Christopher Tool Company

Success Story:
Christopher Tool Company
EDM I Milling I Laser Texturing I Tooling & Automation I Customer Service

Zero Defects Means Zero Defects at Aerospace Shop
Since machining its first aerospace part in the mid-1960s,
Christopher Tool & Manufacturing Co. (Solon, Ohio) has
always met the continuously tightening part-tolerance
requirements of its customers. This success includes
overcoming one particular challenge that began in 2007,
when the initiative of “zero defects” was introduced into the
aerospace industry. While some manufacturers supplying
the industry took the concept with a grain of salt, Christopher
Tool has taken substantial steps to attain that level of
part quality.
The concept of zero defects is very literal, and the mandate
is well enforced. So, aerospace shops continuing to be successful
and competitive, such as Christopher Tool, are those
now producing perfect parts that are always within specified
tolerances.
“These days, aerospace OEMs will refuse any parts that
deviate from tolerance,” said Patrick Christopher, president
of Christopher Tool & Manufacturing Co. “All parts must be
to print and documented with the proper paperwork, and
shops must take initiatives and have corrective measures
and benchmarking in place to ensure any past mistakes will
not be repeated.”
All of this “mandatory continuous improvement” he said
has significantly changed the aerospace industry landscape.
Quality is paramount and must be maintained for
parts that grow increasingly more complex. To fulfill these
requirements, the shop constantly invests in expanding its
technological capabilities – two recent examples being full
simultaneous 5-axis high-speed machining and rotary axis
wire electrical discharge machining (EDM).
Because of these two machines, the shop can now process
previously farmed-out parts in-house as well as shorten
cycle times for many of its existing components. But most
importantly, the machines make it easier to achieve better
surface finishes and much tighter tolerances.
Propelled by its heavy involvement with the Joint
Strike Fighter program, Christopher Tool added a GF
AgieCharmilles HSM (high-speed machining) MIKRON 600U
LP full 5-axis milling machine and CUT 200 wire EDM to its
existing 35 or so pieces of CNC equipment. With a tilt/rotary
table design, the milling machine delivers +30/-110 degree
B-axis travel and 360 degrees in C. The shop’s CUT 200 wire
EDM features a rotary fourth (B) axis specifically for complex
part geometries.
The HSM 600U LP’s high speed comes from a 36,000-rpm
32-hp spindle and rapid traverse speed of 196 ft/minute (60
m/min). And for continuous production, it is equipped with
an integrated pallet-changing system.
The large-size milling machine features linear motors on its
main axes and optimized direct-drive motors for its B and C
axes. Both the GF AgieCharmilles milling machine and wire
EDM incorporate glass scale positioning that provides Christopher
Tool with extremely high precision and superior part
surface finishing capabilities.
In addition to its involvement with the Joint Strike Fighter
program, the shop has a worldwide customer base and
supplies components to all the major aircraft jet engine
builders. And while over half of the shop’s work is in aerospace/defense,
it also manufactures components for the oil
and gas industry, does prototyping for diesel engines and
provides parts for robotics.
Production levels are low to medium volume, job lot sizes
average between 30 and 50 pieces, and between 400 and 500
jobs are shipped per month– with 60 percent of those being
recurring work, the rest new. In aircraft and aerospace
work, the shop typically produces the prototype components
and then gets the job to manufacture at production volumes.
Aerospace jobs can entail parts for pumps, actuation
systems, fuel control systems and auxiliary power units for

