QUALITY INNOVATIONS: Control the Torque of an Impact Tool

A new controller measures the torque of an impact tool.

Controlling torque from an impact tool has never been easy. Until recently, the only way of doing so involved a rather unscientific method—the operator deciding to take his finger off the trigger.

But science has stepped up to the plate in the form of Sioux Tools' (Tequesta, FL) Torque Control System (TCS). The TCS monitors up to seven parameters of an impact tool, which can be changed at the touch of a button. After all the parameters have been met, the control system automatically shuts off the tool.

In doing so, the TCS solves a puzzle that has long troubled manufacturers. An impact tool is basically a hammer mechanism—metal on metal—that generates torque by an internal swinging weight. “The real question is, 'how do you monitor that and control it?'“ asks Mike Balint, business development manager of Sioux Tools.

How it works

The TCS method works on the back pressure of the given tool. Every time the tool hits, it stops for a microsecond; when it stops, it creates a back pressure surge in the air. That is what the TCS monitors and checks.

Balint reports measured accuracies of plus or minus 12%. “That may not sound very good,“ he says, “until you stop and think that up until this point you had no accuracy at all.“ He points to one client, who wanted to achieve 300 foot-pounds of torque on a bolt being used in tractor assembly. Instead, “the average torque of this bolt was actually around 800 foot-pounds. The QC manager went bananas when he saw that,“ Balint reports. Using the TCS, the client was able to regulate torque within 15%.

There is no limit on torque. The device, which costs about $5,700, will control whatever torque levels a tool produces. Balint reports that one client controlled a 1 1/2-inch tool at 1,750 feet per pound. The TCS can control impact or pulse tools—or a combination of the two tool types. It will detect when there is a double hit, cross-thread, stripped-thread, worn tools, or premature shut-off by operator. RS232 or 485 signal output indicating good or bad run is built in.

The system's heavy-gage metal is set up for either wall or shelf mounting. A see-through panel on the lockable access door prevents tampering with the programming controls and pressure regulator.

Options include a remote channel selector switch for locating an automatic impact tool up to 30 feet from the controller and a remote signal tower incorporating a red/green warning light or buzzer for locating the tool up to 30 feet from the controller. The signal tower must be in the operator's line of site.


The control system's red-green warning light system comes into play when a fastener does not meet the program parameters.

“That can happen for any number of reasons,“ Balint says. “It could be a cross-thread or strip-out, or if the operator hit the same fastener twice, or if he shut off the tool prematurely and didn't let the controller shut it off. Or, it could be that the tool itself is wearing out.“ When any of those instances occur, the operator is warned by both an audible and visual signal.

Other features include a pressure gage, lockout-type master power switch, and military-style screw-cap covered connectors for the optional remote light tower.

Balint reports several creative uses of the system. “We have an account that tied it into the conveying system of the product. If they had a red light signaling a bad run, it would shut the conveyor off,“ he says.

At another site, the torque control system is linked to the type of product being built—specifically, frames for two- and four-wheel-drive vehicles, which have different torque requirements. When the two-wheel-drive frames come into the station, “It trips a signal and automatically changes the torque output of the gun the operator is using,“ Balint says.

Typical applications have included heavy assembly, auto and truck assembly and steel shipping containers (55-gallon drums).


• An impact tool is basically a hammer mechanism in which torque is generated by an internal swinging weight.

• When the hammer hits, it stops for a microsecond causing a back pressure surge of air. This air is measured by the Torque Control System.

• The system monitors up to seven parameters of an impact tool. The parameters can be changed at the touch of a button.

• A red-green warning light system, or buzzer, alerts operators when a fastener does not meet the program parameters.

• There is no limit on torque. The device will control whatever torque levels a tool produces. It can control impact or pulse tools or a combination of the two tool types.


For more information on the Torque Control System, contact:

Sioux Tools Inc.
(561) 743-8491
Fax: 561-743-6467

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