How to Connect a GRS Pneumatic Graver to your Compressor

Connecting your GRS pneumatic system to a compressor isn't as simple as it should be. I get a number of enquiries every month from frustrated jewellers and setters who are struggling to connect their Gravermax or Graversmith to a compressor - so let's get this sorted!

Note: For students in Australia I have a quantity of most of the hoses and fittings you need, and can send these to you for a small cost. Please fill out the contact form here to get in touch.

Even when brand new, most of these machines come out of the box with a thin air hose but no obvious way to connect it to a compressor, or no hose at all. It's always baffled me that GRS would sell an expensive and popular piece of equipment without giving many clues about how to plug it in to the required compressor. Imagine buying a brand new car and realising that you're expected to supply and attach your own wheels!

Air intake for a GRS Graversmith

Easy options

Before attempting to DIY it, you can try these and save some time:

• GRS sell compressor attachment kits on their website, and these are included if you buy the compressor from them as well. For some this may be the easiest solution, but air fittings vary across the globe just like electrical plugs do, so if you live outside North America the GRS-supplied fittings probably won't fit your compressor. 
• You may be able to ask your compressor supplier which fittings you need, but you'll need to be very specific about the type of air tube needed. The correct GRS hose is quarter-inch (outside diameter) polyurethane tube, which is easily mistaken for the 6mm equivalent in metric countries.
• And if you're in Australia, I can save you the trouble and post it to you.

Doing it Yourself

If you're not already familiar with air hose fittings, there's not a lot of information available, so working it out for yourself can be frustrating and tedious. Let's break it down.

There are three parts you need:

1. The air tube that plugs into your GRS machine
2. A coupling (plug) that plugs into your compressor
3. A coupling that joins the first two parts together

You may already have some of these, depending on who supplied your machine.

These three pieces all need to connect with each other so the air can flow from your compressor to your GRS machine without leaking. Where it gets tricky is that these parts will be different depending on which country you live in.

 A typical setup for GRS machines in Australia

About the Tubing

The tubing (thin hose) used for most of the external and internal parts of GRS machines is 1/4" PU tubing. 1/4" is the outside diameter and Polyurethane ("PU") is a softer plastic similar to rubber. Many people in metric countries make the mistake of buying 6mm tubing instead, which is similar but not the same - it's 0.35mm narrower, so will fit into the connectors but leak air. So it's important to find the imperial-measurement stuff, which you may need to get online or from a specialist pneumatic supplier.

It's also possible to buy tubing that's made of nylon instead. This will work, but it's much more rigid and can be difficult to bend around corners.

The tubing is usually supplied clear, but can be bought in various colours.

Connecting to your Compressor

To connect the air tube to a compressor, two fittings (called "couplings") are usually needed.

Take a deep breath - this next part gets technical, but you can do it.

The two couplings need to join together on their threaded ends; one female and one male (an innie and an outie). It doesn't matter which is the female and which is the male, but they do need to be the same standard thread type. This will be 1/4" in any of the three pipe thread standards of BSPP (Australia, UK, Europe, NZ, Asia, South Africa), NPT (North America) or BSPT (China, Japan). If you buy both parts in your own country they'll likely match, but it's worth checking just in case. NPT and BSPT require a small amount of thread seal tape too, which is readily available in the plumbing section of any hardware store or supermarket. 

Teflon thread seal tape

Once these two parts are joined, they act as a connector between the air tube and the compressor, so the other ends need to fit these. Fortunately this isn't too difficult.

The compressor coupling will usually be a Quick Connector, meaning it can just be pressed into the compressor outlet rather than screwed in. Naturally there are many different types of quick connector - in Australia we use "Nitto-style", in North America it's "Industrial", and there are different standards for Europe and UK as well, BUT if you buy it with your compressor, it should be standard for your region and you won't need to worry.

A Quick Connector for a compressor outlet (Nitto-style shown)

 The coupling that connects to the air tube is a bit harder to find, so you may need to shop online or visit a pneumatic specialist. The non-threaded end is a 1/4" Push to Connect fitting, which is the same as the air intake on the GRS machine (usually with the orange ring). Again, in metric countries you need to be careful not to get the similar-but-not-the-same 6mm fitting, which looks identical but will leak air.

1/4" Push-to-Connect fitting. Note the 1/4 marking.

Putting it together

The main thing to remember here is to connect all other parts before plugging them into the compressor, otherwise the compressor may empty very suddenly when you plug in the fitting! It's best to leave the compressor empty at this stage too, until everything else is set up.

It's also important not to turn on the power to your GRS machine until the compressor is connected and the tank has filled. Operating the machine without an air supply will cause the internal parts to wear out prematurely, so always turn of the power switch before turning off the compressor.

Summary

To recap, the three parts you need are:

1. A length of 1/4" PU tubing (not the 6mm stuff that looks the same)
2. A compressor air plug, with the standard male- or female-threaded end for your region
3. A 1/4" Push to Connect tube fitting, that screws into the compressor fitting with the help of some sealing tape

Finally, if you want to keep the compressor in a different room to your bench, the 1/4" air tube will maintain pressure over the distance but may not appreciate being stepped on or having objects placed on top. it's usually easier to add a standard compressor hose, for example a 10m 1/4" air hose (1/4" is the inside diameter for this one, so it's thicker, like a garden hose). The thicker hose can connect to the compressor and run to your bench, then the fittings can plug into it so that the thin flexible PU tube can run up the back of your bench to the GRS air intake.

A 10m compressor hose

You made it! Hopefully you're able to connect you compressor and solve what is a frustrating hurdle for many people. If you're in Australia, I encourage you to get in touch here and let me send you the parts you need, currently priced at cost plus postage.

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