this post was submitted on 16 Oct 2025
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Tested a print of a muzzle device after calibrating some PLA Pro. The print came out looking great. However, the 1/2x28 threads in the ID are very loose, so much that with minimal force, you can pull straight past them.

So, I've seen a few different ways to fix this, but I wanted to see what the community agrees to as the "best" practice to adhere to.

Do I adjust for shrinkage, add in additional tolerance in the modeled threads, or do something else entirely?

Bambu P1S

0.4mm Nozzle

0.16mm Layer Height

Overture PLA Pro

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[–] notsuspekt 4 points 1 month ago* (last edited 1 month ago) (7 children)

The way plaboi did it was kinda neat. The can had an internal smooth bore that a production flash can would be hammered into, then pinned inside using steel rods. It was much stronger than threads could be alone.

If you do dimensional calibration and tolerance testing you should be able to fit down to 0.1mm tolerance

How much tolerance did you include in the female threads and how much tolerance can you print down to?

[–] RenegadeSC 2 points 1 month ago (2 children)

I haven't tested tolerance yet. I'll be printing a cauliflower when I get home. I downloaded the file, so idk what tolerance they had baked into it or if it was a true 1/2×28 thread modeled in.

[–] PhilMeGroin 3 points 1 month ago* (last edited 1 month ago) (1 children)

Print the above tolerance test, follow the calibration help page for that print, after that test+adjust for shrinkage, which should be consistent throughout the print, and will be adjusted by a flat % across the entire stl

[–] RenegadeSC 2 points 1 month ago

From the califlower test, I had a -0.1% skew. Fixed that and adjusted for shrinkage. Just printed another flashider, and it's much better now. Tight initially, but once worked back and forth, it threads on well. I imagine a tight fit is better than a loose fit.

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