Mill Motor & ER-16 Headstock/Spindle Upgrades
Mill motor upgraded to 1/3 hp. Headstock & spindle upgraded to
accept ER-16 collets.
Caution: Only use a motor that is either 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.
A new, larger motor mounting plate was made based on the original 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 45º 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"). Gates belts can be purchased in a wide range of flat-belt lengths (or outside circumference) from any of their local distributors. 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 hex head that protrudes & contacts the lead screw bearing block. Counter bore where it contacts the bearing block. This recess for the hex 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 run-out 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° chamfer cutter. ⅜"
shank end mills are an industry standard. Rigidity & versatility are
greatly 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 Taig headstock/spindle upgrade is a big improvement over the original in terns of both strength & utility.
A set of 10, superior, high-precision ground, hardened ETM ER-16 collets (Made
in Israel from Enco).
An eccentric ring locks the collet inside of the nut.
Because of the wide 0.040" holding
range of each collet, the set forms a
continuous range of clamping sizes.
ER-16 collets are very useful on a large mill when used in conjunction with
collet extensions.
NOMINAL COLLET SIZE (in) DECIMAL RANGE
(inches)METRIC RANGE (mm) 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
10-32 die cast zinc ratcheting locking levers from MSC.
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 locations.
In general, locking non-translating axes results in smoother, more accurate cuts.
Taig upgraded spindle now uses a ⅜" sized shank; ⅜-24 drill arbor.
Taig standard tool post modified with a V-groove dimensioned to hold an
8mm diameter (40mm long) centering rod. Held at 45°, 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 ⅜" diameter (0.1875" radius) rod, too.
Noga NF1018 indicator arm with ⅜" 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 tramming mills, lathes & rotary tables.
Do not leave the dial test gage 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° (angled) slot milled for a steel cut-off tool holder.
