Flutes
36
Field note · texture study
Five ways to grip a knob
The TP1 radio's control knob got a side texture, then an adversarial review. Here are five printable alternatives — each shown three ways: an AI beauty shot (gpt-image-2), an accurate CAD render, and a live 3D model you can spin. All five carry the same keyed friction D-bore for the KY-040 Ø6 shaft.
01
What's actually there — and what's wrong with it
First, a correction: it isn't a knurl (a cross-hatched diamond). It's straight vertical reeding. The shipped knob (variant A) has 36 fine scallops — and the numbers put it right at the edge of what FDM can hold.
| Finding | Detail |
|---|---|
| Lands at the resolution floor | Ridge crests are 0.82 mm ≈ 1.9 nozzle widths. They print as ~2 rounded perimeters — the crisp machined edge in the render won't fully survive; it reads soft. |
| Shallow grip | Scallops are only 0.9 mm deep. Fine for a light volume knob; marginal for the only control (rotate + push). |
| "Knurled" overclaims | Docs say knurled; the geometry is reeding. A true diamond knurl prints worse on FDM (rounded blobs + 45° overhangs) — not recommended. |
| Aesthetic drift | 36 reeds at 2.6 mm pitch reads "vintage coarse," not "fine precision." Going finer for a premium look makes lands thinner → worse on the printer. Resolution caps how fine you can credibly go. |
what's right
Vertical reeds run along the build axis → zero overhang, the cleanest print orientation; and the 1.2 mm smooth bottom rim keeps elephant-foot off the texture. Good calls — kept in every variant below.
A
Fine reeding — the shipped knob
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Pitch
2.62 mm
Ridge land
0.82 mm
Depth
0.9 mm
Print
borderline
Grip
light
The current part. Reads great on screen; off the printer the thin lands round over, so it lands softer and slightly "gear-like" rather than precision-machined. Acceptable — but the option most likely to disappoint.
B
Coarse / deep flutes
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Flutes
22
Pitch
4.28 mm
Ridge land
~1.5 mm
Depth
1.4 mm
Print
excellent
Grip
strong
Fewer, bolder, deeper reeds. Lands are well above the nozzle so they stay crisp; the deep flutes grip. Reads industrial-playful (guitar-amp / Chemex). The most print-honest option.
C
Fine reeds + wide flat lands
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Grooves
30
Pitch
3.14 mm
Flat land
~2.1 mm
Groove
~1.0 mm
Print
excellent
Grip
medium
Narrow grooves separated by wide flat lands — the lands are 5+ nozzle widths, so they print dead crisp. The best "fine precision aluminium" read that FDM can actually hold without going mushy.
D
Faceted prism
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Facets
14
Across flats
~27 mm
Edges
crisp
Print
perfect
Grip
good
Read
minimal
Flat faces instead of texture — nothing thin to lose, so it prints flawless. Reads minimal and instrument-like; distinctly Teenage Engineering. The zero-risk choice if "radio knob" isn't a must.
E
Smooth + thumb dishes
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Texture
none
Thumb dishes
2 × Ø9
Print
mild overhang
Grip
low–med
Read
quiet
Note
support?
The quiet, premium option: smooth sides, two finger dishes for purchase. Honest caveat — the dish tops are the one mild overhang in the set, so this is the only variant that may want a touch of support.
02
Pick
C · precision
If you want the brief's "fine precision aluminium" to actually print crisp.
B · grip
If you want tactile grip + an industrial-playful read.
D · zero-risk
Most distinctly-TE, prints flawless, no thin features.
The shipped A is fine, but it's the one most likely to disappoint off the printer. Each swap is a ~10-minute change: texture params → re-export → redeploy.