Taig Mill Motor & ER-16 Spindle Upgrades
 Last updated on
Tuesday, September 19, 2023 04:08:45 PM Mountain US Time Zone


ER-16 Spindle, ER-16 Collets, Locking Levers, Drill Arbor
Low-speed Countershaft, High-Speed Pulley,
Motor Mount, Tachometer,
Indicator Mount

ER-16 Spindle
Mill motor upgraded to 1/3 HP. Headstock &
spindle upgraded to accept ER-16 collets.

Original mill motor photo
      GE motor specs

use a motor that is non-thermally protected or has
a thermal overload circuit that requires a manual reset.

 If the motor automatically shuts down due to excessive
heat, it then has the potential to unexpectedly start-up again
(after cooling down) while you are touching/changing sharp
end mills, saw blades
, belts or other rotating parts.

The motor that the mill came with was only 1/5 HP,
it was surplus, had dual-shafts, capacitor start &

 had automatic thermal protection. The new motor
is a GE H164: 1/3 HP, split-phase, continuous duty,

ball bearing, 1725 RPM, non-thermally protected &
has an open case with extended clamp bolts.

It has a service factor of 1.35 which means that it
can deliver a 35% reserve HP capacity without damage

from overheating. The new motor has 167% (225% in
reserve capacity) more horsepower than the original.

Motor specification speed is 1725 RPM but measured at 1795 RPM.

A new, larger motor mounting plate was
made based on the
original Taig design.
The motor's 1.75" diameter lower bearing housing
passes through & is flush with a very close-tolerance

hole in the mounting plate. This keeps metal debris
from being pulled into the cooling intake vents.

The plate corners were cut at 45 deg for safety. The two
imported 10-32 cap head screws that held the motor plate

were replaced with high-grade US manufactured screws.
The motor weight increased by only two pounds &

the moment-arm increased less than two-inches.
The cradle mount was removed since the motor is

mounted to the plate using its four extended clamp bolts.
The mounting holes were counter
bored for the nuts.
The original 3/8" motor pulley hole was bored to
a 0.5001" diameter for the new motor shaft.

Use the original belt or a new, longer Gates
belt can be installed; 3M 355 (13.98").

 The first number (3M) is the belt's (ribbed) back width, 3 mm.
The last number (355) is the flat-belt length, also
in mm's. To measure the needed belt length,

set the motor/pulley assembly to the desired
location & lock it. Then place a single, insulated wire

from lamp cord (split it in half) around the
center pulleys, pull it taught, cut & measure.

The cord fills the groves enough to give an accurate
indication of the required flat-belt length.

The original wiring connection was duplicated
using a computer power cord extension.

A nylon wire tie was used as the power cord
strain relief under the connection box cover.

This wiring setup allows the entire motor to be
removed without having to open the switch box.

On the top right side of the z-axis slide is a 10-32 cap head
that protrudes & contacts the lead
screw bearing block.
Counterbore where it contacts the bearing block. This recess for
bolt head then allows an additional 0.2" vertical travel.

The more powerful motor does not bog down thereby
making more uniform cuts, especially fly
cutting, &
is inherently safer since it does not have automatic
thermal protection. The ball bearing motor, coupled
with a low runout pulley, runs very smoothly.

Updated Taig headstock & spindle. One-piece housing,
improved shoe clamp, extra accessory rail,
spindle & nut that accepts standardized, professional
ER-16 collets & end mills. The hole through the spindle

is now slightly larger than 3/8" diameter. Both the spindle &
collet closing nut use 1" wrenches. Snap the collet

into the nut's eccentric ring before screwing it onto the
spindle. This ring is the collet extraction mechanism.

CAUTION: Do not over tighten the nut onto
an empty collet as it might cause damage.

Shown holding 3/8" shank 45 deg chamfer cutter. 3/8" shank
end mills are an industry standard. Rigidity & versatility are

improved. After removing the set screw, I warmed
the pulley with a heat gun & then used drill chuck wedge

pairs for removal. Housing & pulley must be heated (expanded)
first before assembly because they are essentially

 a zero-clearance fit.
The  upgrade is a big improvement
over the original in terns of both strength & utility.

ER-16 Collets

A set of 10, superior, high-precision ground,
hardened ETM ER-16 collets (Israel).

An eccentric ring locks the collet inside of the nut.
Because of the wide 0.040" holding range of each collet,
the set provides a continuous range of clamping sizes.

This set range allows clamping of multiple tool bits
having different (non-fractional) shank sizes.

