Precision Cast Iron Machining

Whether you’re making brake discs and flywheels in grey cast iron, or crank shafts and wheel hubs in nodular cast iron, there is always a successful solution.

Over the years there have been a number of CBN grades made available for machining cast iron with CBN. Most notably are DR-80 and DR-85. These grades are made for the following applications:

For rough and semi-finish turning, milling, grooving and boring of hardened ferrous and certain softer ferrous materials:-

• Martensitic cast irons - Ni-hard - High chrome Chilled and heat treated cast irons
• Fully hardened cold-work tool steels
• Bearing steels
• High speed steels (continuous cutting only)
• Martensitic stainless steels
• Cobalt and nickel based hard facing alloys
• Fully pearlitic grey cast iron

DR-80 & DR-85 are high CBN content materials, diffusion bonded at the manufacturing stage to a tungsten carbide substrate.

DR-80 is (80% CBN) has a greater particle size than DR-85, (85% CBN). DR-80 is better for hardened steel, but DR-85 has better wear characteristics when machining cast iron with CBN, particularly when the stucture contains Ferrite.

For more information on machining with CBN Inserts
please visit David Richards Engineering UK or
David Richards Engineering US

Hard Turning with CBN

CNMA 432 Quad Edge CBN Insert Shown

Hard turning with CBN will:

• Reduce Grinding Investment
• Increase Tool Life
• Reduce Cost with Faster Cycle Times
• Lower Tool Change Down Time Costs
• Reduce Scrap Cost
• Reduce By-Product Disposal
• Extend Tool Life In High Production Hard Turn Applications
• Increase Thermal and Mechanical Shock Resistance to Handle the Most Demanding Contouring and Interrupted Cuts

Hard turning requires switching from carbide to CBN inserts. It’s easier and more economical than one would expect. The major adjustment is working with much higher surface speeds.

Earlier posts that deal with CBN Insert questions:

CBN Insert Applications

What is PCBN?

Hard Milling with Ceramic Inserts

Hard milling with ceramic inserts can help a mold shop to reduce manufacturing costs in several ways. First, a mold shop can replace several operations with one operation. Instead of machining, hardening and remachining, the use of ceramic inserts enables a shop to harden the steel first and then machine the part in the hardened form. This reduces manufacturing time and improves job tracking by reducing the number of times that you must set up and move a component through various manufacturing phases. Furthermore, roughing a hardened part with ceramic inserts also can eliminate expensive and time-consuming EDM operations, as well as the need to make one or more electrodes.

Second, ceramic inserts are capable of machining hardened steel at much higher speeds than conventional carbide cutting tools. Combine the higher operating speed with the proper feedrate and a healthy step-over and the shop can achieve some impressive metal removal rates. Another key factor in increased production rates when hard milling is the cutter density. Every additional tooth in a cutter increases the cross feedrate. Higher speed and more feed add up to lower cycle times and money saved.

Third, many times the surface finish achieved by rough milling with ceramics leaves less work for a finish milling operation, and reduces finishing and polishing time. Milling at relatively light feedrates in hardened steel with carbide usually leaves a good finish, but many times with ceramic inserts the rough finish is even better than the required finish. In some cases, additional milling, grinding and polishing can be eliminated, saving several hours of manufacturing.

Cylinder Boring with CBN or PCD Inserts

Boring out cylinders to accept oversized pistons or sleeves has long been a common practice in the engine rebuilding business. Boring allows worn blocks to be salvaged, and stock cylinder bores to be enlarged for more displacement. More recently, boring is also being used to install special cylinder liners with hard surface treatments in high performance racing engines. The hard liners almost eliminate ring and bore wear so the engine can run race after race with no increase in bore clearances blowby.

Like most other machine tools in today's shops, the equipment used to bore engines is also evolving to keep pace with changes in engine technology and the aftermarket. Small shops want equipment that is versatile and can do more than just bore holes. For this end of the market, combination boring/milling machines have become popular. At the other end of the spectrum, production engine remanufacturers (PERs) want equipment that works harder, works faster and requires less operator input. For this type of user, automated high speed boring equipment provides the needed boost in productivity and quality.

