Hard turning with CBN - Finish Machining

Through hardened En31 Bearing Steel Machining

For finish-machining of hardened steels and certain softer ferrous materials:

Surface and through hardened steels

High speed steels

Bearing steels

Hot - work die steels

Cold - work tool steels

Grey and chilled cast iron

Sintered Irons

CBN cutting tools machine hardened steels with apparent ease because, using relatively high surface speeds, heat is generated at the point of cutting so the PCBN tool cuts locally softened material. The heat is carried away by the swarf, which becomes brittle and harmless, and the PCBN tool, which has a high co-efficient of thermal conductivity. If a light cut is required, however, a tool with a high CBN content conducts too much heat away from the shear zone and the conditions for efficient machining cannot be achieved.

DR-50 & DR-50N have a low CBN content and the individual CBN particles are isolated within a ceramic matrix. This gives the materials a lower thermal conductivity and greater wear resistance in finish cutting operations.

Low CBN tools can therefore keep sufficient heat at the cutting point to enable the optimum cutting conditions to be achieved when a light cut is taken. In most cases, even when very light cuts are required, low CBN tools employ negative rake geometry to provide a strong edge. Due to the nature of cutting, however, cutting forces are still very small. Low CBN can be used to provide a productive and cost effective alternative to grinding.Tolerances achieved are comparable but machining time can be dramatically reduced.

DR-50 has a low CBN content and is designed for finishing and semi-finishing applications where grinding with conventional abrasives proves time consuming or difficult. DR-450 is tougher and performs well over severe interruptions.

UK Customers
CBN Inserts for finishing

US Customers
CBN Inserts for finishing

Machines for hardturning

Thanks to David Richards Engineering Limited

Turning Carbon Fiber Composites

What's the best insert for turning carbon fiber composites?

At first it might seem that machining fiber-filled composites with hard cutting tools would be a recipe for disaster. Developers of cutting methods and tools for composites face all kinds of problems. A composite's fiber layers can delaminate from the machined surface; the fibers or other hard reinforcements are abrasive and reduce tool life considerably; and the combination of hard and soft materials that make up a composite complicates the best choice of tool and machining parameters.

What do I use then?

Diamond will interact with carbon in ferrous materials, so its use is largely restricted to nonferrous workpieces. Today, the automotive industry is the major user of diamond tools in machining components made of aluminum-silicon alloys--in particular the 300 series of aluminum alloys. Major applications for silicon-containing aluminum materials are in pistons, engine heads, blocks and manifolds, wheels, and transmission parts. Other significant applications for diamond tools are in machining graphite, carbon-carbon (C-C) composites, metal-matrix composites (MMC), and fiber reinforced plastics (FRPs).


Where do I find the tools?

PCD Inserts
Diamond Coated Inserts

What about speeds and feeds?

Speeds and feeds for machining composites with pcd

special thanks to SME for information on machining composites

What is Cermet?

What are cermet inserts?

Of uniform structure and composition, Cermet is composed of solid titanium carbide (TiC) and titanium nitride (TiN) with a super-alloy metal binder. Cermet has a low friction coefficient which eliminates built up edge and improves surface finish. Its high resistance to thermal deformation and its low conductivity make higher cutting speeds possible and result in lower flank wear and edge cratering. Its high degree of hardness and toughness, with resistance to oxidation, extend tool life.

Inserts for difficult materials

Superalloys are hard; some grades of titanium are machined at 330 Brinell hardness. With conventional alloys, cutting zone temperatures greater than 2,000[degrees]F soften molecular bonds and create a flow zone for chips. In contrast, the heat resistance that makes HRSAs so desirable keeps them hard throughout the machining cycle.

HRSAs also tend to work-harden as they are cut, notching cutting inserts to premature failure. The difficulty cutting HRSAs is compounded where unpeeled stock is covered with abrasive, knife-edged scale that wears cutting edges down even more quickly.

Given their machining difficulty, superalloys are cut slowly. For example, Inconel 718 is milled for brake keys with Sandvik GC2040 grade carbide inserts at 200 sfm. Turning speed for the same alloy with Sandvik 7020 CBN inserts in an outside turning/facing application is 260 sfm. By comparison, uncoated carbide inserts typically cut tool steels at 400 to 800 sfm. Feeds for HRSAs are generally comparable to those used when machining tool steels.

The choice of cutting inserts to machine HRSAs depends on the material and the workpiece. Carbide inserts with positive rake geometries will cut thin-walled HRSA stock effectively. However, thick-walled parts may require ceramic inserts with negative cutting edge geometry to create a more productive plowing action. While dry machining is preferred in most difficult materials to maintain uniform edge temperatures, titanium requires coolant even at very low speeds.

by Wayne Mason

Technical Tips for Drills

Here are links for technical information on drills.

The links cover the following:

Speeds and Feeds for Drilling
Speeds and Feeds for Deep Hole Drilling
Feed Rate per Revolution for drills
Troubleshooting drills

For more information please visit www.toolinghouse.com for drills, taps, and carbide endmills

New Products

PGSTools.com is proud to announce the addition of the following products:

Iscar carbide milling inserts

and

Valenite carbide inserts

Most tools are in stock and ship same day out of Michigan.

Be sure to check out Valenites new inserts for stainless steel

VP8515 and VP8525

VP8515 is for finishing operations, while the VP8525 is for semi-finishing/roughing operations.

Carbide Inserts by Style

An answer to a recent email question I received, here are some of the most common style carbide inserts:

CNMG carbide insert

CNGA ceramic insert

DNMG carbide insert

DNGA ceramic insert

TPG carbide insert

TPG ceramic insert
VNMG carbide insert
VNGA ceramic insert

These links will take you to tools by Taegutec, Korloy, Kennametal, and generic carbide inserts.