Abstract: An electron gun cathode structure includes a support member made of an insulating material, a first grid fixed to the support member, and a cathode disposed on the side of the support member opposite to the first grid. A thermal expansion .DELTA.L.sub.S /L.sub.S of the insulating material constituting the support member due to heat from the cathode is larger than a thermal expansion .DELTA.L.sub.G /L.sub.G of a material constituting the first grid due to heat from the cathode. A manufacturing method of an electron gun cathode structure includes preparing a member including a first face and a second face having a step therebetween, a height of the step being equal to a predetermined distance d.sub.12, placing a first grid on the first face, placing a spacer on the second face, placing an insulating support member on the first grid and the spacer, and grinding a top surface of the spacer opposite to its surface that is fixed to the support member so that an actual distance d.sub.12 becomes a desired value.

Abstract: When three or four panel attachment springs 3 are welded to side portions of an aperture grill 1 (or 21), the aperture grill is disposed so that a grill 107 should be opposed to a predetermined reference plane. The springs are disposed by three or four spring positioning means. A posture of the aperture grill 1 (or 21) is adjusted based on measured results of the respective measurement position Z.sub.0 to Z.sub.4 of the grill 107. Positions of spring pins for supporting springs on the spring positioning means are agreed with positions of panel pins provided on a panel. Thereafter, the respective springs are simultaneously welded to the side portions of the aperture grill. Thus, it is possible to precisely weld the springs to side-portion positions of the aperture grill. When the four springs are welded, it is possible to simultaneously weld the four springs by one equipment.

Abstract: A system and method is available for fabricating a field emitter device, where in an emitter material, such as copper, is deposited over a resistive layer which has been deposited upon a substrate. Two ion beam sources are utilized. The first ion beam source is directed at a target material, such as molybdenum, for sputtering molybdenum onto the emitter material. The second ion beam source is utilized to etch the emitter material to produce cones or micro-tips. A low work function material, such as amorphous diamond, is then deposited over the micro-tips.

Abstract: An electron source is constituted of a substrate, and an electron-emitting element provided on the substrate. The electron-emitting element comprises a plurality of electrode pairs having an electroconductive film between each of the electrode pairs. An electron-emitting region is formed on the electroconductive film of selected ones of the electrode pairs. A method of testing the electrode pairs and/or the thin film for a defect and then generating an electron-emitting region so as to have no defect is available.

Abstract: An electron-emitting device has a pair of device electrodes and an electroconductive thin film including an electron emitting region arranged between the electrodes. The device is manufactured via an activation process for increasing the emission current of the device. The activation process includes steps of a) applying a voltage (Vact) to the electroconductive thin film having a gap section under initial conditions, b) detecting the electric performance of the electroconductive thin film and c) modifying, if necessary, the initial conditions as a function of the detected electric performance of the electroconductive thin film.

Abstract: A picture apparatus includes a vacuum envelope which has a phosphor screen and a plurality of electron gun assemblies for emitting electron beams to the phosphor screen, and a deflection device for deflecting the electron beams emitted from the electron gun assemblies. The deflection device has a plate-like coupling member arranged to face the vacuum envelope, and a plurality of elemental deflection units for deflecting the electron beams to scan the phosphor screen dividedly. The deflection units are fixed to the coupling member and located at predetermined positions, respectively.

Abstract: The present invention includes a method and apparatus for processing gas discharge tubing. The apparatus includes a manifold pumping station, a fill and evacuation station and a data acquisition station. The data acquisition station enables the processor of the tubing to input, record and archive manufacturing data such as the identity of the electrode manufacturer, the tube length and diameter, the date of processing the serial number of the tube, the fill gas, the temperature of the glass during processing, the vacuum pressure inside the tube, the current used to bombard the tube, and other variables.

Abstract: A flat panel display having a repair capability, a process for repairing such a display having defects involving short circuits between a field emission tip and an adjacent conductor, and a process for forming a flat panel display with repair capability, are described. The flat panel display has a dielectric base substrate, upon which are formed cathode columns of parallel, spaced conductors. Gate lines, also formed of parallel, spaced conductors, are located over and perpendicular to the cathode columns. A dielectric layer is formed between the cathode columns and the gate lines. Pixels of the display are located at the intersections of the cathode columns and the gate lines. A plurality of openings are formed in the gate lines and in the dielectric layer, at each of the pixels. A plurality of field emission microtips, at each of the pixels, connects to and extends up from the cathode columns and into the openings.

