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What You Need to Know About Coolant for CNC Machining

Coolant in purpose is widely understood – it’s used to temper high temperatures common during machining, and aid in chip evacuation. However, there are several types and styles, each with its own benefits and drawbacks. Knowing which coolant – or if any – is appropriate for your job can help to boost your shop’s profitability, capability, and overall machining performance.

Coolant or Lubricant Purpose

Coolant and lubricant are terms used interchangeably, though not all coolants are lubricants. Compressed air, for example, has no lubricating purpose but works only as a cooling option. Direct coolants – those which make physical contact with a part – can be compressed air, water, oil, synthetics, or semi-synthetics. When directed to the cutting action of a tool, these can help to fend off high temperatures that could lead to melting, warping, discoloration, or tool failure. Additionally, coolant can help evacuate chips from a part, preventing chip recutting and aiding in part finish.

Coolant can be expensive, however, and wasteful if not necessary. Understanding the amount of coolant needed for your job can help your shop’s efficiency.

Types of Coolant Delivery

Coolant is delivered in several different forms – both in properties and pressure. The most common forms include air, mist, flood coolant, high pressure, and Minimum Quantity Lubricant (MQL). Choosing the wrong pressure can lead to part or tool damage, whereas choosing the wrong amount can lead to exhausted shop resources.

Air: Cools and clears chips, but has no lubricity purpose. Air coolant does not cool as efficiently as water or oil-based coolants. For more sensitive materials, air coolant is often preferred over types that come in direct contact with the part. This is true with many plastics, where thermal shock – or rapid expansion and contraction of a part – can occur if direct coolant is applied.

Mist: This type of low pressure coolant is sufficient for instances where chip evacuation and heat are not major concerns. Because the pressure applied is not great in a mist, the part and tool do not undergo additional stresses.

Flood: This low pressure method creates lubricity and flushes chips from a part to avoid chip recutting, a common and tool damaging occurrence.

High Pressure: Similar to flood coolant, but delivered in greater than 1,000 psi. This is a great option for chip removal and evacuation, as it blasts the chips away from the part. While this method will effectively cool a part immediately, the pressure can be high enough to break miniature diameter tooling. This method is used often in deep pocket or drilling operations, and can be delivered via coolant through tooling, or coolant grooves built into the tool itself. Harvey Tool offers Coolant Through Drills and Coolant Through Threadmills.

Minimum Quantity Lubricant (MQL): Every machine shop focuses on how to gain a competitive advantage – to spend less, make more, and boost shop efficiency. That’s why many shops are opting for MQL, along with its obvious environmental benefits. Using only the necessary amount of coolant will dramatically reduce costs and wasted material. This type of lubricant is applied as an aerosol, or an extremely fine mist, to provide just enough coolant to perform a given operation effectively.

To see all of these coolant styles in action, check out the video below from our partners at CimQuest.

In Conclusion

Coolant is all-too-often overlooked as a major component of a machining operation. The type of coolant or lubricant, and the pressure at which it’s applied, is vital to both machining success and optimum shop efficiency. Coolant can be applied as compressed air, mist, in a flooding property, or as high pressure. Certain machines also are MQL able, meaning they can effectively restrict the amount of coolant being applied to the very amount necessary to avoid being wasteful.

3 Steps to Shutting Up Tool Chatter

Cutting tools undergo a great deal of force during the machining process, which cause vibrations – also known as chatter or harmonics. Avoiding these vibrations entirely is not possible, though minimizing them is pivotal for machining success. Vibrations become damaging when proper machining steps are not followed. This leads to strong, part-ruining chatter. In these situations, parts have what is known as “chatter marks,” or clear vibration marks along the surface of a part. Tools can experience an increased rate of wear due to excess vibration.

Tool Chatter can be kept at bay by following three simple, yet often overlooked steps:

1. Select the Right Tool for Your Job

It seems elementary, but selecting the best tool for your application can be confusing. With so many different geometric styles for tooling – overall length, length of cut, reach, number of flutes – it can sometimes be difficult to narrow down one specific tool for your job. Oftentimes, machinists opt for general purpose tooling that can perform a variety of operations, overlooking the option that’s optimized for one material and job.

