Although seemingly simple, the design of effective chamfering tools needs to take into consideration various factors, including whether the chamfers are external or internal, breaking sharp edges and removing burrs, chamfers in holes, productivity, and versatility. Article by Andrei Petrilin, ISCAR.
Chamfering is perhaps the most common operation in metal cutting. It may be found practically in every machining process. Chamfers and, to a lesser degree, fillets feature on almost all external and internal corners of parts. Chamfers are simpler to manufacture than fillets, which explains why they prevail. We are so accustomed to the presence of chamfers at the edges of various products that sometimes we do not think about the importance of these relatively small sloped surfaces. They prevent hand injuries, make assembly easy, reduce stress concentration, and constitute necessary elements of a product design.
Traditionally, chamfering is considered as a simple operation. Usually, it is performed by different cutting tools, which are not very sophisticated. A straight-turning tool or a milling cutter featuring a 45-deg cutting edge angle or a drill with a 90-deg-point angle are typical representatives of such tools.
At the same time, the application field of rotating chamfering tools is not limited by typical operations but also includes deburring and bevelling, countersinking and undercutting, back chamfering in holes and along edges, undercutting and V-cutting, spot drilling and centre drilling. A rotating chamfering tool is extremely versatile and, in an ideal scenario, should be capable of performing all the mentioned machining operations effectively and efficiently.
However, various objective limitations, primarily dimensional, place serious obstacles in creating this perfect tool and the existing solutions tend to be far from ideal. Understanding the most preferable features of the tool from the customer’s point of view is critical for designing modern chamfering tools to overcome these challenges. Especially here, which seems so simple as to be sometimes disregarded, manufacturers look to cutting tool producers for a simple, productive, cost-effective, and versatile solution.
Such an approach resonates with ISCAR’s concept of advanced intelligent tools. Following this principle, the company has developed various rotating chamfering tools.
MULTI-MASTER, ISCAR’s family of assembled tools with exchangeable cutting heads, provides several options. The economical two-flute MM H heads and fully ground multi-flute MM E heads ensure effective chamfering and removing burrs, particularly when applied to cutting relatively small-size areas or workpieces. One of the heads, the multi-functional MM HCD (Figure 1), is suitable for efficient machining external and internal chamfers, burrs, centre- and spot-drilling, and countersinking. The secret of the head success is a cutting geometry that features combining negative and positive axial rakes. Together with a positive radial rake, the design principle results in a strong cutting edge and excellent chip former to guarantee a smooth and light cut—even in hard machining conditions—and reliable chip flow.
The dovetail-shape heads (Figure 2), another MULTI-MASTER product, are available with 45 deg, 60 deg and 75 deg entering angles. They are capable of both generating dovetail groove or slots and perform back chamfering; the multi-tooth design of the heads ensures high productivity when performing this operation.
Drilling a hole with a chamfer by one single pass, for example in pre-thread drilling, is a preferable option for every manufacturer. The operation can be performed by applying a combined hole making tool that combines drilling and countersinking features (Figure 3). However, an almost endless number of hole depths significantly limits tool capabilities and technically necessitates the manufacture of many special tool versions, each adapted to a specific hole size. This problem is overcome by mounting a chamfering ring in the body of a standard ISCAR CHAMDRILL drill, in the desired position according to the drill tip, to configure a tool that can perform drilling and chamfering in one operation.
One tool design is intended especially for small manufacturers and maintenance departments. This is a versatile chamfering endmill with an adjustable cutting edge angle. The endmill features a rotatable cartridge that carries an indexable insert. Due to adjustability of the cutting edge, the tool enables milling chamfers with various angles and eliminates the need for different tools for different chamfer angles. The angle scale, engraved on the cartridge, makes adjusting simple and friendly. Nevertheless, the ‘cost’ of high versatility is a single chamfering edge—the multi-functional adjustable design provides only one cutting tooth.
ISCAR’s recently launched CHAMFMILL family of indexable milling cutters is designed for front and back chamfering (Figure 4), with applications including machining small outer and inner chamfers and removing burrs. The key element of the family is a pentagonal insert carried by the cutters. The star-like shape features 10 cutting edges: five for front and five for back chamfering.
Although seemingly simple, the design of effective chamfering tools needs to take into consideration various factors, including whether the chamfers are external or internal, breaking sharp edges and removing burrs, chamfers in holes, productivity, versatility, and more. To the question of which tool would be considered as a five-star product, one could answer that the best tool is the one that the customer has chosen according to their needs.
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