This is what it is all about! Using air tools.

Connecting air tools to the compressor

The reducing valve

There is usually a reducing valve on the top of the air tank. You draw off your air through this. A compressor will normally pump the tank to about 150 p.s.i. then cut out. The reducing valve is usually set to 90 p.s.i., which is the designed working pressure of pneumatic tools.

This arrangement gives a constant pressure supply of air to the tool while the compressor does what it has to do to keep up.

The pressure to the tool will only drop if you have been drawing off a lot of air for a long uninterrupted time, so that the air tank pressure drops below the pressure the reducing valve is set to. In this case the reducing valve will be wide open, not reducing at all, and you will be drawing air directly as fast as the compressor can pump at this lower pressure.

In reality, you rarely find yourself in this situation of the power of the tool dropping away, as you rarely work so long uninterrupted

You can use the reducing valve creatively, to reduce the maximum power of your air tools. That can be very useful when you are doing delicate finishing work.

Getting air to the tools - hoses and connectors

Normally you will use flexible air hoses and quick release connectors. So you just plug-in and uncouple your tools as required. Most connectors have a quick two-hand action, one hand pushing the connector inward while the other hand twists or pushes a release collar, then the fitment can be drawn apart. The connector seals against air flow while nothing is connected to it. Very convenient.

Types of air tool

I can think of these categorises of pneumatic tools:

This is nothing like a complete list. For instance, a garage might have a pneumatic polishing mop.

Air blower

A air blower is so useful I knew someone who wanted to get a compressor just for that reason. He had a motorcycle. He used my air blower to blow away the dust and loose dirt. Then he used one of these new water-based degreasants which he could spray on then hose off with water. Then he used the air blower again to drive away the water from the surfaces and nooks and crannies of his motorcycle.

The blower is just a little valve with nozzle which clips into the end of your air hose.

Care of air tools

You drip about three drops of oil into the air inlet each day of use. Done. Regarding spinning free, if you need to let a tool spin free, such as when doing ever so light sweeps around a shape with an angle grinder, just lightly touching here and there, you can turn down the air pressure so that spinning free, the tool is spinning only about as fast as under load at full working pressure

There are some pneumatic die-grinders with a speed governor, so you can keep then spinning and just touch down where needed.

My little extra kindness to air tools. I get some hose which just pushes over the air connector. For each tool, I cut it off some hose with an inch protruding and push a tight-fitting 10mm length of wooden dowel in the end. That forms a nice cap over the air inlet. So when you are cheerfully working away and spreading grit and metal particles all over, it isn't going into the air passages of the tools you are not using at the time.

Why air tools

List again! The important qualities, mainly compared to electric tools are:

Also, a pneumatic hose is lesser safety issue than an electric cable in a workshop environment. Some pneumatic tools have no electric counterpart. A needle descaler is one example.

Disadvantages compared to electric tools:

Pneumatic tools are small and they are tough. You can completely stall them with no consequence. All they need are three drips of oil down the air inlet every day and they run fine. Compared to electric versions of the same tool, they are quieter, smoother, don't get hot (they actually get a bit cooler!). The "smoother" bit is usually important. By this I mean that the tools don't vibrate anything like as much as electric tools. Coupled with low noise, the smooth virtual absence of vibration makes for very relaxed working.

Regarding vibration and noise, generally electric tools have big armature spinning around, a mass of iron sheets and copper wire, which cannot be perfectly balanced, causing vibration. Then the armature needs an attached fan for cooling the electrically windings- which creates noise right in front of the user. On the other hand pneumatic tools are very small and dense, so what imbalance there might be is close-to-centre and constrained by the dense mass of the tool.

Pneumatic tools tend to be "professional", so they are more expensive, but on the other hand this adds to their smoothness and quietness.

Regarding durability, a workshop might have a pile of broken electric tools for if ever one can be raided for parts to make one working machine out of two non-working ones, whereas pneumatic tools can be decades old with their original shape polished down by untold thousands of hours of use.

The biggest disadvantage is the spitting out of oil. If you are preparing joints for welding, oil contamination is what you do not want. Generally oil with the minimum of air tool oil and do some rough work first before using the tool for maximum quality work.

