Exposing the Myth that All Spindle Rebuilds are Equal

Expert spindle rebuilders that pay attention to the details and communicate throughout the process offer fast, reliable rebuilds that last

For manufacturers, CNC machine tool spindles are critical to any drilling, milling,

boring, grinding, routing, cutting, or sawing process. However, when these systems
deteriorate and fail due to contaminants, human error, improper maintenance, lubrication
issues, or poor spindle design, a quality rebuild is often required.
Despite the availability of spindle rebuilders nationwide, not every firm provides the
same level of quality. Even if a rebuilder has the equipment, they may not have the
experience, technical knowledge, or attention to detail necessary to rebuild a spindle that
performs reliably for many years.
Even reputable rebuilders vary in the extent and quality of the initial inspection, accuracy
of quotes, and level of communication with customers. Yet given the direct correlation
between these factors and the ultimate quality and longevity of the rebuild, most
machinist continue to believe that it makes little difference which shop they contact.
In actual practice, however, the difference can be significant and seriously impact shop
productivity. As a result, most machinists can easily relate tales of failed spindle repairs
that led to costly downtime.
"After one spindle rebuild, I had to pull the machine out of production within a short time
for additional repair," says Tom Collins, maintenance supervisor at Edro's Engineering's
Walnut, California facility. Edro Engineering, which serves North America and Europe,2
is a one stop tooling solution shop for machining services, special materials, custom mold
bases, PVD/DLC coatings, and additive manufacturing.
"Any time these CNC machines are down it costs us money, so we never want them
down," explains Collins, who is responsible for more than 50 milling machines, jig
borers, and surface grinders. "Because we run our spindles often at high speeds and we
do surface grinding of stainless steel and specialty materials, frequent rebuilds are
necessary - even expected."
"So, if we send out a spindle and it is not properly repaired, it has to be removed again
for additional repairs and that is going to put the machine down for even more time - and
that's even more money," he adds.
Morgan Stipp, who supervises a grinding operation for Embee Processing in Santa Ana,
California, agrees that minimizing downtime is essential.
Stipp oversees about 20 precision grinders at Embee Processing's 124,000 square foot
metal finishing campus facility in Santa Ana, California. This includes Studer CNC
grinders, Okamoto NC OD grinding machines, centerless grinders, and other equipment
with thread, surface and superfinish grinding abilities.
Most part configurations require the chrome or HVOF surfaces to be ground, polished,
honed, and deburred after plating to achieve the desired surface finish. These operations
are performed to ensure a flawless finish with tolerances as low as 50 millionths of an
inch, according to Stipp.
"We are extremely picky with our precision grinding because it has to be essentially
perfect for our customers. Without the right equipment and properly maintained spindles,
we would not be able to stay in business," says Stipp.3
In this regard, Stipp believes the thoroughness of the initial inspection performed by the
repair/rebuild shop not only impacts the longevity of the spindle after it is rebuilt, but also
the accuracy of the price quote.
"Having a machine down for unexpected extra maintenance because the inspection
missed something can cost us a lot of money," says Stipp. "We also do not want any
surprise upcharges either, due to the original inspection and quote not being thorough
enough."
Both Stipp and Collins found the precision and attention to detail they required when they
contacted MZI Precision of Huntington Beach, Calif., an experienced machine tool
spindle rebuilder with a complete process to supply customers with a fast way back to
maximum productivity.
While most spindle rebuilders only take minimal time to wipe parts before inspection,
during disassembly the rebuilder cleans and polishes each component with emery cloth to
clearly reveal even minute imperfections. Even the nuts are removed, polished, and then
tested to ensure proper fit.
The next step is detailed measurement and documentation of every part of the spindle's
shaft and housing geometry. Micrometers are used to take detailed size measurements,
runout is checked using 50 millionths of an inch dial indicators. The shaft bearing
shoulders are then checked to see that they are true and perpendicular. The housing bores
are checked for size, alignment and shoulders squareness. MZI Precision also takes
video, followed by digital photographs of each part during the disassembly process.
"If I have anything go wrong with our spindles, I will call them before the manufacturer.
They will diagnose the spindle at no cost and send me a detailed quote, which has been
down to the penny on everything. I have never had a surprise charge," says Stipp.4
According to Edro Engineering's Tom Collins, the quality of the repair is also impacted
by the expertise of the rebuilder and level of communication, traits he also found in MZI
Precision.
"Communication is important, and it is a two-way conversation," says Collins. "The
company wants to understand how the spindle is run, the conditions, the types of parts
being made, what metals are cut, the depths of cuts, etc. so the rebuild can be tailored to
my application. Also, when I have a question, they answer it quickly."
Collins also appreciates the spindle rebuilder's use of only high-grade replacement
components and bearings, which help to increase equipment reliability and lifespan. The
rebuilder utilizes aerospace-grade bearings that are ABEC rated 7 or 9, the highest
classification. Depending on the requirements, ceramic bearings are often recommended
despite the nominal additional cost, due to longevity and higher running speeds.
"I have found their rebuilds to be as good as OEM and sometimes better. The spindles
have run perfectly so I expect them to last a long time," says Collins.
While spindle rebuild reliability and lifespan is essential, quick turnaround is also
important since equipment downtime must be minimized. "The turnaround for our
spindle rebuilds has to be timely to keep our production on track," says Collins.
Although spindle rebuilds are available from various sources, for manufacturers that seek
greater production reliability, uptime, and lifespan out of their CNC equipment, working
with an expert spindle specialist is usually the best option.
For more information: Call (714) 475-4016; email info@mziprecision.com; visit
mziprecision.com; write to MZI Precision at 5572 Buckingham Drive, Huntington Beach,
CA 92649.

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