Chain Grades, what are they about?

Chain Grades Quick Facts –

• A Chains Grade is effectively ‘the strength’ of the chain
• The Chain Grade can be expressed as a number or a letter
• Some industries require specific Grades to be used
• Standard convention is Grade numbers are rounded down to the nearest 10
• Grade 20 is low, Grade 100 is very high, there are many in the middle

Chain grades, more marketing crap or something I should know about?

While some dubious mobs do ‘fiddle’ and play up grades for usually smoke n mirrors reasons the vast majority don’t, so while there is a splash of marketing crap we do think Grades is something you may want to take a minute or 2 to think about as the term ‘Grade’ for most people very simply means ‘Strength’. Lets have a closer suss.

You will see chains with tags of ‘G40’ or ‘Grade 50’ or ‘Grade M’ or ‘G40HT’, just using G then a number i.e. G40 is the most common way most will see the Grade expressed.

There are a few add ons like ‘HT’ used a lot in the US. The HT means High Test, not high tensile that is very different. ‘High Test’ is marketing speak for ‘smaller design (safety) margin’, a quick example –

HT – Oh good I like High Tensile –

But high tensile is not want you have, you have High Test, the two are very different.

Chain 1 – 10mm G40 HT chain sold in the US – It’s Working Load Limit (WLL) will be 2560kg with a Design Margin of 2.5:1. It’s Break load is 6400kg.

Chain 2 – The same chain sold in NZ or elsewhere in the world called just G40 – It’s WLL is 1600kg with a Design Margin of 4:1. It’s Break load is 6400kg.

So all High Test (HT) means the safety margin has been reduced quite a bit. It is also why most US chains never show a break load only WLL, doing that makes theirs look so much stronger when in fact it’s just a clever marketer blowing smoke up your transom. Notes: The US doesn’t have a 10mm, they use 3/8” which is different, I used 10mm just for simplicity. As imperial and metric equivalents are not identical in wire size the loads will also vary a little. As usual the US exports it’s strangeness so G43 and HT are popping up all over.

A Maggi made chain with MC denoting Maggi Catene and the A7 stamp denoting it is a seriously strong chain

Chain Grades can be expressed in Numbers and Letters

You will also see the term ‘Grade L’ used by a few, they use it in Aussie. The Grade designation until around about now has been a number, show you why shortly, hence we see G30, G80 etc. But some bright spark decided letter designation was better so started pushing those. Aussie has taken them up, the rest of the world has said ‘Yeah, Na we are happy to stick to numbers’. But that’s OK as the Letters do line up with numbers like this –

Grade L = Grade 30

Grade M = Grade 40

Grade P = Grade 50

an on it goes.

So when you see a Aussie calling a chain a Grade L you now know it has the same strength as what the rest of the world call a Grade 30. If you want some fun when in Aussie ask a chandler for Grade 30 chain and watch them try and process that, mind you to be fair you can to the same thing here in NZ at far too many places as well.

A PWB made chain made in Aussie using the Grade Letter designation ‘L’ rather than the number ’30’ which means the same thing.

Are Chain Grades just about strength?

Nope, but most of it is and it is all the average boater needs to worry about around that term really. Some of the other bits in the grading are around weld zones, bend radius and things like that. Most is pretty deep and only of real importance to the manufacturers or sad buggers like us who have run out of fun things to do in a Covid lock-down so have had to resort to doing bloody work. So from here we’ll just run through a couple of small things that could be handy to know for the end using boater.

How is the Grade derived?

The guts of it is strength so it can be calculated or test gear can be used. Without going head spinning deep there is a simple formula used to find it as long as you know the metal tensile strength. It involves lots of mm², Newtons and other fun things, it looks like this Ts = F/2s. Another way of finding the Grade is back work it from a known load, something we do when testing customers unknown chains. Doing it from a load test gives a current state where calculations don’t.

Why do we have G40 but can’t buy G43 like in the US?

In one simple word, marketing. You can buy G43 in NZ, we sell lots of it. G43 is simply a case of marketing out of the US just like the High Test tag talked about above. In NZ a good 10mm of say a grade 30 or 40 will break above that, it is common for us to bust G40’s and back-work the numbers to see it is a Grade 45, sometimes even higher. But we still call it G40, not G45. The 3 in the G43 is simple a marketer trying to make the product appear that little bit better than the one down the road.

So why don’t we use G43 and stick with multiples of 10?

Convention more than much else, it’s just what the world does. Grade numbers are rounded down to the closet 10 hence G30 and G40. Even the US does the same with some chains but not all. So when you buy reputable made chains called G40 in NZ you are more than likely buying a G43-46. Again the 43 is more a bit US marketing related that much else.

Do Grades apply to other loads like Proof Load?

They sure do. To meet a Chain Grade, which is usually defined in the relative Standard the chain is built too, the chain must meet a couple of loads. One is the ultimate break load as mentioned above but a chain must also comply at Proof Load. Proof Load is 50% of a chains break load, it is the load a chain is loaded to in the factory during the QA process. A chain can’t be called (we’ll use 10mm G40 as the example) a G40 unless it get to Proof Load of 3200kg without changing shape and then breaks above 6400kg, failure to exceed those means it is not a G40, it is a lower grade. Many chains from the East tend to change shape before Proof Load due to their use of soft metals. Also many don’t meet the required break load for the same reason.

