Milling: Entering Angle

Entering angle kr is the angle between the main, leading cutting edge of the insert and the workpiece surface.
Lead angle ψr is the angle between the main, leading cutting edge of the insert and the center line of the tool.

Chip thickness, cutting forces and tool life are all especially affected by the entering angle/lead angle.

The most common entering/lead angles are 90°/0°, 45°, 10°/80° and those eliminated by round inserts, such as cutters using ball nose inserts at smaller depths of cut.

  • Decreasing the entering angle, kr, or increasing the lead angle ψr, on straight edges reduces chip thickness, hex, for a given feed rate, fz. This chip thinning effect spreads the amount of material over a larger part of the cutting edge.
  • Smaller entering angles/larger lead angles provide a more gradual entry into the cut, reducing radial pressure and protecting the cutting edge.
  • Higher axial forces at decreasing entering/increasing lead angles will increase the pressure on the workpiece.

90°/0° cutters

  • Main application area is square shoulder milling.
  • Generates mostly radial forces, in direction of the feed.
  • The surface being machined will not be exposed to high axial pressure, which is advantageous for milling workpieces with a weak structure or thin walls, and in cases of unstable fixture.

Cutter assortment: CoroMill 290, CoroMill 390, CoroMill 490, CoroMill 590, CoroMill 690, CoroMill 790, CoroMill Plura and Auto-FS – and for special purposes, the side and face milling and grooving cutters: CoroMill 331, CoroMill 327/328 and the T-Max Q-cutter.

45° cutters

  • General choice for face milling.
  • Generates well balanced radial and axial cutting forces.
  • Smooth entry into cut.
  • Low tendency for vibrations when milling with long overhangs or smaller/weaker tool holders and couplings.
  • Especially suitable for milling workpieces in short-chipping materials that easily fritter if excessive radial forces act on the gradually reduced amount of material left at the end of a cut.
  • Formation of a thinner chip allows for high productivity in many applications because of the opportunity for higher table feed while maintaining a moderate cutting edge load.

Cutter assortment: CoroMill 245, CoroMill 345, T-Max 45 and Sandvik Auto program.

60°/30° to 75°/15° cutters

  • Special purpose face mills offering larger depth of cut compared to the general choice face mills.
  • Lower axial forces compared to 45° face mills.
  • Better edge strength compared to 90°/0° cutters.

Cutter assortment: CoroMill 360, CoroMill 365, Auto AF.

10°/80° cutters

  • High-feed and plunge milling cutters.
    The thin chip generated allows for very high feeds per tooth, fz, at small depths of cut and, consequently, for extreme table feeds, vf.
  • The dominating axial cutting force is directed towards the spindle and stabilizes it. This is favorable for long and weak setups, as it limits vibration tendencies.
  • For plunge milling of cavities, or whenever use of an extended cutter is required.
  • Effective in hole making using three axis.

Cutter assortment: CoroMill 210, CoroMill 316 and CoroMill Plura high feed cutters.

Round inserts or cutters with a large corner radius

  • Efficient roughing and general purpose cutters.
  • Corner radius provides a very strong cutting edge.
  • High table feed rate capability due to thinner chips generated along the long cutting edge.
  • The chip thinning effect makes these cutters suitable for machining titanium and heat resistant alloys.
  • Depending on cutting depth variations, ap, the entering/lead angle changes from 0° up to 90°, altering the cutting force direction along the edge radius, and consequently the resulting pressure during the operation.

Cutter assortment: CoroMill 200, CoroMill 300 and – at smaller depths of cut – CoroMill 390 radius insert cutters; the ball nose cutters CoroMill 216 and CoroMill 216F. Also, the solid carbide end mills, CoroMill Plura and CoroMill 316, are available in ball nose versions with a large corner radius.

(Content originally published by Sandvik Coromant on

A Message from Hartwig

To You, Our Valued Customer,

As 2017 comes to a close, I wanted to take this opportunity to express how truly grateful our team is for your business. Also, at the end of each year, it is a perfect time to reflect on what all has been accomplished, and as a new year begins, look ahead at what we hope to accomplish. At the center of it all is an effort to strengthen our focus on meaningful and lasting impressions with our customers.

This year, various efforts were put forth such as developing our customer care team, investing in new software and technologies to improve our internal processes, or growing the size of our Technical Services team to increase our base strength, we have positioned ourselves to continue providing you with unparalleled manufacturing solutions and support.