Abstract: In a method of measuring convergence of a CRT and apparatus in use for implementing the same, the convergence can be adjusted more easily by measuring misconvergence using dot patterns so as to minimize the influence of position control, graphically processing the amount of the measured misconvergence and displaying the misconvergence state. It is not necessary to control precisely the relative position of a target CRT for measurement of convergence and the cameras used for measurement. Therefore, in measuring the convergence of a CRT, on each measurement of convergence of a new CRT, the operator does not need to readjust the relative position of a target CRT for measurement of convergence with respect to the cameras used for the measurement.

Abstract: A method for forming a microtip electron source includes the steps of forming a first microtip electron source using a mask, determining deviations in the structure of the first microtip electron source from a structure which should theoretically have been obtained using the first mask, and then correcting the first mask used during fabrication of the first microtip electron source that are designed to generate additional deviations that compensate for the effects upon performance of the deviations determined in the first microtip electron source when subsequent microtip electron sources are fabricated using the mask.

Abstract: A calibration step is carried out on a calibration tube in which magnetizations which cause beam displacements in x and y directions are determined for all the magnet poles and beams, and the adjustments of sensitivity of each beam from the x/y values is determined. A beam deviation of a production tube is then adjusted by determining its initial error in x and y directions and then starting a calculation sequence in which the magnetization currents are calculated by linear superposition of the individual currents on the basis of the known adjustment sensitivities. An additional rotating and decreasing auxiliary field is active during the magnetization of the poles in the rings of the calibration tube and of the production tube. It is also possible to correct twist errors using the invention.

Abstract: An inspection method and an inspection apparatus for the component members of the cathode-ray tube are disclosed. An inspection apparatus composed of normal members other than an object of inspection is prepared at the time of inspecting the phosphor screen of the screen panel, the electron gun or the shadow-mask constituting the cathode-ray tube. In advanced to assembling the cathode-ray tube, the object of inspection is mounted on the inspection apparatus, so that the conformance or rejection of the object of inspection is decided from the illuminated condition of the phosphor screen by irradiating electron beams thereon.

Abstract: Within an ion implanter, a source element or filament may be cured outside of the ion implanter. This may be accomplished within a vacuum chamber using the same source assembly or canister to hold the filament as is used within the ion implanter. The filament within the source canister is inserted into the vacuum chamber and a vacuum is produced at a first set point. Then, the current is gradually increased while monitoring the pressure compared to a second set point. The current is decreased where the second pressure set point is reached to prevent oxidation. Where the chamber pressure is below the second set point, the current is allowed to increase. The curing of the filament is indicated when the filament increases to the third set point, without chamber pressure exceeding the second set point.

Abstract: A system and method for automatically evacuating and filling neon tubing is disclosed wherein an electrical controller is provided to automatically control the evacuation and fill cycles. For this purpose, pneumatic actuator valves are utilized in the manifold system to selectively control the flow functions in the process during the evacuation and fill cycles. A bombarder signal is delivered to a bombarder unit by the controller, which generates electrical current through the electrodes of the tubing being processed to heat the tubing. A pressure gauge is placed in the manifold system to sense tube pressure and generate an electrical pressure signal which is transmitted to the electronic controller. A temperature sensor is placed in temperature sensing relation with the tubing to sense the temperature of the tubing and generate an electrical temperature signal also transmitted to the controller.

Abstract: A method for mounting a filament in a double ended incandescent lamp capsule. A filament assembly, including a filament, filament supports attached to each end of the filament and an external lead connected to each filament support, is located in a tubular lamp envelope. The position of the filament relative to the lamp envelope is determined, and the filament is moved to a predetermined position relative to the lamp envelope, if necessary. Then, the lamp envelope is heated sufficiently to cause the lamp envelope to deform into contact with at least one of the filament supports so as to securely anchor the filament support. The heating of the lamp envelope in regions of the filament supports can be performed simultaneously or at different times. One or both filament supports can be anchored by the tacking process.

Abstract: Magnetization of a magnetic member used for correcting the static convergence and color purity of a color cathode ray tube apparatus must be performed in consideration of the influences of geomagnetism. A magnetization unit used for magnetizing the magnetic member changes the state of geomagnetism around the neck of the apparatus. However, the magnetization unit can establish the same state of geomagnetism as that obtained when the magnetization unit is not arranged. This allows accurate correction of the static convergence and the color purity.

