Alan Miller is engineering manager with BIG Kaiser, Hoffman Estates, IL.Click image to enlargeby Alan Miller

Why pull studs are under more pressure than ever before

 

Whether you think of them as retention knobs, pull studs, or something else entirely, the very fact that you’re thinking of them puts you ahead of the curve. For many, pull studs are a non-thought; regarded as forgettable accessories that don’t get any attention unless something goes wrong. But if something does go wrong, it can be catastrophic –causing damage to the component being machined, or worse, to the machine tool itself.

But what may have seemed like a humble or forgettable part 20 years ago, when machines were lucky to have generated 1,600 lb (726 kg) of grip pressure on the pull stud, has to come back into focus now that those forces are creeping upwards of 2,500 lb (1,134 kg). As the forces exponentially increase, precision and accuracy in machining and tooling increasingly require higher quality of the lone piece connecting the spindle to the toolholder.

This one bolt must stand up to severe conditions, and should be inspected and exchanged regularly to ensure top performance and integrity. Repeated clamping and unclamping during automatic tool changes leads to pull stud bolt fatigue, and can cause breakage. Generally speaking, a pull stud bolt has about a three-year life span, but this can be much shorter depending on tool change frequency and many other operating conditions.

Impurities.Click image to enlargeThe use of coolant in machining should be another prompt for regular inspection, as it can lead to corrosion. Although water-soluble coolant is generally alkaline, it can become acidic with long-term use. This increases the risk of rust and corrosion inside the coolant tank, on the work table, and other parts of the machine, including the pull stud bolts. This corrosion decreases the component’s integrity and can lead to fracture.

With most machine tools, the gripping mechanism relies on a series of stacked, loose washers, and bevel washers that, when under a load, flatten out. Changing the position of the surface where the gripper holds the knob by just a little bit can cause retention force to vary. And .004 in. (0.102 mm) differences can greatly influence the performance of the tools.

Also of note, ASME standards have been revised. In the new spec, retention knob installation torques have been published to make sure the retention knob is installed properly and isn’t bulging out the small end of the taper. This just goes to show how important it is to install knobs with a torque wrench, as opposed to the far less accurate installation method using a wrench and a hammer.

Although small, these single components are mighty. And with so much pressure on their performance, the key is to buy quality products from a premium supplier. Low quality bolts will experience chatter and lead to vibration. Safe and secure production requires a superior product.

Today, premium suppliers are taking extra measures to deliver top performance and part accuracy. Unique designs are now available for different types of machines, for consistency and reliability during production. Going the extra step, some manufacturers mark every pull stud with a serial number for traceability and internal tracking purposes, allowing users to keep track of the age of individual parts and better monitor lifespan.SMT

Alan Miller is engineering manager with BIG Kaiser, Hoffman Estates, IL.

 

Common line cutting

by Sylvain Robidoux

Implement common line cutting/nesting to improve fabricating efficiencies

Doosan's five axis machine in action

Doosan Machine Tools showcases its five-axis machining centre.

Retooling for a Rebound

Retooling is a critical practice in manufacturing, usually taking place when producing a new product or after signing a deal with a new customer.

Can Canada regain economic superstar status?

by Mary Scianna

When the International Monetary Fund cut its 2013 Canadian growth forecast to 1.5 per cent in April from an October
2012 estimate of 2 per cent, Canada abruptly fell to last place among the Group of 20 countries outside Europe for economic growth.

Labour saving breakthroughs

A roundup of new labour saving technologies including a printer that prints roads.

Tool wear observations

Tool wear observations according to Moshe Goldberg, manager of marketing, training and engineering support for Iscar Ltd., Tefen, Israel.

The new normal

Automotive manufacturers shift from working harder to working smarter with bigger focus on innovation and technology

Robotic MIG Guns

by Adam Dagenais

What you should know about robotic MIG gun clutches

Building the ultimate roller coaster

Watch a full engineering documentary about what it takes to build the ultimate roller coaster.

CNC crash fails

It’s a bit easier to watch when it’s not happening to you. Watch these classic confrontations between metal and machine.

Job shops Ontario - Made to Measure

by Andrew Brooks

From its inception in a tough climate, Advantage has been increasing its high precision and automation repertoire

Improved square shoulder milling

Seco has released another advancement for the square shoulder milling process with its new Turbo 10 cutting tool for most roughing, semi-finishing and finishing operations. The cutter offers improved tool life and precision by optimizing cutting properties that reduce heat generation and cutting forces.

Joseph Tabri to head Komet in Canada

Joseph Tabri is the new president at Komet of Canada Tooling Solutions, Newmarket, ON.

Stay In Touch

twitter facebook linkedIn