Aligning holes for a screwed-together lap joint

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Frotz
Posts: 105
Joined: Thu Jun 21, 2018 1:52 am

Aligning holes for a screwed-together lap joint

Post by Frotz »

Suppose I have two squares of metal. One is $foo squared while the other is $bar squared where $foo != $bar. I want to join these along a narrow strip in a lap joint to be secured with screws going through both squares. Doing this by hand with physical pieces, I would to first align the holes, then get the two facing planes to coincide. In other words: insert screws through the holes, add nuts, then tighten.

I've figured out how to align screw holes by first going to the Draft workbench. Then set snap lock and snap center to on. Then press M V (or click the blue Move icon) to start the move process. I thus aligned the two sets of holes, but the two sheets are embedded in each other halfway. The next step I see is to back off the two sheets until the two facing planes coincide. I did that by unsetting snap center and selecting snap near. Then viewing the two sheets on edge, I got the two facing planes coinciding. The two planes coincide, but one of the edges of the first square is made flush with the edge of the other -- the alignment of the screw holes is ruined. I figure that if I could somehow restrict movement to a single direction, I could get the two pieces aligned correctly, but I can't discover the magic combination of snaps.

What am I getting wrong here? Is there an easier way to go about this?

Code: Select all

OS: Debian GNU/Linux 11 (bullseye) (MATE/lightdm-xsession)
Word size of FreeCAD: 64-bit
Version: 0.20.28884 (Git)
Build type: Unknown
Branch: master
Hash: cd53c06b9899b03fe88d2a2fe8258422e7ac9c09
Python 3.9.2, Qt 5.15.2, Coin 4.0.0, OCC 7.5.1
Locale: English/United States (en_US)
Installed mods: 
  * sheetmetal 0.2.49
  * kicadStepUpMod 10.12.0
  * fasteners 0.3.41
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thomas-neemann
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Re: Aligning holes for a screwed-together lap joint

Post by thomas-neemann »

Frotz wrote: Tue May 17, 2022 12:32 am ...
here are 2 examples with aligning parts by holes


https://www.youtube.com/watch?v=IX2Zv8VszIQ


phpBB [video]






https://www.youtube.com/watch?v=FT-CeNRj_Nc

phpBB [video]
Gruß Dipl.-Ing. (FH) Thomas Neemann

https://www.youtube.com/@thomasneemann5 ... ry=freecad
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Roy_043
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Re: Aligning holes for a screwed-together lap joint

Post by Roy_043 »

Frotz wrote: Tue May 17, 2022 12:32 am but the two sheets are embedded in each other halfway.
This means that you have snapped to the center of a cylindrical face for one point, and the center of a circular edge for the other.

Assuming the plates are plane-parallel, you should be able to accomplish the job using Draft_Move (and perhaps Draft_Rotate) relying only on Draft_Snap_Center. In general Draft_Snap_Near should be avoided, See Draft_Snap.
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