Page 83 - THREADING CATALOG

USER GUIDE

Depth Per Pass and Number of Passes

In order to produce threads, the cutting tool needs to Example
make several numbers of cuts along the workpiece Pitch - 1.25 mm
surface. The parameters of depth per pass and number of Total depth of cut: ap=0.78 mm THREAD TURNING
passes have a very important role in threading production. Number of passes: na = 6
These parameters have a direct effect on cutting edge st
wear, tool life, threading surface quality, and threading • Calculation depth of cut for 1 pass:
st
production stability. The two methods most common in for 1 pass: C=0.3
determining the depth per pass and the number of passes
are constant chip area by decreasing depth per pass or ∆ap(1) = 0.78 × √ = 0.19
constant depth per pass. The choice of method does not √6-1 0.3
depend on the selected infeed methods (radial infeed, depth of cut for 1 pass: 0.19 mm
st
flank infeed, modified flank infeed, alternating flank infeed),
nd
which are described in chapter 2.12. The depth per pass • Calculation depth of cut for 2 pass:
nd
and number of passes parameters depend on the type of for 2 pass: C=1
equipment, tool overhang, machine stability, workpiece
material, cutter geometry and the threading depth required. 0 .78
∆ap(2) = × √ = 0.35
1
√6-1
Constant Chip Area by Decreasing nd
Depth Per Pass (recommended) depth of cut for 2 pass: 0.35-0.19=0.16 mm
This is the most common method and is generally • Calculation depth of cut for 3rd pass:
for 3rd pass: C=3-1=2
recommended, as in most cases it ensures high
productivity. The principle of this method is that the initial
cutting depth at the first pass is the largest, and then ∆ap(3) = 0 .78 × √ = 0.49
2
gradually decreases at each pass to ensure material √6-1
removal within a constant chip area. The calculation of depth of cut for 3 pass: 0.49-0.35=0.14 mm
rd
passes is designed so that the last pass, which is destined th
to be a finish pass, will be 0.05 - 0.1 mm (0.0019 - 0.0039 • Calculation depth of cut for 4 pass:
th
inches). Using this method ensures constant loads on for 4 pass: C=4-1=3
cutting edge and uniform wear, which increases tool life. 0 .78
∆ap(4) = × √ = 0.6
3
√6-1
depth of cut for 4 pass: 0.6-0.49=0.11 mm
th
th
• Calculation depth of cut for 5 pass:
for 5 pass: C=5-1=4
th
0 .78
∆ap(5) = × √ = 0.7
4
√6-1
th
depth of cut for 5 pass: 0.7-0.6=0.1 mm
• Calculation depth of cut for 6 pass:
th
th
for 6 pass: C=6-1=5
0 .78
∆ap(6) = × √ = 0.78
5
√6-1
Formula for Calculation of Depth Per Pass
depth of cut for 6 pass: 0.78-0.7=0.08 mm
th
ap
∆ap(i) = × √ C
√n -1
a
When
∆ap(i) — depth of cut i pass (i = 1...na)
I — pass
Ap — total depth of cut
Na — number of passes
C — constant value:
st
nd
for 1 pass: c=0.3; for 2 pass: c=1;
for 3rd pass and higher: c = i − 1

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