French Version

German Version

MALLORY “NO-CHAT”

Vibration Damping Tool Shank Material

for Boring Bars, Parting Off Tools, Grinding Quills

The vibration of a tool shank, commonly referred to as “chatter”, generally occurs as a result of excessive tool overhang for the depth of cut being taken. Such chatter results in a reduced tool life, a poor surface finish and inaccurate work. While chatter can be minimised by increasing the cross-sectional area of the tool shank and by reducing the overhang and depth of cut, such measures may be impractical or result in increased costs.

Mallory “No-Chat” is a high density, tungsten based, heavy metal containing 90% tungsten that is made by powder metallurgy techniques and which exhibits much greater stiffness and strength than conventional tool shank materials. It is, therefore, possible to use smaller shank cross-sections, greater amounts of overhang and larger depths of cut than would be possible using normal tool shanks. In addition, the material also exhibits inherent vibration damping characteristics, further reducing the likelihood of chatter, while its high thermal conductivity aids cooling of the cutting tip and minimises thermally generated dimensional changes. Its high hardness provides good abrasion resistance to the cutting debris.

Fabrication Characteristics

1.                   Machinabilty

Unlike tungsten carbide, Mallory “No-Chat” can be machined without difficulty. Its machining characteristics are somewhat similar to those of cast iron, which means that it can be drilled and tapped so that cutting tips may be attached by mechanical means without difficulty. Specific machining data is available on request.

 2.                   Brazing of Carbide Tips

The attachment of carbide tips directly to Mallory “No-Chat” by brazing presents few problems. The low coefficient of expansion makes it an ideal backing material, reducing the effects of differential expansion, which are a major problem when attaching carbide tips to steel. Since “No-Chat” does not anneal at  brazing temperatures, no loss of mechanical properties occurs and thus it is possible to braze and de-braze tips as required.

 The silver based brazing filler metals and fluxes used for tungsten carbide are also recommended for “No-Chat”. If difficulties occur with any brazing operation please contact us for further advice.

 Applications

 1.         Boring Bars

Under certain extreme conditions the amount of overhang of a conventional steel boring bar has to be limited to only 3.5 times its diameter. By using boring bars made from Mallory “No-Chat” significantly increased overhangs can be employed before the quality of cut is affected. Clearly, if this is possible in extreme conditions, it follows that under normal conditions of operation greater depths of cut and higher machine speeds can be achieved before chatter occurs, resulting in increased machine efficiency. The efficient vibration damping characteristics of the material also help to improve the life of the cutting edge, give finer finishes and reduce the effect of tapering in long holes.

 2.         Parting Off Tools

When used for parting off tools the high strength and stiffness of “No-Chat” permit much narrower tip sections to be used than could be contemplated if a steel shank had to be employed. As a consequence of this narrower tip, less material is removed during a parting off operation, improving material usage.  Although the tip is narrower, no loss in cutting performance results, indeed generally higher feeds and speeds can be applied without difficulty. The high hardness of “No-Chat” gives it good resistance to swarf  abrasion and, since its properties are unaffected by brazing, repeated use can be made of the shanks.

 3.                   Grinding Quills

The rigidity of Mallory “No-Chat” makes it an ideal material for grinding quills holding abrasive wheels  that  work at high speed. Employing quills made from “No-Chat” enables deep holes to be ground at higher rates with greatly improves surface finishes and with tighter tolerances than could be achieved when using a high strength tool steel quill. This high rigidity also helps to prevent shank deflections (and the resultant loss of accuracy when the grinding wheel encounters cross-holes), allows longer quills to be manufactured (by up to 33%) and significantly reduces the failure rate of quills due to fatigue.

 Nominal Physical Properties

 Density g/cc                                                            16.9

 Thermal Conductivity W/m.deg.C                                93

 Coefficient of Linear Expansion (100-200 deg.C) x 10/deg.C          5

Ultimate Tensile Strength MPa                                    760

Elongation %                                                           5

Modulus of Rigidity GPa                                             131

 Modulus of Elasticity Gpa                                          272

 Modulus of Rupture (simple beam) MPa                      151

 Modulus of Rupture (torsional) MPa                            740

 Hardness Rockwell C                                                19

All Mallory Alloys Group products conform to, if not exceed, the relevant standards as assured by the Quality Management System

© Copyright 2004 Mallory Group Limited, all rights reserved.