Opting for Material Specific Tooling is helpful, as each material has different needs. For example, steels are machined differently than aluminum materials. Everything from the chip size, to chip evacuation, is different. Variable Helix or Variable Pitch designs help to minimize chatter by reducing harmonics, which are caused by the cutting edge having repeated contact with the workpiece. In order to reduce harmonics, the time intervals between flute contact with the workpiece are varied.

Overall length is another important factor to consider when deciding on a tool for your job. The more overhang, or length the tool hangs from the spindle, the less secure the spindle-to-tool connection is, and the more vibration. Ensuring that your tool is only as long as needed for your operation is important to minimizing chatter and harmonics. If machining deep within a part, opt for reached tooling or an extended reach tool holder to help solidify the connection.

2. Ensure a Secure Connection

When it comes to secure tool holding approaches, both the tool shank and the collet are important. A loose tool, unsurprisingly, has more ability to move, or vibrate, during machining. With this in mind, Helical offers Shank Configurations to help the connection including the ToughGRIP Shank, which replaces a smooth, mirror-like surface with a rougher, coarser one for increased friction. Helical is also a licensee of the HAIMER Safe-Lock™, added grooves on the shank of a tool that work opposite of the spindle rotation, securely fastening the tool in place.

Machinists must also know the different types of collets available to them to identify if a better solution might be necessary. For example, Hydraulic Tool Holders or Shrink Fit Tool Holders promote a stronger connection than a Mechanical Spindle Tightening method.

For more information, see Key Tool Holding Considerations

3. Choose a Chatter Minimizing Strategy

How a tool is run can mean the difference between stellar job results and a ruined part. This includes both the parameters a tool is run at, as well as the direction by which it rotates – either a Conventional Milling or a Climb Milling technique.

Conventional Milling

In this method, the chip width starts from zero and increases gradually, causing more heat to diffuse into the workpiece. This can lead to work hardening, creating more headaches for a machinist.

tool chatter

Climb Milling

Most modern machine shops will use a climb milling technique, or when the chip width starts at its maximum and decreases during the cut. Climb Milling will offer a more consistent cut than traditional methods, and puts less stress on the tool. Think of it like weight lifting – doing the heavy lifting will be easiest at the beginning of your workout. Similarly, a cut in which the thickest chip is removed first helps the tool maintain its strength. Because the chip cutting process is more swift, vibrations are minimized.

decrease tool chatter

For more information, see Climb Milling Vs. Conventional Milling

In Conclusion

Vibrations are unavoidable during the machining process, but minimizing them can mean the difference between successful machining and scrapped parts. Following three simple rules can help to keep your chatter and harmonics under control, including: Selecting the right tool, ensuring a secure machine-tool connection, and using it in a climb milling strategy. Both Harvey Tool and Helical Solutions have tools that can help, including shank modifications and Variable Helix or Variable Pitch end mills.

Weiss Watches – Featured Customer

Weiss Watch Company is restoring prestige to American watchmaking. They design and build timepieces with mechanical movements by hand in Los Angeles, California. Each timepiece is individually assembled in America. Their practices merge historical techniques and modern technological advances, with every process perfected by a Swiss-trained and certified American watchmaker. Weiss Watch Company strives to increase the percentage of domestic sourcing with each edition, and is the only company resurrecting industry practices that have not been active in the United States for decades.

Grant Hughson is a Manufacturing Engineer at Weiss Watch Company. Grant “lives and breathes” manufacturing, currently working in his spare time as a Manufacturing Instructor at Saddleback College. We spoke to Grant for this latest featured customer blog about the watch-making process, his experiences in the industry, and his thoughts on the state of American manufacturing.

weiss watches

What made you get into machining?

I grew up with a love for finely machined products, like watches, guns, and fishing gear. I also loved car racing, and a lot of the modifications on the cars are machined from various materials. So, from a young age, I was obsessed with the work that went into these products, and knew I wanted to be a part of the manufacturing industry.

