View Full Version : Direct Read Out
08-21-2003, 01:44 PM
Has anyone retrofitted a commercial milling machine (Harbor Freight, Grizzly, etc.) with Direct Read Out?
I have just finished a vertical milling machine and am interested in attaching a scale to each axis. I am talking abot a 7" X axis and a 14" Y axis. The Z axis will be by scale and a dial indicator.
To go one better I want to attach (at least) a dial caliper to each axis to be able to get direct readings versus the vernier scale on the handles. Ultimately I would adapt digital read out calipers to each axis.
Has anyone done this? Do you have pictures you could share on how they are mounted?
Thanks in advance.
Contemporary Blacksmith with building projects from foundry to an S/C Cobra
08-22-2003, 02:37 AM
Yes it has been done. Check the BBS Article Index - it is one of the Village press books.
It can be done with long travel Dial indicators as well. Digital calipers offer a easier way to do readings as you can re-zero where ever and go from there. The article I spoke of used a Mitutoyo caliper to do this. All you need to do is make the appropriate brackets that bolt to your machine and clamp your caliper to teh brackets - and that is all there is to it, really.
You can also buy any of the commercially made DRO systems - these are installed all the time.
[This message has been edited by Thrud (edited 08-22-2003).]
08-31-2003, 06:35 PM
Many such retrofits have been done and many descriptions of the work have been published.
I've been planning and doing some readouts on my small lathe and drill press. The first one I made used a 1" dial indicator for a quill that has a 3/4" range of movement. On this one I used a 1/2-20 screw as the target for the indicator to provied the ability to zero it at any position over the 3/4" range. Dial indicators can be used for ranges up to 2".
I have found that the digital depth gauges are better than the calipers for this purpose. They fit better and do not have the skinny depth measuring tang that a caliper has. The digital variety has three important advantages: 1. they can be zeroed at any point in their range, 2. they usually can be switched to read either English or Metric units, and 3. they do not have a rack and gear for chips to settle in and foul. A dial type read out could be OK for a Z or quill axis where the chips will not easily find their way but the X and Y axies should have either vernier (hard to read, don't even think it) or digital readouts.
If you are designing your own mounts, there is one thing you should keep in mind. There should be some provision for a small amount of misalignment and sideways motion when attaching the two blades of the caliper or the base and slide of a depth gauge. When a dial indicator is used, it's spring loaded tip can simply be allowed to rest against a flat target and any side to side motion will just cause it to slip across that surface by a small amount.
Calipers do not have a spring loaded element and so must be held with more restraint. One technique I have considered is using music wire suspension for one of the attachments. The wires would be about 1" long and parallel to the direction of motion so they would maintain an almost constant dimension there. However, they could flex slightly to the sides to allow for any misalignment.
Import digital depth gauges can be found on E-Bay and from other suppliers in lengths from 6 to 12 inches for reasonable prices.