John Thornton wrote: > I just wonder why you want to put such a nice DRO on a worn out old manual > mill > that needs the ways scraped and the screws are worn out? Hate to argue, but the differential wear in the screws makes it totally impossible to make anything with better than 1/8" accuracy using the dials on the handwheels. With a DRO or any other direct measuring scheme, you CAN make FAR more accurate parts. Even a dial caliper bolted to the slides will work. The differential wear on the screws can easily be more than one order of magnitude worse than any worn spot in the ways. You will not be able to > make an accurate part to the abilities of your DRO if the table won't stay > where you > put it and your Z is always changing because your table moves up and down as > you > move X and Y because the ways are worn. I have a 1938 Bridgeport with all this sort of way wear, but I can make parts of substantial size to within .001" tolerance with little difficulty. With the original Acme screws, I was lucky to get within .025" of where I wanted to be. I put an ancient Bridgeport optical measuring system (glass reflective scales and rear-projection magnifier boxes) on it in 1995 or so, and suddenly I could make a box with holes and a cover with matching holes, and didn;t have to spend a day filing out the holes to match! Wow!
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