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Makign holes for M4 Heat Set Inserts  

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Tango
(@tango)
Estimable Member
Makign holes for M4 Heat Set Inserts

I need to put in some heat set inserts for a project (which will be duplicated several times). I just want to make sure I'm using a good size in my modelling for the inserts. As best I can tell, it looks like M4 inserts are standardized, not just on the inside for diameter and threading, but on the outside, too. First, I've noticed some people seem to be putting inserts into one side of a piece and the screw goes into the same end. This seems to me to be a weaker way to do this and I would think this way, in the sketch below, is a better way: Have the screw go in from the OPPOSITE side of where the insert goes. Am I right about this and, if not, are there any issues to watch out for if I do it this way?

Second, I'm wondering about the size of the insert and the hole I make for it:

This is a rough sketch and I really should have marked the hole sizes with a prime on them to avoid confusing each one with the measurement of the insert itself. I also realize my sizes for the hole may be off. (The sketch on the side is for my reference and comparison, so you can ignore that.)

I haven't been able to find any page that says, "This is the size you need for a hole for an M4 heat insert." So are my measurements for the hole on target or close? Or what measurements should I be using for the hole for an insert?

Posted : 19/12/2023 10:14 pm
JP Guitars
(@jp-guitars)
Estimable Member
RE: Makign holes for M4 Heat Set Inserts

Part of the heat set inserts has no texture on it, ideally the hole for the insert should be the right size for that part so you can fit it in the correct position then heat it.

Regarding what side, it should not make much difference. If you need the full thickness of the holding object you will have either gone under sized, used too few or have insufficient perimeters, as they should not be taking huge loads. And if you put it in from the back there is a chance molten plastic could block the thread, although that has not happened to me.

Posted : 19/12/2023 10:25 pm
Netpackrat
(@netpackrat)
Reputable Member
RE:

I have sometimes done as you suggest, put the insert in from the opposite side to maximize resistance to pull-out, when the part geometry has allowed (or required) it.  For a given thread size, you can find inserts with multiple outside diameters (and of course lengths), so you need to design for what you intend to use.  One of the popular insert assortments on Amazon uses smaller than typical OD, and since I have those inserts that's what I normally size holes for.  On models I have posted to Printables, I usually include a link to the inserts intended, and/or advice to drill the holes out slightly for use of bigger inserts.  As long as enough perimeters and top/bottom layers are used, it shouldn't pose a problem and it's generally easier to drill out a hole that's slightly too small, than order the larger OD inserts and wait.

IMO you are overthinking your hole geometry. Just shoot for a cylinder the OD of the pilot portion of the insert, a little deeper than the depth of the insert, with a slight chamfer on the outside rim.  Done.  If the screw length will protrude past the threaded insert, make the hole deeper as needed.

Posted : 20/12/2023 2:29 am
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Makign holes for M4 Heat Set Inserts

For a given thread size, you can find inserts with multiple outside diameters (and of course lengths)

So there is no standard size, then. M4 tells me about the inner diameter and the thread size and space, but does NOT tell me about the size of the insert, so the insert exterior dimensions are not standardized. Am I right about that?

Just shoot for a cylinder the OD of the pilot portion of the insert

I'm not sure what you mean by "pilot portion."

a little deeper than the depth of the insert

This is the kind of thing I'm finding confusing. It sounds like you're saying to use the same diameter for my hole the OD of the insert. Is that correct? But everything I find gives vague information, like "a little deeper than." What is "a little deeper" in terms of numbers I can use in my modelling program?

You say I'm overthinking, but I'm just trying to get an idea of what size hole to make in the model I create to use this. I get, now that there is no standard size, but I have no clue how big to make the hole compared to the size of the insert. For instance, should I be trying to make the hole the same diameter as the insert? From what you say, I think that's the case.

