Screws for Plastic

Available dimensions top

Product information top

Fastening thermo plastic materials during construction and assembly as well as their load capacities prove to be challenging issues for industrial users on a regular basis. Screwerk has addressed these issues and has come up with the perfect solution for professional applications: the patented STS®plus screw for plastic from the company Schriever. This screw is the optimum way to fasten thermoplastics. It combines high-quality German engineering with a high savings potential for the user.  For this reason, Screwerk has added this product exclusively to the Screwerk product-line as its standard screw with the name STP.

The benefits of the STP geometry:

  1. Optimal connection of plastic parts
  2. Minimal radial stress
  3. Considerably increased durability of screw connection in static and dynamic tensile loading
  4. Low threadforming torque
  5. Elimination of the risk of relaxation
  6. A guaranteed tenfold re-assembly
  7. The thread’s one-of-a-kind geometry results in an optimal fastening and self-locking mechanism for thermoplastics
  8. Increases preload force by higher flank overlapping on pressure side

The STP offers the possibility of using shorter screws and/or smaller diameters to achieve the same connection strength - this offers savings potential for our customers.  With regard to its compatibility with other market standards the STP offers a problem-free substitution to various standards of similar use and applications.

screwerkde.stp.img.geometrie.alt

The STP thread geometry has flank angles and ratios between d1/d2, d2/p that are optimized for strength, retention and minimal stress.

Construction Advice top

drawing screw boss

Advice about Boss Design

The design of the boss geometry is of utmost importance for the function of the entire joint. The balance hole is especially important, as this prevents the boss from bursting. Through experimental trials it was proven that a value of 0.8 x d1 provides the optimal diameter for the bore (d). The value can be increased up to 0.88 x d1 for materials with high proportions of filler material.

For optimal joints in thermoplastics, we recommend designing the bore geometry in relation with the screw diameters and materials. Please use the table below as a basis.

Material Hole-Ø  d External-Ø Boss  B Thread engagement X
ABS 0.86 x d1 2.00 x d1 2.00 x d1
ASA 0.84 x d1 2.00 x d1 2.00 x d1
PA 6 0.81 x d1 1.85 x d1 1.70 x d1
PA-GF 30 0.86 x d1 2.00 x d1 1.90 x d1
PA 6.6 0.81 x d1 1.85 x d1 1.70 x d1
PA 6.6 GF 30 0.83 x d1 2.00 x d1 1.80 x d1
PBT 0.81 x d1 1.85 x d1 1.70 x d1
PBT GF 30 0.86 x d1 1.80 x d1 1.70 x d1
PC 0.89 x d1 2.50 x d1 2.20 x d1
PC GF 30 0.89 x d1 2.20 x d1 2.00 x d1
PE LD 0.76 x d1 2.00 x d1 2.00 x d1
PE HD 0.81 x d1 1.80 x d1 1.80 x d1
PET 0.81 x d1 1.85 x d1 1.70 x d1
PET GF 30 0.86 x d1 1.80 x d1 1.70 x d1
POM Acetal 0.81 x d1 1.95 x d1 2.00 x d1
PP 0.76 x d1 2.00 x d1 2.00 x d1
PPO 0.89 x d1 2.50 x d1 2.20 x d1
PS 0.86 x d1 2.00 x d1 2.00 x d1
PVC (hart) 0.86 x d1 2.00 x d1 2.00 x d1
SAN 0.83 x d1 2.00 x d1 1.90 x d1

Compatibility top

Levels of compatibility to the Screwerk standard:

  Level Meaning
0 identical It is the identical screw design.
1 compatible The screw has the same key dimensions but a slightly different thread design. It can be exchanged without any doubt even if specified in drawings.
2 comparable The screw fits the same purpose and key parameters like diameter, length, head design, drive and material do not differ.
3 alternative If a single key parameter except the diameter is different the screw is considered an alterantive.

Compatibility of Screwerk STP screws to other standards:

DELTA PT® PLASTITE® PT® Schriever STS® Schriever STS® plus

Ejot Delta PT® compatibility with Screwerk STP Compatibility top

Screwerk STP screws have a STS® plus thread. This thread is compatible to the EJOT Delta PT® thread. Screwerk STP screws are generally compatible to EJOT Delta PT® screws.