Are Grades dependent on the material used?

Nope, the same applies whether its mild steel, high tensile steels, stainless steels or what finish it has. As an example a G50 Steel chain will have the same strength as a G50 Stainless Steel one.

Are Grades dependent on what Specification the chain is made to meet?

Yes but also No. These days one or 2 manufacturers do make chains outside to the grade the Standard they are building to dictates but they do for reasons that are bloody good for us end users so we think we’ll let them continue to do that. For example the DIN766/A standard is a Grade 30 Standard meaning in theory all chains built to the DIN Std should be at least G30, as a general rule they are but…. many chains from the east do not meet Standards so that’s one issue with giving a blanket Yes.

The other issue is the opposite of that as the Italians build many chains that meet the DIN766/A Std in every manner but exceed G30, some exceed it by 133% like Maggis AQUA7 and MF’s DAMS7, both are Grade 70 but comply in every other regard to the DIN Std. The same applies to ISO4565 chains, that is a Grade 40 Std. Again chains from the east tend to not meet the named Grade or Standard, many ISO Std chains are sold by China as DIN Std (which does flow into NZ and the pacific). That is a bit WTF when you consider the DIN and ISO standards differ in most ways including the physical dimensions. Anyway back to Italy and they make ISO in G30, G40, G50 SS, G60 SS and in G70. So as we can see while most Specifications are grade specific technologies and us boaties with our often quirky demands means these days the link between grades and Standards isn’t as tight as it used to be.

That is not a stamp of any real importance, it only denotes a DIN766 Std chain made in the east.

So do I need a G30 or a G80 or something in between?

All depends on the application. A G30 is not a grade allowed for overhead lifting but G80 is hence the G30 is fine on a boat but not a crane. But then a G80 is not good on a boat anyway as it is that high tensile galvanising it is a horror show and very very hard to do well. If you have a 30fter on 10mm chain then G30 is overkill but put that 10mm G30 onto a 60fter and overkill turns to ‘let me off now’. The 60fter can use 10mm but will need a stronger one line a G40 or even a G70. So the Grade is relative to it’s application, bigger the load the chain may come under means the bigger grade number will be needed.

Boating around the Coast of NZ needs what Grade chain?

Until some annoying mob called CRA got into the market NZ only had G30 chain and history shows that was perfectly fine for the vast majority of boats. But as boats and uses of them have evolved we see all manner of craft doing all manner of things so that means they need all manner of gear variations, that’s where Grades come in.

A 40ft cruising yacht, 10mm G30 is fine but many will go G40 just for the extra peace of mind. If that 40fter was a stripped out racer then it could go to say a 8mm G70. Doing that saves the boat 1kg per metre in weight yet not lose strength as the 8mm G70 has a break load 2200kg higher than 10mm G30 and 800kg higher than the 10mm G40. So as you can see today we have options.

Cool, I’m a very anal yachtie and hate weight, can I change my 10mm G30 for 6mm G200 to save weight?

If you can find Grade 200 (no one makes it yet) of course you can BUT and a BIG BUT it is, one of the main reasons chain is used in a anchoring system is for it’s weight. So if you go from 10mm to 6mm you will be going from 2.4kg per mt down to 800 grams, a huge reduction in weight. That means you’re system is now relies nearly entirely on the anchor only, there is no significant help from the rode behind it. That’s fine when anchored in 5knts of wind but what happens in 40kts, the boat will be banging back on the anchor system hard meaning shock loads through the boat spilling the Gin and spike loading gear including the anchor. Shock loading is a known boat gear killer and great for pulling anchors out of the ground. If you join the dots you’ll see there is a point where the systems chain is too small no matter how strong it is so it’s all about striking the balance.

Here is a table with Working Load Limits (WLL) of chains of the Grades used in anchor systems. The Design (Safety) Margin we’ll keep at a steady 4:1. Below 8mm is not a area boats need to worry about, boats using 6 and 7m chain do tend to be over anchored.

Size	Grade 30	Grade 40	Grade 50	Grade 70
8mm	850kg	1000kg	1300kg	1800kg
10mm	1250kg	1600kg	2000kg	2800kg
12mm	1750kg	2300kg	2875kg	4000kg
13mm	2000kg	2750kg	3400kg	4750kg

NOTE: Due to some regulations around High Tensile chains the Design Margin used is different than what we are using here so this chart is to demonstrate the differences between grades only.

To put it more graphically –

So while it sounds spooky, Grades are pretty simple. Just remember –

Bigger the Grade number the stronger the chain is

{Disclaimer – this was written with everyday boaters in mind not technically minded Uni professors so there is more to grades than just the above. For the everyday boater wanting to know about Grades and how they apply to their anchor chain all they need to know is there. As always if anyone has any questions or would like more info then click here to get hold of us, we are very happy to answer or explain things to anyone who asks.

Yes this article may reflect on Mrs Akroyd, the writers English teacher. Please don’t let it do that as the spelling problem was brought about by Wakatere Boating Club and the locker the writers boat was kept in. The writer had to walk past WBC to get to Mrs Ackroyds class. When the wind was a rockin 20knts offshore he found it virtually impossible to do that.}