Machining Cemented Carbide

This blog entry focus is on machining the following:

Cemented carbide with a Co content of less than 17%:

1. First choice for machining is CBN
2. Should use a round cbn insert
3. The insert should have a chamfered cutting edge
4. Machining with coolant is recommended
5. Chamfer the workpiece at entry and exit point.

Should you require further assistance in choosing an insert or pricing. Please contact the experts at David Richards Engineering.

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.

Wow

There is a lot of snow! Baby It's Cold Outside

This Song Says It All!

Carbide Insert Identification Chart

Carbide insert identification chart is now available at www.pgstools.com. This chart is helpful for identifying inserts without a home.

The insert identification chart is located here:

Carbide Insert ANSI Designation

CBN Cutting Tools for Grooving

Hard part grooving can be a difficult process without the correct tools. CBN cutting tools for grooving can ease that process. During heat treatment, many features of machined components suffer distortion. If the position or dimensions of a groove are critical to the performance of a hardened component, David Richards can offer a simple solution to this problem - ‘Hard Grooving’. Based on the Top Notch system, David Richards supply grooving tools in a wide range of sizes from 0.5 mm width upwards. David Richards supply tools for circlip and ‘O’ring grooves with controlled corners or full radii, either full form for plunging or undersize for profiling.

Using such surface speeds typical for turning, grooves are machined at low feed rates (0.01 / 0.05 mm/rev). The low feed rate ensures that the swarf is very weak and brittle, decreasing the likelihood of it breaking the tool. Where there are no interruptions to the cutting path, coolant should be used to aid evacuation of the swarf and ensure that the component remains at a stable temperature for ease of measuring. If the cutting path is interrupted, an air blast will serve the same purpose without the risk of thermally shocking the PCBN tool.

If practical, it is better to finish a groove that has been pre-formed at the soft stage. This ensures uniform hardness around the groove and maintains the structural integrity of the component. However, if it is acceptable, satisfactory results are achieved grooving through a hardened layer into the core material. Successful applications include grooving case hardened (58 / 63 HRc) splined shafts and gear teeth, internal circlip grooving hardened EN31 (58 / 60 HRc)
bearing components, and producing profiles in the face of D2 tools steel tools using Full radii face grooving tools. All operations that would be time consuming and difficult to grind.

Whilst the Top Notch system offers an ideal base for most grooving tools, other systems have been employed with excellent results.

It naturally follows that, since David Richards can produce tools for ‘Hard Grooving’ full and partial form cbn threading tools, both external and internal, are available for ‘Hard Threading’. Where the pitch of the thread is large, or the diameter of the component is small, it must be remembered that the feed rate required, at the required surface speed for ‘Hard Turning’ will be relatively fast. But, producing a 90 mm diameter internal stub Acme thread 150 mm deep,
with a 6 mm pitch in 58 HRc Ni-Hard iron, at 120 m/min from blank bore, though somewhat exciting, proved a major cost saver.

To purchase CBN Grooving Inserts please visit

www.pgstools.com

Machining Soft Steels with CBN Inserts

Finding it difficult to machine soft steels with cbn inserts? I would suppose that soft steel is relative, so generally speaking, cbn inserts will machine steels from 45-65 HRc. For soft steels (the ones on the lower end of the 45-65 HRc), the lower you are on the hardness scale, the faster you will want to machine the material.

CBN needs heat to cut at its fullest potential. A quick lesson: CBN generates heat in the shear zone, thus locally anealling the material, cutting it as if it were soft.

If you are having trouble with turning using CBN inserts or PCD inserts, please call to discuss your application with David Richards Engineering or email to sales@drengus.com

Purpose and Use of the Cut-Off Tool and Holder

After completing a part in the lathe it is frequently necessary to separate the part from the excess material used for chucking. This operation is best accomplished with the use of a cut-off tool or "parting tool" as it is sometimes called. The Cut-off Tool and Holder consists of a very slender high speed tool steel cutting blade mounted in a special tool holder. The thinness of the blade (.040") enables it to feed into the part quite easily and at the same time minimizes the amount of waste material. The turning speed for parting should be approximately one half the normal turning speed for any given material. One word of caution; never use a parting tool on a part mounted between centers. The part may bind on the cutter and result in a scrapped part or a broken cutting tool.

Parting off material (free machining) over a 1.00" (25mm) diameter will always present problems on a machine of this size.

Always try to lay work out so the cut-off tool is used as close to the spindle as possible. Set blade height by sliding the blade in its slot in the tool holder. It should be set so the tip is aligned with the centerline of the part being cut. An unusual diameter may require a shim to be placed under the front or rear of the holder to accomplish this.

NOTE: ALWAYS USE CUTTING OIL WHEN USING THE CUT-OFF TOOL. The cut will be made much smoother, easier and cooler.

Speed should be slower than normal turning speed and feed rate should be a little heavy so the chip will not break up in the slot. If speed and feed are correct, there will not be any chatter, and the chip will come out as if it were being unrolled. Coolant (cutting oil) plays a major roll in this occurring properly.

If the tool chatters, first check to see if the work is being held properly. Then decrease speed (RPM) or increase feed rate or both. Once the blade has chattered, it leaves a serrated finish which causes more chatter. Sometimes a serrated finish can be eliminated by turning the spindle off, adding a liberal amount of cutting oil, bringing the blade up so there is a slight pressure on it without the spindle turning, and then turning by hand or as slowly as possible with the speed control.

BY: Joe Martin

Where to use ceramic inserts and silicon nitride inserts

All Irons... use silicon nitride in all applications...turning, boring, milling & facing. Use for roughing, semi-roughing, semi-finishing & finishing applications. Generally speaking, silicon nitrides can be used in all iron applications.

All Irons... use the black (CC-20) and/or white (CC-10) ceramic on semi-finishing & finishing applications. They are less costly and harder than silicon nitride (more abrasion resistant & longer lasting).

Steels below Rc58 in hardness... use the black (CC-20) and/or white (CC-10) ceramic in almost every semi-finishing & finishing applications. They can even cut with mild interruptions. If your customer isn't using CC-10 & CC-20 on almost every finishing application, he's losing money.

Steels above Rc58 in hardness... use the black (CC-30) for finishing applications, especially to replace grinding. You can also use silicon nitride for roughing.

Aerospace Metals... Inconel, Hasteloy, Waspeloy, Renee, Etc. For roughing or finishing use CC-5477 Silicon Nitride specifically designed for these materials.

Click on the link below for tools:

Ceramic Inserts

Carbide Insert for Turning Wood

We have found that this insert performs quite well for turning wood. There are two choices available for chipbreakers. In the first picture is the "TA" and the "HA" is in the second picture. Each one serves a different purpose, so read carefully. Both inserts are from Korloy. These inserts are available in packs of 2. For pricing on carbide inserts for turning wood: www.pgstools.com

Recently added to the collection are these carbide inserts for cutting wood:

http://www.pgstools.com/servlet/the-Carbide-Inserts-cln-Wood-Cutting/Categories