 

 

Posted : 20/12/2023 5:30 am
Neophyl
(@neophyl)
Illustrious Member
RE: Makign holes for M4 Heat Set Inserts

No there is no standard on the inserts.  I've not used M4 heat set inserts but I've used loads of different M3 ones.  Every manufacturer will have their own profile (cross section), usually multiple different ones for different tasks.  For M3 I have had outside diameters ranging from 4mm to 5.6mm.  

Quality ones from a good manufacturer will also have data available on the profile required for the holes too and not just dimensional specs of the insert.  That greatly aids in design as it takes guesswork and trial and error out of it.  Even with such data its best practice to print a small test part as our printers and filament do vary in tolerance so we might need to tweak the manufacturers ideal for our process, especially as they spec for injection moulded parts.

Many of the insert profiles start with a small straight shoulder section to aid insertion and then swell out to the grooved diameter.  Some then also have a small lip.  Cheaper ones sourced from the usual places are often just cylindrical with grooves starting immediately (often with a small band around the middle).

So I took Netpackrat's comment on just make the diameter of the hole to be the same as the start shoulder for simplicity.  Do not do the hole the same diameter as the insert.  There will be little to no interlock.  After all the idea is to melt the plastic out from the hole walls so it flows into the grooves to give a good mechanical join.

That's also where the 'little extra' at the bottom comes into play.  There are no firm rules, as you insert it the plastic will have a tendency to be pushed ahead of the insert and so not flow into the grooves but end up below the insert.  That's a problem more seen on the cheap ones as the grooves start immediately.  Some makes it upwards into the grooves, but not all.  Of course that also depends on how tight a tolerance the hole has.  The tighter the hole the more likely it wont make it past the leading edge and back up the hole.  Insertion technique and speed also plays a role there too.  Insert slowly and more plastic can make it into the grooves, insert fast and you will get more below the insert.  It is all based of the physics of plastic flow, just like our extruders.  So temperature, plastic type, insert geometry etc all interact.

That's why doing it through hole with the screw pulling the insert into the part is not usually done.  Its easy to get a build up of plastic that blocks your holes.  Too much and the plastic also backs up into the threads making the insert useless. The plastic has to go somewhere.  If you are doing that then why even both with an insert ?  Just model a hexagonal hole for a normal nut, or a square one for a square nut and press fit in.

 

Posted : 20/12/2023 7:04 am
Netpackrat
(@netpackrat)
Reputable Member
RE:

Basically, what Neophyl said.  All of the heat-set inserts I have used have looked more or less like this:

 

 

Note the pilot diameter at the end of the insert, where it is inserted into the hole (bottom on the picture). Size the hole in your printed part such that this initial diameter is a tight slip fit or a light drive fit.  When the insert is installed, this will aid in getting it in straight, and hopefully prevent too much material from being pushed ahead of the insert as Neophyl described, where it could potentially get into and foul the threads.

 

Posted by: @neophyl

That's why doing it through hole with the screw pulling the insert into the part is not usually done.  Its easy to get a build up of plastic that blocks your holes.  Too much and the plastic also backs up into the threads making the insert useless. The plastic has to go somewhere.  If you are doing that then why even both with an insert ?  Just model a hexagonal hole for a normal nut, or a square one for a square nut and press fit in.

The most recent part I designed using the insert installed from the side opposite the screw, there was not sufficient distance between the hole and the edge of the part to allow for a normal nut.  The part could not be made any larger because the whole assembly had to fit inside a cavity also of fixed size, and the hole location was likewise set by the purchased component that mounted there.  It's possible that a square nut could have worked, but I didn't have any M5 square nuts, and I did have M5 inserts.  Also, since I went to the trouble of making an insert press, I want to use it.  🤣 

Posted : 20/12/2023 9:05 am
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Makign holes for M4 Heat Set Inserts

I wrote a reply last night, but it got eaten and I don't see it here now.

No there is no standard on the inserts. 

Thank you for a direct confirmation!

Quality ones from a good manufacturer will also have data available on the profile required for the holes too and not just dimensional specs of the insert.