In addition to the above, I’m excited to introduce our new Hartwig Vision Statement:

To be the first choice for manufacturing solutions and support through customer-driven innovation, best-in-class equipment, product and industry expertise, superior customer care, and unsurpassed value. Hartwig strives to be the name people know, trust, and enjoy partnering with.

This vision statement will guide us to continually raise the bar in all aspects of our business in the years ahead.

There is no time more perfectly suited for expressing our gratitude than this holiday season. Thank you for your trust in us and we wish you a joyful holiday season and a prosperous New Year!

Geoff Hartwig, President
Hartwig Inc.


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Okuma HMCs with Rotary Tables Speed Accurus Aerospace’s Hard Metals Production

As parts requiring five-axis machining have risen in demand, especially in the aerospace and medical industries, manufacturers are faced with the challenge of justifying a dedicated five-axis machine for a limited number of parts or parts series.

Shops can now achieve five-axis capabilities with high precision without incurring the cost-prohibitive financial commitment of a dedicated machine.

Accurus Aerospace has been machining complex aerospace parts at its Tulsa, Oklahoma facility since 1974. The company has worked on major programs for customers such as Boeing, Spirit AeroSystems, and the Triumph Group. When looking for a 5-axis solution, they selected Okuma HMCs with Tsudakoma rotary tables from Koma Precision Inc.

The company specializes in hard metal, 5-axis machining in titanium and steel. The sheer power of high-torque spindles on their Okuma MA-600HII and MB-8000H machines and the addition of a 5th axis via a double-sided rotary table set the stage for success. Accurus is able to cut 4-axis parts on one side and 5-axis parts on the other side.

In explaining the choice, Senior Engineering Specialist Don Moody said adding a rotary table costs much less than a dedicated 5-axis machine. “It also allows us to get to the center of the part easier.”

The spindle utilization of an HMC can often be more than twice as much as that of a vertical machining center. Unlike a full 5-axis, trunnion-style machine, an HMC plus a rotary table allows for setting up parts on the pallet outside the machining area while parts loaded on a second pallet are being machined. This drastically reduces downtime caused by stopping the machine to set up the fixture.

“Having two pallets on the HMC increases our efficiency and time management,” Moody said. “The operator is more flexible as to when he can load/unload the part. Plus, the machine is not waiting for the load/unload.”

“We have applied this same concept on the diff­erent size Okuma MA machines in our facility. The Okuma design is so powerful that we are able to cut and surface the part in one pass with a custom, slotted cutter,” stated Larry Johnson, VP of Operations.

To maintain the automatic pallet changing capabilities of the HMC, Koma installed a cable management system on-site. It allows the rotary table to remain connected throughout the pallet change while keeping all the cabling out of the way of fixtures and metal chips. Furthermore, if there are hydraulics or air-sensing lines involved, this system can monitor and actuate automatic fixturing.

When machining high-quality aerospace parts, high rigidity and positioning repeatability are key. In this case, Tsudakoma’s hydraulic dual-disc clamping system was the ideal choice. It maintains the fixture and part positioning while the machining center is taking its cuts. The machine is only as accurate as the rotary table, so positioning repeatability throughout the entire production run is critical to making good parts.

Johnson confirmed the benefits of a rotary table setup. “We have many Okuma machines with Tsudakoma rotary tables. We run them day in and day out, 24/7, and they all provide, highly-accurate, steady machining.”

This modular approach enables manufacturers to generate high-precision five-axis parts without investing in a dedicated five-axis machining center. Despite the seeming complexity of the system, the entire five-axis modification is said to be easily removable from the machine table and stored for later use.

Accurus Aerospace
12716 E Pine Street
Tulsa, OK 74116

Phone: (866) 299-ZTM1

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We Are Listening…

Over the past three months, we have had real conversations with over 100 of Hartwig’s customers. Hearing the feedback from you, our valued customers, learning about our organization from your eyes has been an incredible gift.

For over 57 years, Hartwig remains committed to learning from your feedback and continues to unceasingly pursue a reputation for delivering best in class customer service with positive impressions.

An area that will always be front and center for Hartwig’s Technical Services team is response time.  Through an investment in new service scheduling software, Hartwig will be able to better manage our case distribution amongst our team more effectively, track parts required for cases more efficiently, and improve the overall scheduling experience for you – the customer.

While implementing software advancements is important to help us become more proficient, our organization’s sales growth also makes staffing a regular conversation to ensure we are prepared to serve our customers every day. In order to improve service lead time, Hartwig continues to concentrate on increasing the size of our technical services team across our entire territory. This year alone we have hired almost 20 new technical services engineers, including both service and application engineers.

