How to make
grinding safer
and more productive
Progressive shop culture, better tools lead to greater efficiency in finishing
By Tim Heston, Senior Editor
ven people who sell hand power tools for a living
aren’t shy about an obvious truth: No child dreams
of one day working in a fab shop’s grinding department. The job can be dirty. It can be loud. And without the
proper tools, protection, and training, it can be dangerous.
On the other hand, the job of finishing metal has
never been more important. “Good enough” just doesn’t
cut it anymore. Shops may spend millions on new and
complex machine tools, such as tube cutting lasers and
automated punching and bending cells. Automation can
do wonders for efficiency and quality, but it’s all for
naught if a subpar grinding operation forces excessive rework and late deliveries.
Some grinding is expensive and often not practical to
automate. A blank can be finished in a flat-metal graining
and deburring machine. A mechanized stroke sander can
be used for some applications. And a torch-cutting bug system or even a stationary router or specialty mill can automate weld prep in some cases. But if a job shop has welded
assemblies of various shapes being sent to the finishing department, cost-effective automation options are limited.
For this reason, manual grinding pervades the industry. It’s a basic shop tool. According to sources, creating a
safe grinding operation should be the first step in making
life easier for the grinder and the entire operation more
efficient. Operators should be trained and given the right
tools for the job (see Figure 1). Once this happens, more
can be accomplished in one shift with less operator effort.
When they work safer, their jobs become easier and more
productive.
E
Hidden Costs
Quality tools and abrasives may have a greater upfront
cost, but they can help support a safer, more productive,
and less costly work environment. Although this goes
against some conventional thinking, numbers often support the story.
Scott Saunders, a salesperson for CS Unitec, explained
it this way: Consider an operator who makes $50 an hour,
when considering his hourly wage, overtime, insurance,
and benefit costs. He uses a 6-amp grinder with a low-end abrasive wheel that costs $5. This disk can remove 5
linear feet of material in one hour. So the total hourly cost
is $55, or $11 per foot of weld metal removal. Now, replace that abrasive wheel with one that costs twice as
much, but can remove 6 linear feet in one hour using a
12-amp grinder. This makes the total cost $60 ($50 an
hour, plus $10 abrasive), but the operator just removed 6
linear feet. That makes it $10 per foot of weld.
“Upfront, an abrasive might cost 50 percent less, but
the total cost for the job is more,” Saunders said.
An added benefit: A more powerful tool, matched to
the specific job, requires less operator effort, meaning less
fatigue, which reduces the chance of injury.
Designing Safety Into Tools
Powertool-makers have gone to great lengths to ensure
operator safety. Jens Gschloessl, product manager for
FEIN Power Tools Inc., explained that operators will duct
tape the pedal switch on the side, and even glue the side
safety switch into a permanent “on” position, all in a
quest to reduce fatigue and improve efficiency.
Gschloessl described some models with four touch pads,
all of which need to be activated to start the tool.
“They’re embedded into the motor housing, so it’s difficult to duct tape and lock the tool [in the on position].”
Other tool features include restart protection, in which
the tool won’t start immediately when plugged in if it’s
switched on. Some safety guards also are designed so operators can’t remove them without a special tool.
Gschloessl added that some grinders have safety
clutches that engage to shut off the tool under extreme
load conditions, such as when a cutoff disk becomes
stuck in a material (see Figure 2).
Some tools use specialized fixtures on flat plate, tubes,
or other surfaces to provide support (see Figure 3).
“These fixtures always keep the tool at the same setting,”
said Iwan Antonow, executive vice president of Saar-Hartmetall USA LLC, “so you cannot overgrind or undergrind
it. They also reduce the fatigue factor and block all access
to the grinding wheel during operation.”
Building a Culture of Safety
Shops have established safety rules, but that doesn’t
mean they’re always followed, even when operators are
using tools with advanced safety features. Workers aren’t
trying to hurt themselves; they’re just trying to meet efficiency goals and make their job easier, sources said. As
with any safety issue, the best approach is to design out
the hazard from the process.
Why are operators taping buttons? Their hands hurt.
Why? They may have the wrong tool for the job. Why are
they removing the guard? They may be using a standard
angle grinder and contorting themselves to reach into a
tight space. Here, a belt file or another tool designed for
tight spaces might help.
Abrasive wheels of specific grits operate best at specified RPMs, offering efficient metal removal and long
abrasive life. An operator need only apply a firm, consistent force during operation, Gschloessl said. Excessive
force reduces the abrasives’ effectiveness, shortens consumable life, and adds operator fatigue. If the operator
needs to use excessive force, he’s probably using the
wrong abrasive or tool for the job. To ensure the most efficient abrasive use, some grinders have electronics that
helps the tool maintain RPMs even under increased pressure from the operator, Gschloessl said.
Avoiding an Overload
As Saunders explained, an efficient grinding operation is
one where managers have chosen the right abrasive of
sufficient quality and matched it with a portable grinder
of sufficient power. If a part requires a No. 8 finish, and a