oth defense and commercial aircraft. Most part sizes fall
within a 10” cube, and they are machined from both raw
stock material and castings.
Christopher Tool defines part complexity based on its geometric
intricacy and tolerance requirements. The shop routinely
works in true position tolerances between 0.0002” to
0.0005”, flatness/squareness tolerances to within 0.00005”
– some parts even 0.00002” – and to Ra 2 surface finishes.
Adding to the challenge, all parts are made from exotic
and tough-to-machine Nickel alloys and hard to machine
steels with low coefficient of expansion. Such materials
include Monel, Hastalloy, titanium, carbide and powdered
metal (CPM 10V) as well as precipitation hardened materials
(17-4 and 15-5) and some high-speed steels such as T1, T15
and M2. And with all of its experience, the shop definitely
categorizes itself as an expert in machining these materials
and in constantly holding extremely tight tolerances in every
part it produces.
The shop also has turning machines, vertical and horizontal
machining centers, grinders and a coordinate measuring
machine (CMM). But with the 5-axis machine and rotary-axis
EDM, many jobs previously done on the shop’s other CNC
machines have been moved to these two newer machines.
“In addition to the impellers now machined in-house, we are
processing several other parts on the HSM 600U LP, and
doing so in single setups, allowing us to access all necessary
part surfaces to shorten cycle times and further improve
precision,” explained Craig Peck, vice-president of operations
at Christopher Tool & Manufacturing Co. “Many of
these parts previously required several different machines
with multiple setups and operations. And with the rotary
fourth-axis on the CUT 200 wire EDM, we can quickly and
accurately burn extremely complicated features on round
parts to eliminate any secondary operations on a turning or
milling machine. Plus, we are NADCAP certified in EDM.”
He continued saying that the shop has experienced significant
production improvement with about 30 part numbers
now done on the HSM 600U LP. One part, for instance,
required about four operations on a horizontal machining
center and five separate ones on a knee mill. It is now
machined complete in only two operations on the HSM 600U
LP.
For an aerospace titanium end cap part that transferred
over to the HSM 600U LP, processing previously required
three CNC operations and three manual drilling operations.
The 5-axis machine not only completes the part in just two
operations, but also reduces cycle time down to 75 minutes
from a previous two-hour run time.
According to Peck, much of the shop’s part-processing improvements
can be attributed to the shear speed of the HSM
600U LP, in addition to its 5-axis capability.
but at extremely fast feedrates. For instance, the heaviest
cut we take is 0.125”. However, the machine is feeding at 200
IPM. This capability has significantly reduced cycle times for
all the parts now done on the machine.”
Christopher Tool typically uses small-diameter solid-carbide
tools on the HSM 600U LP, which are mostly ballnose
endmills held by REGO-FIX powRgrip mechanical toolholders.
For these particular endmills, the machine’s simultaneous
5-axis motion (tilt/rotation) keeps them in a constant
optimum position during the cut and prevents any machining
with the “dead points” at the top of their radii. For an
aerospace turbine shaft component previously farmed out,
this capability will allow the shop to machine the part’s
intricate vanes with a 0.046”-diameter endmill, and do so at
drastically shorter cycle times than would be the case if the
part was done on a 4-axis milling machine.
The HSM 600U LP processes all Christopher Tool’s impeller
parts for the Joint Strike Fighter. For the engine, the shop
manufactures about 20 part numbers and two main assemblies
each with about 25 part numbers of their own. Before
the 5-axis machine, the shop was producing other parts for
the project, but not the impellers.
“As the project ramped up, we realized we could no longer
rely on outside vendors for our 5-axis machining,” said
Peck. “And when we looked at the HSM 600U LP, we knew
its fast, high accuracy linear motor technology would give us
a significant advantage in machining speed and precision,
but service and application support is what really convinced
us. We conducted some inquiries, and many shop people
we know praised the support from GF AgieCharmilles. For
us, the company was very instrumental in getting us up and
running quickly. They walked us through our first impeller,
and by the second one, we were doing them on our own.”
Additionally, the machine has pallet changing. And according
to Peck, the shop often has three or four completely
different jobs – both long and short running, as well as multiple
parts on single pallets – set up on the machine at one
time. It then basically works around the clock (23 hours per
shift), five and a half days per week and mostly unattended.
“Such capability to do more with less through state-ofthe-art
technology and automation,” added Christopher,
“will further increase our agility to quickly meet changing
customer demands. The disciplines we’ve acquired from our
experience in the aerospace industry are benefitting us as
we expand into other industries. For these new customers,
we can provide them the same care and attention we give
our aerospace work and at a much more competitive price,
thanks in part to manufacturing innovations such as those
from GF AgieCharmilles.
“The machine’s 36,000-rpm spindle allows us to machine
much faster,” he said. “We now take very light depths of cut,

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