Before DRO, how was it done?

[Gary Gill]

Before digital scales how did one go about stepping off a hole pattern on a mill? It seems counting the turns on the hand wheel would work but one could lose count. Maybe a stop was set at zero on each axis?

[SGW]

There are tables of coordinates for various hole patterns of diameter 1 in Machinery's handbook. You chose the correct pattern, multiplied the values by the diameter of the circle you were doing, and did it. Or used a rotary table.

[Mcgyver]

same way its done still in my and tons of other shops, using the graduated handwheels and being careful

[JeffKranz]

When I started in the trade (1977), we had some very large boring mills that had vernier scales for the X & Y axis. When we wanted to go up 80” we would put a mark on the scale and dial with a grease pen. We knew where zero was set on the scale (might be something like 12.231) and if we wanted to move up 65.223 we would just add the two numbers up and rapid traverse up to the close and climb up and down the moveable steps until we got to our correct dimension. In the first few months of working for them they added digital readouts to all the boring mills. This was probably the best money they ever spent. For movements in Z (which never had readouts) we used dial indicators and planer gauges set it micrometers for in and out movements.

On most boring mill work, you never really needed a Z digital readout since most of the work was in X & Y. At one point we added a right angle attachment to one of the boring mill for some slight production work and we then added a Z readout so that one machine has X,Y, &Z.

[John R]

I sometimes place a ruler with a magnet or tape to give a rough location to the next point to verify that I got the correct number of turns on the hand wheel
Good luck
John R

[vpt]

Whats a DRO?

[Lew Hartswick]

I have even taught high school kids how to count by "two's" as
they turn the crank on the X or Y axies. Then the next step is to keep
track of how many times you go through 10 on the fingers of the
other hand (from the cranking one). That's good for 5 inches. :-)
...lew...

[Rustybolt]

First you account for the backlash, then you start counting turns. A pencil and a pad of paper help

[TriHonu]

It depends upon the accuracy you are trying to achieve. As the screws wear the hand wheels will retain their accuracy as long as the nut is capturing a group of threads that are all worn the same amount.

As you move further along the screw to an area that has less wear, the table will move farther than indicated on the hand wheel as it enters the unworn area.

For larger parts that require higher accuracy, you can establish a zero and use gage blocks (jo-blocks) set on the part or table at the zero point and then move your tool to the precise distance of the gage blocks. If you are now "outside" of the main wear on your screw, you can use the handles to measure out to the dimensions near your "Jo-block" move. Two pair of good quality 1-2-3 blocks stacked together can be used to make a 12" move with very good accuracy.

You can also increase accuracy by clamping your part near the end of the table where the screws usually have less wear. We all tend to use the middle of the table for some reason. I am getting better at leaving my vise on one end of the table. There is less wear on the screw and I can use my RT or indexer on the other end with out having to keep removing and re-indicating the vise.

There are also measuring devices (Trav-A-Dials and long range dial indicators) that you can use that allow you to quickly make those larger moves with a higher degree of accuracy on machines with some wear in the screws.

I have a 10" travel dial indicator I use on both my lathe and mill when I need to make those larger moves quickly.

[TGTool]

And it helps to mark the layouts first, even if they're not dead nuts, to give you quick feedback on whether you've miscounted turns on the screw.

Also just pulling out a tape or scale to double check. The dials provide the accurate point, but the tape can tell in you're a tenth or a quarter of an inch off.

And finally, use the eyeballs. A visual look at the spot you're about to drill will usually give you a clue if you're working in the right ballpark or not.