Infastech Insert Design Guide
Infastech
Offices
www.infastech.com
The characteristics of Knurl and inserts
• Crystalline plastics is relatively insensitive to stress, can apply for a variety of inserts.
• Non-crystalline plastic is very sensitive to stress, the choice of inserts models should
avoid sharp Knurl. For plastics who need to shield plating should be particularly careful,
Helix angle
the plastics buried inserts can cause serious cracking issue after acid washing process.
It is best to plating first, then buried inserts.
Knurl
• Thermoset plastics does not apply for hot melt and ultrasonic burying, if it’s necessary,
you can choose sophisticated and sharp Knurling with compression inserts process.
Groove
Pitch
Lead
Plastic characteristics
Thermoset Plastics
Thermoplastic Plastics
Will not soften by heating
Will soften by heating
High hardness and easy broken
Good flexibility
Good surface hardness
Can be recycled
More stable with microstructure
Easy for injection molding process
Twist-pull relationship with the helix angle
Good heat resistance performance
Helix angle vs strength
Difficulty for injection molding process
Pull force
Crystalline plastic
KN (KN.M)
infastech brass inserts
The relationship between the plastic and inserts
Torque
30
35
40
45
Helix angle
Non-Crystalline plastic
50
55
60
Groove and Oriented
Inserts materials and surface treatment
• Standard Brass C3604
• Low-lead copper in line with the EC ROHS environmental protection requirements
• Stainless steel / tin, free cutting iron
• Surface Treatment: Under normal circumstances, inserts is not necessary for the
particular surface treatment. If a special request, the plating can be used for processing.
Lead
• The effect-oriented role of lead can
enhance the efficiency, at the same
time to avoid the deflection and boss
hole crack
• Make sure the size of D is larger than
d 0.03mm at least.
Groove can accommodate the plastic
to improve the pull force
Brass Insert Applications
Inner Thread Specification
Herringbone For thermoplastic plastics application with ultrasonic and
Nominal Size
Toleranc e
Aiguille dia
m.m.
Inch
Hole dia, GO
m.m.
Inch
Hole dia, NO-GO
m.m.
Inch
M1X0.25
5H
0.77
0.0303
0.75
0.0295
0.785
0.0309
M1.2X0.25
5H
0.97
0.0382
0.95
0.0374
0.985
0.0388
M1.6X0.35
6H
1.3
0.0512
1.25
0.0492
1.321
0.052
M1.7X0.35
6H
1.39
0.0547
1.35
0.0531
1.421
0.0559
M2X0.4
6H
1.64
0.0646
1.61
0.0634
1.679
0.0661
M2.5X0.45
6H
2.12
0.0835
2.058
0.081
2.138
0.0842
M2.6X0.45
6H
2.23
0.0878
2.184
0.086
2.26
0.089
M3X0.5
6H
2.58
0.1016
2.515
0.099
2.599
0.1023
& pull out performance
M3.5X0.6
6H
2.97
0.1169
2.926
0.1152
3.01
0.1185
Symmetry II For small plastic products with thin boss hole wall thickness
M4X0.7
6H
3.38
0.1331
3.34
0.1315
3.422
0.1347
M5X0.8
6H
4.29
0.1689
4.2
0.1654
4.334
0.1706
Symmetry III For non-crystalline plastic application. Round knurl can avoid
M6X1.0
6H
5.08
0.2
5
0.1969
5.153
0.2029
M7X1.0
6H
6.09
0.2398
6
0.2362
6.153
0.2422
M8X1.25
6H
6.83
0.2689
6.75
0.2657
6.912
0.2721
M10X1.5
6H
8.61
0.339
8.5
0.3346
8.676
0.3416
M12X1.75
6H
10.38
0.4087
10.25
0.4035
10.44
0.4111
hot-melt install process. Herringbone knurl can improve pull-out performance
Shoulder For bigger draft angel (8 degree) plastic boss hole application.
Groove with taper I For bigger draft angel plastic boss hole application.
Diagonal knurl & taper can increase 25% torque & pull out performance
Groove with taper II For bigger tolerance plastic boss hole application and
provide good performance
Symmetry I Fit with Auto install line. And herringbone knurl offer great torque
sharp teeth.