Increasing the size of our technical services team while also improving our internal processes with the assistance of new software, Hartwig continues to live our mission of helping people in manufacturing control their destiny every day.

Thank you for your valued feedback. If you have additional improvement suggestions for us, you can email me ( or call anytime at (314) 684-4120.

We are still listening…

Heather Johnson, Project Coordinator

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M04 – Simple Command, Powerful Result

By Joe Thole, Application Engineer

If I could intone my text, this article would be in that old 1950’s PSA films for fallout shelters and gas mask sales pitches. What I have to say is going to sound about as comical as some of the gadgets and propaganda spread about around that time. So in my best 1950’s PSA voice:

  • Are chips and coolant splashing on the door glass of your CNC lathe obscuring your vision?
  • Is your machine not holding tolerances as well as it once had?
  • Are your parts showing chatter you don’t traditionally expect?
  • Is that chatter causing unpredictable tool life?

What if I told you about an amazing option available to use your CNC lathe that will add $0 cost to your machine while alleviating the aforementioned ailments?
This simple option can help all of those areas, and more!

It’s called “M OH Four” That’s right: M04.

M04 is an often forgotten feature with few limitations but many benefits which greatly outweigh the downfalls. However, this is one of the most overlooked, simple techniques that can be used in this ultra-modern world to help your shop become that much better.

If you’re already using M04, you are in a small but growing group of people who have seen these benefits first hand.

Why is this Simple Command So Powerful? … Simple Physics Really.

As you program your lathe to run, typically, one would use “M Oh Three” or M03, “spindle rotation, clockwise”. However, when they say “Clockwise” it is from the spindle’s perspective looking to the tailstock or what I refer to as the top of the chuck towards the operator. Simply put, anything that flies around inside your machine will promptly be thrown at the door, and its glass. This is not only irritating but can be dangerous. As chips fly, so will large parts, chuck jaws or anything else that may come loose. This means a part will have the tendency to fly towards the door and the operator. With the chuck rotating in M04, these chips, coolant, and parts will tend to fly first to the back of the machine, or, if they come loose on the downward portion of the rotation, be thrown first into the chip conveyor or at the way covers.

By the way, operators, wouldn’t it be easier to change your inserts out if they were on the top of the stick tooling instead of the bottom?
Well, with M04, it is! How about that?

What does that have to do with chatter and tolerances? I’m glad you asked! You see, with M03, as your part rotates, a tool needs to be mounted upside down in the turret to be in cutting position. This means the forces transferred to the tool are pushing up, or in the theoretical Y+ direction. That means all those cutting forces being used to shear metal are being transmitted into an area, the smallest area possible really, on your box ways, almost negating all gains boxed ways offer. I say almost because using linear or roller guides in the same fashion, the boxed ways STILL offer more rigidity. In fact, I would argue that using boxed ways incorrectly and linear guides correctly, the boxed ways are still the better choice, but I digress. Transmission of these forces on such a small area will, obviously, wear that small area out much more quickly than if it was 3-4x the area. Not to mention, pulling up on the turret is going against gravity, which means as you engage in a cut, you are pulling the turret off its ways, and as you come out of the cut, the turret is falling. This could also be caused by varying depths of cut or hardness of the material, which could, in turn, cause vibration. Don’t we all know what vibration does to carbide too well as it is? With M04, those cutting forces are playing a game of Follow the Leader and follow gravity, pushing the turret back into the X axis ways, and the carriage into the Z axis ways. As a result, there is no room for vibration; No vibration, less premature tool failure caused by vibration from the turret being lifted from the ways.

In one easy step, we’ve limited vibration to limit chatter, extended machine life by spreading the cutting forces to a larger area of ways, helped prevent premature tool failure, AND made it easier for the operator to change/service tooling.

But wait, there’s more!

This paragraph is usually exciting to the bean counters, I won’t lie. You see, when you use M04, not only do you get the above-mentioned perks, but you also get the added peace of mind that your tolerances will continue to hold tight for years and that you and your company are doing everything in its power to keep it that way. All those forces being pushed into an immovable object like the base casting prevent vibration and wear on the ways. This also assures the best setup for finish and tolerances. Using M04 will help assure the longest possible machine life, with one less issue possible. Then there’s one final perk. At least, for those using a sub-spindle machine, there is. When using a sub spindle, so many times, the main spindle runs in M03 and so does the sub spindle. This means that in relation to each other they are rotating BACKWARDS! Sub spindle tooling is, of course, mounted to be right side up, while main spindle tooling is upside down. This means, when you pick off a part, you must stop the sub spindle, rotate it in relative “reverse” to pick off a part, then stop it again to rotate it the correct direction for cutting. This equals lost time and extra wear just stopping and starting the spindle for no actual manufacturing good. Simply using M04 on the main spindle, and improving main spindle manufacturing means now your two spindles both rotate top away from the operator, meaning with regards to bar fed machines with pick-off, you never even need to stop the spindle unless you choose to when ejecting the part except during bar load.

