DRO questions

I am just asking. How much does one use the z-axis scale? I am contemplating if I must get a 3-axis or 2-axis DRO.
I rely on my z axis DRO for my round column mill. There is enough backlash in the old beast to create uncertainty and with the fine feed dial at .085"/rev., counting turns and doing the math to calculate travel is too much, not to mention calculation errors. The DRO eliminates all that.
 
On a Bridgeport, the Z-Axis dial is large, easy to read, and stable. I have not found a need for DRO there. I added a quill DRO, but I use it rarely...mainly when drilling to a critical depth or countersinking.
 
One advantage of a z axis DRO is the ability to zero tool offsets off the part the subdatum positions. Below is an example of manual machining using an RT for a 4th axis and the DRO for positioning. It involved 20 tool changes and would have been virtually impossible without the DRO.

StepOperationFaceToolRotary TableDRO DisplayCoordinates, inches
degreesFunctionXYZ
Notes: The following operations are executed on the rotary table in vertical position with the central axis aligned with the mill X axis. The rotary table should be adjusted so that it is square to the mill table to within 0.0005" over 5" travel, using shims if necessary. The 4" 3-jaw chuck is used as the workpiece clamping device. The flexible electrical contact datum point is assigned ABSolute 0,0,0 coordinates and located so that the X and Z coordinates will coincide with those of the workpiece (~8.65" above mill table and 4.75" from rotary table bed). The mill head should be set so there is 1.75 inches of clearance between the top of the head and the column retainer. Operating speed should be set at 1325 rpm. All tools excluding the 1/2" and 7/32" end mills and taps should be chucked in the Tru Center chuck adjusted for < 0.0002" runout.
1​
cut blankbandsawNANA
2​
weld blank to stubsoldering ironNANA
3​
level piecerotary table90/270NA
4​
face side of piece1/2" end millNANAAs Req.VariableN/A
5​
set DROABS0.4600N/AN/A
6​
1st face top1/2" end mill180ABS0.0000VariableAs Req.
7​
set DROINC0.0000N/A0.0000
8​
1st face bottom1/2" end mill0INC0.0000Variable0.0000
9​
measure top-bottom (XXXX)micrometer
10​
set DRO to -1/2 (XXXX)INC0.0000N/A-.5(XXXX)
11​
find top face, set DRO Y1/2" edge finder90INC0.00000.0000As Req.
12​
find bottom face, set center find on DRO Y axis1/2" edge finder90INC0.0000.5(YYYY)As Req.
13​
set absolute coordinates at Z axis datumsharpened scribeABS0.00000.00000.0000
14​
find top face, set DRO Zsharpened scribe, 50X microscope180INC0.19000.0000-.5(XXXX)
15​
find bottom face, check DRO Zsharpened scribe, 50X microscope0INC0.19000.0000-.5(XXXX)
16​
set DRO X,Y,ZSDM 1990.00000.0000-.5(XXXX)
17​
set backup SDM coordinatesSDM 1980.00000.0000-.5(XXXX)
18​
set 2nd backup SDM coordinatesSDM 1000.00000.0000-.5(XXXX)
19​
zero tool Z axis1/2" end millABS0.00000.00000.0000
20​
final face top1/2" end mill180SDM 1990.0000Variable-0.4500
21​
final face bottom1/2" end mill0SDM 1990.0000Variable-0.4500
22​
face SMA1/2" end mill270SDM 1990.0000Variable-0.4490
23​
faceinsert1/2" end mill90SDM 1990.0000Variable-0.1928
24​
zero tool Z axis0000 center drillABS0.00000.00000.0000
25​
drill insert pilot insert0000 center drill90SDM 1990.00000.0000-0.0500
26​
drill bypass pilot bottom0000 center drill0SDM 1990.00000.0000-0.1600
27​
zero tool Z axis0.1875 center drillABS0.00000.00000.0000
28​
drill sample port pilot top0.1875 center drill180SDM 1990.00000.0000-0.1800
29​
drill SMA coupler pilot SMA0.1875 center drill270SDM 1990.00000.0000-0.0500
30​
zero tool Z axis3.35mm carbide drillABS0.00000.00000.0000
31​
drill bypass capillary bushing holebottom3.35mm carbide drill0SDM 1990.00000.0000-0.2373
32​
zero tool Z axis1.55mm drillABS0.00000.00000.0000
33​
drill bypass capillary hole bottom1.55mm drill0SDM 1990.00000.0000-0.0550
34​
zero tool Z axis0.042" carbide pc drillABS0.00000.00000.0000
35​
drill clearance hole for 0.008" drill bottom0.042" carbide pc drill0SDM 1990.00000.0000-0.0250
36​
zero tool Z axis0.020" carbide pc drillABS0.00000.00000.0000
37​
drill large bypass passage bottom0.020" carbide pc drill0SDM 1990.00000.0000-0.0100
38​
zero tool Z axis0.039" carbide pc drillABS0.00000.00000.0000
39​
drill secondary pilottop0.039" carbide pc drill180SDM 1990.00000.0000-0.0500
40​
zero tool Z axis7o taper toolABS0.00000.00000.0000
41​
bore lower sample port top7o taper tool180SDM 1990.00000.0000-0.0600