Tooling has also been improving. The latest generation of coated carbide inserts provides longer life and better cutting action. For high speed boring, polycrystaline diamond (PCD inserts) provides the longevity needed for this type of operation. The speed at which the boring bar turns has a significant impact on tooling life. High speeds just kill the bits unless you use a PCD or cubic boron nitride (CBN inserts) type of insert. The high speed boring machines that go up to 1,500 rpm need these type of inserts.

Face Grooving Inserts and Tools - Korloy MGT Series

Horizontal Type MGT Face Grooving Tool

Vertical Type MGT Series Face Grooving Tool


Korloy MGT Face Grooving Inserts or MGT tools, have double ended cutting edges, provide economic tooling cost. More so than conventional single ended type tools.

Insert grades available for the machining of carbon steel, alloy steel, stainless steel, and cast iron.

To cope with the increased needs for face grooving and boring of various material, the newly designed chip breakers are able to acquire good chip control.

Korloy Face Grooving Inserts provide various holder line-ups to expand your option, while adding more features and benefits.

Inserts Shown Below
MFMN300 (Cutting Width 3mm)
MGMN400-M (Cutting Width 4mm)

Recommended Cutting Conditions (Speeds and Feeds - Workpiece Material)

If you have questions, would like to purchase, and trial the MGT Face Grooving Inserts please contact us at: sales@pgstools.com

Sumicrystal Blanks - Synthetic Single Crystal Diamond

Sumicrystal Blanks - Synthetic Single Crystal Diamond

Sumicrystal PD/PDX Dresser Blanks
2 pictures above

Sumicrystal UP Cutting Tool Blanks
2 pictures above

What is this stuff?
Synthetic Monocrystalline Diamonds: Perfectly flat, defect free synthetic diamonds- Monodie-100 and Monodie-111 from DeBeers, U.K. and Sumicrystals from Sumitomo Electric Industries, Limited., Japan-are used for specific customer requirements.

What is a PD Dresser Blank?
The Sumicrystal PD dresser blanks are single crystal diamonds processed into the shape of a long, thin prism. They provide automated and high precision dressing through reliable performance and long tool life.

Ok, now what about the UP Cutting Tool Blanks?
The Sumicrystal UP cutting tool blanks are just that...cutting tool blanks. They were developed by Sumitomo Electric to provide high performance and reliability for high precision cutting tools. They work well in ultra-precision machining processes, for machining products such as memory discs and polygon mirrors.

Now that I know, where can I get it?
Interesting that you should ask. The pictures above are tools that are available. If you are s, interested in purchasing these tools, please contact us a sales@pgstools.com.

Ceramic Inserts vs. CBN Inserts

CNMA CBN Insert (shown in picture above)

VS.

CNGA Ceramic Insert (shown in picture)

An important criterion for the economical application of cutting tools is their life in relation to the metal removal rates, especially with two materials such as ceramic and CBN. The latter is much more expensive. Thus, comparison of tool wear becomes most important.

The two materials show marked performance differences in both size and surface finish in roughing, interrupted, and finishing cuts. In comparison to grinding, however, both materials will achieve much higher metal removal rates.

CBN will out-perform ceramic in interrupted cuts. With depth-of-cut of 0.060 inch to 0.120 inch and a speed of 350 sfpm with 0.010 to 0.020 inch feed per revolution, ceramic often will fail when entering the interruption. With CBN, a tool life up to 20 minutes can be achieved with a half-inch round insert, under the above conditions. Flank wear in interrupted cuts is more irregular than in continuous cuts and can shorten tool life. Solid CBN inserts have greater flank wear resistance and are superior to ceramics for roughing, especially where the turning has interrupted cuts.

For finishing cuts where small depths of cut and low feed rates are required to achieve superior surface finishes, CBN inserts cannot equal the tool life of ceramic inserts. Under these conditions, the ceramic insert has less than half the flank wear of CBN after 30 minutes cutting time.

Considering that CBN is ten times more costly than ceramic for the same size and geometry insert, CBN economically can be justified only for machining heat treated steel in those situations where ceramic fails completely or breaks down before finishing the workpiece.

excerpted from gardner article