Introduction: Improving 3D Printed Gears

Picture of Improving 3D Printed Gears

Here is a quick method of improving 3D printed gears using hot melt inserts. I have always found the failure point of 3D printed gears to be the nut trap method of shaft clamping. The hub usually breaks when you are trying to apply enough force to secure the shaft with the set screw.


  • 5mm hot melt insert
  • 5mm bolt ~30mm
  • 3d printed gear with well for hot melt insert
  • Drill bit ~5mm
  • 5mm Reamer (optional)
  • 3mm tap
  • 2.5mm drill bit
  • Soldering iron

Step 1:

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Step 2: Insert the Insert

Picture of Insert the Insert

Using the tip of your soldering iron, slowly heat up the insert and press the insert into the gear until it is flush. Be careful not to get the insert to hot.

Step 3: Keep the Insert Straight

Picture of Keep the Insert Straight

Quickly before the hot melt insert cools, screw the 5mm bolt into the insert from the opposite side of the gear. This will help keep the insert concentric to the shaft.

Step 4: Make the Bore the Correct Size

Picture of Make the Bore the Correct Size

Using the 5mm drill and optional 5mm reamer, drill through the gear from the back side to increase the bore to 5mm.

Step 5: Set Screw

Picture of Set Screw

Through the set screw hole drill through the insert with the 2.5mm bit.

Follow this with a 3mm tap for the set screw.

Step 6: Conclusion

This is quick and easy. It only takes a few tools and can be completed in about 2 minutes.

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gravityisweak (author)2017-08-07

What type of gear is that with the teeth shaped the way they are? Does that design keep the gears aligned?

They are called Herringbone gears. They have the advantage of transferring power smoothly because more than two teeth will be in mesh at any moment in time

NeilRG (author)2016-10-24

I use these

Nikus (author)2016-07-10

Great! Where can I buy hot melt insert?

DylanD581 (author)Nikus2016-07-15

Sparkfun and Adafruit used to sell these - not sure if they still do.

TigerPilot (author)Nikus2016-07-14

You can also get them on eBay. Search for 'Knurled brass insert'

Solidus_Labs (author)Nikus2016-07-10

I purchased mine from

They are also named ultrasonic inserts.

DylanD581 (author)2016-07-15

Does the hot melt insert provide a very strong mounting point? I've been thinking about incorporating this into some of by 3D printing designs.

DIY Hacks and How Tos (author)2016-07-09

Great idea. This makes me really wish that I had a 3D printer. I could make some really nice gear boxes.

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