Archive for July 2015

Generating holes for countersunk screws in FreeCAD

Update 1 Aug 2015: Add option for countersunk holes to be matched to a selected screw type

When working with countersunk screws in FreeCAD there is usually a need to pass over all the screw holes and add a recess/chamfer to the holes to match the countersunk screw.

This process can be rather tedious to do manually. For this reason and by requests from users I have added a “Make countersunk hole” function into the Fasteners Workbench. If not yet installed, see installation instructions here.

How to use:

Prepare a part with adequate holes for screws. For the automatic sizing to work, the holes should be based on the desired screw diameters. (For example for M5 screw, prepare a 5mm hole. You can also place a 4.2mm hole for holes that supposed to be tapped)

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Select the desired part and press the “Make countersunk” (fscsicon) button in the toolbar. A task dialog will appear on the left:

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The dialog will show a list of possible circular edges that can be chamfered to accommodate countersunk screws.

Move you mouse over the part and select the desired holes you want to put screws in. Select the top edge of the hole. You can select holes one by one (no need to press CTRL) or you can click on a face and all holes in that face will be selected. Each selected edge will be checked in the Dialog list, and automatic screw diameter will be selected. You can also check/uncheck edges directly in the list – but in this case no automatic sizing will occur.

When finished, Click the OK button at the top of the dialog. (This process is very similar to creating standard chamfers/fillets). For each selected hole, a chamfered recess matching the screws will be created:

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This process is of course parametrized. So if the result is not satisfactory, you can simply double click on the created Countersunk and you can edit the parameters. For example you can change the countersunk diameter by double clicking on the desired diameter, and selecting a new one from the combo:

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It is also possible to change the diameter for all the selected edges by selecting the new diameter from the bottom Diameter box.

Click OK when finished. The Countersunk part will be updated:

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Now let’s add some screws. Select the top edge of the new chamfered holes. Multiple selection can be done by pressing and holding the CTRL key. Click on the desired countersunk screw from the toolbar. A matching screw for each hole will be placed.If some screws came out upside down, select them and use the Invert(fsinverticon) button to flip them back:

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Note: Countersunk screws are matched by their head diameter and other screws are matched by their body diameter.

Have Fun!

SHS