Sem Screws - Captive Washer Screws
MOUNTING CONSTRAINTS FOR ELECTRONICS APPLICATIONS
– Temperature variations: cause expansion and loosen fasteners
– Vibration: loosens fasteners
Internal: electro-magnetism, motors
External: vehicles, motion
– Pressure on the mounting surface of the part to fasten: expands the material and causes a loss of tension in the assembly
BENEFITS
The pre-assembled fastener has many advantages:
– Guarantees locking and resists loosening
– Facilitates assembly and disassembly (parts are pre-assembled)
– Simplifies stock management and logistics
– Eliminates non-compliance related to improper assembly or missing washers
– Let’s you combine washers without forgetting any on circuits (DC)
– Improves productivity: no need to fit washers prior to assembly
– Improves quality
We supply fasteners that meet ISO, DIN or NFE requirements and we can also produce bespoke products to your drawings.
CHARACTERISTICS – SEM SCREWS SPECIALLY MADE
| Thread diameter d1 | a max. | Min. Useful screw length l2² | In excess of the lengths stated partial threading l3 | Washer dimensions | ||||||||||||||
| Hex. / hollow head screws | Slotted screws and philips/Pozi screws | Washer to DIN 6902 | Spring washer to DIN 6904 | Split lock washer to DIN 6905 | Ribbed washer to DIN 6906 | Star washer to DIN 6907 | Conical washer to DIN 6908 | |||||||||||
| Shape A | Shape B | |||||||||||||||||
| s | d2 | s | d2 | h | d2 | h | d2 | h | d2 | h | d2 | h | d2 | |||||
| M2,5 | 0,9 | 5 | 16 | 25 | 0,6 | 6,5 | 0,8 | 8 | – | – | 1,1 | 4,55 | 0,8 | 5,5 | 1,2 | 5,5 | 1 | 6 |
| M3 | 1 | 6 | 22 | 25 | 0,6 | 7 | 0,8 | 9 | 1,05 | 8 | 1,3 | 5,65 | 0,8 | 6 | 1,2 | 6 | 1,2 | 7 |
| (M3,5) | 1,2 | 7 | 25 | 25 | 0,8 | 8 | 0,8 | 11 | 1,15 | 8 | 1,3 | 6,1 | 1 | 7 | 1,5 | 7 | 1,2 | 8 |
| M4 | 1,4 | 8 | 25 | 30 | 0,8 | 9 | 1 | 12 | 1,65 | 9 | 1,4 | 6,95 | 1 | 8 | 1,5 | 8 | 1,5 | 9 |
| M5 | 1,6 | 10 | 35 | 35 | 1 | 10 | 1,6 | 15 | 1,75 | 11 | 1,7 | 8,55 | 1,2 | 9 | 1,8 | 9 | 1,8 | 11 |
| M6 | 2 | 12 | 35 | 35 | 1,6 | 12,5 | 1,6 | 18 | 2 | 12 | 2,2 | 11 | 1,4 | 11 | 2,1 | 11 | 2 | 14 |
CHARACTERISTICS – SEM SCREWS FROM STOCK
| Screw standard | Washer standard | Material | Diameter | |
| Pan head screw with flat washer | DIN 84 | DIN 6902A | CL 4,8 + ZN | M3-M5 |
| Pan head screw with spring washer | DIN 84 | DIN 127B | CL 4,8 + ZN | M3-M4 |
| Rounded head philips screw with flat washer | DIN 7985 | DIN 6902A | CL 4,8 + ZN | M3-M5 |
| Rounded head screw with ribbed washer | ISO 7048 | DIN 6797A | CL 4,8 + ZN | M3-M4 |
WIDE RANGE
SEM screws offer a wide range of assembly options. Inserco can meet all your needs by working to your drawings and/or specifications.
| Type | Standard | Material & Treatment | Diameters / Dimensions | Combinations | |
| Screw | TH, CS, CHC, CZX, … | ISO, DIN, NFE, UNC/ UNF, … | steel, zinc plated steel, stainless steel, etc. | M2,5-M6 | |
| Washer | flat, wave, conical, star, Grower, CS | DIN 6900 or non-standard | steel, zinc plated steel, stainless steel, etc. | To DIN 6900 or other | flat + wave, flat + Grower, etc. |
WHICH WASHER AND WHY?
| Flat washer | Used to spread the load for tightening No lock function |
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| Toothed washer | The teeth have an anti-slackening function Partially damages the pressure side |
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| Spring washer | Compensates for longitudinal motion due to material expansion or creeping Assembly tension is maintained |
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| Dual-function washer | Grower (spring + one tooth) Contact (spring + teeth) |
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Quality
All our sites are ISO 9001 certified and our quality systems meet the specific requirements of the automotive and aerospace industries.