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I want a thread in a part, but I want something a lot more DURABLE and accurate than what I can print.
So, how to embed a stainless steel nut in the face of a part ?
and does molten ABS stick to stainless steel ?

One way would be to make it the bottom face when printed, lay the nut(s) onto the glass and print around/over them.
Problems;
a) requires very precise agreement between where I place the nuts and where the printer assumes them to be
b) limited to the bottom face, not a problem for the part I'm considering but not a good general solution
c) the height of the nut means the nozzle would hit it, I think this is the show stopper.
...hmmm, printing around the nut(s) is probably impractical, although I would like to hear from anyone who has succeeded with this.

Another way would be to just leave hex cavities and somehow "glue" the nuts in later.
This reduces it to a mere "adhesives problem", so is there a practical method for "gluing" ABS to stainless steel ?
Problems;
Slightly rounded corners in the hex cavities means I either have to do clean up to cut them out or make them a bit oversize.
Either way whatever adhesive I use would need to have good filling properties for any gaps.

This is for a few parts, not any sort of volume, maybe 3 to 6.

PS
3/8" x 16TPI nuts for THIS project, so neither tiny nor huge, but a general solution would be nice to have.

Some people use things like these:
http://www.ebay.com/itm/20pc-Metric-Sta ... 1e8cbd3042

They are inserts that you thermally heat up and push in to your ABS part.

I suppose you can do the same thing with your nuts. Generally the DIY crowd uses a soldering iron. However i have heard of small blowtorches being used, the nut is inserted on to the bolt which is held by means of pliers or welding gloves to protect your hands. The nut is heated by some means and then pressed in to the plastic. A cold and flat surface is ready near by, and the whole part is pressed on to that to level any bulge of molten ABS the insertion process has created.

Look up berry bot or barry bot on youtube. He has a nice tutorial on this.


PS: Personally i have some inserts M2 M3 and M4 that i have not yet utilized myself. This is just data i have accumulated for when the need arises.

Thanks, I was familiar with those from "a previous life", they would be useful to have around for other projects anyway.
Since posting I have thought about dissolving some ABS filament in acetone, the exact mix would take some experiment and it probably takes a while to dry out.

This is what you need right here....heat set inserts for plastic. They are made of brass, not stainless though.

http://www.mcmaster.com/#heat-inserts/=ui9av7

You can also design a slot into your part, then press fit the nut into it. Or you can make a circular groove around the nut and use a retaining ring. If you make a hex cut into the part for the nut to fit into, just draw small circles on each corner of the hexagon to prevent radii from getting in the way. If you use a small enough nozzle, the radii can actually help secure the nut.

If you have some taps for the size you need, I found that printing an undersized hole and tapping threads into it makes very, very strong threads, especially with nylon. Just print the part hot enough to get good layer adhesion. Using steel inserts means that the threads won't break, but the insert can break the plastic around it or even pop out of place under too much force.

I make stuff that's designed to capture hex nuts sometimes. There is also the option of using a tap and die set to thread your own printed stuff. However, you may not need to for some parts, especially if they don't have to be super-strong. I have printed planetary gearsets with threaded bolts and nuts, and they actually do screw together really well as long as your filament flow is just right for the model. It can take a few test prints to figure that out, but it is pretty good when it works right. I don't know whether PLA or ABS is better for threaded stuff, but I do all mine in PLA and it holds up quite well.

I've ripped threaded inserts out of injection molded PA-66, so they certainly aren't bulletproof, but they are very strong and are probably the strongest way to place threads into a printed part. I've also had good results even with relatively fine pitch machine screws simply threaded in a slightly undersized hole. If you have a tap set I'd probably give that a try first since you don't have to buy anything. If that's not strong enough for your application then thermally inserted inserts are probably your best option.

NETio wrote:I've also had good results even with relatively fine pitch machine screws simply threaded in a slightly undersized hole.

This is my preferred method for a cheap and simple solution that doesn't take much load.

I am no expert but saw this article and thought it might help give some ideas.

http://formlabs.com/en/company/blog/201 ... ted-parts/