Stainless steel is an important material in the lapidary industry so we thought it might be a good idea to go over some information to help you understand more about it.
Stainless steel is an alloy of steel with a minimum content of Chromium (at least 10.5%) – there are a range of different alloys available which are designed for different jobs and have different properties. The commonly used alloys have a chromium content of around 18% but content of other metals (notably nickel) varies and does alter physical properties of the steel. When comparing between products or suppliers, it is a good idea to know exactly what you are purchasing.
IMPORTANT: Although Stainless Steel does not readily corrode, rust or stain with water like carbon steel, is CAN rust or discolour under certain types of conditions (namely high humidity, salinity, etc). A more accurate name would be stain-resistant steel – not quite as catchy but it would alert people that you still need to take care of your stainless steel products. Important warning: do not mix stainless steel and carbon steel shot when tumbling – the carbon steel shot may contaminate the stainless and cause rusting.
The 3 most common types of stainless steel we would normally encounter are as follows:
- Grade 202 – low nickel alloy with less corrosion resistance compared to the 300 series alloys (less common in Australia)
- Grade 304 – General Purpose; the most common grade with good corrosion resistance for most jobs
- Grade 316 – Marine Grade; more expensive but recommended where high corrosion resistance is required
The two main products we stock that are made of stainless steel are the Stainless Steel Shot (mixed shapes) and various sized cabbing arbors.
It is important to note that our Stainless Shot is made from Grade 304 with accompanying certification tests from the manufacturer. We have noticed some other suppliers selling Grade 202 shot – if made from 202, then it SHOULD be cheaper and will be less rust resistant. When comparing prices, be aware that these products are NOT the same.
We do recommend that whatever grade of steel your shot is made from, it should either be stored completely dry OR completely covered by shot storage solution. If you store your shot in a sealed container when it is still damp, even stainless will rust under these conditions. If you notice some discolouration on your stainless shot, then quick action can retrieve the situation if you wash it thoroughly in a weak acidic solution.
More info in the link below:
For your reference, our Lortone Stainless Steel arbors are made from Grade 304 stainless with grade 416 shafts for maximum strength. This gives the best combination of corrosion resistance and strength – they are more expensive than the power-coated classic options but you know you are buying long-lasting quality.
Even so, we always recommend wiping down your arbor after each use to keep it in top-top condition. Cleanliness when cabbing or faceting is a good habit to get into – it helps protect your equipment and significantly reduces the chance of scratching occuring due to rock dust/diamond contamination.
See these links for further reading:
Hope this information helps clarify some issues around stainless steel – if you have any other queries, feel free to contact us any time.
Cheers from the Aussie Sapphire team