Flute Length Research Articles

Modeling Chip-Evacuation Forces in Drilling for Various Flute Geometries

In this paper, a chip-evacuation force model is presented to predict the torque and thrust required to evacuate the chips during drilling for various flute geometries. The model considers the chips in the flutes as granular solids and determines the chip-evacuation thrust and torque from the normal and lateral pressure distributions in the chips that fill the flutes. The model requires two coefficients of friction that are established via a calibration procedure. The critical depth for the process is determined by setting a threshold value on the chip-evacuation torque, which is based on the onset of chip-clogging. The effectiveness of the chip-evacuation force model in determining the chip-evacuation thrust and torque and predicting the critical depth has been assessed via a set of validation experiments using both standard and parabolic drills. The parabolic drill produced lower chip-evacuation forces and increased critical depths relative to the standard drill. While the standard drill has a modestly larger effective flute cross-sectional area for most of the flute length, the parabolic drill has a significantly smaller contact area between the chips and the flute surface, which is the main reason for the superior chip-evacuation performance of the parabolic drill.

Flute engagement in peripheral milling

Researchers have typically used a flexible model in an attempt to accurately simulate peripheral milling forces. The approach generally described in the literature divides the model into manageable pieces by modeling a cutter as several disk-like elements in its axial direction and by dividing the turning cutter into several angular increments. When the forces calculated at each differential element are integrated, it is important to consider the angle (δ λ) measured back as the flute engagement wraps up the helix. Therefore, flute engagement is very influential in determining the milling force profile and magnitude, and thus the effects of engaged flute length in the milling operation is of interest. In this paper, the concept of flute engagement is presented, and the equations calculating the engaged flute length (FL e) are derived. In addition, a method for determining the number of engaged flutes caused by the radial and axial depths of cut is presented. It is felt that the results of this research may provide the basis for a machining force model.

Applying the finite element method to drill design based on drill deformations

The design of the twist drill with special cross-sectional shape using the finite element method based upon drill deformations was presented in this paper. In order to improve the unfavorable distribution of the total orthogonal rake angle along the primary cutting edge of a thick web drill, a thick web drill with curved primary cutting edges was devised. The profile of the curved primary cutting edge was mathematically determined by changing the distribution of the tool orthogonal rake angle along the primary cutting edge. A three-dimensional finite element analysis based upon the drill deformations was applied to obtain the “secondary” flute shape and to specify the web thickness, the helix angle, and the flute length. The effect of these geometric [arameters on drill deformations was also investigated. Experiments were conducted to evaluate the drill's cutting performance. Experimental results indicated that the thick web drill with curved primary cutting edges was effective in reducing the thrust force, the torque, and the tool wear, a strength that definitely provided a better cutting drill and longer tool life for drilling the JIS S50C heat-treated steel.

A Twist Drill Drillable Deep Hole under Continuously High Feed Rate.

This paper describes a new type of twist drill. The web of this drill is three times thicker than that of the conventional one. Thus, it has high flexural and torsional rigidity. The main flank and the rake of the central part are formed by a flat grinding method and the drill tip forms a point perfectly. The chip is a conical helix type at first, successively changes to segment type, and then to a long-pitch helix type. In spite of the narrow flutes they do not clog with chips ; all types of chips are exhausted out of the drilling hole very well. Therefore, it can drill a deep hole under continuous feed and with a high feed rate. Under conditions of wet drilling of a S50C strip, a 12 mm-diameter twist drill with a carbide (M20) tip achieved deep drilling of 22 times the drill diameter, which is the limit of its flute length, and a 10 mm-diameter HSS drill achieved a total drilling depth of 80 m (through hole drilling of 60 mm x 1 340 holes).

Les vagues d'érosion

Current markings or scallops The scallops pattern on the wall of limestone cave result from the interaction of a soluble surface and an turbulent flow. The main results of Curl, particularly, the dependance of the velocity flow on the flute length are presented.