Abstract: An optical interrogation system has camera arrays useful for determining the locations of a plurality of apertures on a flat tension shadow mask and fiducial marks on a screened front panel of a CRT. The system determines the actual location of apertures or fiducial marks with respect to the cameras' field of view. By eliminating gray scaling, the processing only for light/dark transitions in single-bit binary valued pixels from each of the cameras in parallel, i.e., simultaneously, remarkable rapidity is obtained in the interrogation of widely spaced fields with minimal hardware. The system may also be used to interrogate mask support surfaces on the front panel prior to welding the mask thereto.

Abstract: An oxygen detector for use in a double envelope lamp is described. The detector may be formed by nitriding a metal surface to produce a metal piece with a first visual color or state. The surface thickness is sufficient to exclude oxygen during normal assemble, but thin enough to change colors during lamp operation if oxygen is present.

Abstract: A method of manufacturing a display tube comprising an envelope having an envelope portion and a display window. The quantity of X-rays released from the envelope portion is determined, after which discrete X-ray absorbing means are provided in those places of the envelope where the quantity of X-rays released exceeds a limiting value. In a display tube manufactured according to such a method and comprising, in particular, a substantially rectangular display screen and a cylindrical neck portion having an electron gun the diagonals of the envelope of which are provided with discrete X-ray absorbing means, the desirable quantity of X-rays is absorbed in a simple and cost-effective manner.

Abstract: A method for producing a gas discharge light source for emitting an electromagnetic radiation comprising a gas discharge tube filled with at least one discharge gas material and having a means for generating a gas discharge includes the following method steps: igniting the gas discharge tube filled with the discharge gas material, performing a forming operation in which the electrical operating power of the gas discharge light source is at least as high as the desired continuous operation power, the gas discharge tube is held at a temperature which is at least as high as the subsequent operating temperature, the intensity of the emitted electromagnetic radiation in the region of the desired wavelengths is monitored and the partial pressure of the vaporized discharge gas material is varied until the intensity of the selected electromagnetic radiation has reached a maximum value, whereupon a reservoir with excess discharge gas material is separated from the gas discharge tube in such a manner that the gas disch

Abstract: A method for optimizing the photo-response of a photocathode having a gallium-arsenide layer and a cesium-oxide surface coating includes the steps of overcesiating the photocathode, sealing it in a vacuum tube and baking the assembly in an oven. The photo-response of the photocathode is measured while it is baked, such measurements comprising an input to a microprocessor which controls the baking process by varying the temperature and/or time of baking. The rate of increase of photo-response due to heating and optimizing the photo-response attributable to the cesium-oxide coating is determined by utilizing a formula which relates temperature and photo-response and permits room temperature photo-response to be projected from a measurement taken during the baking process. When the rate of increase shows a characteristic diminishing pattern, the photo-response has been maximized and the baking is terminated.

Abstract: A method of manufacturing gas lasers, such as He-Ne lasers or Ar lasers characterized by positioning the laser housing within a vacuum chamber, evacuating the vacuum chamber to evacuate the laser housing through a filling tube provided in the housing, baking the housing, then filling the vacuum chamber with the laser gas, which enters into the laser housing through the filling tube, subsequently forming a solder closure in the end of the sealing tube, the removing the laser housing from the vacuum chamber and subsequently permanently sealing the filling tube by pinching off the solder closure to form a cold-weld seal of the tube.

Abstract: In a method for manufacturing small tubular lamps, a moving amount of a tube stock is adjusted according to a wall thickness thereof to make the stock-guide amount uniform, and the internal pressure during the stock-guide step is also adjusted so as to produce a suitable dimension of the outside diameter thereof, whereby the working amount in the succeeding step is reduced to decrease errors in dimensional tolerances, particularly in wall thickness and internal volume.

Abstract: The present disclosure describes a method for determining the condensate location within an HID lamp. The method involves monitoring current and voltage waveforms during the glow phase of lamp starting. If the voltage drop during the glow phase is low with a corresponding high current, then the volatile component of the lamp fill has condensed on the electrodes during the previous cool down period. If the voltage drop is high and current is low then most of the condensate has localized on the arc tube wall. An automated detection apparatus is used to carry out the measurements to determine condensate location.

