Burton noted that although current processes may be working, upgrading to newer cutting tools with different coatings or grades can provide significant productivity gains and better surface finishes.

"One misconception is that turning almost no material on the last pass will improve surface finish," said Tonne. "In most cases, the finishing pass depth should be equal to the radius of the tool used for turning. Using zero-depth passes will often fail."

Tonne added that titanium is much more sensitive to small changes in speed due to its heat-resistant nature. Speed should only be bumped up in 5-m/min. (15-SFM) steps. It’s also important not to run too slowly, because running below the recommended speed for a given tooling system will cause material to build up on the cutting edge, which effectively dulls the edge.

Wipers are considered primarily as high-feed-rate machining inserts. Using them shops can increase the feed rate, which translates into less time in the cut, effectively increasing tool life. But if wipers are used at a normal feed rate, shops can gain measurable improvements in surface quality.

A wiper insert is built up through a number of extra radii. This makes the engagement surface longer, which also affects the surface in a positive way. A long engagement surface also affects the cutting force and the vibration sensitivity.

Finish turning of titanium must be a wet process. A high-precision coolant offers significant advantages, particularly as it can be directed to the cutting zone.

The experts recommend using a physical vapour deposition- (PVD-) coated insert because it is thinner. With titanium, it’s not advisable to use a thick coating because of the chemical reaction that can occur. Many of today’s coatings have titanium in them, like TiCN, which is used in chemical vapour deposition (CVD). This is why PVD is more commonly recommended.

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"When we start finish-turning with PCD, it looks totally different than with other inserts," said Burton. "The titanium will look really nicely polished and almost have a hardened steel, superfinished look."

"We noticed this many years ago when we introduced wipers," said Burton. "Because of the refraction of light, wipers produce a different-looking surface, showing a grey scale surface appearance. But the surface quality, when measured, is still better. That’s a challenge that many shops have to understand and overcome."

V7 INOX - Despite it’s name suggesting a more dedicated Stainless Steel type cutter, the V7 inox from YG-1 is actually a very good option on a wider range of materials which also include Steel <40HRc, Cast Iron and Titanium Alloys. The main feature is the original V7 variable helix design which eliminates vibration to ensure an excellent surface finish. The special geometry also provides higher speeds, deeper cuts and larger metal removal rates compared to general purpose milling cutters.

"All titanium runs with the same general parameters is one misconception," said Tonne. "Usually the phase of the metallurgy is the best starting point. Alpha phase titanium alloys tend to run higher speeds and feeds. Alpha beta, which is the most prevalent, is well-documented, and finally beta alloys are the most difficult. The key is to research the material and understand the properties."

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There are many factors to consider when purchasing a high-performance multi-purpose milling cutter, however the first consideration should be if you have a suitable set up or machine capability to run them because they generally require a higher power machine. The next thing to consider is generally what you are looking for from a high-performance milling cutter. Below is a summary of our ranges to point you in the right direction:

For example, Ti-5553 requires a very hard surface coating to basically get through it. This material can run at only around 50 per cent of the speed of Ti6Al4V.

Single point threading is ideal where multiple thread sizes or forms need to be created at an economical cost (using just one holder).

Get unmatched productivity in high performance thread turning applications. 60% less machining time. 60% reduced number of passes. 25% more tool life.

Tonne added that it’s important for shops to inspect tooling centre height positions frequently. Incorrect cutting heights will result in reduced surface finish quality.

Finish turning of titanium must be a wet process. High-precision coolant offers significant advantages, particularly as it can be directed to the cutting zone. Photo courtesy of Sandvik Coromant.

Smooth-cut anti-vibration threading heads with through coolant up to 70 bar for better chip evacuation and optimum tool life.

Our knowledgeable team of experts can help you find the right high performance multi-purpose carbide milling cutter to suit your requirements. So why wait? Browse through and buy from our range of high-performance multi-purpose carbide milling cutters online or alternatively please call 01924 869 610 or email sales@cutwel.net for any advice or queries.

Through coolant for improved chip flow and tool life. Screw clamp threading holder for internal right hand thread turning.

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"The rule of thumb is the surface finish will be twice as good when a normal feed rate is maintained; doubling the feed rate will maintain normal surface finish," said Burton.

Titanium generally is used to produce critical aerospace components and medical devices. It offers a high strength-to-weight ratio and excellent corrosion resistance, which enables it to be used for designs with thin walls.

For finish turning, Burton suggests that polycrystalline diamond (PCD) inserts are the way to go because of the much higher surface speed, which of course reduces cycle time drastically. However, he noted that some shops have a difficult time accepting a visual difference of the surface.