What is your favorite part of this profession?

I love the entire manufacturing process. It always starts with a dream, or an idea. Then you take that idea and turn it into a drawing, and soon after, you’ll be modeling it. The best part is when you go to actually machine the part, and watch your original idea turn into a tangible part or product.

watchmaking

What is the most challenging part of the watch-making process?

There are a few challenging parts of the watch-making process, starting with the super-tight tolerances. Surface finish is also extremely important, and can be difficult to nail. Many surface finishes in watchmaking are visual, so roughness can be deceiving. We also were forced to design all of our workholding from scratch, as nothing currently existed in the market that would work for our machining process.

You mentioned your tight tolerances. What tolerances do you typically work in?

My tolerances are in the tenths. The holes that hold the jewels (watch bearings) are +0.0002, -0.

weiss watches

What sort of machines do you have in your shop?

We have a 3 axis vertical milling machine and a 9 axis Swiss style lathe in the shop.

What type of materials do you work in?

We work in steel, stainless steel, aluminum, brass, and titanium every day. It is a wide variety, but it keeps things interesting!

How have Harvey Tool products impacted your overall shop performance?

Harvey Tools have been great tools for me. I do a lot of prototype work, and constantly need odd sized tools or specialty profiles to finish a job. Thankfully, the Harvey Tool selection is HUGE. Somehow you guys always have what I need!

Tell us about your favorite project that Harvey Tools helped to create.

I love what I do everyday, so my favorite project is an ongoing one; making watches!

watchmaking tools

Why is high quality tool performance important to you?

It’s a must! Tool to tool accuracy and performance is vital in this business, especially with our extremely tight tolerances. High quality tools make sure that we get the same performance time after time without needing to scrap parts. This saves us valuable time and money.

What is your favorite process to work on as a machinist?

I really enjoy fixture design. Holding small parts for fixture design is an art! If it’s too tight, they’re smashed. If it’s too loose, see you later; your part is gone!

As a manufacturing engineer, I also enjoy the programming aspect of CNC machining. Being able to program the toolpaths and turn my programming skills into tangible parts is why I got into this business.

weiss watches

If you were stranded on a desert island with only one Harvey Tool or Helical tool, which would it be, and why?

It would have to be the Harvey 1/4″  30° engraving tool. I could mount it to the end of a stick. It would make for a hell of a spear!

Why is manufacturing products in America important to you?

Manufacturing products in America is a crucial part of the success and security of our business. When someone else makes your parts, its not hard for them to make a competing product. Making everything on-site keeps our proprietary information safe.

If you could give one piece of advice to a new machinist ready to take the #PlungeIntoMachining, what would it be?

Ask a lot of questions and never stop learning. It’s not easy but it’s worth it. If you consider yourself a maker or inventor, it’s the only place to be! Manufacturing is awesome, and anyone who tells you different is on the way out. Keep up the good work, and keep manufacturing your products in America!

weiss watches

Would you like to be considered for a future “Featured Customer” blog? Click here to submit your information.

Photos courtesy of Weiss Watch Company.

Harvey Performance Company’s Jeff Davis Interviewed in Advanced Manufacturing Article

Harvey Performance Company Vice President of Engineering Jeff Davis was interviewed in Advanced Manufacturing’s May 2, 2017 article entitled “Coatings Expand Cutting Tool Capabilities, Reach New Markets,” in which he discusses the proper use of tool coatings.

As the lead engineer for the Harvey Tool and Helical Solutions brands, Davis is well versed in the world of miniature and large diameter tooling, as well as several different coating options.

“Different coatings address different concerns,” said Davis. “Some coatings, when used improperly, can cause problems, including stickiness and galling. Although diamond works well in graphite and composites, ferrous applications could result in excessive thermal build-up, coating breakdown, and damage for both the tool and the part.”

View the article in its entirety.

Harvey Tool Company was also mentioned in Advanced Manufacturing’s post “What Machine Shops Need to Know about Deburring.” For more, click here.