RF-25 Mill Spindle Reflective E-O Tachometer & Surface Feet per Minute (SFM)
RF-25 Mill
DRO
X Y Z
Axes Scales
9x20 Lathe DRO X
& Z1 Axis Scale.
9x20 Lathe
Tachometer & SFM
Taig Mill
Taig Mill DRO &
X Y
Z Axes Scales.
Taig CNC Mill DRO
Taig
Mill Tachometer & SFM Taig Micro
Lathe DRO
Mark the pulley edge inside the housing so you know where
to mount the E-O sensor.
To keep the spindle from turning,
I protected a fully seated (tightened) boring head with tape then lightly clamped it in the vise.
The spindle nut is about 1.9" & has a left-hand thread.
Next, I used a large gear puller
to slowly separate the pulley from the tapered spindle.
The spindle had a little paint overspray from the factory, so I cleaned it & the
threads.
I used blue Loctite when the nut
was replaced.
Do not over tighten the pulley nut.
Masked off half the bottom pulley edge.
Knocked the surface shine off with a scrub pad &
then cleaned with
alcohol so the flat-black enamel paint would stick really well.
A 50% duty cycle encoded pulley, results. A much lower value, like
5%, should work, too.
Used an
Unibit to drill an access hole for the optical sensor mounting.
Squared the hole with a file.
The
Fairchild QRB1114 IR electro-optical (E-O) sensor & perf board circuit
are mounted in
a small plastic case.
The circuit design is from the
DRO-350 site.
The signal cable has an internal strain relief. Access is via cover screw removal.
The sensor's full length projects through the squared hole in the mill's plastic, double-walled belt
guard housing.
Cleaned the painted surface & box with alcohol to remove any oils.
Sensor was mounted using thin, double-sided foam tape.
Sensor shown aimed up at the bottom of the encoded pulley rim &
where the second
hole is for the gray signal cable.
The cable was then dressed along the same path as the lathe
Z-Axis cable & plugged into the AUX input
jack.
The gray cable is for the tachometer & the black cable is for the
Z-Axis scale.
I know what the fixed speeds are, though it's easier to look at the DRO RPM than
the chart,
but
it's the SFM calculator that I find useful.
I have since removed the three quill
levers.
SFM is only a starting point. When cutting metal,
one attends to (among other things):
speed, feed,
chip size,
chip length, chip coloration,
coolant, rigidity, surface finish, sound, smell &
vibration.
There are numerous, interacting variables that are unique to
any given
machine & setup that simply can not be accounted for by SFM tables.
The rigidity, coolant, and feed in a vertical machining center is a bit
better than a hand drill.
So to say that one SFM value should be
the same for both is a stretch.
Mill Surface Feet per Minute (SFM)
SFM = (RPM· π· DIAMETER)/12 where: π = 3.14159 & the diameter is in inches
Operation is similar to the Lathe Tachometer & SFM
For the ShumaTech DRO-350M.
AUX ON in DRO setup (Function 0)Select "no tool offset" (Function 6, 0)
Zero DRO scales
Define tool offsets (Function 5, #1~9, diameter of end mill (or other) , Z offset)
Select mounted tool offset (Function 6, #1~9)
Function 7 toggles display between RPM & Z-Axis DRO
Function 8 toggles display between SPM & Z-Axis DRONotes: Scales directions & polarities must be correctly defined in the DRO setup.
SFM changes as the cutter diameter changes.
Larger diameters have higher SFM than smaller diameters for a given RPM.
Double check initial DRO calculated SFM values by using hand calculations.
SFM is applied equally for either mill or lathe operations.
RF-25 Mill DRO & X Y Axes Scales.
