Testing Brass Heat Insert

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parkview
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Testing Brass Heat Insert

Post by parkview » Sun Jun 28, 2015 10:40 pm

I had been reading about how people have been using brass inserts as embedded bolt nuts in PLA/ABS housings. I had to give it a go, as it looked a neat and professional method of joining two 3D printed surfaces together. I ordered some M3 brass inserts from dx.com, but at the time, they had a limited range to choose from. I placed it on my shopping list for Shenzhen and yes, while they where not popular item, I did find a few stalls that sold them. They where very kind in opening a bag of 5,000 and counting out a hundred pcs for me:

bolt and brass insert stall - Shenzhen.jpg
bolt and brass insert stall - Shenzhen.jpg (72.97 KiB) Viewed 10639 times


To test it out, I quickly whipped up a test block of PLA, using holes the same diameter as the smooth part of the outside diameter of the brass insert. I initially made the hole 0.5mm deeper that the insert, but made it 1mm deeper so as to collect spare molten PLA. I also added a 0.5mm inset lipp to help stabilise the insert before melting it into place, but it could have been a bit wider and a bit more deeper:

Brass Insert Test rig - 3D Printed.jpg
Brass Insert Test rig - 3D Printed.jpg (21.22 KiB) Viewed 10639 times


I ended up with a range of M2, M3 and M4 brass heatset inserts to play with. Unfortunately, I don't have the correct insert attachment for my soldering iron, so I just tried turning the iron up and perching it carefully on top of the cut off bolt:

inserting the brass insert.jpg
inserting the brass insert.jpg (53.72 KiB) Viewed 10639 times

parkview
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Re: Testing Brass Heat Insert - 2

Post by parkview » Sun Jun 28, 2015 10:57 pm

This is the range of brass inserts that I have picked up:

M2 M3 and M4 Brass heat inserts.jpg
M2 M3 and M4 Brass heat inserts.jpg (59.36 KiB) Viewed 10638 times


It's tricking trying to heat them up so they melt evenly into the PLA. Even with a hole below the heated brass insert, they had a tendency to slip off to the side. I had pondered this when I designed up the test block, so I made sure to increase the wall thickness to be four layers deep. Admittedly, the infill was set to 20%, so that doesn't help. I have since read that someone was recommending that you have a 2mm solid wall around the insert, at four layers deep around my walls, I was no where near his recommendation.

Also, don't push hard on the brass insert as it's melting into the PLA. I did on a few of them and it deformed the plastic into a crater shape. I thinks it's best to just let the heat do it's work. It's hard to see it into the small image above, so i have added some arrows to help show the deformations and I will bring them along to the July meeting.

ToDo:
  1. Get someone to machine up a metal M2, M3, M4 bit to fit my soldering iron and the brass inserts.
  2. ditch the long M3 brass insert. It's not needed and it's too long.
  3. more practice

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BeJay
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Re: Testing Brass Heat Insert

Post by BeJay » Tue Jun 30, 2015 10:53 pm

Good research Paul,

I just hit the iron on a M4 nut and sink it into position. Works well on PLA, but ABS can get a bit tricky..

My latest creation that needed this was our soap holders..

Image

Image

parkview
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Re: Testing Brass Heat Insert

Post by parkview » Wed Jul 01, 2015 8:53 pm

Ah, but how do you stop the plastic from filling up the nut hole? Using a Soldering iron directly on the brass insert was the first thing I tried, but I quickly found that plastic flowed up through the bottom, and up into the bolt space:

flowing plastic example.jpg
flowing plastic example.jpg (6.72 KiB) Viewed 10629 times


I tried using a cut down bolt to block that, but I have trouble with the lack of heat flow from the iron onto the bolt, onto the brass insert. Of course, that's why you can purchase special soldering iron tips to match each brass insert.

I don't have a lathe, but I am thinking of getting someone to make up same samples for me. It wouldn't take long, or do it my self if I was allowed on the lathe. Unfortunately, I don't think the proposed Makespace will have room for a wood and metal lathe :(

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BeJay
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Re: Testing Brass Heat Insert

Post by BeJay » Wed Jul 01, 2015 9:48 pm

I used the bolt in the nut trick (M5), and my Hakko 926. Worked a treat at 450oC

parkview
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Re: Testing Brass Heat Insert

Post by parkview » Wed Jul 01, 2015 10:35 pm

Yes, the same as my no. 2 attempt. Well, bolstered by your blog post, I have stripped down my Hako 936 soldering iron, and measured up the tip. I might check out the local Men's Shed this Sat. to see if I can make up a special M2 & M3 tip. It doesn't look that difficult to make up.

Thanks.

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Re: Testing Brass Heat Insert

Post by parkview » Thu Jul 02, 2015 10:22 pm

I discussed this with an Engineer at work. He wondered if I could use a nail that was inserted into a cheap screw down soldering iron. Bingo! :idea:

This evening I pulled out the draws of nails and screws and dug up an my first non regulated soldering iron. It didn't have a screw down soldering bit. This one had a copper bit that actually screwed into place. It turns out the inside diameter was a clean 4mm.

It didn't take long to find some recycled steel screws with a 3.95mm straight shank. I also found a nail that fit inside a M3 brass insert with 0.2mm spare:

ready to weld screw-to-nail.jpg
ready to weld screw-to-nail.jpg (44.2 KiB) Viewed 10626 times


Now I just had to some how join the two together and cut to size. The best I could do was have a go at using an old home ark welder. Perhaps having 15yo rods didn't help. I played around with a few tests trying to weld two nail heads together. Just not enough hands.. After 3 goes, I managed to join/tack the nail and screw shank together. It's no where near perpendicular, but in a pinch, it does the job nicely and cleanly:

ready to insert brass insert.1.jpg
ready to insert brass insert.1.jpg (14.46 KiB) Viewed 10626 times


clean_insert.jpg
clean_insert.jpg (19.07 KiB) Viewed 10626 times


Success! :)

I am not going to bother trying to arc weld a 1.5mm nail to a 4mm screw shank for my M2 brass inserter. Ideally, a gas welder would do the job cleaner and easier. I will keep an eye open for one.

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Re: Testing Brass Heat Insert

Post by parkview » Thu Jul 16, 2015 10:06 pm

I woke up one morning and I realised that I hadn't tested to see what kind of thread the old 1970's soldering iron might be using. Sure enough it was one that a common 3/16" bolt would screw into. I just happened to have a bag of long bolts.

Stephen was kind enough to turn down three of them to fit the M2, M3 & M4 brass inserts. This evening I cut them down to size and tested them out:

New Brass Insert Tools.jpg
New Brass Insert Tools.jpg (228.72 KiB) Viewed 10624 times


Sure enough they fit perfectly and they are nice and easy to use and as long as the soldering iron is vertical, the resulting bolt should be too.

PS. Bunning's are currently sell cheap screw down (not in like my old one) soldering irons for $29 - $35.

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Re: Testing Brass Heat Insert

Post by parkview » Fri Mar 01, 2019 11:34 am

Hack-a-Day posted an article about using Brass Heat Inserts: https://hackaday.com/2019/02/28/threadi ... t-inserts/

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