Comparison between the EJOT WN and Screwerk STP norm:

Ejot WN Screwerk Compatibility Advice
WN5411 KA STP31 compatible  
WN5411 KB STP31 Alternative While the STP31 is having a cross recess type H drive, the WN 5411 KB has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
WN5412 KA STP32 compatible
WN5412 KB STP32 Alternative While the STP31 is having a cross recess type H drive, the WN 5412 KB has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
WN5451 STP38 compatible
WN5452 STP39 compatible
WN5453 STP41 Alternative Screwerk does not offer countersunk with round heads. Please use countersunk heads as an alternative.
WN5454 STP41 compatible
WN5454 STP33 Alternative Screwerk also offers countersunk heads with cross recess type H drive.

Plastite® compatibility with Screwerk STP Compatibility top

Both STP and Plastite type threads are made to form threads in plastics, but do so with very different designs. The main characteristics of the Plastite 45 are its trilobular design and 45 degree flank angle. The main characteristics of the Plastite 48-2 are its double lead, trilobular design and 48 degree flank angle. The STP is round, and has a compound flank angle of 30/52,5 degrees. The recommended substitutions are listed in the table below.
Plastite 45 US Screwerk STP d1
#0 1.4 1.6*
#1 1.8
#2-19 2.0 2.2*
#3-18 2.5
#4-17 3.0
#5-15 3.0 3.5*
#6-13 3.5
#7-12 3.5 4.0*
#8-11 4.0
#9-10 4.5 4.0*
#10-9 4.5 5.0*
#12-9 5.0*,6.0*
Plastite 48-2 Screwerk STP d1
#00-51 1.2
#0-42 1.6 1.4*
#1-32 2.0 1.8*
2-28 2,2 2.5*
3-24 2.5
4-20 3.0
6-19 3.5 4.0*
7-18 4.0
8-16 4.5 4.0*
9-15 5.0 4.5*
10-14 5
12-14 6.0
1/4" 7.0
Plastite 45 Metric Screwerk STP d1
M2 1.8 2.0*
M2.5 2.5
M3 3.0
M3.5 3.5
M4 4.0
M4.5 4.5
M5 4.5 5.0*
M6 6.0
* dependent on hole diameter and material. Please consult our Design Guidelines

Ejot PT® compatibility with Screwerk STP Compatibility top

Screwerk STP screws have a STS® plus thread. This thread is compatible to the EJOT Delta PT® thread. Screwerk STP screws may however be used as an alternative to the EJOT PT® screws.

Comparison between the EJOT WN and Screwerk STP norm:

Ejot WN Screwerk Compatibility Advice
WN1411 KA STP31 Alternative The head dimensions of STP31 are deviating.
WN1411 KB STP31 Alternative The head dimensions of STP31 are deviating. While the STP31 is having a cross recess type H drive the WN 1411 KB has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
WN1412 KA STP32 Alternative The head dimensions of STP32 are deviating.
WN1412 KB STP32 Alternative The head dimensions of STP32 are deviating. While the STP32 is having a cross recess type H drive the WN 1412 KB has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
WN1413 KA STP33 Alternative The head dimensions of STP33 are deviating.
WN1413 KB STP33 Alternative The head dimensions of STP33 are deviating. While the STP33 is having a cross recess type H drive the WN 1413 KB has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
WN1441 KA STP31 Alternative The head dimensions of STP31 are deviating.
WN1441 KB STP31 Alternative The head dimensions of STP31 are deviating. While the STP31 is having a cross recess type H drive the WN 1441 KB has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
WN1442 KA STP32 Alternative The head dimensions of STP32 are deviating.
WN1442 KB STP32 Alternative The head dimensions of STP32 are deviating. While the STP32 is having a cross recess type H drive the WN 1442 KB has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
WN1443 KA STP33 Alternative The head dimensions of STP33 are deviating.
WN1443 KB STP33 Alternative The head dimensions of STP33 are deviating. While the STP33 is having a cross recess type H drive the WN 1443 KB has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
WN1444 Not part of the product line
WN1445 Not part of the product line
WN1446 Not part of the product line
WN1447 Currently not part of the product line
WN1451 STP38 Alternative The head dimensions of STP38 are deviating.
WN1452 STP39 Alternative The head dimensions of STP39 are deviating.
WN1453 STP41 Alternative The STP41 has a slightly deviating head and deviating head dimensions.
WN1423 STP41 Alternative The head dimensions of STP41 are deviating.

