Miller spectrum 375 X-treme

Here’s how to convert your x-treme 375 :slight_smile:

You don’t have to do this step but this is how I figured to look for the purple and orange wire:

Open up the box and find the purple and orange wire:

Here I spliced it and used a BNC connector so I could attach a port to the back:

How it looks from the back:

Made a male plug so I could have a quick disconnect to the control box.


Did you have to do anything with the post flow, or is it not an issue? thanks

Not sure yet just got it wired up pulling it back out to start some cuts. But I dont think there is a post flow adjustment on this anyways.

So not an issue.

For post flow my main concern was start the cut then having to wait till post flow finished before being able to fire for the next cut which would be terrible. Luckily the way it work is if you cut out a section once it stops cutting postflow happens but if it needs to fire it will stop post flow and fire. Only at the very end of your last cut will postflow actually stay on for the 20sec. What I would like to do is have it move back to Zero after the last cut instead of staying at the end of the cut but not sure how to do that.

I did my 1st test cuts yesterday. The came out beveled and horrible. I put my welding helmet on and got close noticed the plasma angle was weird. Turns out to be bad consumables. Heres what I noticed after troubleshooting for a few hours.

-1/8th mild steel go slow. Im going at 20in/min even though the manual says 40 (which is suppose to be only 80% of max… unless i’m misreading this manual)
-30amp setting
-at least .2inch for lead in or you risk blowing your edge

I guesstimated kerf (if you happen to know this let me know)

Let me know how your 375 is working ! Good luck!

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@chowpay here is a snip of the 375 extreme manual. Im reading 30 amps 1/8" steel as 98.4 ipm! It concerns me that you are having to run it so much slower than that. Im planning on running my 375 extreme but Im starting to reconsider.

Have you put together anymore cut speeds for other thicknesses yet?

I actually need to try it faster. The reason I was running slow was due to these terrible beveling cuts I had. Grab’d my welding helmet and watched it closely and the spray was not straight. Bad consumables. But I kept the setting the same after replacing the consumables and ran it the cuts looked great. I’ll have to up the speed and see it goes.

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ive been running my spectrum 375 for a few weeks now and i have it 30 amp and 50ipm. seems to be working good

On what gauge material?

1/8" mild steel, could probably go a little faster even

Im finally up and running with my 375 and wanted to report back.
Your torch wiring instructions worked perfectly! Thank you for that!

Im running 30ipm at 30 amps on 10ga(0.135") steel with basically zero dross and a very nice edge.

I started playing with 14ga(0.074") last night and found it much more difficult to get a dross free cut. I ended up at 80ipm at 30 amps and got a decent cut but I feel there is still some room for improvement.

Have you guys cut any other thicknesses yet?

I actually haven’t tried anything but 1/8 mild but I’ll let you know as i’m trying to cut some stainless 1/16th … if I can get my drawing right.

What did you set your Kerf Width to?


I ended up at 0.045 and my parts were perfect to size when measured with calipers.

thannk you! did you do any special settings for your tool in CAM? if so can see them

in feed and speed what are your default settings?

anybody cut 1/4 inch yet, having hard time getting nice cuts

what do you have set for your pierce delay?

0.5 seconds on 14 gauge.
0.75 on 10 gauge.

Those are the only thicknesses I have cut so far

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This is awesome and I just finished this same Mod on my 375 X-treme. I love the clean look of this and being able to disconnect the torch fire so that it isn’t just hanging out of the box when using the cutter away from the CNC. Thank you so much for posting this.

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Thank you for this it has helped, only question I have is which wire goes to what. The red wire goes to the purple and the ground goes to the Orange?
From the picture with the handle pulled apart that is what I gathered.
Or does it not matter?

doesnt matter because its a contact relay. So fire = those 2 wires touching