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Many bicycle cranks have permanently assembled spindles on one side, as shown in the picture. This is a steel spindle inside an aluminum crank arm. I am not sure how these are manufactured. But I sometimes build custom cranks and I want to duplicate this because it might be easier to press together a joint than to machine a spline on both sides for a joint that technically never needs to be disassembled.

Given the moderate forces involved, do you think this can be done just with a tight press fit? Can you suggest tolerances for the hole and spindle?

If a press fit wouldn't hold, what if I use a retaining compound like loctite 680? enter image description here

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    $\begingroup$ Look up limits and fits - these are well documented. $\endgroup$
    – Solar Mike
    Commented Nov 13, 2020 at 6:57
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    $\begingroup$ You say "moderate forces" - have you quantified the forces? $\endgroup$
    – Jonathan R Swift
    Commented Nov 13, 2020 at 10:35
  • $\begingroup$ Look up shafts press fit into hubs and their retention forces. For a mostly hollow 1" diameter steel shaft in an aluminum hub with 0.001" interference you get about 3,600 psi of pressure at the interface. $\endgroup$
    – jko
    Commented Nov 13, 2020 at 12:39
  • $\begingroup$ You may be able to heat the crank, or cool the spindle and then slip fit (aka shrink fit). I would just do it and test one. $\endgroup$
    – Drew ♦
    Commented Nov 14, 2020 at 4:37
  • $\begingroup$ I used to race, and I have snapped cranks and bent pedal spindles on hill climbs. Back when I weighed 135 pounds, I could leg press 1000 pounds and calf curl 740 pounds. (21 inch thighs, 25 inch waist, really hard to find pants.) So I would look pretty hard at the cyclic loading issues. People make about the same peak torque as a school bus diesel engine. $\endgroup$
    – Phil Sweet
    Commented Nov 14, 2020 at 5:11

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