I got tired of using my cheap Chinese mill without a DRO. Linear
scales are $400 and up per axis. Complete DRO's run about $1000 and
up.

An Omron rotary encoder is $25 with 2000 pulses per rev. You can't
gear it to the ball screw as that has backlash. So I came up with
this scheme.

I am using a $50 Maximite to display the numbers on a PC VGA
monitor. An old  PC keyboard to zero the numbers. I have half a
dozen. A simple BASIC program will get the job done. I will upload
the source code shortly.

First step to a cheap NC mill.
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"Wait a minute. Suppose the cable slips on the drum?" you might say
Well here is the answer for that. Use a MXL cog belt. The proper
pulley for .001" resolution is .611" pitch diameter 1/4 inch wide.
The Maximite floating point math can correct that to exactly .001"
resolution.

Utilizing the Maximite storage capabilities  on 64 Gig SD card, it
can do things no expensive DRO on the market can match. How about a
complete history of what you made, how you made it and the time and
date you made it?

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Really cheap DRO. These 2 inch travel dial indicators are about $20 each.

Paul Lamar




You can do the same thing without all the fuss and bother of cables, belts,
computer programs, etc. by using inexpensive digital calipers - I published
plans for that in a couple of my "Home Shop Machinist" columns quite a few
years ago -

Roland Friestad

Good idea.
If you still have  those planes I can publish them again here if you wish.

Paul Lamar


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