Abstract: So as to detect and remove tubes having too low a vacuum before gettering, a d.c. voltage which continuously increases from a low value to a maximum value is applied between the anode (g4) and a second electrode (g3) of a television display tube, the increase in this voltage being stopped as soon as a spark discharge current flows in the tube. The associated value of the d.c. voltage is evaluated as a criterion for the selection of the tubes.

Abstract: In a method for manufacturing a liquid crystal display device, address and data lines are provided over a substrate, and a short-circuit area and an area to be made short-circuit are provided to cause short-circuiting between the address and data lines. It is prevented a TFT array from dielectric breakdown by static electricity in manufacturing processes, and examination is made for a connection breakage, and short-circuiting, at a TFT array for the liquid crystal display device, prior to the manufacturing step by cutting the short-circuit. Moreover, it can be presented from dielectric breakdown by static electricity in later processes to short the area to be made short-circuit after the examination. It is possible to both decrease a faults percentage of liquid crystal devices and improve their productivity.

Abstract: A method of manufacturing CRT tubes with binary coded faceplates including dispensing a frit paste on the faceplate in the form of a bar code. The frit is devitrified as part of conventional faceplate processing either during normalizing or during devitrification of the mask rail frit without any additional steps. In one embodiment the frit is dispensed through a single dispensing nozzle and the nozzle is moved relative to the faceplate in x and y coordinates to form a single undulating line. In another embodiment, frit is selectively dispensed through a plurality of nozzles for each character pair to form either narrow bars or wide bars.

Abstract: A method of testing an electron discharge device incorporating a cathode electrode heated by bombardment of electrons emitted by a heater electrode so that selected parameters of such device may be determined without requiring that such device be operational, the method in particular including the steps of causing the cathode electrode to be brought to operating temperature within a short period of time and determining that the current due to electrons bombarding the cathode electrode is within predetermined limits.

Abstract: A method is disclosed for use in the manufacture of a color cathode ray tube having a foil tension mask with a central pattern of apertures. A transparent flat front panel has a cathodoluminescent screen pattern on its inner surface. A plurality of mask support means, located on opposed sides of the screen pattern, have respective mask-receiving surfaces for receiving a shadow mask in tension. Q-height error data is developed according to the invention, and the aperture pattern of the mask in expanded and positioned in response to the error data to compensate for errors in Q-height to bring the mask apertures into registry with the screen pattern. Apparatus for measuring Q-height is also disclosed.

Abstract: A system for measuring the Q spacing of a kinescope panel without removing the mask from the panel includes an adder which stores the known thickness of the shadow mask and a known spacing. The adder also receives transducer inputs representative of measurements of the glass thickness, the distance of the shadow mask from a first reference plane and the distance of the panel from a second reference plane. The adder algebraically combines the stored and input data to yield an output representative of the Q spacing.

Abstract: Process and apparatus are disclosed for use in the manufacture of a color cathode ray tube having a shadow mask with a central pattern of apertures mounted in tension on a transparent flat front panel. The mask aperture pattern is registered with a catholdoluminescent screen pattern of corresponding geometry and position on an inner surface of the panel. The shadow masks and front panels are respectively interchangeable. Signals are developed which are indicative of the positions of a mechanically stretched mask aperture pattern and an associated front panel screen pattern relative to a reference or to each other. Responsive to such signals, there is effected a relative positioning of the mask and screen until registration between the patterns is achieved.

Abstract: A position adjusting method for a deflecting yoke of a color cathode-ray tube, where measurng equipment is positioned so that the measuring surface of the equipment is directed upwards, the color cathode-ray tube is positioned so that the panel surface of the tube directs downwards and the panel surface of the color cathode-ray tube is mounted on the measuring surface of the measuring equipment.

Abstract: An improved method of making a color picture tube electron gun includes the selection and assembly of a plurality of cathodes and a plurality of electrodes longitudinally spaced from the cathodes. The improvement comprises at least three additional steps. First, the amount and direction of electron beam misconvergence at the tube screen, as caused by the thermal expansion of each individual electrode during electron gun warmup, is determined. A first group of electrodes will cause misconvergence in a first direction, and a second group of electrodes will cause misconvergence in a second direction. Second, the individual contributions of the electrodes to misconvergence during tube warmup are summed. The net effect of thermal expansion of the entire electron gun is a misconvergence in the first direction.

