From the Loftsmith Workshop

M6 to M12 thread tolerance test, printed bolt and nut ladder

Saves you printing a whole bracket just to learn your nuts are too tight. A short strip has a row of threaded holes, each a touch looser than the last, with the gap stamped beside it. Thread the bolt through and see which one turns nicely.

2 parts · 8 g · 94 × 22 × 18 mm

by Loftsmith Workshop

Orange strip with five threaded holes labelled .1 to .5 and a grey hex bolt standing in one
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No adjustable sizes

Ask for the sizes you want to tweak, e.g. “make the width adjustable”.

Change it in the Studio

Parts

  • nut-ladder · PLA · Flat on its bottom face, labels up

    94.2 x 22.4 x 6.4 mm at the defaults, about 7 g, about 14 min. Five ISO M8x1.25 threaded holes at 0.1, 0.2, 0.3, 0.4 and 0.5 mm of clearance on the diameter, engraved .1 to .5, with 45 degree countersinks on both faces. The end tab is engraved with the size and pitch. PLA because it is stiff and sho

  • test-bolt · PLA · Upright, hex head down on the bed

    M8x1.25 at the nominal ISO basic profile, 13 mm hex head, 8.4 mm of thread with a lead-in chamfer. About 1 g, about 7 min. All of the clearance is in the nuts, so a steel bolt of the same size can be used in its place.

Print settings

Layer height
0.2 mm (the figures here are for 0.2 mm; finer layers give cleaner threads but take longer)
Walls
2 walls
Infill
15%
Supports
None. The areas the engine flags as overhangs (5.4% of the ladder at the default M8, about 0 g estimated support) are the 30-degree flanks of the internal threads and the undersides of the countersinks. Both print without support. At M10 and M12 the slicer may also suggest about 1 g of support on th
Notes
About 8 g and 21 minutes for both parts at 2 walls and 15% infill (engine estimate at the defaults). Print with the same filament, nozzle and settings as the threaded part you plan to make, because the result belongs to that setup. Keep elephant's foot compensation on, or clean the first layer of th

Hardware

  • Steel bolt of the chosen size (optional) · Not needed. Screw a steel bolt through the ladder to find the clearance for printed nuts on steel bolts.

Assembly

  1. Print the ladder flat and the bolt head down, both without supports.
  2. Starting with the tightest hole (.1), screw the bolt in by hand from the top face. The countersink starts it straight.
  3. Work along the ladder. Note the first hole the bolt turns through by hand without forcing, and the first hole where the bolt rocks noticeably once it is in.
  4. Your clearance is the hole that turns freely without wobble. The labels are total clearance on the diameter (half of it shows as sideways play). If your thread model adds clearance to both the bolt and the nut, give each half the number.
  5. For a finer answer, set the Tightest clearance and Clearance step sliders around that value (for example 0.15 to 0.35 in 0.05 steps) and print again.

Good to know

  • This is a fit test, not a structural fastener. The engine check covers a finger-and-thumb turn of about 0.2 N m; do not tighten it with a wrench.
  • The fit you find belongs to your printer, nozzle, filament and slicer settings. Change any of them and test again.
  • The loosest hole is capped so it keeps at least 35% of the thread depth. On the diameter the cap is 0.53 mm for M6x0.75; 0.70 mm for M6x1 and M8x1; 0.88 mm for M8x1.25, M10x1.25 and M12x1.25; 1.06 mm for M10x1.5; and 1.23 mm for M12x1.75. If the Number of nuts, Tightest clearance and Clearance step
  • Only ISO metric 60 degree threads are covered. It does not identify other threads such as 3/4"-5 Acme painter's poles or radiator valve threads.
I printed this Remix

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