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Question about material thickness of ABS and Acrylic



i’m interested in your custom laser cutting service. On your website when you talk about the material thickness of ABS and Acrylic, you state that the thickness in inches is only nominal and the actual thickness is in Millimeters. So what is the actual thickness in Millimeters for the different inch-sizes? I would assume: 1/16" -> 1.5 mm, 1/8" -> 3 mm, 3/16" -> 5 mm, 1/4" -> 6 mm, 3/8" -> 10 mm and 1/2" -> 12 mm. Am i correct with these numbers and with the assumption that for an actual design one should rather work with these numbers than with the inch-values?
I’m planing to use some interlock features to build a 3D-case out of lasered sheets of Acrylic or ABS. The slots and corresponding tabs woudn’t have to fit absolutely tight, because the design will be glued together in the end. What slot width (in relation to material thickness) should one use for a particular material (ABS or Acrylic) and thickness, so that the tab fits in the slot in any case (even considering the thickness variation of a particular material). As said above, it doesn’t need to fit very tightly, it’s more important that it actually fits inside the slot.

Many thanks and best regards



Thank you for your interest in our laser cutting. It is difficult to get tight fits using laser-cut plastic since plastic sheet thicknesses can vary by + or - 10% (not only from sheet to sheet, but even within the same sheet). If you are not too picky about the fit, this might help:

Below are the nominal plastic thicknesses and their corresponding actual thicknesses. (Suppliers such as mcmaster.com do have plastic sheets available with actual thicknesses in inches, but we do not stock any.)

Nominal acrylic or ABS thickness, actual thickness
1/16", 1.5 mm (~ 0.06") + or - 10%
1/8", 3 mm (~ 0.118") + or - 10%
3/16", 4.5 mm (~ 0.177") + or - 10%
1/4", 6 mm (~ 0.236") + or - 10%
3/8", 9 mm (~ 0.354") + or - 10%
1/2", 12 mm (~ 0.472") + or - 10%

You are correct that it is more accurate to use the actual dimensions in millimeters. Note that the laser cuts down the center of the lines you draw and removes some material from either side of the line, so holes will be slightly larger than what you draw, and the parts that fall out of holes will be slightly smaller than the drawn dimensions. For laser-cut acrylic or ABS parts, relative to your drawing, your parts will be larger or smaller in diameter by about the laser beam thickness of around 0.005" - 0.01". The kerf is bigger for other materials that burn or melt more, such as rubbers, foams, and nylon.

If you want to ensure that a tab fits inside a slot, you could make the slot thickness be in the upper-end of the plastic thickness range of the tab. With the kerf of at least about 0.005", that would probably ensure the slot is wide enough. To be extra sure, you could try adding 15% to the plastic thickness instead of 10% (maybe even more if you want to leave space for some glue). For the other dimension, if you make the male and female parts the same length in the drawing, the kerf will ensure that those sides will fit together.

Acrylic is generally cheaper to cut than ABS (and less smelly; ABS parts might need to get aired out for a few days), so if you do not need the parts to be particularly sturdy, you might consider using acrylic. You can learn more about the two plastics at pololu.com/docs/0J24/3#abs.

I hope this helps!

- Candice



many thanks for the fast and very detailed and profound answer. Now i can really start to plan the parts. I hope to be ready to order the parts from you in a month or so (the planing depends also on the finished electronics for the project).

Actually, since i’m located in Switzerland, it’s even more convenient for me that i can work with metric values for the thickness etc.
Is it possible to design the whole 2D-Layout with metric values (metric grid and preferences in the corresponding design-software) or is it necessary for your cutting-service to send you inch-based layout-files?

Best regards


It is fine to send us a file in metric as long as it is very clear what the part sizes are; please clarify the size in the special instructions field when you submit your quote request. For example, “The part in the upper-left corner of the layout is 14.5 mm x 25 mm” or “The blue square is not to be cut; it is a 1 cm square for size reference”. We always provide a PDF proof with dimensions so you can verify the parts before we actually cut them.

(If you have dimension labels in your file, please be sure to put them on their own layer. You should still provide us a note about dimensions outside of the file since if the file has scaling issues in our programs, the dimension labels in the file might also be affected.)

You can learn more about laser cutting at https://www.pololu.com/docs/0J24; you might find the same information easier to read at our old site, http://www.customlasercutting.com/ (we are currently working on polishing the information on our current site). Please be sure to read the section on the capabilities and limitations of laser cutting for more tips.

Best of luck designing your parts!

- Candice