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Probing new depths in hole measurement.

Probing new depths in hole measurement

A lot is happening in hole and thread measurement. More advanced materials are being incorporated in time-honored techniques for measuring hole diameter. Equipment and processes are being improved to make them faster and more repeatable. The computer is being used to control the automating of inspection operations. More optics and video methods are being used to make sophisticated measurements and analyses of parts, with the results fed back to quickly correct or recalibrate the manufacturing process.

Here's a review of some of the latest products and technology in the world of hole and thread measurement:

Borescope improvements

Improvements in fiber-optic materials and proprietary lens systems are providing borescopes and holeviewing systems that deliver brighter, larger, and sharper images from deeper and previously inaccessible holes. The technological developments include improved optical lens systems with new rod lenses and wider field of view, improved optical glass, and a more sophisticated illumination to project light over an expanded area. The results are improved visibility, enhanced images, and more detailed analysis than previously possible; i.e., a new generation of internal inspection equipment.

For example, the Olympus OES borescopes, Figure 1, employ a hybrid system of optical-glass rod lenses and convex lenses to reduce glass-to-air transmission of the image to reduce light scattering and produce more brilliant images. Because the lens system is more compact, it allows space for a larger light guide bundle to project more light on the subject. The image also has greater contrast and a simulated 3D spatial effect. Also, an optical-glass formulation transmits 30 percent more light and an opticallyclad glass rod is used to transfer and diffuse collected light across the face of the light-guide fibers for additional illumination. A heat-resistant cover glass protects the glass rod from thermal shock.

Beyond optics, mechanical-design improvements include a fuller 370-deg orbital scan so the user can rotate the shaft more than a full circle, convenient finger controls to change scan and focus, and an ergonomic design to fit the user's hand more comfortably and reduce fatigue.

The OES is also available as a measuring borescope for defining wear, corrosion, cracks, and contamination effects. A calibrated reticle is multiplied by eyepiece magnification to obtain an inch or metric measurement of the object in view.

For more detailed analysis, the VA-1 portable video analyzer can be used with either flexible fiberscopes or rigid borescopes. This compact, 27-lb unit contains a 9" color monitor, VCR, control panel, and keyboard, and uses a digitized color freeze-frame technique and video cursor to make measurements with an accuracy of one part in two thousand.

First, the unit digitizes and freezes a full frame for analysis. The operator then places the movable calibrated video cursor over the portion of the image to be measured, and an automatic system computes its value based on a known reference dimension. This value is displayed in real time and updated as the cursor moves from a reference point. Various images can be stored, compared, superimposed, and text data added via the keyboard.

Olympus Corp, Industrial Fiberoptics Div, 4 Nevada Dr, Lake Success, NY 11042 or circle 451.

Interior grooves and threads

A fast and accurate measuring system has been developed for checking the precise position of internal grooves, chamfers, and threads in hard-to-reach locations. Figure 2. It includes a 13"-long, 0.254"-dia rigid fiber-optic borescope that an operator moves on a carriage to view magnified images of otherwise inaccessible interiors. As the operator moves the borescope inward from a zero starting point, a magnetic sensing system sends precise positional information, accurate to 0.001", to a digital display that shows longitudinal displacement distances in inches or millimeters.

By superimposing the borescope's reticle centerline on the zero point and the beginning and end edges of the interior feature being measured, the operator can obtain exact location and width information. Mounted on a cast-steel table, the system also includes a closed-circuit tv monitor that shows a magnified image of the location to aid in positioning the reticle and viewing the area. For an even higher resolution image, the operator can use the borescope's eyepiece.

By combining the borescope with magnetic displacement measurement and computer readout and storage, the system provides up to a ten-to-one time savings over micrometer techniques while boosting measurement accuracy. Four to five longitudinal measurements can be made in five minutes.

The system is an easily set, repeatable method for checking exact position and surface finish in parts with IDs as small as 0.254". It was developed for internal measurement of engine parts and hydraulic systems in the construction industry. Prior methods for accurately measuring hard-to-reach grooves and threads required either sawing the part in half or filling its interior with liquid rubber and measuring the extracted hardened rubber form.

Lenox Instrument Co, Scottsville Industrial Park, 265 Andrews Rd, Trevose, PA 19047-3427 or circle 453.

Shifting IDs

The challenge was to simultaneously measure three different IDs on a pump housing when the distance from the reference face to the center of one of the IDs, a snap-ring groove, could vary plus or minus 0.005". The other two dimensions were the impeller cavity and impeller-shaft bushing bore.

"We knew we had a tough nut to crack to achieve the required accuracy," says Control Gaging's Rick Scholz. "The solution was a unique floating-ball gage finger we designed to accommodate variations in snap-ring groove height."

The resulting gage system 5284, Figure 3, uses three ID gages with 20-millionth repeatability and a special slip-clutch mechanism that cuts gage setup time to less than 30 sec. A self-mastering feature provides automatic verification if adjustment is necessary.

The complete system includes six stations housed in a single-enclosure with a microprocessor controlling operations. A gaging cycle is approximately 15 sec. If gaged diameters fall outside programmable limits, a compensation signal is sent to the turning-machine controller.

Control Gaging Inc, 5200 Venture Dr, Columbia Center, Ann Arbor, MI 48108 or circle 454.

Other hole-measuring

products:

Expanding plug gage

Basic bore gage can be expanded to cover unusual or difficult gaging problems. With proper tooling, it can be adapted to measure spherical, groove, hub, or bearing diameters; bore depths, interrupted bores; or internal or external spline dimensions. Other applications include thin-section bores, trepanned bores, shaft diameters, and tapered bores.

