Measuring Kerf with the Kerfometer

[dan]

I was making some boxes, and had to figure out the right measurement for a tight fit. I might have gotten a little carried away…

When a laser cuts material, it removes a thin slice of material along the way, called the “kerf”. For that reason, if you cut a 1" circle, you’ll get a slightly smaller circle and a slightly larger hole. If you want a circle that’s exactly 1", you’ll need to make it 1", plus the width of the kerf. For a hole that’s 1", you’ll want to make the hole 1" minus the width of the kerf.

And this is really important if you want your project to fit together tightly.

Kerf is hard to measure because it’s really, really small. It is different with every material, with every laser, and with every choice of settings. You have to carefully use precision tools like calipers or feeler gauges. It’s easy to make mistakes, and you can ruin some projects with errors of even a few thousandths of an inch (or tenths of a millimeter).

We figured out a better way, and used a $20,000 inspection tool to be sure it was absolutely accurate.

Step 1: Grab the kerfometer, below, in inches or millimeters

Step 2: Print it on the material you want to measure

Step 3: Put it on a flat surface and flick your wrist. The line will point to the kerf for that laser, with those settings, in that material.

IMPORTANT NOTE: The kerformeter only measures the kerf of the material you printed it on. It’s not like a ruler where you measure other material with it! You’ll want to print one on every material you use, write down the measurement, and then frame the kerfometer on the wall as a piece of art to cherish (or throw it away) because you’re never going to use it again.

Get the kerf tool pattern from the Catalog:

• Kerf Measuring Tool - Inches – Glowforge Shop
• Kerf Measuring Tool - Metric – Glowforge Shop

I’d love your feedback on this!

[bill.m.davis]

Now that is a clever tool!!

[evansd2]

One caveat: it will matter a great deal if you flip mate the pieces (which imo you should). You’ll get a much larger kerf value if you do.

[ellencadwell]

@dan, I did grab both mm and inches, but didn’t realize they had to be cut for each material used. So reading your notes is great. Maybe I just didn’t read it in the catalog description, I just grabbed them! But I am a little confused on the lay it “on a flat surface and flick your wrist.” So do you keep it flat the whole time? At any rate, it looks great and I can’t wait to use it/them!

[dklgood]

I saw this file this morning and reported an issue with it because the “how to use” link went to a page not found error. I see that the link is working now, so I guess I jumped the gun. I hope users will find the tool helpful.

[LauraZM]

Clever design! Thank you, Dan.

@evansd2

if you flip mate the pieces

Would it work to remove the center piece and flip it? Would the resulting measurement be correct?

[eflyguy]

I don’t have premium but I see how it works. Clever.

[dklgood]

The file is free for everyone. Get it and give it a try.

[wenning08]

Very cool

[ptodd]

Cool! Who doesn’t like a new tool?

[deirdrebeth]

Looking at the gif it’s flat on the surface of the with a finger at the top and bottom. You pull it down quickly which forces the loose piece up, where it stops when it hits the kerf difference, then you can pick it up because it’s stuck.

Hopefully that helps!

[trually]

Did you watch the little video? It is hard to explain in words but just a simple action.

[eflyguy]

Threw me. I’ve never used the catalog…

[amanda.hewes7684]

I just added this to my dashboard yesterday? Great idea!!

[markevans36301]

I found these the other day and was going to say something even before you posted this.

This file is a winner for two reasons, one, it is unreasonably cute and, two, it works pretty well.

That said, my recommendation to make a file using a sample joint remains. If you are setting off to make a set of boxes that eats up two or three sheets of expensive plywood it just makes sense.

[eflyguy]

That’s what I have, a selection of little test pieces like combs, one each for my favorite materials, with varying slot widths either side of what typically works for them - even proofgrade has had variance in the past. I will cut a new one from the intended sheet if I plan to use it for a big project where a failed cut would be unacceptable. That’s also the time that I typically will give the optics a quick wipe as well.

[stardust_lilith_orio]

Thank you!

[rvogt]

This is a great lil device!! Thanks.

[dan]

@evansd2

One caveat: it will matter a great deal if you flip mate the pieces (which imo you should). You’ll get a much larger kerf value if you do.

It’s a good, advanced point - it depends on if you’re going to flip the pieces that intersect. It’s more of an issue on thicker pieces, where the kerf has more tilt.

[dan]

@ellencadwell

@dan, I did grab both mm and inches, but didn’t realize they had to be cut for each material used. So reading your notes is great. Maybe I just didn’t read it in the catalog description, I just grabbed them! But I am a little confused on the lay it “on a flat surface and flick your wrist.” So do you keep it flat the whole time? At any rate, it looks great and I can’t wait to use it/them!

Yes, you keep it flat when you flick it down, so it slides in the groove. I wanted to make it as simple as possible while still making it easy, accurate, and fun!

@deirdrebeth

Looking at the gif it’s flat on the surface of the with a finger at the top and bottom.

Exactly! But I can see it’s not obvious if I might have picked it up slightly, so it’s good to check.

@markevans36301

That said, my recommendation to make a file using a sample joint remains

Yes! Best to do both for big projects to be sure.