That Everlast manual also says about postflow:
"
As a rule of thumb, use 1 to 2 seconds of post flow for every 10 amps. Longer post flow times may be used in cases where long, uninterrupted cuts are being performed.
"
So, postflow duration versus amps might look like this:
AMPS / Postlow duration
10 / 1-2 sec
20 / 2-4 sec
30 / 3-6 sec
40 / 4-8 sec
50 / 5-10 sec (which explains why the duration is 10 seconds on many machines that have FIXED postflow duration)
This relationship between amperage and postflow is a pretty important thing to know, whether using an air compressor or a gas cylinder as your air supply, since a fixed OR too-long postflow can cause an air compressor to start-stop-restart much more frequently, and a gas cylinder to have to deliver much more gas in postflow than it does in cutting flow!!
Example:
Let's say you are making a cut of 1.5 inches at 20 amps, at the slowest recommended travel speed of 10 inches/minute, using 5 CFM, with 10 seconds of postflow.
Your air or gas consumption for actual cutting is 1.5"/10" x 5 = 0.75 cubic feet
Your air or gas consumption for postflow is 10 sec / 60 sec x 5 = 0.83 cubic feet
Total air or gas usage for that 1.5 inch cut = 0.75 + 0.83 = 1.58 cubic feet
Per the Everlast recommendation, your air or gas consumption for postflow should have been 2 to 4 sec /60 sec x 5 = 0.17 to 0.34 cubic feet.
Your total air or gas usage for that 1.5 inch cut = 0.75 + (0.17 to 0.34) = 0.92 to 1.09 cubic feet
So, you used 1.58 / (0.92 to 1.09) = 45% to 72% more air or gas than you needed to use.
If you are using a 300 cubic foot gas cylinder as the gas supply, you'd get only about 190 such cuts out of that clyinder, versus 300 if you adjusted the postflow to what it SHOULD have been.
On long cuts, the air or gas wastage on excess postflow is proportionately much smaller, but the CFM used, from EITHER a compressor or a gas cylinder, is problematic:
Let's say you are making a cut of 20 inches at 20 amps, at the slowest recommended travel speed of 10 inches/minute, using 5 CFM, with 10 seconds of postflow.
Your air or gas consumption for actual cutting is 20"/10" x 5 = 10 cubic feet!
Your air or gas consumption for postflow is 10 sec / 60 sec x 5 = 0.83 cubic feet
Total air or gas usage for that 1.5 inch cut = 10.0 + 0.83 = 10.83 cubic feet!
Per the Everlast recommendation, your air or gas consumption for postflow should have been 2 to 4 sec /60 sec x 5 = 0.17 to 0.34 cubic feet.
Your total air or gas usage for that 20 inch cut = 10.0 + (0.17 to 0.34) = 10.17 to 10.34 cubic feet
So, you used only 10.83 / (10.17 to 10.34) = 4.7% to 6.5 % more air or gas than you needed to use.
BUT, look at the total cubic feet used!
If you are using a 30 gallon air compressor, that 30 gallons = only 4 cubic feet. So you blew through your entire air tank less than 40% of the way through the cut and started cycling your compressor. Hopefully, its NET (not gross) air delivery capability exceeds the 5 net CFM you need to make the cut.
If you are using a 300 cubic feet gas cylinder, you have used up about 3.3% of its gas. If you are making such lengthy cuts rarely, no problem. But if you are doing one after the other, you are are going to want a bigger cylinder.
Running these numbers really opens your eyes . . .
Jim G