Focus lens and mirrors

Thanks, So would it be good for me to go from a 18mm to a 20 or 25 mm lens or is it just a waste of time and money.

Thanks Travis, my beam appears to be pretty well focus in the middle of the mirrors without loss so I am probably good with 18mm focal lens but wanted to make sure there was no advantage in jumping to a larger lens.

Have you done the 1 mm dot test that Russ uses to dial down his laser for sharp engraving ?


Not yet, I watched the video you provided and need to determine how he created the file for the test. I am assuming it is several pixels with a line and a dashed line but have not had a chance to create it yet.

Here is the file
It’s that small right click and save as



@firemine you are also going to need one of these


It will help out has a fixed scale that will help you identify how far apart the dots are in mm.

Take this as a personal testimonial I own one and absolutely love it. Look at all the positive reviews

All the best


If everything seems to be working as it should, you’re hitting the middle of the mirrors, hitting the middle of the lens, etc. then I can’t see why you’d want to change to larger diameter mirrors or lenses. I’m strictly speaking about lens diameter here, not focal length. I don’t think you’d see any appreciable change solely from going to a larger diameter lens. Curious what others think about this as well.

Focal length and compound lenses are a whole different discussion.

Thanks for the file. Still working through this process.

Thanks for the help.

I don’t suppose you have the file for the acrylic focal length gage do you?

By the way Billet aluminum is good compared to cast aluminum ! Billet is worked (hot or cold) to harden and basic forming the piece ,then machined. This will find flaws in the metal before it is machined. Cast, which is what a lot of things are , is cast then machined. Cast aluminum is not as good as billet .

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Don’t disagree. But it all depends on what you’re using it for.

Those types of gauges will be specific to your machine.

I use stepped gauges in several different heights to accommodate a wide range of lenses and nozzles.

Here’s a file for the 2 shortest ones. If you need them taller just boolean weld a rectangle of the desired height to the bottom of the gauge and change the numbers. to suit.
The numbers on these are a little small for my old eyes. I’d probably make them a little bigger next time.

focus gauge 10a.lbrn (219.1 KB)

Thanks for the file. I will give it a go.

Yeah, I was looking for a gauge with multiple heights. I can buy a step gauge but they can be pricey or I can just cut one from acrylic and be pretty close.

It is a laser. If tuned properly, I doubt you will find a more accurate cutting tool in the shop. It is a very simple shape to markup in LightBurn to the exact size you desire.

One suggestion if you make your own focus gauge… make them out of colored acrylic.
If you make them from clear they try to play hide 'n seek with you when you set them down.

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Height Gauge.lbrn (55.5 KB)
I misunderstood. I thought you just meant the standard rectangular block that so many lasers come with. Here’s a file for a stepped height gauge in whole millimeters and half millimeters.

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That is a fantastic idea. I can see how that would happen.

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