Locking Nut Improves Tool Change-Outs

This company can run its operations safely since it has implemented a mini-nut locking system specifically for Swiss-type automatic lathes.


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Cutting tool change-outs were sometimes a painful undertaking at TOMZ Corp. in Berlin, Connecticut. Operator injuries were occurring on some of the Swiss-type machines. The work areas, especially the small machine models, offer limited room for operators to change out worn or broken tools. Packed with between 15 and 20 tools, space between each toolholder in a gang-type setup on these machines can measure only 2 inches. So any slip with an ER collet toolholder nut spanner wrench can damage neighboring tools and, far more serious, cause operator injury. 

“As a medical shop, we make very small parts, and our tooling is equally small in size. Some of our end mills are only 0.024 inch in diameter and extremely sharp,” says Mike Fries, lathe department manager at TOMZ Corp. “With tools that tiny and sharp, little pressure is needed to have one severely puncture the skin and penetrate completely into a person’s hand or arm. For us, those injuries sometimes required stitches.”

Mr. Fries added that while injuries requiring stitches occurred maybe once a year, those that simply needed a bandage from the shop’s first-aid kit happened quite a bit more frequently. According to him, the shop simply lived with these injuries as the nature of using these Swiss-type automatic machines.

TOMZ dedicates 60 Swiss-type automatic lathes for a major portion of its medical implant manufacturing operations, and operators typically change out the tooling on each of those high productivity machines at least once, if not multiple times, per day.

The company’s machines have always used a lot of ER 16 and ER 20 collets from Rego-Fix, and the company has been satisfied with the products. So, Mr. Fries was receptive when a local distributor approached him with a Rego-Fix intRlox MX mini nut locking system specifically for Swiss-type automatic lathes. 

The nuts incorporate a design that keeps the ER toolholder wrench from slipping—even when it is worn—to virtually eliminate tool damage and most importantly, operator injury.

“From our past experience with Rego-Fix and its reputation for quality and precision, we had no doubts about the locking nuts,” he says. “If we get one or two injuries within even a year’s time, that’s one or two injuries too many. The nut locking system has basically eliminated injuries related to tool change-outs on our Swiss-type machines. Plus, tool change-out speeds inherently increased because our operators don’t have to move so carefully to prevent the collet nut wrenches from slipping. They trust the tool and what they are doing.” 

According to Rego-Fix, standard ER collet toolholder nuts for Swiss-type machines typically lack any type of locking design, so spanner wrench slippage is common. However, once properly engaged, the mini nut locking system wrench will not slip off the nuts.

The nuts feature an anti-slip design that uses rounded locking grooves situated around the nut profiles as opposed to end face surfaces. Wrenches grip from the sides of the nuts, and the action of tightening or loosening temporarily locks wrenches in place.

Without any type of raised or protruding teeth, the nut profiles are slim and compact, a further benefit in the tight areas within TOMZ’s Swiss-type machines. And unlike standard spanner wrench patterns that wear, round and weaken, the design of the intRlox MX nuts help them retain more of their material for added strength.

The intRlox MX extension accessories TOMZ uses have the same profiles as the mini nut wrenches at one end and the anti-slip profile at the other ends. With the extensions, the shop’s operators gain a deeper reach between tooling and additional room for the wrench because it’s further away from the cutting tools. Plus, the extension provides room for using a ratchet-type wrench as well as torque wrenches to ensure proper nut tightening.  

As with all Rego-Fix collet nuts, the intRlox MX mini nuts also incorporate the company’s special collet locking system. Collets push into the nut and click into place. The collet and nut assembly then screws into the toolholder for easy and precise positioning, the company says.

Within a year’s time, according to Mr. Fries, the staff at TOMZ converted all the Tsugami and Citizen Swiss-type machines over to the new nut locking systems. The shop also uses the Rego-Fix extensions that pair with the nuts.

The shop operates two full shifts, averaging 50 hours per week of production and considers itself a medium- to low-volume producer with lot sizes that can vary from 500 to 2,000 pieces. The shop ships about 1 million surgical implant assemblies per year, and those can encompass three or four individual components/pieces. 

Precision, quality and fast delivery are critical at TOMZ. Once a production-improving part process or new technology is proved out on one machine, the shop quickly implements it to all the Swiss-type machines, as it did for the MX locking system. Now the company can run its operations safely, with no operator injuries.  

For more information from TOMZ Corp., call 860-890-0670, or visit