Comtorgage Corp., Industrial Dr, Slatersville, RI 02876 or circle 456.

Snap-open ID gage

Battery-powered Borematic LCD-reading instrument uses three selfaligning snap-open contacts to quickly measure hole diameters to 1-micron accuracies. Display face swivels 330 deg of ease of reading, and gage series covers ranges from 0.275" through 4.4". Special functions are preset, inch/metric conversion, zero, hold, and on/off to conserve battery life.

Mitutoyo Measuring Instruments, 18 Essex Rd, Paramus, NJ 07652 or circle 464.

Air rings/plugs

A variety of air rings and plugs are offered in tool steel, chrome-plated steel, and tungsten carbide in many sizes and styles. Plug styles include leaf contact or open jet in blind, close-to-shoulder, and through-hole configurations. Sizes range from 0.120" to 6.010" (3.05 mm to 152.65 mm).

Edmunds Gages, Farmington Industrial Park, Farmington, CT 06032 or circle 466.

Thread sensor

RW-80 thread detector is a noncontact solid-state electronic sensor that eliminates the problems of air sensors. In automated thread-tapping operations, it is inserted in the tapped hole and provides a greenlight indication if that hole is properly tapped or a red light if it is not. It also provides a 120-V output to the machine's programmable-logic controller to signal a defective part. It is available in 1- to 4-channel models, a variety of thread sizes and probe shapes, and as a panelmounted card rack.

Mectron Engineering Co Inc, 3934 Varsity Dr, Ann Arbor, MI 48108 or circle 470.

Hand-held bore gage

Electronic bore gage makes measurement a simple, one-handed operation. Self-centering, three-point system yields consistent readings part-to-part, person-to-person. Functions that can be measured include: Direct measurement to display exact size of hole diameter, comparative measurement to display variation from a mastered zero setting, classified measurement to display compliance to toleranced limits, maximum hold mode to display only the largest diameter measured, and the statistics mode that offers SPC output through the RS 232-C port. Diameter range is 0.4" to 4" with interchangeable measuring heads. Resolution is 0.000 05" with an accuracy of 0.000 02" Setting rings are provided, and deepbore extensions are available. Gage operates 9 hr on a rechargeable battery, or can be used with a charger/adapter.

Standard Gage Co Inc, P O Box 271, Poughkeepsie, NY 12602 or circle 471.

Hole-depth gage

The 745 electronic depth gage can be integrated with data collectors and processors for trend or SPC analysis or hard-copy documentation. Linear accuracy is plus or minus 0.0001", and measuring range is 0 to 6" with instant inch/metric conversion. LCD readout flashes when tolerance limits are exceeded. Extension expand measuring range to 7" or 12".

L S Starrett Co, Marketing Dept 8A, Athol, MA 01331 or circle 476.

Bore obstructions

Series 282 and 283 four-point-contact bore gages are for measuring critical recessed internal dimensions encumbered by obstructions such as housings. Internal diameters within front recesses are measured with the 282, and axle-end ODs within front recesses with the 283. A variety of depths can be accommodated, from shallow to deep.

With modifications, gages can check concentricity of hub/obstruction to the bore, as well as taper and distortion for the entire bore length. Gages can be fitted with electronics for data acquisition and SPC.

Dyer Co, 1500 McGovernville Rd, Box 4966, Lancaster, PA 17604 or circle 473.

ID/OD comparator

Models 36B-10 and 36B-20 adjustable comparators provide a wide range of inside and outside diameter measurements. Gaging pressure is adjustable and construction is rugged for shop use. Electronic indicator provides both digital and analog display, and flashing limit signals can be set for anywhere in the measuring range. The B-10 has a 0.75" to 5.50" ID range and the B-20 range is 0.75" to 7.75".

Federal Products Corp, 1144 Eddy St, P O Box 9400, Providence, RI 02940 or circle 475.

Pistol-grip gage

Quick-action 3-point bore gage is self centering. Pistol grip retracts measuring heads before entering bore. Available ranges are 0.236" (6 mm) to 3.937" (100 mm) for standard heads and 0.394" (10 mm) to 3.937" (100 mm) for blind bores measured at the very bottom of the bore. Gages are used in conjunction with electronic or dial indicators for comparison measurement or interfaced with data-collection software. Display resolutions are 0.001" 0.0001", or 0.00005", and viewing angle can be rotated for reading convenience.

Chicago Dial Indicator Co, 1372 Redecker Rd, Des Plaines, IL 60016 or circle 478.

Bore gage kit

Fitted wooden case contains a series of adapter contacts for converting the 251 Series bore gage to measuring diameters from 2" to 6". A precision bell crank motion-transfer mechanism assures repeatability and accuracy of measurements. Indicator options range from 0.0001", 0.0005", 0.002 mm, and 0.01 mm graduations.

Measurements are between opposed fixed and movable contacts with a spring-loaded centralizer to assure repetitive readings as the gage is rocked in the hole. Movable contact is carbide tipped, and the fixed contact and centralizer are collected balls that can be rotated as wear occurs. All contact balls can be carbide for abrasive measuring conditions.

Gage Master Corp, 42327 Rio Nedo, Rancho California, CA 92390 or circle 474.
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Copyright 1989 Gale, Cengage Learning. All rights reserved.

Article Details
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Author:Sprow, Eugene E.
Publication:Tooling & Production
Date:Apr 1, 1989
Words:1916
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