Do you mind sharing names of a few manufacturers who do this so I can start with a reputable source? Or even links to some of their products? (I know you're using M3, but I figure the companies you like will have M4s as well, of course!)

Even with such data its best practice to print a small test part

Always - I'm just trying to start my test prints with a good idea of what I'm doing, rather than starting them blindly by going with specs as "a little deeper," or "a small amount," or anything else that leaves me guessing what to do.

Do not do the hole the same diameter as the insert.

Thank you for the clarification!

Insertion technique and speed also plays a role there too.

This and the other tips on what to watch for are also much appreciated.

That's why doing it through hole with the screw pulling the insert into the part is not usually done.  Its easy to get a build up of plastic that blocks your holes.

I had been thinking of a few possible ways to handle this, such as putting the screw in the insert and touching the soldering iron to the screw. It'll take longer for it to heat up, but if I can make the screw protrude through the end going in first, it could help - but that could also lead to plastic getting in the threads of the protruding screw and locking it in place where it stands.

If you are doing that then why even both with an insert ?  Just model a hexagonal hole for a normal nut, or a square one for a square nut and press fit in.

Several reasons. One (not the most important, though) is this is a good chance for me to learn about putting in inserts and practicing with them. The other is that this is for a wall plate and this particular part, with the inserts, goes inside the wall, on the other side of the drywall. So it's hard to get to and it'll be hard to make sure I can put a nut on the tip of my finger and slide it in place where I can't see it and where it'll likely end up dropped into the wall. Nuts aren't expensive, but this can still be a pain to deal with. I've thought about using painter's tape on the back side to hold a nut in a recess I print for it, but it's possible the screw could push it out of place before the thread catches on the nut and keeps it from slipping out. (I'm also concerned about using glue to hold it in place - since glue could clog up the hole for the screw.)

I have been thinking about leaving a slot for the nut, since I see that for an M4, the slot would have to be under 10mm, which a lot of sites give as the maximum bridge distance. (The nuts used for this would be parallel to the side sitting on the print bed when it's printed.) I remember seeing that done in the print head on my Prusa in at least one case. If there's an easier way to do this, I'm certainly open to it!

(Since the wall plate won't be bearing a lot of weight - just a few feet of 3" flexible conduit, I've also considered making the needed hole size in the wall a bit bigger so I can print my own screws, which would be plastic-on-plastic screws, which should hold this. I figure using metal screws in a plastic hole means they'll only work a few times if the plate has to be removed.)

All of the heat-set inserts I have used have looked more or less like this:

Thank you for the picture. Now I realize the ones I bought are not shaped like that and from what I'm seeing here, I did not get ones from a good manufacturer. As I asked neophyl, could you let me know who you find to be a good supplier or possibly post a link to a good example of an insert?

Note the pilot diameter at the end of the insert, where it is inserted into the hole (bottom on the picture). Size the hole in your printed part such that this initial diameter is a tight slip fit or a light drive fit.

Thanks! Enough specificity that it helps me figure out actual sizing!

The most recent part I designed using the insert installed from the side opposite the screw, there was not sufficient distance between the hole and the edge of the part to allow for a normal nut.

How did you make sure the screw hole was kept clear of plastic when you put the insert in?

Also, since I went to the trouble of making an insert press, I want to use it.

I know the feeling - plus, if you haven't done it before, there's the whole drive to learn and use something new so you can list it as a skill you may find helpful in the future.

Posted : 20/12/2023 5:30 pm
Netpackrat
(@netpackrat)
Reputable Member
RE: Makign holes for M4 Heat Set Inserts

Thank you for the picture. Now I realize the ones I bought are not shaped like that and from what I'm seeing here, I did not get ones from a good manufacturer. As I asked neophyl, could you let me know who you find to be a good supplier or possibly post a link to a good example of an insert?