Rivet For thin plastic plate application
Direct Push-in For most of thermoplastic plastics application and needn’t
special equipment
Full Burial For most of thermoset plastic application with sharp knurl.
Outer thread One kind of self-taping insert, use for both thermoset &
thermoplastic application.
Outer Thread Specification I
Internal
Inch
Direct Push-In Type
T Head
Thickness
Inches
H Head
Diameter
Inches
W Insert
Diameter
Inches
N Pilot End
Diameter
Inches
No of Fine
Rec.Hole
-0.000
+0.004
Inches
.157
.018
.189
.147
.123
2
.126
.063
.226
.023
.217
.178
.154
3
.157
.079
M3.5x0.6
.281
.029
.250
.209
.185
4
.189
.094
#8-32
M4x0.7
.321
.035
.281
.240
.218
5
.220
.110
#10-24
-
.375
.042
.312
.274
.248
5
.252
.126
#10-32
M5x0.8
.375
.042
.312
.274
.248
5
.252
.128
#1/4-20
M6x1.0
.500
.052
.375
.337
.310
7
.315
.157
T Head
Thickness
Inches
H Head
Diameter
Inches
W Insert
Diameter
Inches
#2-56
M2x0.40
.236
.023
.236
.177
.157-.161
.161-.159
#2-56
#4-40
M2.5x0.45
.236
.023
.236
.177
.157-.161
.161-.159
#4-40
M3x0.5
.236
.023
.236
.197
.177-.181
.181-.189
#6-32
#6-32
M3.5x0.6
.315
.029
.295
.236
.209-.213
.217-.224
#8-32
M4x0.7
.315
.035
.315
.256
.228-.232
.236-.244
.394
.042
.374
.315
.280-.283
.287-.299
#10-24
-
Min.Wall
Thickness
Inches
L Insert
Length Inches
L Insert
Length
Inches
-
Rec.Hole
Rec.Hole
Size
Size
Thermoplastics Thickness
Inches
+0.004 Inches
Internal
Inch
Thread Size
ISO Metric
Evaluate by
pre-production
tests
Thread Size
ISO Metric
M2x0.40
M2.5x0.45, M3x0.5
Min. Wall
Thickness
as
Inches
#10-32
M5x0.8
.394
.042
.374
.315
.280-.283
.287-.299
#1/4-20
M6x1.0
.551
.052
.472
.394
.339-.346
.354-.370
#1/4-28
-
.500
.052
.375
.337
.310
7
.315
.157
.591
.052
.472
.394
.339-.346
.354-.370
#5/16-18
M8x1.25
.500
.052
.433
.400
.374
7
.378
.189
.591
.052
.551
.472
.417-.425
.433-.449
#5/16-24
-
.500
.052
.433
.400
.374
7
.378
.189
.591
.052
.551
.472
.417-.425
.433-.449
.709
.062
.630
.551
.496-.504
.512-.528
.709
.062
.630
.551
.496-.504
.512-.528
#1/4-28
#5/16-18
M8x1.25
#5/16-24
#3/8-16
M10X1.5
#3/8-24
-
Shoulder Type
Outer Thread Specification II
Internal Inch
Thread Size ISO Metric
Internal
Inch
L Insert Length Inches
W Insert Diameter
Inches
Rec.Hole
-0.0000 +0.004
Inches
Min.Wall Thickness
#4-40
#2-56
M20x0.40
.157
.146
.126
.063
#4-40
M2.5x0.45,M3x0.50
.228
.177
.157
.079
#6-32
M3.5x0.60
.283
.209
.189
.094
#8-32
M4x0.70
.323
.242
.220
.110
.374
.272
.252
.126
#10-24
-
#10-32
M5x0.80
.374
.272
.252
.126
#1/4-20
M6x1.0
.500
.335
.315
.157
.500
.335
.315
.157
.500
.398
.378
.189
.500
.398
.378
.189
#1/4-28
#5/16-18
#5/16-24
M8x1.25
-
#2-56
Thread Size
ISO Metric
M2x0.40
M2.5x0.45, M3x0.5
L Insert
Length Inches
T Head
Thickness
Inches
H Head
Diameter
Inches
W Insert
Diameter
Inches
N Pilot End
Diameter
Inches
Rec.Hole
-0.000 +0.004
Inches
Min.Wall
Thickness
Inches
.157
.021
.187
.141
.123
.126
.051
.226
.024
.218
.181
.154
.157
.063
#6-32
M3.5x0.6
.281
.030
.250
.214
.185
.189
.071
#8-32
M4x0.7
.321
.036
.281
.248
.218
.220
.083
#10-24
-
.375
.043
.312
.278
.249
.252
.102
#10-32
M5x0.8
.375
.053
.312
.278
.249
.252
.102
#1/4-20
M6x1.0
.500
.053
.375 .
