Why My Laser Crosshairs Lied (And How I Fixed It)

This post is part of my beginner laser engraving jig series where I experiment with different ways to align small blanks accurately.

In my previous post I showed how to make a simple cardboard jig to hold small blanks in place when engraving.

If you haven’t seen that post yet, start here:

How to Measure a Blank and Make a Simple Cardboard Jig

That jig fit my blank keychain perfectly.

So naturally I assumed the next step would also work perfectly.

Spoiler: it didn’t.

So how did I go from this… to this?

Materials Used

For this test I used:

• The round wooden keychain blank used in the previous tutorial
• Digital calipers (great for measuring blanks accurately)
• Masking / painter’s tape
• The cardboard jig from the previous post

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Some of the links below are affiliate links. This means if you purchase through them, I may earn a small commission at no extra cost to you. I only recommend tools and materials I personally use in my own workshop.

• Keychain blank
• Digital calipers
• Painter’s tape

Step 1 – Using The Jig With Crosshair Alignment

My plan seemed simple.

1. Place the cardboard jig on the laser bed
2. Use the crosshair positioning laser to align it
3. Run the engraving

The jig fits the keychain blank perfectly, so if the crosshair alignment is correct the engraving should land exactly where it should.

Everything looked perfect.

Watching the laser burn is always satisfying.

Always wear proper eye protection when using a laser.

Step 2 – Something Went Wrong

When the engraving finished, I immediately saw something was wrong.

The engraving was clearly shifted off center.

Not massively wrong — but wrong enough to ruin the keychain.

So what happened?

Why The Crosshair Was Wrong

The problem turned out to be height.

My blank is almost 7 mm thick, which I confirmed with digital calipers.

The crosshair laser is aligned to the engraving beam at a specific height.

When the material is thicker than expected, the crosshair and the engraving beam can shift slightly relative to each other.

This effect is basically parallax.

So while the crosshair looked perfectly centered, the actual laser engraving happened slightly off position.

Result: a ruined keychain.

Step 3 – Fixing The Problem With Tape

Instead of trusting the crosshair again, I decided to use a physical placement guide.

I placed masking tape on the honeycomb bed and used the laser to cut the shape where the blank should sit.

I double-checked that my jig still fit perfectly inside the tape outline.

At this point I was slightly paranoid.

Then I peeled away the burned tape from the hole.

Now I had a perfect physical placement pocket for the blank.

Step 4 – Trust The Jig, Not The Crosshair

This time I placed the blank inside the tape cutout.

When I ran the framing preview, the crosshair looked wrong, but this time I knew not to trust it.

The blank was physically positioned exactly where the laser had already cut the outline.

So I ignored the crosshair.

And pressed start.

Step 5 – Perfect Alignment

This time the engraving landed almost perfectly.

And the final keychain looked exactly how it should.

Lesson Learned

Crosshairs are useful.

But when material thickness changes, they can sometimes lie slightly due to parallax.

A physical jig or placement guide removes that uncertainty completely.

Which is exactly why I like using jigs whenever possible.

Next In This Series

In the next post I’ll show another jig method that many laser users suggested in the comments — the cardboard pocket technique.

It works even if your laser doesn’t use absolute coordinates.

Stay tuned.