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High-Torque Retention Knob Gives Job Shop Spindles The Competitive Edge

Jim Lorincz
By Jim Lorincz Contributing Editor, SME Media

Despite the addition of more than 750,000 CNC mills in the past 15 years in the US, CNC machining job shops often hover at the bottom of the totem pole, where there’s little room for error as most bids are won by a 1–2% price variance. Plus, most low-to-mid volume run production machine shops struggle in achieving their share of the 5–10% maximum profit margins typically realized on most jobs, according to JM Performance Products (JMPP: Fairport Harbor, (OH).

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JM Performance Products offers patented high-torque retention knobs that reduce or eliminate toolholder expansion responsible for CNC milling and boring problems.

Given these challenges, along with changing consumer demands, overseas competition and lack of skilled labor, the goal becomes how to improve efficiency, quality, and profits. CNC machining job shops are essentially multi-stage process operations where there is potential for improvement at each stage. Achieving a shop’s potential while expanding its business depends on how many of those improvements can be capitalized upon.

One of the investments a job shop can make starts at the spindle with JMPPs’ patented high torque retention knobs. The knobs overcome a key design flaw inherent in CNC V-flange tooling, eliminating the toolholder expansion responsible for costly and ongoing CNC milling and boring issues.

JMPP designed the knobs to be used in existing toolholders to eliminate the bulge at the small end of the holder, which stops it from making full contact with the taper of the spindle. By increasing contact with upwards of 70% more spindle surface, a range of CNC milling issues are overcome, including vibration and chatter, poor tolerances, non-repeatability, poor finishes, shortened tool life, excessive spindle wear and tear, run-out and shallow depths of cuts.

Toolholder Must Fit the Spindle

Since tight tolerances are essential in high-speed machining, if the toolholder doesn’t fit the spindle precisely, decreased productivity and reduced tool life are inevitable.

“Bridging this gap of missed productivity can conservatively help job shop operations achieve a 10–20% competitive advantage per hour via faster setups, better feed rates, and more rigid tools—reducing tooling cost by 20–50% or more,” said JMPP President John Stoneback. “Every tool on the machine works better and faster to make job shops more competitive and increase profit margins.”

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A high-torque retention knob (right) is longer than a traditional retention knob, but shares the same head dimensions.

The power of combining lean manufacturing with modern technology is even more important to today’s small-to-medium job shop. The positive effects of optimizing production methods can help shops realize their full potential with a low risk / high return ROI ratio.

“A small advantage in labor hour savings alone can help impact a job shops’ leverage in getting the job,” said Craig Fischer, JMPP plant manager. “With payroll hours reduced and machine hours freed up, the collective ability to get more work goes up. Additionally, everyone’s tooling budget keeps going up as the cost of buying carbide from China increases. Factoring in a conservative savings on carbide tooling costs of even 5% when using our knobs is significant.”

An increasing number of job shops are performing machine tool monitoring in some way to analyze everything from managing tooling for jobs, scheduling jobs, configuring production and daily rates. To aid a job shop in identifying key cost analysis in converting to the high torque knobs, JMPP offers a free ROI calculator which can help determine annual projected savings. It starts with an equation—at a conservative minimum of 10% productivity increase using the high torque knobs vs. conventional knobs.

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Eliminating toolholder expansion increases spindle contact and reduces downtime and costly production issues like fretting and tool taper damage.

“Take the number of mills in your shop and multiply that times the number of hours per day you run; now take that number and multiply it by the number of days per week that you’re running the mills; multiply that number by your hourly billable rate,” said Stoneback. “Now multiply that number by 52 weeks. The number you calculated is your unadjusted yearly revenue. Now, take that yearly revenue figure and multiply it by 10%—that’s the number that represents your annual lost revenue.”

Success Stories

Following are two CNC machining job shop examples of conversion success.

Digital Machining Systems (DMS; Lafayette, LA) is a custom machine shop that manufactures small-to-medium sized CNC machined parts and assemblies. DMS invested in two new machine tools from Milltronics USA in 2013, which required a knob style they didn’t previously have. After investigating options, they decided to go with two machines worth of JMPP’s high torque style retention knobs.

Replacement Program Started

According to Jeff Heels, DMS manufacturing engineer, the company is pleased with its performance as there have been no problems on these machines, like fretting or tool taper damage. “We also decided to start a replacement program for the worn out knobs we used on our older Fadal CNC machine tools, and have been pleased with the performance there as well,” said Heels.

Also, the date of manufacture is printed on the knob. “This helps us keep track of how old the knobs are getting, and will be helpful when it’s time to start replacing them,” said Heels. “It will help us gage long-term performance data value.”

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DMS Machining Systems has implemented more than 300 of JMPP’s high torque style knobs on two machines because the toolholder tapers and machine spindles last longer and deliver better performance and part quality.

Enterprise Welding and Fabricating Inc. (Mentor, OH) is a family-owned metal fabricator specializing in sheet-metal fabrications with core component parts for large OEM companies with a heavy trucking and agricultural focus.

In 2017, Enterprise purchased two new DMG Mori machines (CMX 1100 and NHX 6300) which required a quick, full tool-up conversion to JMPP High Torque knobs—30 for the CMX and 60 for the NHX. The NHX machine leveraged a higher-strength version of the knobs since it was a bigger machine.

“We needed to get these machines up in one day and JMPP came out and filled the order with our applications engineer on site,” said Enterprise Manufacturing Engineer Bob Ludwig. “These were new machine investments and the previous knobs and toolholders we used had bulged in the past, so we didn’t want to go down that path again. The assembly was simple, and we’ve used the knobs for over six months with high efficiency and no problems.”

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