341
.312
.315
.130
#1/4-28
-
.500
.053
.375
.341
.312
.315
.130
#5/16-18
M8x1.25
.500
.053
.437
.403
.374
.378
.177
#5/16-24
-
.500
.053
.437
.403
.374
.378
.177
#3/8-16
M10x1.50
.500
.063
.551
.494
.465
.469
.236
#3/8-24
-
.500
.063
.551
.494
.465
.469
.236
Symmetry Type
Single Groove with Taper
Thread Size
Inch
Thread Size
Metric
Overall
Length
L
Insert
Diameter
W
Pilot
Diameter
N
Recommended
d
+/_.001 D
Hole Size
+/_.001
S
Minimum Wall
Thickness
Internal
Inch
Thread Size
ISO Metric
L Insert
Length Inches
T Head
Thickness
Inches
H Head
Diameter
Inches
W Insert
Diameter
Inches
N Pilot End
Diameter
Inches
Rec.Hole
-0.000 +0.004
Inches
Min.Wall
Thickness
Inches
#2-56
M2x0.40
.115
.136
.115
.123
.118
.080
#4-40
M2.5x0.45
.135
.172
.157
.159
.153
.093
#2-56
M2x0.40
.155
.020
.187
.137
.123
.126
.055
#6-32
M3x0.50
.150
.220
.203
.206
.199
.116
#4-40
M2.5x0.45,M3x0.5
.228
.023
.217
.174
.154
.157
.071
-
M3.5x0.6
.150
.220
.203
.206
.199
.116
#6-32
M3.5x0.6
.281
.029
.250
.206
.185
.189
.083
#8-32
M4x0.7
.185
.250
.230
.234
.226
.133
#8-32
M4x0.7
.320
.035
.280
.239
.218
.220
.094
#10-24
-
.225
.296
.272
.277
.267
.159
#10-24
-
.374
.042
.312
.270
.249
.252
.110
#10-32
-
.225
.296
.272
.277
.267
.159
#10-32
M5x0.8
.374
.042
.312
.270
.249
.252
.110
-
M5x0.8
.265
.328
.308
.315
.303
.171
#1/4-20
M6x1.0
.500
.052
.375
.333
.312
.315
.142
#1/4-20
M6x1.0
.300
.375
.354
.363
.349
.194
#1/4-28
-
.500
.052
.375
.333
.312
.315
.142
#1/4-28
-
.300
.375
.354
.363
.349
.194
#5/16-18
M8x1.25
.500
.052
.437
.393
.375
.378
.197
#5/16-18
M8x1.25
.335
.469
.439
.448
.431
.245
#5/16-24
-
.500
.052
.437
.393
.375
.378
.197
.335
.469
.439
.448
.431
.245
H Head
Diameter
Inches
W Insert
Diameter
Inches
N Pilot End
Diameter
Inches
#5/16.24
#3/8-16
M10x1.50
.375
.563
.530
.540
.523
.293
#3/8-24
-
.375
.563
.530
.540
.523
.293
Full Burial Type
Twins Groove with Taper
Internal
Inch
Thread Size
Inch
Thread Size
Metric
Overall
Length
L
Insert
Diameter
W
Pilot
Diameter
N
Recommended
d
+/_.001 D
Hole Size
+/_.001
S
Minimum Wall
Thickness
#2-56
Thread Size
ISO Metric
M2x0.40
M2.5x0.45,M3x0.50
L Insert
Length Inches
T Head
Thickness
Inches
Rec.Hole
-0.000 +0.004
Inches
Min.Wall
Thickness
Inches
.162
.020
.187
.131
.117
.122
.063
.208
.023
.217
.165
.146
.150
.079
#2-56
M2x0.40
.188
.136
.115
.123
.107
.080
#4-40
#4-40
M2.5x0.45
.219
.172
.144
.159
.141
.093
#6-32
M3.5x0.60
.247
.029
.250
.196
.178
.181
.098
#6-32
M3x0.5
.250
.220
.190
.206
.185
.116
#8-32
M4x0.7
.292
.035
.281
.228
.209
.213
.098
-
M3.5x6
.250
.220
.212
.206
.185
.116
#10-24
-
.326
.042
.312
.259
.241
.244
.098
#8-32
M4x0.7
.312
.250
.251
.234
.208
.133
#10-32
M5x0.8
.326
.042
.312
.259
.241
.244
.098
#10-24
-
.375
.296
.251
.277
.246
.159
#1/4-20
M6x1.0
.362
.052
.375
.322
.304
.307
.110
#10-32
-
.375
.296
.283
.377
.246
.159
#1/4-28
-
.362
.052
.375
.322
.304
.307
.110
-
M5x.8
.438
.328
.332
.315
.278
.171
#5/16-18
M8x1.25
.362
.052
.437
.383
.365
.366
.150
#1/4-20
M6x1.0
.500
.375
.332
.363
.321
.194
#5/16-24
-
.362
.052
.437
.383
.365
.366
.150
#1/4.28
-
.500
.375
.406
.363
.321
.194
#3/8-16
M10x1.50
.362
.062
.551
.499
.481