I have bought a couple of these assortments just to have some to get started with:

https://www.amazon.com/dp/B0B46YBNV4?th=1

They seem to be of good quality, the only issue is that they have a smaller OD than others, so if you are printing models that others have designed, if they used a bigger OD insert, these may be too small.  In that case you would need to modify the part, or try to source the specific insert they used.  Another good option might be the CNC Kitchen inserts; I have not used them, but they appear to have a good reputation.

 

How did you make sure the screw hole was kept clear of plastic when you put the insert in?

With the part I described, I had a little trouble with this.  Fortunately the plastic didn't get into the threads, but there was some build up at the bottom of the insert which would have prevented insertion of the screw.  I carefully used a drill bit to clean the plastic out of the hole so the screw could thread into the insert.  One thing I could have done different would be to use a shorter insert, since a shallower insertion depth would have meant less plastic built up ahead of the insert.  But I was trying to maximize thread engagement, so I went with the longer inserts.

Posted : 20/12/2023 6:48 pm
Netpackrat
(@netpackrat)
Reputable Member
RE: Makign holes for M4 Heat Set Inserts

Posted : 20/12/2023 6:59 pm
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Makign holes for M4 Heat Set Inserts

I have bought a couple of these assortments just to have some to get started with:

https://www.amazon.com/dp/B0B46YBNV4?th=1

Thanks!

I had to run some errands since my last reply and, since we're a ways out from any shopping centers and so on, that gave me time to think things over while I was on the road. While it wasn't my first preference, I think, for this immediate project, I'll use printed screws for several reasons:

  1.  Even though you point out that drilling can be used to clear the bore hole for the screw, that can lead to problems and just makes things more complicated for a first project using inserts.
  2. I was thinking of just leaving slots in this part so I could slide nuts into place, but decided against it, since variations in printing could lead to some slots being tight, but even one loose one would be a problem, since a nut could fall out and be lost and it might be hard to keep a nut in any particular slot while trying to fasten them together with a screw.
  3. If I can't use metal nuts, I do not want to screw a metal screw into plastic, whether it's a self-taping screw or not. That leads to stripped threads after only a few uses, in case, for some reason, I have to dismantle things and put them back together. Since using metal nuts looks like it's going to be a real problem in this case, I'm going to have to use a printed and threaded hole for the screw, so I'll make it bigger and print my own screws.

While this means some redesign work, I think, ultimately, it'll make it easier to make. I like frontloading the work in the design phase if it saves time and material in printing - I do the design once, then often print it many times. If extra work once at the start reduces the work needed later, I see that as good.

BUT -

- with all that said, I think this is something I need to learn. So I'm still reading everything here and checking it all out. It may be a week or so until I can experiment with it, but I'm eager to add this to my list of tools I can use with printing, so, please, any other advice or info on this is still much appreciated!

Posted : 20/12/2023 11:09 pm
Netpackrat
(@netpackrat)
Reputable Member
RE: Makign holes for M4 Heat Set Inserts

 

Posted by: @tango
  1.  Even though you point out that drilling can be used to clear the bore hole for the screw, that can lead to problems and just makes things more complicated for a first project using inserts.

To be fair, I have incorporated heat set inserts into several models, and I only had that issue on one of them, probably because I was using an overly long insert in order to maximize thread engagement.  Another model I printed recently (not one of mine) had a recess for an M5 hex nut.  Probably because I printed it out of ABS and it shrunk slightly, the nut could not be easily inserted.  I ended up using my heat set insert press to install the nut, which worked very well.  So that's something to keep in mind too, if you are worried about plain nuts falling out of your parts.  There's nothing stopping you from making the fit a little on the tight side, and installing hex nuts almost as though they were heat set inserts.

Posted : 21/12/2023 2:42 am
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Makign holes for M4 Heat Set Inserts

I ended up using my heat set insert press to install the nut, which worked very well.

Again, asking as an ignorant newbie on this - could you include a pic of a heat insert press or a link to one? With the set I got, I have a tip for my soldering iron, no press.