42​
zero tool Z axisdual taper cone toolABS0.00000.00000.0000
43​
bore upper sample port topdual taper cone tool180SDM 1990.00000.0000-0.0500
44​
zero tool Z axis0.008 micro drillABS0.00000.00000.0000
45​
drill final passagetop0.008 micro drill180SDM 1990.00000.00000.0030
46​
drill final passagebottom0.008 micro drill0SDM 1990.00000.00000.0030
47​
zero tool Z axis120o c/sinkABS0.00000.00000.0000
48​
cut 120o bevelSMA120o c/sink270SDM 1990.00000.0000-0.0090
49​
cut 120o bevelinsert120o c/sink90SDM 1990.00000.0000-0.0090
50​
zero tool Z axis0.008 micro drillABS0.00000.00000.0000
51​
drill optical passageSMA0.008 micro drill270SDM 1990.00000.00000.0160
52​
zero tool Z axis0000 center drillABS0.00000.00000.0000
53​
drill locating pin #1 pilotinsert0000 center drill90SDM 1990.12000.3100-0.1256
54​
drill locating pin #2 pilotinsert0000 center drill90SDM 199-0.1200-0.3100-0.1256
55​
drill #2-56 fastener #1 pilot insert0000 center drill90SDM 199-0.1000-0.1950-0.1070
56​
drill #2-56 fastener #2 pilot insert0000 center drill90SDM 199-0.10000.1950-0.1070
57​
drill #2-56 fastener #3 pilot insert0000 center drill90SDM 1990.10000.1950-0.1070
58​
drill #2-56 fastener #4 pilot insert0000 center drill90SDM 1990.1000-0.1950-0.1070
59​
zero tool Z axis#51 drillABS0.00000.00000.0000
60​
drill #2-56 fastener #1 hole insert#51 drill90SDM 199-0.1000-0.19500.1820
61​
drill #2-56 fastener #2 hole insert#51 drill90SDM 199-0.10000.19500.1820
62​
drill #2-56 fastener #3 hole insert#51 drill90SDM 1990.10000.19500.1820
63​
drill #2-56 fastener #4 hole insert#51 drill90SDM 1990.1000-0.19500.1820
64​
zero tool Z axis1.55mm drillABS0.00000.00000.0000
65​
drill locating pin hole #1insert1.55mm drill90SDM 1990.12000.31000.0572
66​
drill locating pin hole #2insert1.55mm drill90SDM 199-0.1200-0.31000.0572
67​
zero tool Z axis7/32 end millABS0.00000.00000.0000
68​
c/bore SMA connector holeSMA7/32 end mill270SDM 1990.00000.0000-0.1690
69​
tap #2-56 hole #1insert#2-56 tap90SDM 199-0.1000-0.1950N/A
70​
tap #2-56 hole #2insert#2-56 tap90SDM 199-0.10000.1950N/A
71​
tap #2-56 hole #3insert#2-56 tap90SDM 1990.10000.1950N/A
72​
tap #2-56 hole #4insert#2-56 tap90SDM 1990.1000-0.1950N/A
73​
tap SMA connector holeSMA1/4-36 plug tap 270SDM 1990.00000.0000N/A
74​
tap SMA connector holeSMA1/4-36 bottoming tap270SDM 1990.00000.0000N/A
75​
zero tool Z axis1/2" end millABS0.00000.00000.0000
76​
cut weldSMA1/2" end mill270SDM 199As Req.Variable-0.4700
77​
cut weldbottom1/2" end mill0SDM 199As Req.Variable-0.4700
78​
cut weldinsert1/2" end mill90SDM 199As Req.Variable-0.1950
79​
cut weldtop1/2" end mill180SDM 199As Req.Variable-0.4700
Notes: the final operations are performed on the mill table using a conventional mill vise. The vise should be adjusted so that it is square and parallel to the mill table to within 0.0005" over 3" travel, using shims if necessary. The flexible electrical contact datum point is assigned ABSolute 0,0,0 coordinates and located so that the Y and Z coordinates will aproximately coincide with those of the workpiece. A buildup block should be used to bring the bottom workpiece support to 0.32 to 0.33" from the top of the vise jaws. This block can be milled in place to ensure parallel conditions for the workpiece.
StepOperationFaceToolRotary TableDRO DisplayCoordinates, inches
degreesFunctionXYZ
1​
find top face, set DRO Y1/2" edge finderINC0.00000.0000As Req.
2​
set absolute coordinates at X, Y axis datum1/2" edge finderABS0.00000.00000.0000
3​
set absolute coordinates at Z axis datum2mm pinABS0.00000.00000.0000
4​
find buildup block floor, set DRO Z2mm pin, feeler gaugeSDM 001NANA0.0000
5​
find buildup block far surface, set DRO YSDM 001NA0.0000As Req.
6​
zero tool Z axis1/2" end millABS0.20000.00000.0000
7​
clamp workpiece in vise, milled side down
8​
first face back1/2" end millSDM 199As Req.Variable-0.5800
9​
second faceback1/2" end millSDM 199As Req.Variable-0.5200
10​
third faceback1/2" end millSDM 199As Req.Variable-0.4600
11​
fourth faceback1/2" end millSDM 199As Req.Variable-0.4000
12​
fifth faceback1/2" end millSDM 199As Req.Variable-0.3600
13​
final faceback1/2" end millSDM 199As Req.Variable-0.3571
14​
reverse workpiece in vise with sample port to fixed jaw
15​
final facefront1/2" end millSDM 199As Req.Variable-0.3543
16​
drill mounting hole #1 throughfront120o c/sinkSDM 1990.19900.1500through
17​
drill mounting hole #2 throughfront120o c/sinkSDM 1990.19900.7500through
 
