Dumont N5 HP crossover tweezers

There are three grades of Dumont tweezers:

• High precision grade is suitable for most laboratory and fine engineering use.
• Biology grade has the thinnest tips, and is used for the most demanding laboratory applications including microscopic work.
• Electronic grade offers high quality for electronics and general purpose use. Most of the electronic grade tweezers are coated with a coloured epoxy resin which is insulating, shock resistant and provides better grip.

The various grades of tweezers are also available in a range of materials with differing mechanical and corrosion resistance and magnetic properties:

Carbon steel is an extremely hard alloy composed of C, Mn and Si. This ensures the tweezers have the hardest tips but they are the most vulnerable to rust and corrosion. The tweezers stain easily, are less flexible and more brittle than other grades. They can become highly magnetic, and cannot be sterilised.

Stainless steel is an alloy of C, Mn, Cr and Si. The tips are not as hard as those of carbon steel but are more resistant to rust and corrosion. The tweezers will withstand temperatures of about 400°C but are not suitable for autoclave sterilisation at 180°C. They can also become magnetic.

Medical grade tweezers are manufactured from a special stainless steel alloy composed of C, Mn, Cr, Mo and V that provides an excellent resistance to corrosion and a good resistance to salt. Although not as hard as carbon steel, this alloy supports temperatures of approximately 400°C and is suitable for autoclave sterilisation at 180°C.

Medical mirror polished tweezers are manufactured from the above alloy and the main part of the tweezer is mirror polished which gives increased resistance to corrosion during sterilisation in an autoclave. The tips are given a micro-matt finish to minimise reflections which might hinder visibility.

Dumoxel® is the trade name for an anti-magnetic grade of stainless steel. This alloy is composed of C, Cr, Ni, Mo and Cu which makes the tweezers marginally softer than other stainless steels. This alloy offers good resistance to corrosion from sulphuric and hydrochloric acid and other mineral and organic acids. It is 95% anti-magnetic and resistant to temperatures of around 400°C. The tweezers can be sterilised in the autoclave at 270°C.

Dumostar® is another patented alloy containing 40% cobalt. It is 100% non-magnetic and is resistant to sterilisation temperatures of up to 500°C. It is more flexible and more resilient than other stainless steels. It is also compatible with human tissues and resistant to mineral and organics acids, as well as to salt.

Titanium alloy is composed of C, Fe, O, H, N and Ti. It is 100% non-magnetic, resistant to corrosion from nitric acid, chloride, salt water etc. The alloy is not as hard as some of the other alloys but it is lighter, more flexible and resistant to temperatures around 430°C.