Better tapping productivity in tough metals.

Better tapping productivity in tough metals

Up to 50 percent of both ball and butterfly valves manufactured by Neles-Jamesbury, Worcester, MA use 300 series stainless steel to help withstand the effects of corrosive liquids, extreme pressures, hazardous materials, and wide temperature variations. The company also uses other tough materials such as alloys of Hastelloy, Inconel, and Monel.

Machining performed at Neles-Jamesbury includes tapping holes in valves to attach actuators; to assemble two-piece valve body designs; and to mount valves in pipe installations. Tap sizes range from 5/16-8UNC through 1 1/8-8UN, with the most common types varying from 3/8-16UNC through 5/8-11UNC. Tap hole depths range from 5/8" to 2 1/2", in both through-hole and blind-hole applications. Larger tap sizes up to 1 1/8" diameter are used in flange areas where either split-body valves are butted or where mating flanges connect valves to pipes. Flange holes on the generally larger butterfly valves are tapped through various thicknesses, reaching 4".

The company produces their multiple valve components on CNC lathes and machining centers, as well as on Goss & DeLeeuw machines and Wickman automatic screw machines. To enhance machining operations, TRIM[TM] oil-based, water-soluable lubricants and tapping compounds are used as supplied by Master Chemical Co.

Tapping speeds of 20 to 30 sfm are used with stainless steel parts produced on screw machines. Hastelloy usually requires 5 to 10 sfm, and Monel is tapped best at 16 to 20 sfm. Cast carbon steel calls for 40 to 50 sfm, and aluminum components are tapped at 80 to 100 sfm.

Testing tap performance

A vital consideration in the machining of these advanced materials is the selection of tools for optimum performance, enabling parts to be produced as economically as possible. Neles-Jamesbury's tapping requirements, for example, have been fulfilled with ST-application taps supplied by Emuge Corp, Worcester, MA. The selection of these taps to replace conventional taps came after six months of intensive testing.

Production management at Neles-Jamesbury found during testing that Emuge taps outperformed conventional taps in several areas, gaining benefits such as: longer tap life in terms of reduced wear, less chipping, and reduced breakage; improved cutting capability, particularly on metals such as Hastelloy and Monel; better thread finish and quality. Also, the Emuge taps were found to produce more pieces per tap - on the order of 200 to 1000 percent output improvement.

Such performance derives from special characteristics of these taps, starting with the material from which they are made. An advanced high-speed tool steel has been formulated by Emuge for fine edged tools to resist cutting edge breakdown caused by heat. Part of the reason for this lies in the use of cobalt in the steel formulation along with refined heat treat techniques.

Emuge's cutting edge geometry, combined with a short thread length, prevents excessive heat buildup at the cutting edge, reduces chip loading, and results in a free-cutting tap with exceptional wear characteristics and accuracy of cut. Each tap is designed with a specific hook/rake angle, thread form relief, back taper, flute shape, chamfer, chamfer relief, and pitch diameter for the material the tap is to machine.

Productivity results

Longer tool life translates into less machine downtime along Neles-Jamesbury's production line. The Emuge taps are known to save up to two hours per week in tool change time. With 60 machines on the production line, cost savings are significant.

As for performance, the company points to a recent production experience involving 1" dia Hastelloy valves that were tapped conventionally at a rate of 4 to 6 parts before tools required resharpening. A single Emuge ST-application tap turned out 148 workpieces and then tapped holes in another 400 valve parts in 300 series stainless steel in a follow-up application. In this case, production count before a required tool change rose to a level 80-times greater than with conventional taps.

For more information on taps and tapping, contact Emuge Corp, 325A E Mountain St, Worcester, MA 01606, or circle 511. 1003

SPC tightens inspection tolerances

Post-process inspection and statistical process management (SPM) are helping a defense contractor maintain tight tolerances in machining critical dimensions on 155-mm ordnance shells. Tolerances are: 0.0016", ID; 0.008" several ODs; and 0.010", length.

In the inspection setup, three automatic inspection machines, consisting of fixturing and a Digital Techniques 763 modular gaging system, are linked with three machining cells, each with two single-spindle CNC lathes. After machining in each cell, the shell is lifted manually with a hoist and loaded into vees in the corresponding inspection machine where it is precisely located by a female center and special detail. The inspection machine checks size on one inner diameter, several ODs, and part length. Based on size measurements, information is fed back to the lathe CNC to update tool offsets.

The three inspection machines are linked to a remote Digital Techniques Concept 2000 statistical process management system that extracts QC information (histograms, upper and lower control limits, standard deviation, etc) and generates printouts.

Results have been excellent. Part rejects have been virtually eliminated. Automatically offsetting cutting tools reduces cost. Worn tools are automatically detected. Continuous documentation demonstrates conformity to military specifications.

For more information, GTE Valenite Marketing Services, 750 Stephenson Hgwy, P O Box 3950, Troy, MI 48007 or circle 301. 1902

Tubing wrap-and-bend

lines

Komo Machine recently installed custom wrap-and-bend lines for a major appliance manufacturer. The firm uses the lines to bend aluminum fin tubing for refrigerator evaporators. Previous difficulties in part production centered around excessive damage to delicate aluminum fins wrapped around the core tubing.

Komo designed and built five integrated CNC lines equipped with tubing-payoff reels, fin-wrapping machines, straighteners, benders, and conveyors. The lines now produce parts at twice the efficiency of previous machines, according to the user, cutting cost by 50 to 75 percent. Cycle times now average 42 sec.

The equipment is designed to operate continuously and automatically without operator assistance after initial setup. Workpiece output is varied or staggered to complement requirements of the take-away conveyors.

Tubing preparation

Small-diameter aluminum tubing uncoils from a vertical payoff reel and feeds into a Venables highspeed slitting and wrapping machine. At the same time, aluminum strip from an internal coil is partially cut, then bent in half. The slit-and-bent strip winds around the incoming aluminum tubing with its cut-edge outward. The fin-wrapped tubing then passes through a straightening unit. At this point, the fin tubing is ready for bending.

Part production

A hydraulically operated clamping vise supported on linear ways and actuated by a programmable cylinder advances the tubing into bending dies. Here, bi-directional shifting heads perform serpentine bending through hydraulic operation. The multiple-pass machines can produce bend angles from zero to 180 degrees - in almost any serpentine pattern.

Part length is programmable, controlled by direct computer encoding. A hydraulically-operated transfer arm on linear shafting moves each finished part to a take-away conveyor line. The lines use General Electric Series 6 controls with backups and diagnostics.

Komo Machine Inc, 11 Industrial Blvd, Sauk Rapids, MN 56379 or circle 475. 1102

PHOTO : Six holes are tapped in the flange area of a 3" dia, 316 stainless steel butterfly valve at Neles-Jamesbury. Four spiral point 3/8-16 taps are used initially to tap 5/8" deep through holes. A rectangular tombstone fixture, designed for the job, mounts a total of 12 valve workpieces, aranged with three valves stacked vertically on each side.

PHOTO : Emuge taps are used on stainless steel, carbon steel, and cast iron. Here a cast iron actuator housing is tapped with a 5/8-11 straight flute tap.