Abstract: A method of manufacturing a color display tube in which after the envelope is formed the shadow mask is displaced relative to the display window via movable positioning members provided in the envelope. After the color display tube is assembled a test pattern is displayed on the display screen and is optimized by means of positioning members 23, such that the shadow mask is accurately aligned relative to the display screen 6. The adjusted position is fixed by forming a number of welds, using a laser 33, between the connection means 12 and the support elements 10 in the display window 1.

Abstract: A sealed beam headlamp that includes a collar bonded to an annular flange formed on the rear of a reflector and having an opening with a cylindrical support surface for receiving a plug-type lamp bulb assembly formed with a spherical portion that allows the lamp bulb assembly to be moved as a unit axially and pivoted for adjusting the position of the filament of the lamp bulb assembly relative to the reflector of the headlamp.

Abstract: For the automatic determining of the characteristics of the corrections to be made in trichromatic cathode tube deflectors, measurements are made of the coordinates of the midpoints of the bars R and B of a crossed bar test pattern at "strategic" places. With the deflector in the "mean" position on the tube, the values obtained are standardized by computation to re-establish virtually the ideal position of the deflector, the convergence errors due to this deflector are computed and the pinpoint or overall corrections to be made to it are deduced therefrom.

Abstract: An internal electrostatic field-generating, beam-controlling element in a cathode ray tube is formed by depositing an initially continous layer of resistive material on a substrate and applying a voltage differential across the coating to generate a field-generating current therethrough during operation of the tube. After completion of tube assembly and sealing of the tube envelope, the element is custom fine-tuned by projecting an externally-originating laser beam through the envelope wall to selectively remove portions or areas of the resistive material, thereby predeterminately distorting the electrostatic field and selectively changing the effect of the field on the imaging electron beam. This procedure readily enables both correction of perceived deficiencies in and intentional modifications to one or more characteristics of the electron beam.

Abstract: A dual arc tube high pressure discharge lamp with a locating element for one end of each discharge tube in which the locating element comprises an H-shaped piece of stamped metal with a leg of the H inserted in the tubular electrode assemblies of each of the dual arc tubes.

Abstract: A method of manufacturing a cathode ray tube, in which the positions of the tube envelope and the gun assembly are adjusted so their respectively longitudinal axes coincide, and then fixed against non-axial movement prior to insertion and sealing of the gun assembly into the neck of the envelope, wherein the gun assembly position is fixed by clamping at least three of its connector pins.

Abstract: A system and method for monitoring the spot-knocking of electron tubes includes individually identifying each tube carrying hanger and each cart which applies a spot-knocking voltage to the tubes. The hangers and tubes sequentially engage a series of anode bus bar segments and the spot-knocking discharges are counted. The counts for each hanger and for each tube are averaged and compared with stored averages to identify faulty tubes, spot-knocking equipment and carts.

Abstract: Subdivided pixels are provided with interconnected and hence redundant row and column bus lines to reduce fatal defects. The respective redundant row and column lines also can be interconnected between subpixels to further reduce defects. One defective subpixel is generally an acceptable non-fatal defect, since the rest of the subpixels are still operative. The subpixels also can be formed with common row and column bus lines. The pixels or subpixels can be connected in a serial serpentine pattern to test all row or all column bus lines at once. After testing, the serial connections are broken.

Abstract: The invention describes a method of accurately mounting a deflection unit on a cathode ray tube envelope. The deflection unit is provided with three V-shaped connecting devices and globally positioned with respect to metal mounting pads thermal compression bonded to the envelope. Three adjustable manipulators, each provided with a socket for engaging a semi-spherical part on one of the V apexes, accurately position the deflection unit on the envelope to obtain an accurate test pattern on the cathode ray tube screen. Finally the V-shaped devices are laser-welded to the mounting pads by laser devices incorporated with said manipulators.

Abstract: In a method of manufacturing a colour television display tube, a reference system is used for adjusting the various components of the tube relative to each other. The system fixes the deflection centre and the electron-optical axis of a deflection device, provided afterwards on the tube, in an early stage of the manufacturing process of the tube. The adjustment of the components is carried out while being referred to the fixed deflection centre or the fixed electron-optical axis. The method simplifies the subsequent positioning of the deflection device on the tube.

