Encased thumbscrews M3, M4, M5

ISO 4014 & ISO 4017 hexagon head screws with encased thumbscrew head. M3, M4 & M5 are available up to 50mm in length. 

Updates:

2025-09-06: Filament change note added for Prusa Slicer

2026-09-19: Revision 2 Update. Assembly thumbscrews M3&M4 added. Oversized M4 Thumbscrews added.

1. Encased thumbscrews

1.1 Printing

Print without supports. You need to setup a pause (or filament change, read below) before the top bridging starts. During the pause, push the screw in with the help of the middle ring as shown on picture below. 

IMPORTANT: Prusa Slicer doesn't prime the nozzle during pause but does after a filament change. For this reason select filament change instead. Otherwise the nozzle can have low pressure caused by oozing and the first layer after the pause will fail to print properly.

1.2 Sizing and scaling

The fit around the screw should be tight so that the screw doesn’t fall in but needs a gentle push down. If this isnt the case right from the start, this means you might need to scale the model up or down to get good results. I recommend to use 0.5 or 1% increments.

There is a size range around 0.15mm where it works very well which well tuned printer can achieve, but if you add variance of the screw sizes between suppliers, making a sure fit solution is a lost cause, so there is about 50% chance you'll need to scale a bit. If the fit is too loose, you still get useful result, but not so satifying as the head will move. You can also scale Z direction separately as there tends to be large variance of screw head height or marking height.

1.3 Finishing

After the print is finished, cut off the support bit with a hobby blade in the weakspot. You might be able to just break it off by hand if you printed from PLA or PC.

2. Assembly thumbscrews

These do not look as nice fully encased thumbscrews but have 2 advantages - It is easy to achieve zero play on the thumbscrew head and they are much quicker to print in larger quantities.

2.1 Assembly

You will need an appropriate nut to tighten the head. The cap that covers the bolt head is push fit but it's better to secure it with glue.

Onshape source 1, 2

You can edit the fit from the variables tab.

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