Manufacturing and trading

We like to produce the critical joints ourselves, in order to maintain complete control of the manufacturing process. Every parameter is continually controlled and assessed. Nothing is left to chance in any of our manufacturing units in China, Germany, Poland or Sweden. Being a Full Service Provider means we carry the entire product range available in fasteners.

1. Engineering

Drawings are made.

2. Tooling

All fastener parts have their own tool that is prepared before production.

3. Material

Fasteners are mainly made of steel wire using so-called cold forging technology. The iron wire is supplied as wire in rolls, usually weighing about two tons each, are transported from stock to the production area. The wire is pre-rolled, phosphated and reduced on a draw-bench down to the required dimension before being fed into the cold forger.

4. Cold Forging

After set up and control the production starts. When the wire is fed into the cold forger, it is cut to the right length and then cold forged in various steps. Cold forging is an efficient production method where between 100 and 300 fasteners are forged every minute, depending on dimensions and machine.

5. Threading

Once the fastener has been shaped, threads are formed by rotating the screw in a threading die.

6. Heat Treatment

During the heat treatment the screw is hardened to the right mechanical properties. The process starts with a washing and de-phosphating operation and then the fasteners are heated to approximately 900 degrees. Thereafter, the fasteners are cooled in oil to 60 degrees, then heated up again to 350 – 450 degrees and then finally cooled again which ends the hardening process.

7. Surface treatment

The fasteners are further processed through e.g. surface treatment and other steps to further develop the product. This is done by transporting the fasteners through a range of baths depending on the requirements.

8. Quality assurance

Besides going through continuous quality checks at each production step, the fasteners are finally checked in the laboratories and all values are documented in data bases.

9. Inspection

The fasteners are inspected for e.g. cracks, length and diameter as well as number of screws per bin.

10. Packing

After inspection, the fasteners are packed according to the customer’s requirements and then sent to the warehouse.

11. Shipping

The fasteners are ready for sending to the customer. Logistics is the final leg of our production cycle, and the final factor in our assessment of overall quality.

What we don’t manufacture ourselves, we buy from our suppliers in order to deliver complete solutions. We categorize our suppliers by quality, but also by delivery precision, volumes and product range.

Our nuts and bolts are delivered around the clock and have been for quite a few years now. And since we or our partners are located pretty much everywhere – we’re always nearby.

Head office

Bulten AB
Box 9148
400 93 Gothenburg, Sweden

Visitor's address:
August Barks gata 6A, Gothenburg

Tel: + 46 31 734 59 00
Fax: + 46 31 734 59 39