.484
.197
#5/16-18
M8x1.25
.562
.469
.406
.448
.401
.245
#3/8-24
-
.362
.062
.551
.499
.481
.484
.197
#5/16-24
-
.562
.469
.439
.448
.401
.245
#3/8-16
M10x1.50
.625
.563
.493
.540
0.488
.293
#3/8-24
-
.625
.563
.493
.540
0.488
.293
Plastic Hole Size and Wall Thickness
Slotted Type
Internal
Inch
Thread Size
ISO Metric
#2-56
M2x0.4
#4-40
L Insert
Length Inches
M2.5x0.45,M3x0.5
T Head
Thickness
Inches
H Head
Diameter
Inches
W Insert
Diameter
Inches
Recommended
-0.000 +0.004
Inches
Minimum Wall
Thickness Inches
.155
.017
.187
.124
.126
.094
.186
.020
.218
.156
.157
.126
#6-32
M3.5x0.6
.249
.026
.250
.186
.189
.142
#8-32
M4x0.7
.312
.032
.281
.217
.220
.157
#10-24
-
.371
.039
.312
.249
252
.189
#10-32
M5x0.8
.371
.039
.312
249
.252
.189
#1/4-20
M6x1.0
.497
.049
.375
.311
.315
.236
#1/4-28
-
.497
.049
.375
.311
.315
.236
#5/16-18
M8x1.25
.497
.049
.437
.374
.378
.276
#5/16-24
-
.497
.049
.437
.3744
.378
.276
Production Process
L1= insert length
L2= min. hole depth
W= wall thickness
T= draft angle
Plastic Hole - Taper
L1= insert length
L2= min. hole depth
W= wall thickness
T= draft angle
Plastic Hole Contour
Production Process
Design Engineering
QA Final Inspection
Tool Fabrication
Move to Package Area
Raw Material
Packing
Cutting
Shipping
Washing Part
Final Audit
Drying
Note: Under normal circumstances,
inserts has oriented segment , do
not need bevel on the plastics
Permanent Weld Removable Assembly
Permanent Weld
Removable assembly
• Adhesive connection
• Welding
- Ultrasonic Welding
- Friction welding
- Hot-melt welding
• Self-drive screw clip
• Plastic thread
• Metal Insert
- Forming mold
- Secondary burial (thermography,
ultrasound)
Plastic Hole Depth
Note: Depth of plastic design, plastic overflow
space must be considered, under normal
circumstances is between 0.5-1.5mm
Plastic Conjugation Line
Insert Outside Diameter and Plastic Hole factor
Outside Diameter (Body)
Note: the location of the plastic boss
hole should be advised not to set
up onconjugation line, to avoid the
breakdown of the plastic hole with stress
• Fit into the hole
• Length (Body)
• Fit into the hole depth
Knurling length (Performance Consideration)
• Knurl
• Pitch
• Number of knurl division
Thread
Inserts Application
• The relationship between outline of the inserts and boss hole
• The relationship between size of the inserts and boss hole
• Installation method of insert
• Application information of insert
• Performance test of insert
• Design of Blind hole
• Quality of inserts
Insert Figure and Plastic Hole Factor
Pilot lead-in:
• Tapered Hole (8 degrees): With ribs lead in hole
• Straight Hole: With a Flat head lead in hole
Knurls provide:
• The performance function (torque ,tensile)
- Diamond Knurl (Raised/ Inverted)
- Diagonal Knurl ( Single knurl/ Opposing knurl)
- Straight Knurl (Increases Torque Performance)
Undercut:
• Allows plastic to flow into grooves for higher pullout resistance
Flange:
• To eliminate direct contact of plastic with mating parts
• Increases push in performance
• Thread standard
• Chips
Brass Insert Installation
• Ultrasonic Installation
• Thermal/Heat Installation
