Taig Mill Motor & ER-16 Spindle Upgrades
 Last updated on
Wednesday, March 04, 2020 10:36:32 AM 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 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 counterbored 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 the 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, hardened
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 extensions.

  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.

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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. The pulley & bracket are usually removed for regular milling operations.
Lower speeds may be required when I start using involute cutters & the 4th-axis to CNC brass clock gears.










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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 not gouge the motor shaft & leave burrs.

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. See Taig mill tachometer modification.

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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.

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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