ER-16 collets are also very useful on a large mill
when used in conjunction with collet

  SIZE (in)
1/32 .0197 ~ .0394 .5 ~ 1
1/16 .0394 ~ .0787 1 ~ 2
3/32 .0787 ~ .1181 2 ~ 3
1/8 .1181 ~ .1575 3 ~ 4
3/16 .1575 ~ .1968 4 ~ 5
7/32 .1968 ~ .2362 5 ~ 6
1/4 .2362 ~ .2756 6 ~ 7
5/16 .2756 ~ .3150 7 ~ 8
11/32 .3150 ~ .3543 8 ~ 9
3/8 .3543 ~ .3937 9 ~ 10

ER-16 Taig spindle arbors both
blank & for 1/2" shank end mills.

Not the most rigid setup & it uses up a lot of Z travel.
This end mill is large for a Taig; only very light cuts.

Locking Levers

10-32 die-cast zinc ratcheting locking levers.
The motor-mount lock has an extension & uses two large

custom-made brass washers. The extension allows
easier access & lessens the chance of bumping the

Z-axis crank. The motor pivot has a lever with brass washer.
The Z & Y axes have lever locks, too.

Ratchets allow selection of desired lever positions.

In general, locking non-translating axes
results in smoother, more accurate cuts.

Drill Arbor

Taig upgraded spindle now uses a 3/8"
straight shank; 3/8-24
drill arbor.

Low-speed Countershaft

Two oil impregnated bronze radial & thrust
bearings press-fit into the Taig OEM pulley.

A 1/4" hardened dowel pin is used for the axle.
A set screw holds the axle in the bracket.

The bearings were drilled & precision reamed to 0.251".

There was not enough room for the thumb knob
so a T-nut, washer, & bolt were used instead.

This design copies that of the
Taig lathe speed-reduction pulley modification.

A 10-32 tapped hardened steel
T-nut locks into in the bracket slot.

Runs very smoothly.

Lowest speed is now 179 RPM. 

High-Speed Pulley

A high-speed motor pulley for CNC engraving. 3-1/4"
aluminum stock for the pulley mounted in a
4-jaw chuck.

After a #2 center drill bit, made a 15/32"
(0.4687") pilot hole using a stubby drill bit.

Chamfered the hole before reaming.

Used a 0.4990" undersized reamer
for a close fit to the motor's shaft.

Lowest speed, lots of lubrication, & stop
turning before withdrawing the reamer.

Cut the set-screw shoulder area.

Using the center gauge to set up
the 60 deg tool
bit cutting angle which matches the Taig OEM pulley.

Cutting the pulley V-groove.
Set & feed the
compound at 29 deg to
reduce chatter; same method as thread cutting.

ting off the part.

Faced the other side of the pulley & chamfered the hole.

Mounted in t he RF-25 mill, showing a #2 center
drill bit which was then followed by a #21 drill bit.

Held the part in a smaller 2" vise so the setup could
be easily transferred to the hand tapper for threading.

See how to center a hole on a part.

Hand tapper used to make the 10-32 threads.
This set screw matches that used on the OEM pulley.

Ground the set-screw tip smooth & flat so it
would properly engage the motor-shaft flat.

Finished high-speed motor pulley.

Motor Mount

The small OEM spindle motor mounting post restricted
the range of movement when using the short belt.

The new motor mounting post is 80% larger, held on
with 3, 10-32 bolts, & uses hardened steel T-nuts.

On the bottom of the motor mounting plate, one of the
motor bolts was made flush to clear the new post.

The larger, spindle motor mounting
post holds the motor much more
rigidly & it's easier to adjust the belt.

Top speed is now 8160 RPM.
The pulleys are easily re-positioned
via their matched set screws.


 The Fairchild QRB1114 940nm E-O sensor
housing was mounted using Taig,
pre-existing 10-32 tapped holes.

Tachometer output showing 8160 RPM
(136Hz x 60) using the larger pulley.
Taig mill tachometer modification.

Indicator Mount

Taig standard tool post modified with a V-groove dimensioned
to hold an 8mm diameter (40mm long) centering

rod. Held at 45 deg, the slot side is milled down to a scribe
mark that is 4mm (the rod's radius) from the bottom of

the original tool post slot. An 8mm rod (Noga arm)
then securely rests in the V-groove & touches the slot

bottom when clamped. The V-groove could have been
made to hold a 3/8" diameter (0.1875" radius) rod, too.

Noga NF1018 indicator arm with 3/8" clamp held by the
modified V-groove tool post, mounted off the headstock

side T-slot. Setup shows indicating a work piece before
rotating to a specific cutting angle. The Noga arm is very

good for aligning mills, lathes & rotary tables. Do not leave
the dial test gauge mounted on the head during motor

operation, too much vibration on a delicate mechanism.
There is also a
magnetic base Noga indicator holder.

Another example showing a 4 deg (angled)
slot milled for a steel
cutoff tool holder.

ER-16 Spindle, ER-16 Collets, Locking Levers, Drill Arbor
Low-speed Countershaft, High-Speed Pulley,
Motor Mount, Tachometer,
Indicator Mount