There's nothing stopping you from making the fit a little on the tight side, and installing hex nuts almost as though they were heat set inserts.

I've thought about that, but I'm also aware that when you're working with a tight tolerance, like wanting to make sure nuts fit in a slot, but fit in tight, but you can't control the width or height of parts of a layer but so closely due to filament and print head nozzle sizes, I'm thinking I'd rather not depend on that if I don't have to. But it's also something I'm keeping in mind.

I see learning any kind of skill, like playing an instrument or 3D printing, as getting a bag and continually putting new tricks, tips, and techniques into that "bag of tricks." So, like I said, while I realized I won't be using inserts in this particular project, I do want to be sure I can use it in the future, since I can see it being incredibly useful. I am also incredibly thankful for all the help on this forum on this and other topics! (This and Blender Artist Forum, which I use for help in Blender for making my 3D designs, have proven to be two of the most helpful forums on the internet that I've found in years - and that's from someone who remembers having to ask for help for programming on Usenet!)

Posted : 21/12/2023 4:43 am
Netpackrat
(@netpackrat)
Reputable Member
RE: Makign holes for M4 Heat Set Inserts

 

Posted by: @tango

Again, asking as an ignorant newbie on this - could you include a pic of a heat insert press or a link to one? With the set I got, I have a tip for my soldering iron, no press.

I built the Adafruit press, but I don't really recommend it.  I had to do a bunch of fitting, and hand select the most oversize v-wheels from the pack I had purchased in order to take out the significant slop that it had, since the design has no provision for adjustment.  I modified the parts to use the inserts from the assortment that I linked in a previous post, and made a bunch of other changes to make the parts suck less.  As originally designed, several of them either didn't print well, or didn't fit the 2020 extrusion well.

https://www.printables.com/model/328130-remixalternate-parts-for-adafruit-heat-set-insert-

It works OK, but again I had to do a bunch of tweaking after the fact.  I see that the Voron community now has the "Stealthpress" out, and if doing it again I would maybe try building that one.  Or maybe buy Naomi Wu's insert press, since I seem to be using inserts a lot.

Posted : 21/12/2023 5:07 am
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Makign holes for M4 Heat Set Inserts

I built the Adafruit press, but I don't really recommend it.

Thanks for the warning and issues about it!

I also looked at the commercial one (by Naomi Wu) and it's nice - costs a bit, but if I get to the point where I'm doing production and selling what I print, I'd go for that. I was envisioning something a little different than just a basic drill press, so thanks for giving me a good idea what they look like.

Posted : 21/12/2023 5:15 am
JP Guitars
(@jp-guitars)
Estimable Member
RE: Makign holes for M4 Heat Set Inserts

Honestly, in my opinion you are over thinking it. In reality they are not that hard. Make yourself a test block and try setting a couple of inserts into it (you can cut them out and reuse after), that will show you how easy they really are

Posted : 21/12/2023 8:54 am
fuchsr and Netpackrat liked
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Makign holes for M4 Heat Set Inserts
Posted by: @jp-guitars

Honestly, in my opinion you are over thinking it. In reality they are not that hard. Make yourself a test block and try setting a couple of inserts into it (you can cut them out and reuse after), that will show you how easy they really are

Getting a starting point and knowing which way to go in size (like making them smaller or bigger than the insert) is a big issue. Also, bluntly, I save a lot more time by asking questions like I have here and having time to think about it while driving or exercising than by starting the trial-and-error process without knowing where to start. I'm also learning a lot from those providing details and background on what they're doing and that will help me, too.

So overthinking? No. I'm making sure I understand the process. I spent years working as a special ed teacher and learned that every person has a different learning style. Some people jump in without knowing what's going on and some need to have the information in their head so they can arrange it as needed when they start doing their trials. I used to be a "jump in and figure it out" kind of person, but then I found that gathering information and analyzing it first saves me a lot of time and money. That "overthinking" you're talking about saved me tens of thousands when we built our house and renovated our barn and even in smaller things like this, I find it helps me know what I'm doing from early on.

