Cut Time Question

I have a circumstance that I have yet to see anyone post about. In my shop I currently only have one 220v
plug. When using my hand torch on my Cutmaster 52, I have to plug in the air compressor, let it fill up then unplug it and plug in the plasma. Cut as long as I can till the air runs low then repeat the process. While this is a bit of a hassle I can deal with it as I am not making one long continuous cut like you would on the table.

So my question is, about how long of a cut time can I expect to get out of a full 80 gallon compressor before it runs too low to run the plasma?

I plan on adding another 220v receptacle later but the wiring in my shop would need some upgrading.

I’m thinking on adding an extra tank to get more capacity also.

i would go with a 110v compressor for now to avoid all that hassle. anything can go wrong during all that exchange when using the table as opposed to just hand cutting.

I’ve been running the Harbor Freight 29 gallon belt driven compressor along with the Primeweld CUT60 for about 2 years now with no issues.

I lucked out and got it for $150 at a pawn shop practically brand new.



Depends on the tank pressure. Lets say you set in to 140 PSI.

80 GALS at 140 PSI =10.72 FT3 + maybe 1.28 FT3 for piping for easy math = 12 FT3

We are storing 12 FT3 of air at 140 PSI.

the cutmaster 52I with the sl100 machine torch requires 70 PSI at 245 CFH to operate according to the manual.

I am going to leave out line loss and temperature change for ease.

12 FT3 @ 140 PSI is also 24 FT3 @ 70 PSI

245 CFH @ 70 PSI is about 4 CFM @ 70 PSI.

24 FT3 used at 4 CFM =

Approximnetly 6 minutes of operation. ( torch on and secondary gas flow time )

About 2 minutes and 12 seconds of arc time.

James is right so you have half the time I stated before.


3 minutes of operation
1 minute of arc time

At this point you’ll have 70 PSI left in your system and have to pause, plug it back in, spool up the compressor back up to 140 PSI. The amount of time it will take you from 70 to 140 will vary on the output of your air pump. Then repeat.

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Dang it man, are you a engineer? Pretty technical answer there. So if I can get six minutes of run time, that should be plenty I would imagine? I doubt that I will ever have to cut anything 6 minutes long? Does anyone on here cut for that long in a single cut?

Sorry, I didn’t see the arc time @ 2minutes and 12 seconds in your answer. Still does anyone cut that long?

What is the longest cut time some of ya’ll have done?

dragonfly 6 m 2

I may run up to ten different nests like this in a row.

This is a 30 x 30 inch nest and take 6 minutes at 270 inches a minute.

Ten nests may take an hour and a half or 2 hours with unloading and loading.

You can always pause

I don’t think that’s correct. There’s only 12 cuft of air in the system regardless of the pressure. Since he’s unplugging it, he’s not adding back to the tank as the air is being consumed. So regardless of the pressure he uses, he’s only going to get 12 cuft of air.

Practically speaking he’s going to get less usable air because it will fall below 70PSI before the tank/hose runs out of air which will cause the torch to stop.

I’m betting more like 1 minute or so of cutting time.

Your calcs only work if he’s got the tank plugged in and filling it back as the tank drains at 70PSI but then the calc is made complicated by the refill rate - if the compressor is rated for 4CFM at 70PSI he can run forever as long as it’s plugged in. But if it’s either rated lower or he unplugs it, the compressor can’t refill it as fast as he’s using it. Plugged in a 220V compressor is likely to be well within spec to run the plasma as long as he wants it. Unplugged he’s dead after he uses some portion of the 12 cuft that’s in the system - probably once he’s used about 6 or 7 cuft at which point he’s gotten the arc and cut for about a minute if he’s using 4 cfm (really 4.08 cfm for the 245 cfh spec) to run the torch.

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Obviously you can’t use the whole tank, only half of it. :upside_down_face:

After equalizing the tank which would be the 12 FT3 @ 70psi that would be the end and there’d still be 70 PSI in the tank.

Sometimes I miss those trees in the forest.

Good catch

So 1 minutes of arc time 3 minutes of operation.

If I had two 80 (12 ft3 +/-) gallon tanks side by side with a valve in between them. one and 140 PSI and one at 0 PSI. When I open the valve the pressure will equalize and I’ll have 70 PSI in both tanks (24 ft3 +/-).

In our scenario the other tank is the plasma torch.

I’m not saying literally it’ll be 24 cubic feet I’m saying that the equivalent of 12 cubic feet at 140 PSI is the same as 24 cubic feet at 70 PSI.
It’s the same amount of air.

Thanks guys for the responses.

I do the same exact thing. Plug one in at a time. I have a 80 gallon tank and fill it up to 140 psi. I can go about 10 minutes on mine before I hit 70 psi. I than pause my fire control in between cuts and after my plasma cutter cools down and shuts off I unplug it and fill up my compressor again. The longest sign yet I have cut is a 3’ X 2’ Harley sign at 45 ipm that took 15 minutes to cut out.

So, Someone does share my problem. Ernesto, when you restart fire control does it continue to cut with no issues? I’m gonna have to do this until I get another plug wired or get a 110 volt compressor as nicaDd suggested. Does anyone else use a 110 compressor?

i use a sanborn 30 gallon110v compressor, supplies air to the razor weld 35 just fine, but in constant use for 2 years and change. Supplies 6.0 CFM@90psi max psi 155, 1.9 RHP