Tapping a print


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Well-Known Member
Nov 20, 2020
Printed some Skiff drivers in petg, bottom 12mm are solid. Would a 1/4"-20 tap cut threads clean enough for a nylon thumb screw?
I would think so. 1/4-20 is a large thread size. I think it will take the form and hold. My son did some brass inserts in a project he was building. It came with an adapter to mount in soldering iron and you melt them in place. He printed a void in the area the screw went. Then melted them in. I would think you could do the same with the 1/4-20 for your tap hole.
I've tapped a lot of holes in 3D prints. Even 3 mm and 4-40 threads work. Don't expect high strength or wear resistance. Like Mike said, use inserts for those situations.

Lohring Miller
I also done both and had success with both. I've recently done some testing using a formed thread tap. IMO, I think they provide a tigher thread pattern in printed parts. The cut threads work, but they can have more runout when tapping by hand.
Another thing to note is that if you use a power tool to do this it will generate some heat.
All of mine have been 3mm threads. I found running the bit down and letting it cool down for 5 mins before retracting it back out made it considerably better than rushing and having the plastic get too hot.
You can actually 3D print threads. I've printed down to 1/2" coarse threads that just needed a little cleanup with a tap.

Lohring Miller
I use threaded inserts in my prints.
Works great!
Here is a link how to do :