Dorsey Metrology, one of the world’s most respected gage makers manufacturing optical comparators in the US, is proud to announce the latest addition to their expanding range of products.  This new comparator has the same high quality features as the current product line, but in a smaller package and at a lower price point.

The New 14″ Industry Standard The 14HE has a 14 inch/350 mm diameter screen and an 8″ x 4′ X andY travel.  The nickel plated cast iron work-stage has both coarse and fine adjustment control together with a massive 50lb working capacity.  As always, cross roller bearings are on all three axes.  Dorsey is known for their unique internal edge detection, which is optional on this model.  A variety of digital readouts from different manufacturers are offered to compliment this. Features:

• 14″ (350mm) screen for optimum viewing
• High resolution ground glass screen with 90 degree cross lines and chart clips
• Machined chart ring with vernier protractor, 1 minute graduation
• Output for electronic rotary screen protractor
• Coated telecentric par focal optics
• Available optional internal edge sensing
• Quick change single lens mount
• Optional Fiber optic surface illumination
• Nickel plated, completely cast iron workstage with single universal dovetail
• Triple axes solid crossed roller stage system
• 16″ x 4″ overall stage size
• 8″ X axis travel with “glide release”
• 4″ Y axis travel (rise & fall)
• 50 lbs. capacity
• ± 5 degree lightsource helix adjustment
• NIST traceable calibration certificate
• 2 year limited warranty

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We are getting ready to start producing video podcasts too. Keep your fingers crossed.

In the meantime we will try to keep this blog constantly updated with more information about optical comparators.

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I’ve been using linux distributions for 11 years now and I saw a lot of changes. Perhaps too many. From solid rock server system developers took different approach to make it more user friendly. And I agree with that, but that famous Unix simplicity has disappeared somewhere along the road. Linux systems became more user friendly, thus more available for ordinary users.

However, developers aiming at wider user base introduced new challenges for old school sysadmins and geeks. These days I hardly see Windows or Mac system crash, Linux starts to remind me of Windows 98. I don’t get blue screens but hard crashes occur quite often. Probably the problems behind it are faulty device drivers. Linux community did a fantastic job making that system work on various hardware configurations, but it’s still far from perfect.

However, it’s all community driven. Linux needs powerful company behind it. Linux needs someone that can influence hardware and software makers to release their products with Linux support. Linux needs company that can provide enterprise class support. And Linux needs a company with worldwide marketing capabilities. Without it it will never shine on desktops. It needs a push in corporate market. And without powerful company support it doesn’t stand a chance.

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Dial test indicator shown above is Dorsey Metrology model TI4-005D. Indicator can be purchased as a standalone dial test indicator or as a kit with additional contacts. For more information visit Dorsey’s dial test indicator page.

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14HE optical comparator made by Dorsey Metrology.

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When ordering optical comparator chart, please specify the following:

• style of chart (more available – images coming soon)
• type and model of optical comparator
• lens magnification
• chart material – glass or plastic
• additional information required for particular chart or scale

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Squareness of X axis to Y axis is checked by placing a square on the center of the optical comparator table banked up against one of the stage vees. Face it to the right or left side. Place a magnetic base indicator on the face of the comparator near the chart ring. Lower the Y-axis to the bottom and place the tip of the indicator on the side of the square. Raise the Y-axis and check the squareness of the X axis in relation to the Y axis travel. It should be .0001” or less per inch (≤ .0006” for 6” travel). If adjustment is needed the knee bracket must be loosened and twisted to correct.

Squareness of Y axis to focus plane

Squareness of Y axis to focus plane is checked in the same manner as squareness of X axis to Y axis only with the face of the square facing forward or back. This should be .0005” per inch or less (≤ .003” for 6” travel). If this is not correct you would need to shim under the lower focus bearings to bring into spec.

X axis stage linear traveling accuracy

For this specification we use the formula ± (150+L/.02)µin. For a 10” travel optical comparator stage we would divide 10” by .02 to get 500 then add to it 150 for a ± total of 650 micro inches over 10” travel (±.00065”). The optical comparator stage is inspected using the 6” scale on the Acu-Rite master in the center of the stage. The deviation from the expected reading is recorded on the inspection sheet in micro inches (.000001”), a minus sign before the value indicates the measurement was under size. If corrections are needed a new comp. value can be entered into the optical comparator digital readout for the axis you are working on. Errors that are linear in nature are easily compensated for. If your readings are very non-linear it could indicate damage or looseness. The remarks section of the inspection sheet shows any error compensation set in the digital readout for that axis.

Y axis stage linear traveling accuracy is checked the same as X only with the master standing vertical on the stage.

ERP calibration counts

This value indicates the number of pulses recorded by the rotary encoder during calibration. The idea is to have a point of reference to use in the future if any errors or changes are needed to make the digital angle display more accurate. To re-calibrate the rotary encoder follow the instruction in the optical comparator manual and record the new value on the inspection sheet after a satisfactory value is achieved on the display.

ERP Repeatability

A check in this box indicates that the angle display is within ± 30 minutes of angle over a 360° rotation (±0.5°).

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With the table now square to the focus travel, optical comparator lens and projected image check the image horizon in relation to the screen vernier 0. To do this place a pointy object (like the corner of a razor blade) on the center of the stage. Have it stick straight up from the stage. Bring the object into focus in the center of the optical comparator screen. Turn the screen until the 0 protractor mark on the glass screen is lined up with the 0 mark on the vernier under the screen. Now (without moving the screen) move the point of the image on the screen to just touch the bottom of the horizontal (horizon) line. Now without moving the screen move the X axis left and right the pointer (image) should stay just touching the bottom of the optical comparator screen horizon line as it is moved. If the image moves diagonally on the screen the image horizon is off. This can be corrected two ways. Adjusting the vernier on the chart ring to match the image horizon (for a slight adjustment) or by adjusting the mirrors (for a gross adjustment). Twisting one mirror left or right will dramatically affect the horizon. The lower mirror has more affect on this than the upper one. The idea is to keep an eye on the horizon while you are adjusting the optical comparator magnification this way the horizon is good when the magnification is finished.

If the magnification is not correct adjust the optical comparator mirrors as needed to optimize the magnification. If when you are done with the magnification the horizon is slightly off you can correct it by loosening the three chart ring screws and rotating the ring slightly. Zeros on the calibration sheet indicate the magnification in that quadrant of the screen is within the acceptable limit listed on the sheet. Once the magnification is set for one lens, other lenses can be easily checked for proper magnification.

This can be done by placing another lens in the comparator and looking at the image from the Acu-Rite Measurement Master on the screen. For instance the one inch scale on the master should measure ten inches on the screen if you are using a 10X lens. If it does not measure exactly ten inches loosen the three screws on the back side of the lens and screw the back part of the lens in or out until the correct magnification is achieved. Use this technique for any additional lenses. The optical comparator mirrors only need to be adjusted for one lens. The remaining lenses are adjusted to set their magnification. The circle around the lens magnification on the inspection sheet indicates the final inspection was performed using that lens.

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