From the Loftsmith Workshop

C-joint vs dovetail vs dowel tolerance test for split prints

A small card that tests C-joint, dovetail and dowel sockets at five gaps side by side, so you know which joint and gap to use when you split a model too big for your bed. At the default settings the card is 109 x 43 x 5 mm, with gaps from 0.10 to 0.30 mm per side in 0.05 mm steps. Three keys (C-joint, dovetail and dowel pin) drop into each socket from above, and every socket is engraved with its gap. Sliders set the smallest gap, the step, the number of gaps (4 to 6), the neck width (4 to 8 mm), the coupon thickness and the dowel diameter. It prints flat with no supports: about 15 g of PLA in

4 parts · 15 g · 109 × 69 × 7 mm

by Loftsmith Workshop

C-joint vs dovetail vs dowel tolerance test for split prints
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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

  • card · PLA · Flat, engraved labels up

    109 x 43.2 x 5 mm at the defaults, about 12 g and 20 min. C sockets on one long edge, dovetail sockets on the other, dowel holes in the middle. Columns go from the tightest gap (left) to the loosest. Socket mouths have a 0.4 mm bed chamfer so elephant's foot does not close them up. Print it in the m

  • key-c-joint · PLA · Flat, the 'C' label up

    Round head (neck + 5 mm across) on the neck width you set. About 1 g.

  • key-dovetail · PLA · Flat, the 'V' label up

    Dovetail with 15-degree flanks, as narrow as the neck where it meets the shoulder. About 1 g.

  • key-dowel · PLA · Flange down (the script rotates it for you)

    Dowel pin with a grip flange and a chamfered tip. Under 1 g.

Print settings

Layer height
0.2 mm
Walls
2 walls (default); joints behave the same with 3
Infill
15%
Supports
None
Notes
All four parts together: about 15 g and 39 min at 2 walls / 15% infill (engine estimate). At 3 walls / 15%: about 21 g and 52 min. Use the same layer height, flow, and elephant's-foot compensation as for the model you will split. A gap only transfers if those match.

Assembly

  1. Print the card and the three keys. Don't sand or clean up the sockets, because the test is how they come out of the printer.
  2. Starting from the left (tightest) column, press the C key straight down into each C socket on the upper edge until its shoulder meets the card edge.
  3. Do the same with the dovetail key in the sockets on the lower edge, and push the dowel pin into each middle hole.
  4. For each joint, note the tightest column that goes in fully by hand without forcing. That is the per-side gap engraved above the column.
  5. Use that gap when you model or cut the joint in your split model (the gap goes on every side of the tenon; the total clearance across the joint is twice the label).

Good to know

  • Labels give the gap on each side of the joint in mm. Slicer cut tools label their tolerance field in different ways, so check how yours defines it before typing the number in.
  • This card tests fit only. It does not measure joint strength. Any strength comparison between C-joints and dovetails comes from published studies, not from this model.
  • Sockets run through the card's thickness, so this tests joints whose profile is drawn in the XY plane. A joint printed lying on its side will fit differently because of layer stepping.
  • Results depend on your printer, filament, flow and elephant's-foot settings. Reprint the card if you change any of them.
  • The engine checks the geometry: keys clear every socket, and the C head and dovetail still lock at the loosest gap. It has not been printed or tested on a real printer.
I printed this Remix

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