Wednesday, November 4, 2015

bridgeport optical system

My Bridgeport came with this optical system for reading the location of the table. This is listed as a Bridgeport accessory but i've never seen one before and there is limited info on the web about these. There is a small box mounted on the side of the mill that coverts 110V to 6V and there are small 6V bulbs inside the x and y readout boxes that illuminate the graduations that are magnified inside the window (sidetone: the bulbs look like small motorcycle taillight bulbs). The graduations are actually on small glass/mirror? like scales that are fastened to the x and y. The surface is protected by small rubber flaps that keep the scales clean. The graduations are in .0001 increments....CRAZY! Think of this as something similar to a Digital Readout or "DRO".

For more on this read below and check out images I found of one of these mounted on someone's machine.

Before the advent of electronic measuring systems, milling machines commonly had two methods of precisely locating work - mechanical and optical.  

Optical Measuring System for longitudinal and cross feed.
Another pre-electronic era device for the precise setting of work that involved no mechanical contact - and so avoided wear and consequent inaccuracy. The unit bolted to the machine using a majority of existing holes - and was protected in use by a neoprene guard. The longitudinal travel was 20 inches, cross travel 9 or 12 inches, the magnification x17 and the reading accuracy 0.0001 inches on a direct, single line scale. The scale had just one line to read - and no vernier estimations to be made.

This is an Bridgeport Milling Machine optical measuring system. It operates like an old school DRO. It “reads” the table position in both the X and Y axis using optical lenses to view the glass scales, then transposes them measurements into the viewing screen. The viewing screen looks similar to a ruler, but is graduated in .001, with a smaller scale below for .0001 It is original Bridgeport equipment. The viewing devices are mounted on aluminum dovetail brackets the have thumbscrew adjustments. The whole system bolts up to the milling machine using the factory Bridgeport holes. It has a power supply with it that converts 110v power to 6 v DC, that powers the lamps for viewing. It uses little 6v motorcycle bulbs, readily available at auto parts stores. The only real drawback to this optical system is that you can not zero out the scales after you find and edge, bolt center, etc. You will have to manually keep track of your starting point, but it is not hard, and it works really well. There is a rubber protection strip that mounts above the scale as well to help protect from chips and fluids. These are very cool, work well, and have a certain Bridgeport coolness to them that any Bridgeport aficionado should appreciate. 

The item “Bridgeport Mill Optical Measuring System, old school cool DRO”.

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