Free efficiency gains, no investment required (other than tooling if you don’t already have it), better parts, potential longer tool and machine life, happier operators…

How much better can it get?

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Modig’s HHV – Changing the Way of Manufacturing

Innovative manufacturing solutions are the standard for Modig Machine Tool’s offerings, and the HHV line is further proof of this. Consisting of the Modig HHV-3 and HHV-2, both machines in this line are ready to offer your operation serious return on investment.

The Modig HHV-3 (formerly known as the Extrusion Mill or BarMill) has the ability to rotate 200-inch bar stock to allow for all-around access for aluminum milling of 3- and 4-axis parts within a 6″ x 10″ cross section in one operation. Reducing raw material waste by 20-30% and boasting faster cycle times of 40-60%, this revolutionary machine is ready to optimize your production while lowering costs. Machining aluminum or composite extrusions, the HHV-3 is ready to optimize aerospace production seat tracks, floor beams, stringer clips/brackets, fuselage stringers, or fuselage floor grid components, and various automotive components. Perfectly designed for all extrusions up to 60 feet long, this machine has three chucks to guarantee higher accuracy on long parts. This is ideal for parts such as seat tracks, with two chucks holding the piece at all times to reduce slippage between shuttling. The ground-breaking rotatory chuck design allows the HHV to control the reference jaw by using the CNC system, allowing for the jaw to clamp surfaces machined to a new position.

The Modig HHV-2 (formerly known as the HHV Professional) is a smaller version of the HHV-3. It utilizes two chucks instead of three. This extrusion mill also offers reduced cycle times and less raw material waste compared to traditional machining methods.

When Modig Machine Tool was founded in 1947, offering customers the same industry standards as the rest was never the goal. Modig has always focused on exceeding the norm through constant advancement, unparalleled quality, and a tireless ingenuity. Innovation is a brand standard at Modig Machine Tool, and this is exemplified masterfully by the HHV line. Manufacturing companies who have experienced Modig’s game-changing technologies, like Accurus Aerospace, love the improvements to productivity combined with the support and industry expertise of the Hartwig and Modig teams.

Video Testimonial from Accurus Aerospace:

See the Modig HHV in Action:

For more information, please contact your local Hartwig office or click here.


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Preventive Maintenance Provides Peace of Mind, Minimizes Costs and Downtime

When you hear the words “preventive maintenance” what comes to mind? Do you shudder at the thought of taking a machine tool out of production, losing precious time and money? Or are you meticulous about taking care of your investment so it will last for the long haul?

At Hartwig, we encourage our customers to have a proactive preventive maintenance plan in place for all machine tools and accessory equipment in their shop. Regular inspections and service can help to significantly reduce unnecessary downtime, lost production, late deliveries and expensive machine repairs.

Regular inspection and service lessens the likelihood of equipment failure. Preventative maintenance is performed while the equipment is still working so it does not break down unexpectedly.

While Okuma lathes are rugged and highly reliable, they even require routine maintenance. Robbie Williams, Applications Engineer for Okuma America Corporation posted this handy checklist of typical lathe maintenance items.

Daily Care and Feeding of Your CNC Machine

  • Check hydraulic pressure to make sure it’s at 4.5 MPa
  • Check hydraulic fluids to make sure they’re at the right operating level
  • Check to make sure the chuck pressure is at the right operating pressure
  • Make sure the way lube level is at the right operating level, and replenish if needed
  • If your CNC machine has a cooling system, make sure the cooling unit level is at the right operating level
  • Clean the chips out of the chip pan, and grease any part that may need to be greased
  • Clean off the window of the door and the light so you can see inside your machine
  • Wipe down any stainless steel way covers and lubricate them with hydraulic oil so they move smoothly

On a weekly basis, or every 40 hours, take the filter off the CNC control cabinet and clean it so air will be able to flow through for cooling.

