What should be the hole diameter (tolerance) at a given (fixed) diameter of the shaft, to mate the head of the tripod and the guide shaft? For example, shaft diameter is 20mm. Material of head detail: aluminium 6082, and shaft material - stainless steel.(not polished)

For example, to mount vertically a focus arm holder head on guide shaft, something like in this pic ..........

  • $\begingroup$ Depends if you want it permanently fitted, a friction fit or a sliding fit or like a pr*ck in a bucket. $\endgroup$
    – Solar Mike
    Commented Sep 4, 2022 at 15:16
  • $\begingroup$ Of course, the head must allow movement along the guide post, up and down, and be reliably fixed at the desired height with a side screw. $\endgroup$
    – Lexx Luxx
    Commented Sep 4, 2022 at 15:50
  • $\begingroup$ @DKNguyen Sounds like a good answer to me. Perhaps you can post it as such. $\endgroup$
    – Eric S
    Commented Sep 5, 2022 at 3:44
  • $\begingroup$ Note the flat on the shaft so that damage by the screw doesn't cause interference with the hole. $\endgroup$
    – Transistor
    Commented Sep 5, 2022 at 5:12

1 Answer 1


For steel the difference is 0.0002"-0.0003". If the hole is undersized or shaft is oversized by this amount it is a press/interference fit. If the hole is oversized or the shaft is undersized by this amount it is a slip fit but this kind of slip fit is tight enough that unless you have a way to apply force squarely and evenly, it will tilt and jam.

If the shaft is undersized or hole is oversized by 0.001" you can start to feel slop. Get a micrometer and set it to the shaft diameter and open it up by the amounts listed and pull the micrometer along the shaft to get the feel.

I would try and aim for the hole oversized or shaft undersized by 0.0005"-0.001".

  • $\begingroup$ Is the same true for aluminium head? $\endgroup$
    – Lexx Luxx
    Commented Sep 5, 2022 at 18:02
  • $\begingroup$ @LexxLuxx I've never tried to get that same fit in aluminum. But still probably within 0.001" clearance for slip fits since you're not trying to deform material and squeeze one material into another like an interference fit which makes material hardness or pliability matter. Get a micrometer that can measure 0.0001". $\endgroup$
    – DKNguyen
    Commented Sep 5, 2022 at 18:47

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