Why it is important to measure your stones!

Joanne Tinley Author

A 5mm round faceted stone it will be exactly 5mm won't it? Not always! Find out how stones can differ & what that means for your jewellery making.

I love using faceted stones in my work, and love teaching other people to use them in tube settings, collet settings and more! However I always measure the stones carefully, looking at all the proportions.

Read on to find out why and what that means for your jewellery making.

Faceted stones are wonderful for adding a sparkle to your jewellery, and we're very lucky nowadays that a wonderful range of gemstones of all colours are easily available. No matter what your tastes you are bound to find a stone you love!

Have a look at this set of garnets... They were all bought from the same supplier (wonderful Kernow Craft!) at the same time. I hope that you can see a difference in their diameters - it's small but it is there! I've put them all upside down to make it easier to compare them. 

I've found that anything from a 4.8mm to a 5.2mm diameter can be sold as a 5mm stone, especially when buying in the "beginners stone" market. The suppliers aren't doing anything wrong, this is just the acceptable variation. I ask Kernow Craft to pick me out stones that are, for example, as close to 5mm as possible and (wonderful people that they are!) they do it, even when I'm ordering 100 stones at a time. All good stone suppliers will do this. I ask for this as I know it is easier for my beginner students to set stones that are as close to their intended size as possible. Once they've got a few of the easier to set stones under their belt we can move on to the stones that need a little bit more TLC!

But why is it easier to tube set a 5mm stone than a 5.2mm stone

It all comes down tube size and burr size.

Ready-made tube is sold as a combination of inside diameter and outside diameter. The inside diameter need to be small enough to stop the stone from falling through the tube. The outside diameter needs to be big enough so that when the setting is cut there is still enough metal left around the stone to push over the stone's girdle and hold it in place. The garnet in this picture is exactly 5mm. The tube has an inside diameter of 4.2mm and an outside diameter of 5.5mm. The fit is perfect!

This stone measures 5.4mm across and is sitting on the same piece of tube. There wouldn't be enough metal left in the wall after cutting the seat to hold the stone securely.

Of course you can solve the problem of matching tube and stone size by making your own tube to just the right diameter, but there's something else to consider and that's burr size.

It is important to match burr and stone diameter.

I use a ball burr followed by a stone setting burr to create a seat inside the tube. If I choose a burr that's larger than my stone diameter the seat will be too big and the stone will rock in it's setting. If I choose a burr that's too small the seat will be too small and the stone won't even fit into the seat! By the way, it's important to measure your burrs too and not assume that they are exactly the advertised size. When we're working with such small sizes a difference of 0.1mm is important!

So far I've only focused on stone diameter, but stones can differ in height too.

Have a look at these five pretty garnets in a row. Again, I've put them upside down as it's easier to compare them like that.As you can see, there is quite a difference between the heights of the stones, and also the angle between the girdle (the widest point of the stone) and the table (the flat top). Although this doesn't affect the tube or burr size that you need it will make a difference to how deep you burr the seat for your stone. Making yourself aware of the proportions of your stone before you start will help you create the perfect seat.

Just to prove that it's not just garnets that differ in size here are some beautiful green agates. The differences in height is quite amazing!

All of these are perfect for tube setting, but creating the seat in the tube is much easier if you measure the stone you choose and can then adjust your work to suit the proportions.

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I've put together two classes for you that will teach you how to match up tube and burr size to create a beautiful tube setting for your chosen stone. The first one, the Tube Set Ring class, takes you through the sizing and teaches you how to use a ball burr and a stone setting burr to create the perfect seat inside the tube. The Ocean Blue Ring class builds on that knowledge but in this class I've deliberately chosen a stone that doesn't match any of the burrs I have so that I can show you how to solve the problem - oh, and it teaches you a different style of ring too! Using the method in the Ocean Blue Ring class even the largest garnets in the pictures above can be tube set in a suitable sized piece of tube, even if you don't have quite the right sized burrs.

Want to find out more about using gemstones in your jewellery?

Here are a useful blog post and links to two tube setting classes.

Start with a simple hammered ring and then learn how to set sparkling gems in smooth modern settings	How to repair your burnisher - and why you need to!	A new tube setting project - including tips for setting oversized stones
The Tube Set Ring class teaches you everything you need to know to create your own beautiful settings from simple lengths of tube.	A burnisher is a must-have for stone setting - and for many other jobs too! However, burnishers must be looked after carefully if they are going to give you the best results. To find out why and how to look after them read on!	A second tube set ring class - with a twist! This class uses the stone setting techniques taught in the Tube Set Ring video to create a bypassring, a stone set between two sides of a ring shank that twist past each other.

Categories: did you know, jewellery facts, jewellery making tips, problem solving, stone setting