Schriever STS® compatibility with Screwerk STP Compatibility top

Screwerk STP screws have a STS® plus thread. All STP screws are exclusively manufactured by Schriever Schrauben in Germany. Therefore STP screws are compatible and can be used wherever STS® plus screws are used.
As an evolution of Schriever's STS® screw design, the STS® plus / STP design differs only slightly. Therefore STP screws can be used without disadvantage in exchange of the STS screws. In addition, Screwerk provides STP screws upon special request in co-operation with Schriever.

Comparison between the Schriever KN and Screwerk STP norm.

Schriever KN Screwerk Compatibility Advice
KN 1031 - H STP31 Alternative The head dimensions of STP31 are deviating.
KN 1031 - Z STP31 Alternative The head dimensions of STP31 are deviating. While the STP31 is having a cross recess type H drive the KN 1031 - Z has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
KN 1032 - H STP32 Alternative The head dimensions of STP32 are deviating.
KN 1032 - Z STP32 Alternative The head dimensions of STP32 are deviating. While the STP32 is having a cross recess type H drive the KN 1032 - Z has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
KN 1033 - H STP33 Alternative The head dimensions of STP33 are deviating. Screwerk also offers countersunk heads with cross recess type H drive.
KN 1033 - Z STP33 Alternative The head dimensions of STP33 are deviating. While the STP32 is having a cross recess type H drive the KN 1032 - Z has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
KN 1034 Not part of the product line
KN 1035 Not part of the product line
KN 1036 Not part of the product line
KN 1037 Currently not part of the product line
KN 1038 STP38 Alternative The head dimensions of STP38 are deviating.
KN 1039 STP39 Alternative The head dimensions of STP39 are deviating.
KN 1041 STP41 Alternative The head dimensions of STP41 are deviating.

Schriever STS® plus compatibility with Screwerk STP Compatibility top

Screwerk STP screws have a STS® plus thread. All STP screws are exclusively manufactured by Schriever Schrauben in Germany. Therefore STP screws are compatible and can be used wherever STS® plus screws are used. In addition, Screwerk provides STP screws upon special request in co-operation with Schriever.

Comparison between the Schriever KN and Screwerk STP norm.

Schriever KN Screwerk Compatibility Advice
KN 6031 - H STP31 identical  
KN 6031 - Z STP31 Alternative While the STP31 is having a cross recess type H drive the KN 6031 - Z has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
KN 6032 - H STP32 identical  
KN 6032 - Z STP32 Alternative While the STP32 is having a cross recess type H drive the KN 6032 - Z has a cross recess type Z drive. Generally Screwerk does not offer cross recess type Z drives.
KN 6038 STP38 identical  
KN 6039 STP39 identical  
KN 6040 STP41 Alternative Screwerk does not offer countersunk with round heads. Please use countersunk heads as an alternative.
KN 6041 STP41 identical  
KN 6041 STP33 Alternative Screwerk also offers countersunk heads with cross recess type H drive

Screw size equivalents top

US size Metric equivalent Screwerk standard diameter
#0000.86 mm1.0 mm
#001.19 mm1.2 mm
#01.52 mm1.6 mm
#11.85 mm1.8 mm
#22.18 mm2.2 mm
#32.51 mm2.5 mm
#42.84 mm2.5 mm or 3 mm
#53.18 mm3 mm
#63.51 mm3.5 mm
#73.84 mm3.5 mm or 4 mm
#84.17 mm4 mm
#94.50 mm4.5 mm
#104.83 mm4.5 mm or 5 mm
#115.16 mm5 mm
#125.49 mm5 mm or 6 mm
#146.15 mm6 mm
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