I got this one for my lathe

1571802883373.png

It's decently made and has been trouble free, quite satisfied.

I see the one you're looking at is even cheaper, that's a spectacular price.
I like the colors too.

On a mill, the scale width is not a real big issue. You might lose a little travel, but not enough to worry about (unless it's a mini).

I put an ARO (analog readout) on the quill of my mill. Only 1 in. range, but infinitely adjustable.
WP_20191022_21_25_18_Pro[1].jpg
 
Last edited:
What type of mill will the DRO be going on?

For my mill, it has a separate (factory) Digital Scale on the Quill. In most cases it's all I need. But the occasions when I've needed to raise or lower the head because quill travel was too short, I was glad I had a Z axis on my DRO. Also on my Medium sized bench mill, I find keeping the quill choked up gives me better accuracy when taking deeper cuts, so in those cases I again use the Z axis DRO and lower head over extending the quill.
It is a knee mill
20180518_091652.jpg
 
I got this one for my lathe

View attachment 304465

It's decently made and has been trouble free, quite satisfied.

I see the one you're looking at is even cheaper, that's a spectacular price.
I like the colors too.

On a mill, the scale width is not a real big issue. You might lose a little travel, but not enough to worry about (unless it's a mini).

I put an ARO (analog readout) on the quill of my mill. Only 1 in. range, but infinitely adjustable.
View attachment 304466
Your DRO looks nice,but shipping to SA is very expensive, almost half the price of the DRO.
 
I have had a three axis glass scale DRO on my mill for fifteen years and have yet to have it malfunction. IMO, the secret is providing a suitable scale guard. The x and y scale guards are mounted so that any oil, coolant, or chips would have to reverse direction to reach the scale seals. The z axis is more vulnerable but still no problems.
Do you have some pics of your setup?
 
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