Wouldn’t that depend on where the kerf was being placed? Inside the line, splitting the line, or outside the line? I feel like that choice was something that was put into the hopper at some point… or was glowforge going to decide for us (the auto-adjustment for kerf from the original marketing material)?
That would certainly matter. For the sake of this situation I assume splitting the line.
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Please remember that it’s against forum policy to offer safety advice. Use the manual that comes/will come with your Glowforge to determine safe operation. If you see unsafe behavior, remind people to review their safety manual. If you believe a safety hazard exists that is not covered in the manual, email us at support@glowforge.com.
There are many well-intentioned people here who might have information or opinions, but we can’t vet every post to determine if it’s correct, and incorrect advice can be dangerous.
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BTW: Some folks noticed that the early Beta and Pre-release machines had been significantly exercised. The crumb trays showed lots of use. The pre-release received yesterday was purty darn clean.
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For the 1/8" Proofgrade I cut a bunch of squares and added up widths and divided and subtracted and whatever else was needed. My standard is .007" when I need to figure in to get a tight friction fit. It varies with material composition, cut speed, and thickness.
As to the other egraving of the trailer if @rpegg used a default dark on this he might have had a little more burn than desired for something this small.
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Proofgrade 1/8" clear acrylic.
Minus
Equals
0.07mm (0.002") for this material. If I am looking for a interference fit I usually cut a smaller ver. of this test to figure out what it’s going to be. Then design around that.
This technique is what I use to figure out end mill wear. In LinuxCNC you can adjust the tool diameter to compensate.
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Kerf will change depending on material composition, material thickness, power used to cut, and passes it takes to cut.
If you have 2 pieces of the the same acrylic, but different thicknesses, (let’s say 1/8 and 1/4), there’s a good chance the kerf will be higher on the 1/4 piece of acrylic.
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Sorry about that, I forgot. When I see the manual, I’ll check for that.
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Cooler and awesomer 
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Yeah! Congrats
Nice work so far with the tag. 
looks cool
Looking forward to seeing what else you laser!
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But the hole is smaller than the circle, so that is negative kerf!
This illustrates my point that measuring inside diameters accurately is difficult. I have these for large holes. They have rounded tips with a radius smaller than the hole. You expand them to fill the hole and then lock them, take them out and measure them with calipers / micrometer.
These for smaller holes, but I find them not very accurate because they are springy.
This for tiny holes. It drops a tapered pin into the hole and measures how far it drops.
And these are limit plug gauges for checking H7 tolerance holes. The red end is above top tolerance so should not fit. The plain end is spot on, which is bottom tolerance, so should go in the hole. In this picture they are in a printed part.
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No kidding!
And things will only get worse/uncertain if the material being measured has significant elasticity or softness, like wood or cardboard.
One of the first exercises we would do in our materials lab class is to make repeated measurements of objects and get a sense of what we can trust in each measuring instrument.
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Yes and tapered walls like laser cut parts.
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Wow, you da Tool Man!
I got them all for studying the subject of 3D printing holes the correct size.
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Gratz to you as well on the early GF…this to I am looking forward to learning from you.
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I’ve found cutting a square and measuring with calipers to be perfectly adequate. If I want to get fancy, I’ll cut a 20mm line through the material (don’t cut the material into two pieces, just cut a line through it) and use a set of feeler gauges to measure the cut width - it works well, uses very little material, and is accurate enough.
I’d love to watch someone measure a hole in a piece of 1/8" acrylic with telescoping gauges… LOL
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Lets get some analytical views on the performance and improvements - it will be great to hear your feedback @rpegg
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Decent calipers should get you pretty close, +/- 0.003" or so. Accuracy improves with experience, of course.
PS: Congrats on the pre-release!
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Yeah, understood and agree. Just not remotely interested in measuring something that will prompt 43 more questions. If it were .03 or .19 everything I ever intend to do can still be done. Yeah, I’m like that.
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