What to Look For in an Air Compressor

Sunday, January 3, 2010

A couple of articles ago we talked about air tools and I have been asked a number of questions about the air compressors that people should buy to complete the set.

Air CompressorThe real trick to buying a compressor is to know ahead of time what you are going to use it for.

Before I go any further here are some useful terms that you should know about when looking for a compressor.
– They include: PSI: Pounds per Square Inch,
– CFM: Cubic Feet per Minute,
– Duty Cycle: is the amount of time a compressor can run compared to the amount of rest time (storage tank) over a 30 minute period … such as it can operate for 10 minutes, then rest for 20 without creating significant head wear.
– Single Stage: is where the compression piston compresses all the air in one stroke.
– Two Stage: is where there are two pistons that work together to compress the air.
(Generally a two stage requires less horse power, and produces less heat).

Therefore knowing what you want to use it for and what the air-tool ratings in PSI and CFM are for those particular tools will give you a better idea of the duty cycle you will need. But you will also need to look closely at the air tools you are considering (make and model) because the same tool can vary widely in the amount of compressed air it will consume. For example a series of six inch random-orbital sanders have CFM differences of 8 to 24. That’s huge! It means the difference between buying a mid-size compressor or large fixed compressor. It pays to examine the tools you will be using and select the appropriate ones.

Compressors fall into three general areas:
1. Small portable units, often with one pancake or two small storage tanks which can be moved from one location to another simply by picking it up and carrying it.
Air Compressor2. Mid-size units, which have larger storage tanks and heavier motors and normally have wheels to help move them around.
3. And large compressors with fixed bases for shops and industrial sites with large storage tanks.

In terms of capacities, smaller units start around 1.5 horse and larger unites can exceed 6 horse power motors. The pumps themselves can be either oil-less or oil-lubricated and vary between one or two cylinders.

As a rule, the types of tools that are harder on air volumes are those which run continuously like sanders, grinders and cutters. Tools that require less cycling are tools that run intermittently like nailers, staplers and in some cases drills or even sprayers.

Therefore if you are a hobbyist woodworker, who is looking for a nailer or stapler, one of the small portable air compressors is probably ideal.

If you are planning on running some continuous tools like sanders, buffers, grinders etc. you will want to consider something in the mid-size to large shop size compressor with a 25 gallon storage tank and around a 4 or more horse power rating.

Air CompressorIf you are planning on using a number of tools at the same time, some of them continuous draw, (like grinders, sanders and buffers) you will want to consider a large fixed base compressor. These will have around 6 horsepower and a storage tank of 50 gallons or more. You might be looking at a 220 Volt version as well.

There are many manufacturers like Porter-Cable, Delta, Campbell-Hausfield, Makita, Craftsman or Ingersoll-Rand and many more. Each company will have different types and levels of quality for you to be able to choose the right one for you.

Other considerations in selecting an air compressor are what other uses will you find for it?
For example if you select one of the portable units, it is conceivable that you will carry this around to odd jobs, in the house, for friends. This is less of an option with the mid-size and out of the question for the large units. Then again the portables will not likely be suitable for sander/buffers. So in the end you will have to make that tough decision, but what ever you do, make sure you get a good selection of tools designed for your compressor. It will make your woodworking more fun, quicker and even more enjoyable than it is now.

A compressor and associated air powered tools can be a big help in getting your job done and be a real time saver, even for the hobbyist’s work shop.

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