Posted : 21/12/2023 4:24 pm
JP Guitars
(@jp-guitars)
Estimable Member
RE: Makign holes for M4 Heat Set Inserts

Yeah, but we are not talking about building a house. We are talking about heating up a bit of metal on a soldering iron then pushing it into a lump of plastic. It took me less than 30 seconds to learn how to do it, and I did it on a model I wanted not a test piece. If the hole is a bit too small or a bit to big it will still work. You've been talking about it for two days. There is just not the amount of complexity in the process that you seem to think. My post ten minutes after your first post gave you adequate information to get on with it.

At some stage you have to just do it and no amount of thinking or discussing will make up for the experience doing it, which you could have done two days ago.

But it is your life, if you want to procrastinate even more, go for it.

Posted : 21/12/2023 5:01 pm
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Makign holes for M4 Heat Set Inserts

Yeah, but we are not talking about building a house. We are talking about heating up a bit of metal on a soldering iron then pushing it into a lump of plastic. It took me less than 30 seconds to learn how to do it, and I did it on a model I wanted not a test piece.

Okay, I'm trying to be polite here. I started trying to explain that I think differently and that I'm doing it differently because I'm doing what works for me. If this were about physical abilities, such as, say, climbing stairs, and I said, "I can't do it that way, I have to use a lift," most people would catch on and say, "Oh, he's got some issue that keeps him from walking up and down stairs, perhaps a disability," and most people would just leave it like that

I made it clear I know what works for me. Most people would just politely leave it at that, but the point is I have reading and learning issues. That's part of why I went in to teaching in Special Ed for a number of years. When I was a kid, there weren't SpEd classes except for the more obvious issues students might have, so I spent years struggling until I found out, "Oh, I AM different and I DO learn differently from others." I made it clear I know what works for me and didn't want to have to come out and say, "I have learning and reading disabilities," but apparently my attempt to say I do things differently was not enough.

I do not think like you do. Nobody does. Nobody learns like you do. We all learn differently and it took me decades to work out what works for me. So when I say, "My brain doesn't work like that," the polite thing to do would be to RESPECT THAT and NOT try to get me to think like you. I'm not trying to be disrespectful, but this reply would have been unnecessary if my point that I think differently had been accepted and respected from the start.

Posted : 21/12/2023 7:02 pm
JP Guitars
(@jp-guitars)
Estimable Member
RE: Makign holes for M4 Heat Set Inserts

I accept that you learn differently from me and everyone else, however in my experience of teaching I have frequently come across people who think that it possible to learn a physical act, as this is, by reading about, talking about it etc. Sooner or later you just have to do it and no amount of theory will help that, it could be today, tomorrow, Christmas 2024, until you actually try to do it you cannot take the next step.

Whether you agree with me or not, I am actually trying to help. You are exhibiting all the signs having a fear of taking the next step, something I regularly saw when teaching. I am trying to explain that the fear of doing something is often worse than actually doing it. We are talking about a very trivial thing here but I understand that can be scary, which is why I suggested making a trial object to give it a go, that way you are taking a tiny step towards your goal, which was the only way to deal with my students that were showing a reluctance to move forward. As you used an analogy I will use one as well. What you are doing at present is the equivalent to trying to learn to swim from a book and refusing to get in the pool.

Ultimately it is your choice, but you will never know if I am talking total BS or not until you try it. I hope you can find it in yourself to move forward.

That's it from me, I have said my piece so will not bother posting again.

Good luck.

Posted : 21/12/2023 7:38 pm
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Makign holes for M4 Heat Set Inserts

You know what? By rationalizing, you're just making it worse. Really. Just drop it. It was enough when you first said something. I get that you have good intentions, but it just keeps getting worse.

Posted : 21/12/2023 7:46 pm
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