• Mold-In Installation
• Press-In Installation
Ultrasonice Installation
Installation Principle: Ultrasonic installation uses electrical energy to create high frequency vibration. The
vibration creates friction and thus melts the plastic material around the insert. The insert is forced into the
plastic and the plastic flows around the insert body. Once the plastic material cools the insert is locked in-place.
Notes: Ultrasound can release energy instantaneously during installation, the great impact is easy to damage the
insert during the process, specially on thread area. Suggest to not use the process for M1.6 or smaller brass insert
Electric Heating Installation
Principle: Heating the inserts to certain temperature and then force the insert into the plastic and the plastic
flows around the insert body. Once the plastic material cools the insert is locked inplace.
Molded In Installation Method
Plastic Material
Principle:
• Thermoplastic plastics: PC/ABS ..…. Usually used in mobile phone industry. Preferred insert
installation method: ultrasonic and hotmelt.
• Thermoset plastics: Can not be used for the installation of ultrasonic and hot-melt. Preferred insert
installation method: Mold-in; Threaded in & Press-in
• Knurl
- Straight knurl: Provides maximum torque out performance
- Diamond/ Diagonal knurl: To increase the torque out and pull out resistance
• Use Molding Pin as fixture
• Counter bore design for accurate alignment of the insert to the plastic part
• Blind Insert
• Blind-end or closed-end inserts help prevent plastic ingress
Notes:
• In order to improve the accuracy of the thread, all the thread tolerances should
follow with the old version of the ISO standard screw holes regulation.
• Attention to the choice of moulding point in order to avoid inserts displacement
caused by the plastic flow.
• The tolerances of pin must be strictly controlled, the specific parameters should
reference the old version of the ISO standard. (Should be less than the under
limitation about 0.01-0.03mm)
Brass Insert Performance Testing
Torque
Thermal/Heat Installation
Force
Pull Force
Temperature is too high
Temperature
wall up
Plastic hole
is scrap
Plastic
spillover
surface
Not in place
Temperature is too low
Plastic hole
crack
Lower pull and
torsional
Plastic hole
scrap
Nut scrap
Under the better burial process,
there will be plastics on the surface
when pull out the inserts from the
plastic hole
Blind Hole Design Guide
Brass Inserts Testing Contents
•General Boss Design Information
•Hole Depth = “L” +0.9mm
•Hole Diameter = “C”+0.1~0.15mm
•Boss Outer Diameter = “C” x 2~2.5
curve of torque
under the assembly
Torque
Fastener Specifications
Material: Brass
Finish: Cleaning
Thread: Class 2B, per ASME B1.1, 6H ISO Metric
Installed with heat or molded in. Designed for use
in straight holes. Flange provides a large loading
surface
• Turns
Pull
Torque force
Indirect torque
Indirect tensile
Installation Type
Plastic Family
Thermo-Plastic Thermoset
Ultrasonic
•
Thermal/Heat
•
Pre-Molded
Hole
•
Performance
Normal
•
Normal
Mold-In
•
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