Every Three Months or 500 Hours

  • Check and grease the chain on the chip conveyor
  • Check and clean the filters on the coolant tank

Every Six Months or 1000 Hours
Contact Hartwig to have the following preventive maintenance performed by our certified technicians:

  • Have the coolant tank cleaned of sludge, chips, and oil
  • Have the chuck and jaws taken off the machine and cleaned
  • Have the hydraulic tank drained and replace the hydraulic oil with fresh hydraulic oil – also have the line filter and suction filter changed
  • Have the radiator cleaned and make sure the radiator fins are straight
  • Have the lubrication unit drained and cleaned out – then add fresh way lube
  • If your machine is equipped with a cooling unit, have the unit drained and refilled
  • Have the leveling of your machine checked and adjust if necessary
  • Have all way wipers inspected for any damage – clean and replace any wipers that are damaged

Once a Year or Every 2000 Hours
Contact your local Hartwig office and have the following inspected:

  • Have the headstock checked for taper
  • Have the spindle checked for radial and end play
  • Have the chuck cylinder checked for run out
  • Have the tailstock checked for taper
  • Have the turret parallelism and inclination checked
  • Have your distributor run a backlash program to check the backlash in X and Z axis and adjust if necessary
  • Have your distributor check the X and Z axis gibs and adjust if necessary

PM Savings
Our preventive maintenance service and inspections will:

  • Extend the life of your CNC machines
  • Entitle you to a discount on all service parts for repairs made (or recommended and ordered within 30 days)
  • Reduce repairs and unplanned breakdowns by exposing potential problems before they lead to larger-scale, more expensive repairs

Hartwig’s Service Engineers are certified to perform required maintenance on all Okuma CNC machines. Even if your machine tool has no problems, our PM inspection makes sure that everything is working in the most efficient manner. They can also provide training and can design customized, planned preventive maintenance programs to fit your shop’s needs.

Contact Hartwig for more details.

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The Speed of Efficiency

By Rick Spencer, Productivity Specialist, CMfgE

In today’s world of digital technology, we can find answers to problems in a matter of seconds where previous generations had to research for hours or days in books and other printed text. As a result of this technology, we have become more efficient with our day to day communications and research. We can diagnose problems over the internet and watch videos on YouTube of how to fix them.

As a machine tool distributor we work with many facets of manufacturing. Some produce a high volume of parts with fully automated processes whereas other manufacturers are running smaller batch runs on less complicated equipment. Typically the annual quantity and tact time are the determining factor for the equipment. In this day and age we try to look at things from a lean manufacturing point of view and minimize waste anyway we can. That waste could be time, resources, extra steps within the process, or scrap.

As we look for ways to help improve our customer’s efficiencies, we try to minimize the extra steps within a given process and decrease the changeover time. The changeover is done when switching to a different part number or setup; for instance, on a lathe an operator will change out the chuck jaws and maybe tooling before running the next part number. These may seem like simple things to change during the setup but each one of these has other steps associated with it (e.g. re-boring jaws, setting tool offsets, etc.) unless quick change workholding and tooling have been implemented within the machine.

Rick Article 1Both of these quick change examples come with an upfront investment but can pay for themselves in months. With a quick change chuck, there is rarely the need to re-bore jaws as the guaranteed repeatability is around <0.02mm (.0008”) and jaw changes can be completed in less than one minute. There are other benefits to the quick change chucks as well such as:

– Longer stroke
– Modular center sleeves
– Large center holes
– One piece jaws (monoblock)
– Increased safety factor due to the wedge bar serrations

Once we have implemented the quick change setup, we can create a simple setup sheet for each job that shows where the jaws are positioned from the OD of the chuck. This will give the operator an easy way to set his jaw position the next time he runs the job.

Rick Article 2Similar to the quick change chuck, quick change tooling saves time during the setup process and can eliminate the need to touch off tooling with the tool setter. It is also possible to have the offset read from a barcode that is on the toolholder. This works great for shops that set their tooling offline on a tool pre-setter. The operator can scan the barcode and the offset is automatically loaded to the proper tool offset on the machine. This removes the possibility of the operator accidently keying in the wrong offset. Other benefits of quick change tooling include:

– Coolant plumbing through the tool
– Rigid & repeatable tool connection
– High Pressure Coolant ready (some tooling is specifically designed to be used with High Pressure Coolant which can aid in breaking chips and running higher surface footages)

Our Engineering team at Hartwig Inc. implements this kind of technology on machine tools on a daily basis. This helps make our customers more efficient with their day to day operations. If you feel you could benefit from more efficient processes or technology please feel free to give your local Hartwig Sales Engineer a call or you can call your local Hartwig office and speak with one of our Application Engineers.