Tutorial: Understanding Material Thicknesses and Slots (or "1/4 Isn't Really 1/4")

One of the most important things for new laser owners to understand is that materials are rarely the thickness that they are labeled. 1/4" is almost never actually 1/4".
Why does that matter, you ask?
Because when you're wanting things to fit together - like a tab into a slot, for example - you have to know exactly how thick your material is to get a good fit. You can't make the slot the size the material is labeled. You need to make it at what it measures (or actually a bit thinner to account for kerf).
And here's where it really starts to get important for you to understand:
When someone creates a design, they have to make a tough decision:
1. Do they make the slots at 1/4" (0.25"), for example? If they do, almost no one will have material that is that thick, so everyone will need to adjust the slot down to whatever their chosen material is.
2. OR the designer can make the slots at the size to fit the material they have on hand... but again, many people won't have that exact material, so they will have to measure their material and adjust the slots to fit their material.
Do you see the struggle?
No matter what size a designer makes a slot, many people will have to adjust it.
THIS is something that every beginning laser owner needs to understand and embrace.
Adjusting files for different materials is part of being a laser owner.
And so is owning a pair of digital calipers (if you don't have any, order some today)!
The next video you should watch is my 90-second overview of kerf. It's right here. Let me know how I can help you make great things faster! • A Quick Look at Kerf

[@rommiemex9532]

Recognised your avatar, had just purchased one of your designs, thanks!

[@MattLaClear]

Thank you for explaining this to me.

[@ldmmpb]

Great video. Thank you.

[@thecreativecardinalbyl.bet7012]

So helpful!

[@FrankieG411]

Ok i'm a newbie to laser cutting... so the glowforge laser is something like .008 cutting kerf right.... ok so question where does the laser cut, on the line? the outside of it? and so then how much do you accommodate for this? less a .090? ....so that then leads me to when designing what stroke weight should I use? Thank you !!! Glad I found you very helpful videos! ~Frank

[@BigBlueLaserDesigns]

Hi Frank! Typically the kerf is around 0.05” and it cuts right down the middle of a line. I’ve got quite a few videos that touch on various parts of this - most from an Adobe Illustrator perspective, but the principles are all the same. Check out my playlist here on my channel called, “Adjusting Slots and Working with Kerf.” I think it’ll help you!

[@ImaginationPlaza]

Hello Mark, from what I watched, is it my understanding that .01 of material disappears? and when referring to a slot cut out to be a quarter inch, does that mean that .02 has to be accounted for when designing so I'm guessing that the slot would be measured at .23 and with the kerf thus it would create a slot that measures .25? Thanks Mark, we're still learning to understand everything.

[@BigBlueLaserDesigns]

Hi! No. If you are cutting a slot that is .25” in one direction - let’s say the height - then when you cut it, it’ll be approximately 0.26” in height due to kerf. If you want it to end up at 0.25”, you’ll design it at around 0.24” high. I say “around” because 0.01” is a starting point and isn’t the same under all circumstances.

[@ImaginationPlaza]

@@BigBlueLaserDesigns, thanks Mark that helps me in the right direction. I'm guessing that the circumstances are different by thickness and the type of material mdf to plywood?

[@BigBlueLaserDesigns]

@@ImaginationPlaza Yes, but that’s primarily from the power and speed needed to cut those. The slower the speed and/or higher the power, the wider the kerf.

[@kimberlylewis5501]

Hello I have a Thunder and in lightburn it a spot to put kerf in do I just put .005 in or do I measure? I buy all my files. Thank you

[@BigBlueLaserDesigns]

Always measure. 0.005” is just an average starting point.

[@stacysnoveltygifts6993]

omg I am wasting material I have a design I bought im using 1/4 and the slots are not lining up and my calipers are say .24 so I'm adjusting so I'm doing it manually in my gf I need help

[@BigBlueLaserDesigns]

Happy to help! Message me at facebook.com/bigbluelaserdesigns

[@jondoe5866]

LOL growing up in America Inches are so easy. I thought CM and MM measuring was stupid. Im wondering like why is this never a problem for me... Oh yeah i measure in MM.

[@BigBlueLaserDesigns]

Haha! Totally get it. However, mm doesn’t change anything. Material thicknesses vary and the method of measurement doesn’t change that. Metric or Imperial, it’s still something all creators have to learn and deal with.