Grinding type tools - angle-grinders, belt linishers, ...

Angle grinders

Pneumatic angle grinders an amateur and small workshop user will meet will be small, with a 4inch / 100mm grinding disk. This is because bigger air angle grinders use huge amounts of air.

A pneumatic 4inch angle grinder can be held one-handed, comfortably fitting in your hand with your fingers wrapping around its main body. This allows you to "sweep" along the job in a smooth action, like a barber does with shears. All electric grinders need a two-hand grip, one on the body which the hand won't neatly wrap around and the other hand on a handle sticking out of the front of the grinder, to guide and hold it. In fairness, the electric grinder is more powerful so has more "kick".

But this is all OK, because it is horse-for-courses. You will use your pneumatic angle grinder for detailing, small and precise stuff. On the other hand, for big metal removals, you will use one of those machines which plugs directly into the electricity socket!

I had a 4inch pneumatic angle-grinder and 4~1/2inch and 9inch electric angle grinders. The 9inch one vibrated so much you had to wear gloves (good idea anyway for the rough work you would be doing) and made so much noise you needed ear protectors (well, I like to style myself as a reasonably tough practical guy, but I see no advantage in hearing loss). But the 9inch angle grinder would send a huge spray of sparks up to 10metres through the air, flying over the fence of the yard. And that is a lot of metal removal. Good for quickly getting a thick piece of metal dressed down to "silver" and near shape after plasma-cutting. The 4~1/2inch electric angle grinder would run rings around the pneumatic angle grinder regarding metal removal. But it too vibrated and was quite loud - enough as ear protectors are a good idea. But the 4inch pneumatic angle grinder was quiet and smooth.

So the 4inch pneumatic angle grinder was just the machine for "precision angle grinding"(!). These days computer printers tend to be very dimensionally accurate (well certainly when connected to an Apple Mac! Thanks my friend with an iMac - used to cycle across town to get prints). To the thousandth of an inch. Rectilinear, for sure. That is how you can check if your printer is a good one. If a line is 100mm on the drawing, is it 100mm on the printed paper? But if it is there, that accuracy is maintained for curved shapes. That opens a new possibility of "precision angle grinding" for curved shapes. For instance for welding jigs in sheet metal work. These are the stages involved:

The odd touch of the grinder onto the template leaves nicks, but not as matters given the full width of the template. With the big wide template as a guide, fraction-of-millimetre accuracy is achievable. ,

Belt linishers

I haven't used mine for much "power filing". Belt linishers are otherwise referred to as "power files". I have used mine for removing oxide mill-scale prior to welding. For box-section and other tube, this can be a real blessing. I've included a note I put to the newsgroup about how I found a belt linisher is very useful.

I have rarely used the belt linisher for more normal use, but have found it useful for linishing across the direction of the angle grinder's grinding marks, so that the surface can then be emery-cloth rubbed to a very smooth finish.

Die grinders

These spin little grinding burrs and are used for detailing around the inside of jobs. Cheap to buy and useful to have.

Pneumatic "twist" drill

I found this very useful in applications where the drill can "snatch", such as when drilling particle board and you do not have a specialist drill of the right size. By reducing the air pressure, you can have your air-powered drill drill smoothly with a normal metal bit and refuse to "grab". Otherwise, it's the usual advantage is small size so it fits easily in the palm of the hand for accurate fine work.

Grit blasters

Big grit blasters and grit blasting cabinets need a lot of air. However, there is a very useful type of small grit blaster, for cleaning an area about 6mm diameter. The girt gun has a rubber fitment around the nozzle, with a circular opening you press to the area you want to blast. The grit is collected in a bag hanging from the underside of the rubber nozzle, so you don't get grit flying all over the place. It's pretty clean. If you have a line to do, you can move along step by step pulling the trigger for a couple of seconds then moving on. If you didn't do this you would have to get the item you are cleaning into a grit-blast cabinet, which might take time, so this is not a bad option. Quite useful, in fact.

That's it...!

That's the limit of my experience with air tools.

(Richard Smith, June 2005)