The Good Life for Reconditioned Thread Grinders
grime off of that “old metal” sitting on your shop
floor for a glimpse of the treasure that may lie beneath—thanks
to a machine makeover by Drake Manufacturing.
By Jim Vosmik
many times can a thread grinder be reincarnated? So far, four—but
stay tuned. Twenty-eight Jones & Lamson thread grinders at
Delphi Automotive have undergone quite a transformation in their
60-plus years of service life. And now, due to complete machine
makeovers by Drake Manufacturing, they’re operating as “like-new”
Drake is a mid-sized manufacturer of new and re-manufactured
CNC grinders, many of which are used in automotive part, cutting
tool, and gearbox production. Its product line includes thread
grinders, internal and external grinders, gear grinders, rack
mills, hobbers, and piston ring grinders. The company also offers
CNC control renewal services for mechanically sound machine tools
that are “losing their minds.”
In their first incarnation as manual thread grinders, 28 J&L
6x36s were put to use grinding threads on aircraft propeller shafts
during World War II. A typical setup took three hours while operators
changed gears, cams, and sine bars in preparation for grinding threads
on new parts.
After the war these machines were converted
to grind threads on automotive steering components, but used the
same mechanical systems originally built into the machines during
the war. The hydraulic power steering units in which the ball
screws were used were on virtually every rear-wheel drive GM vehicle.
In the mid-1990s, after 50 years of grinding
threads, Drake Manufacturing won their first contract to remanufacture
and CNC retrofit them. GM Saginaw Steering (now Delphi Automotive)
chose Drake for the remanufacturing project because of the company’s
experience with automotive steering components and its solid reputation
in the grinding industry. The remanufacturing and CNC transformation
resulted in like-new CNC thread grinders.
Drake took out the geared transmissions, lead screws,
change gears, mechanical dressers, and taper and sine bars and
replaced them with precision ground ball screws, servos, CNC controls,
and closed loop glassscale feedback. It also added CNC diamond
roll dressers for consistent wheel conditioning and process control.
The rebuilding process essentially transformed these 50 year-old
thread grinders into full-blown CNC machines.
third-generation Drake J&L grinders started life with a flourish—setup
times were reduced from three hours to 15 minutes, part quality
and consistency was drastically improved, and throughput increased
by 50 percent. Delphi was also pleased with the cost, which was
about 25 percent less than the price of the new CNC thread grinders
that were commercially available.
The grinders were not just delivered to Delphi.
Drake also developed and proved out the entire grind process and
programmed it into the Fanuc CNC. As with all of its machines,
the controls were programmed with Drake’s PartSmart™
menu-driven software. No programming knowledge was required by
the customer or its operators since they were simply required
to enter part-specific parameters.
By 2005, new developments in the power steering
market lead Delphi into “e-steering.” With electronic
steering, an electric motor drives a worm gear set. This new product
called for multi-start worm grinding. Drake was again called on
to work its magic—or, more precisely, to re-work it.
with the CNC machines that reduced product, volumes had idled.
Drake replaced ball screws, headstock bearings, rebuilt the wheel
and dresser spindles, added linear ways, and replaced all cables.
In addition to the mechanical refurbishment, Drake also added
automated loaders and converted the machines to a front dress
from the previous rear dress configuration.
The front dress conversion accomplished two things.
It located the dresser and workpiece close to each other, and
it put them on the same thermal mass—all but eliminating
thermal errors and increasing accuracy. Size, thread pitch diameter
Cpk are in the double digits range, with grinding performed in
The three-start worms arrive at the Drake grinder
with threads pre-machined. With no orienting features on the part,
centering the wheel in the pre-machined groove would typically
present a difficult loading situation. Finding the center of the
pre-machined thread is exactly what Drake’s SmartSpindle™
was designed to do. Smart Spindle utilizes acoustic emission feedback
from the wheel to locate the workpiece groove and divide the available
stock. This allows equal amounts of stock to be ground from both
sides of the thread and assures that the part is cleaned up.
In addition, Smart Spindle technology allows parts
to be machined closer to final size before grinding. With a smaller
amount of stock to grind, cycle times are further reduced.
The current generation Drake thread grinders are
fully enclosed and equipped with mist collectors. The operator
has no need to open the door during production, and the machines
are believed to meet all present and proposed OSHA safety regulations.
For Delphi Automotive, the economics keep getting
better. The 2005 version of Drake thread grinders are a real bargain—priced
55 percent less than a comparable new grinder.
While every machine tool builder wants to sell new
machines, Drake realizes that it’s not always in the customer’s
budget. Remanufacturing is a smart alternative that minimizes
a customer’s capital outlay and maximizes its use of depreciated
property. Drake suggests that companies take a hard look at that
old iron out in the shop before scrapping it.
Underneath the dirt, there may be hidden gold.
Not every machine needs to be completely rebuilt.
Sometimes they just need new controls. For example, a typical
Drake Control Renewal project is about one-third the cost of a
new machine and half the cost of a complete remanufacture. For
machines that have failure-prone controls, this is an ideal solution.
Drake builds both new and remanufactured machines, it can outfit
older machines with its latest grinding wizardry and CNC programming
at a fraction of the cost of new. In fact, Drake’s expertise
in control system renewals has earned it recognition as a certified
GE Fanuc 5-Star retrofitter.
Customers around the world are getting the message.
Drake recently exhibited at the China International Machine Tool
Show and is aggressively pursuing the Asian automotive and cutting
tool parts market. Its new and remanufactured grinders are operating
all over the world, including China, Korea, and Australia as well
as Eastern Europe and the Americas.
About the author: Jim Vosmik is president of Drake
He can be reached at 330.847.7291
Visit online at www.drakemfg.com.