Abstract: A sealed beam lamp having an outer envelope defining a gas-tight enclosure filled with an inert nonreactive gas at a pressure in the range of 5 to 50 Torrs, and an illuminating burner capsule mounted within the enclosure. The integrity of the gas-tight enclosure as well as the pressure of the gas is verified by creating a predetermined electrical potential within the enclosure to form a glow discharge in the gas if the gas pressure is within a predetermined range indicating the lamp is serviceable and an arc discharge if the gas pressure is in excess of the range indicating the lamp is defective.

Abstract: A method of determing the actual temperature of a layer of an infrared material, especially during heat cleaning, which includes measuring the thickness of the layer and the amount of radiation being emitted from it. An apparent temperature corresponding to a desired actual temperature is found from a curve of apparent temperature, which are derived from the radiation amount, versus thickness. The apparent temperature which corresponds to the desired actual temperature compensates for interference effects on the radiation measurement. A computer may be utilized to calculated the apparent temperature which corresponds to the desired actual temperature and to regulate and maintain the infrared material at the apparent temperature.

Abstract: Process for the production of a matrix of electronic components.The matrix and the associated control circuits are produced in redundant form. The redundant elements can be interconnection lines between the electronic components of a matrix row or column and the associated control circuits or the actual electronic component. A row or column of electronic components represents a subassembly, which is tested by means of optical addressing, consisting of transmitting light rays onto photodiodes located at the periphery of the matrix and connected to each subassembly. As a function of the test result, the matrix is reconstituted by disconnecting the defective electronic components in the redundant subassemblies and then reconnecting the satisfactory subassemblies to one another. This process is more particularly applicable to a matrix of elements used for the control of a matrix display.

Abstract: The present invention relates to a headlight comprising a glass lens element and a support element, such as a reflector, of thermoplastic material, such elements being associated at their periphery by matching assembly shapes of interlocking type which are fixed by an assembly glue. The headlight is characterized in that the lens is provided with three fixed internal supports cast in one piece with the lens which define a bearing plane. The lens is also provided with a further internal support having a positive offset with respect to the bearing plane. This offset is compensated by an interposed support member whose thickness is determined by the actual features of the lens.

Abstract: A method of manufacturing a cathode ray tube which comprises an envelope portion (1) having a longitudinal axis (8) and a gun assembly (32) having a longitudinal axis (8), in which:a. the envelope portion (1) is fixed in an assembly device (30,31) in a given position,b. the gun assembly (32) is provided in the envelope portion (1), the axes (8) substantially coinciding,c. the location and/or the orientation of the gun assembly (32) is adjusted with respect to the axis of the envelope (1), andd. the gun assembly is secured in the envelope. The adjustment of step c is carried out by means of a structure (15), connected to the gun assembly (32), which consists of magnetically half hard material and is magnetized as a multipole, and by means of a device having magnetic field-sensitive sensors (20, 21, 22, 23) provided around the envelope (1) at the level of the structure (15).

Abstract: A method of and a device for use in manufacturing a color display tube in which magnetic poles are provided in or around the neck (4) of the tube envelope (1) and around the paths of the electron beams (18, 19, 20) extending substantially parallel to the axis (8) of the tube, said magnetic poles generating a permanent multipole magnetic field for the correction of the convergence, color purity and frame defects of the color display tube. The magnetic poles are formed by magnetization of a configuration of a magnetizable material (15) which is provided around the paths of the electron beams (18, 19, 20), said configuration being magnetized by energizing a multipole coil unit (21-28) by means of a combination of currents (Ia-Ih) which generate a static multipole magnetic field and the magnetization is produced by means of a decaying alternating magnetic field which initially drives the magnetizable material on both sides of the hysteresis curve into saturation.

Abstract: A method for assembling a spark plug 20, 66 which includes providing a ground electrode 24 on a spark plug shell 22 having a predetermined final configuration and position and then mounting an insulator 34 in the shell. The distance from a step 38 in an insulator bore 37 to the ground electrode is measured. Based upon this measurement and a desired dimension for a spark gap 56, the dimension on a center electrode 48, 68, 74 between a shoulder 50, 76 and a tip 52, 80 is adjusted so that when the center electrode is disposed in the insulator bore with the shoulder seated on the bore step, the tip forms the desired spark gap with the ground electrode. The center electrode then is assembled into the insulator.