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Research Papers

Wear of Form Taps in Threading of Steel Cold Forged Parts

[+] Author and Article Information
Javier Fernández Landeta

Department of Mechanical Engineering,
ETSI of Bilbao,
University of the Basque Country (UPV/EHU),
Bilbao E48013, Spain

Asier Fernández Valdivielso

Department of Mechanical Engineering,
ETSI of Bilbao,
University of the Basque Country (UPV/EHU),
Bilbao E48013, Spain

L. N. López de Lacalle

Department of Mechanical Engineering,
ETSI of Bilbao,
University of the Basque Country (UPV/EHU),
Bilbao E48013, Spain
e-mail: norberto.lzlacalle@ehu.es

Franck Girot

IKERBASQUE,
Basque Foundation for Science,
Bilbao E48013, Spain;
Department of Mechanical Engineering,
ETSI of Bilbao,
University of the Basque Country (UPV/EHU),
Bilbao E48013, Spain

J. M. Pérez Pérez

CDTI – Center for Industrial
Technology Development,
Madrid E28001, Spain

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received March 12, 2014; final manuscript received January 7, 2015; published online February 16, 2015. Assoc. Editor: Patrick Kwon.

J. Manuf. Sci. Eng 137(3), 031002 (Jun 01, 2015) (11 pages) Paper No: MANU-14-1104; doi: 10.1115/1.4029652 History: Received March 12, 2014; Revised January 07, 2015; Online February 16, 2015

Tapping of blind or through holes is a common operation in several applications in the automotive, windmill towers, general machinery, and other industrial sectors. On the other hand, tapping is usually performed at the final manufacturing stage of components, so operation errors can lead to very expensive scraps. This article focuses on the performance of different forming taps since there are no standardized procedures for evaluating form tapping, beyond the mere visual assessment or go/no-go tests. Tool behavior was studied according to four aspects: (a) wear analysis of tap forming lobes, (b) measurement of thrust force and torque during tapping, (c) metallographic study of threads, and finally (d) evaluation of coating and tap geometry. In the work presented here, tap wear and thread quality are correlated with processes monitoring parameters. A useful conclusion for tap manufacturers is that taps with hexagonal section and 5 pitches in the chamfer zone led to lower thrust forces and torques than pentagonal section ones, along with a lower wear. Hexagonal/5-pitch taps led to better results due to a more gradual deformation process for producing a thread. A larger number of pitches before reaching the nominal diameter resulted in a reduction of strain between successive lobes, generating lower force and torque values.

Copyright © 2015 by ASME
Topics: Wear , Thread , Torque
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References

Figures

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Fig. 1

General aspect of a thread with cut taps and with roll taps. Material microstructure after a (a) cut tapping operation and (b) form tapping operation.

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Fig. 2

Geometry and terminology of forming taps

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Fig. 3

Tap profile and wear for a new tap and after 3000 and 5000 threads

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Fig. 4

Laboratory device with the ARTIS system for thrust force and torque measurement, forming tap and cold forged part to be thread

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Fig. 5

Forming lobe wear: (left) action of a lobe and (right) wear on the relief and rake flanks

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Fig. 6

Evolution of the type 1 forming tap wear

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Fig. 7

Evolution of the type 2 forming tap wear

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Fig. 8

Evolution of type 3 forming tap wear

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Fig. 9

Evolution of the torque during a form tapping operation

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Fig. 10

Torque mean generated in dry threading

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Fig. 11

Torque mean generated in lubricated operation

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Fig. 12

Thrust force generated in dry form tapping

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Fig. 13

Thrust force generated in lubricated form tapping

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Fig. 14

View of a form tap profile

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Fig. 15

Threads formed with the forming taps with coolant and in dry condition

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Fig. 16

Distribution of the microhardness indentation points

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Fig. 17

Microhardness values in lubricated conditions

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