interrupted cut, no coolant is used. Use of fluid adds to the thermal shock of getting into and out of the cut, and it results in unwanted heat treating during machining. These factors can shorten tool life and cause other problems. It is important to note that, without coolant, there is no thread galling on the workpiece.

"Originally, I had to handle this part three times on turning machines, and anytime you handle a part, it costs money," Dickey says. "Now, I can index the part and put all three threads on it before I have to touch it. When the machining center completes the cycle, the part is finished."

Because threading of the valve body runs so smoothly (production averages 55 units per shift), Hydro-Seal has expanded production on the HMC to four additional parts, all using Snap-Tap thread-milling cutters.

PHOTO : Snap-Tap threading mill travels around workpiece circumference to cut threads.

PHOTO : K&T HMC machines a high-pressure oil-field part at Hydro-Seal Valve Co Inc
COPYRIGHT 1989 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Hydro-Seal Valve Co. Inc.'s tooling system
Publication:Tooling & Production
Date:Jul 1, 1989
Previous Article:Manned cell puts brakes to competition.
Next Article:High-precision tools cut secondary operations.

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