V7+ 6 Flute TRP Milling Cutters - The highest performing multi-purpose milling cutter available from global market leaders YG-1. The range is split in two depending on your machining requirements, but once you experience the ultra-high feed rates of the TRP series or the ultra-deep cuts of the chip splitter range you won’t look elsewhere. The revolutionary 6 flute design ensures phenomenal performance and outstanding surface finish on Steel, Stainless Steel, Cast Iron and HRSA’s.

For many years shops have been using uncoated inserts in titanium, and many still do. But now with so many different types of titanium, there are additional factors to consider for better surface finish when turning.

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Similar to PCD inserts, wipers are the first choice in stable conditions and it’s recommended to use wipers whenever it is possible.

Upgrading to newer cutting tools with different coatings or grades can provide significant productivity gains and better surface finishes. Photo courtesy of Sandvik Coromant.

"We have seen that many shops are unwilling to change from their current processes, even if it means better finishes," said Kevin Burton, turning product and application specialist, Sandvik Coromant, Mississauga, Ont. "If the certified process uses an uncoated carbide insert, shops may not want to change to a coated or diamond insert because of the extra cost both from a time and financial standpoint. It’s the same with grades. With the new generation of grades out, some look different with different colours even though they typically have the same elements, just different percentages. Yet shops tend to be concerned about the coating being left behind on the surface of the part."

"Speed is the killer in all materials but very much so in titanium," said Burton. "If you go from uncoated to coated, then your speed can go up. Speed is productivity because your feed per revolution stays the same, but the speed goes up. This allows the feed per minute to increase, which is an advantage. Typically, this can be around a 20 per cent gain in productivity. If a shop goes to, say, a PCD insert for finish turning, there will be an even bigger productivity gain. With coated carbide you can expect 150 to180 SFM but up to 600 with PCD. The gain in productivity is huge."

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The low modulus of elasticity causes greater workpiece springback in these materials. This modularity is one of the material’s strengths, particularly when it comes to structural aerospace components that require that movability quality. However, this makes it a challenge to machine, often resulting in tool vibration, chatter, and poor surface finish.

Single Point Thread Turning Holders & Inserts designed for general threading applications. Solid & through coolant holders with inserts covering all common thread forms.

"Titanium in general does not shear efficiently, so the material springs back and the size control of a component is more difficult," said Edwin Tonne, training and technical specialist, Horn USA Inc., Franklin, Tenn. "The finishing pass depth must be carefully maintained to account for this behaviour. Additionally, during finishing the forces and heat are concentrated over a small region of the cutting edge, which breaks down the edge more rapidly than in other materials."

Lindsay Luminoso, sr. editor/digital editor, contributes to both Canadian Metalworking and Canadian Fabricating & Welding. She worked as an associate editor/web editor, at Canadian Metalworking from 2014-2016 and was most recently an associate editor at Design Engineering.

Luminoso has a bachelor of arts from Carleton University, a bachelor of education from Ottawa University, and a graduate certificate in book, magazine, and digital publishing from Centennial College.

Having the ability to direct the coolant to the cutting zone is particularly important with titanium. It’s also recommended that shops use both over- and under-coolant for finishing operations and depth of cuts below the nose radius. This allows for the full effect of the high-precision coolant for better chip control, surface finish, and tool life.

Tonne noted that there is a misconception that shops can use a roughing insert for finishing. Geometries and edge preparations are specifically designed for an application, so he recommends inquiring with the tooling vendor on the best insert, not a universal insert.

"PVD coatings have high temperature resistance and lubricous surface, which reduces built-up edge and heat," said Tonne. "When it comes to inserts, the best shape is round, but it is often not practical due to part shape. C- or W-style inserts offer the best finish with clearance for part features. For negative-type inserts, make sure the top rake is positive. If tight tolerances are required, fully ground inserts can improve outcomes."

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Our range of high-performance multi-purpose milling cutters are the next step up compared to general purpose tooling. They offer a wide array of additional benefits such as longer tool life, faster machining, better surface finish and higher metal removal. These are all achieved due to the unique geometries and special features that higher performance milling cutters tend to have. Many high-performance milling cutters are also material specific. This is because of their enhanced performance; however, it limits the amount of materials they can machine, which is why a high performance multi-purpose milling cutter is an excellent choice for engineers who machine a wide range of materials but need better performance than a general purpose tool.

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Certain applications, particularly critical components in aerospace, have stringent surface integrity requirements. Many shops have had tried-and-true certified processes in place for years. These processes may be working, but with the latest cutting tool advancements, there are often better or more production options available, particularly as they relate to finish turning.

It’s no secret that titanium alloys are difficult to machine, particularly compared to general and stainless steels. It has poor thermal conductivity and generates high cutting forces and heat at the cutting edge. The demand this material places on cutting tools is significant and can lead to both premature tool wear and poor surface quality if not done properly.

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