How to go from self tapping to machine thread?

[Nicadraus 6748]

43 minutes ago, El Gecko said:

Oh HI! I'm so glad you decided to drop in and share your "expert" knowledge with us!

In fact, I do all of those things you mentioned above and have never had a problem with super glue.

I know you think I'm just some moron bush mechanic but you need to get off your high horse.

Super glue IS the answer if you want threadlock that DOESN'T destroy plastic.

Now explain to the class why we shouldn't use it.

Because the designers and engineers over at Tamiya, Kyosho, AE, Traxxas, X-Ray, HPI, HB, and the list goes on would've recommended it if it were necessary. 

If properly built and screwed on, you don't need super glue. Like I said, in all my kits, I've never used them and that is based on facts from experience not just  me but majority of RC modelers/builders worldwide. Now if you think you're better than us because we DON'T use super glue as you insist on here, then go ahead and shout it out loud and let's see who gonna look and sound silly.

Grow up. You're too stubborn. Stop being a joke.

[Willy iine 18842]

I’m a grown man that plays with little RC cars and some of my vintage M38’s use CA as thread locker as it arrived to me pre-stripped and my short 40+yrs experience with RC has proven that CA works safely as thread locker in these situations.  

I tried other adhesives too.. and like the Chinese Great Wall that Joe Wong spoke about, they don’t work.  

[El Gecko 1631]

1 hour ago, Nicadraus said:

Because the designers and engineers over at Tamiya, Kyosho, AE, Traxxas, X-Ray, HPI, HB, and the list goes on would've recommended it if it were necessary.

Thank you for reiterating your previous message. I understood it the first time. They don't recommend it because they are the ones who spec the hardware. If a Traxxas calls for a machine screw into plastic, that's what goes there and usually nothing else. You're not starting from the same initial conditions.

OP has already put self-tappers in, so even with the correct tap, there will still be voids in the material. The superglue (I use Gorilla brand superglue which is actually a CA type glue) helps fill those voids and provide more thread surface for the screw to mate with, as if it was done that way originally. It's not rocket science.

1 hour ago, Nicadraus said:

If properly built and screwed on, you don't need super glue. Like I said, in all my kits, I've never used them and that is based on facts from experience not just  me but majority of RC modelers/builders worldwide. Now if you think you're better than us because we DON'T use super glue as you insist on here, then go ahead and shout it out loud and let's see who gonna look and sound silly.

Whoa there buddy. I never said I was better than anyone. You are the one claiming you have So.Much.Experience. and insisting it's "silly" to use superglue. Got any actual facts to back this up, or just "people are saying"? That sounds pretty silly to me.

1 hour ago, Nicadraus said:

Grow up. You're too stubborn. Stop being a joke.

Yikes. Icing on the fart cake.

[Juggular 5171]

Now, Gentlemen, 

People com to Tamiya Club for friendly discussions. Most of us being men, we tend to be rash. But being diplomatic can be a positive thing. 

On 9/11/2021 at 8:02 AM, jonboy1 said:

The root diameter of a 3mm self tapper is 2.1mm and the outer diameter is 2.9 with a pitch of 1.1mm. An M3 thread has a root of 2.5, an OD of 3 and a pitch of 0.5mm

That explains why going from tappers to machine-threads could work.  Machine-thread is just bigger!  I've done it decades ago.  But I always felt uneasy about it.  The only actual problems were the badly loosened holes. 

On hard ABS plastic that does not flex, I wouldn't mind using superglue.  If it's soft A-arms, I might try some kind of an epoxy that gives a little. (Shoe glue would be too soft, JB weld might be too hard? )  

 

 

[silvertriple 4192]

I still believe the only long term solution is M3 metal inserts inserted hot in a redrilled hole to fit the inserts specifications...

It is reliable, the outer diameter to port the effort is wider, and the machine thread screw will work fine within the insert metal thread, allowing for any unmount/remount as needed

[El Gecko 1631]

24 minutes ago, Juggular said:

On hard ABS plastic that does not flex, I wouldn't mind using superglue.  If it's soft A-arms, I might try some kind of an epoxy that gives a little. (Shoe glue would be too soft, JB weld might be too hard? )

FWIW I haven't had any issues with flex. Generally the area around the screw hole is reinforced (or at least thicker material) and relatively inflexible compared to the rest of the arm.

[Willy iine 18842]

I've not tried it, but E6000 might also be a good candidate for flexible surfaces.  CA works on glueing tires to plastic wheels so it can be applied on flexible contact areas.  It really depends on material, application, and how severe the repair is, and most importantly how much time and cost one is willing to spend on it, I think.

The weakest screw holes on the M38 are the ones holding the front pogo stick suspension brackets to the flexible lower arms.  Most of them on my restore were pre-stripped.  A drop of CA and gentle tightening goes a very long way to fix the problem permanently especially since the arm has a travel limiter on the bottom side of the chassis, the screw only needs to keep the pogo sticks in position.  It is not what is holding the entire suspension together.  If it was, I would use a completely different approach to fix it.  

 

[Juggular 5171]

32 minutes ago, silvertriple said:

M3 metal ins

Do they look like these?

I've seen on Youtube that people heat these up and stick them in 3D printed parts. 

I have not seen it done on RC cars (but Tamiya plastic would melt just as easily).  I confess, I am afraid to try it.  If holes of the thread were ruined, these might be a perfect solution, though. 

 

[silvertriple 4192]

Yes they look like this... The most difficult is to insert them within the right direction. That being said, it would work only if there is enough room for it as it is larger than the original hole... One of the problem I have with my Marui Hunter chassis where they placed the threads in tubes... 

[nowinaminute 3342]

32 minutes ago, Juggular said:

Do they look like these?

I've seen on Youtube that people heat these up and stick them in 3D printed parts. 

I have not seen it done on RC cars (but Tamiya plastic would melt just as easily).  I confess, I am afraid to try it.  If holes of the thread were ruined, these might be a perfect solution, though. 

 

I've used them a fair bit on RC stuff now. If anything, they work better on molded plastic as the insert is completely surrounded in solid plastic which melts and conforms to the shape of the insert.

Most 3d printed stuff isn't 100% solid, even if you order 100% from somewhere like treatstock, it will usually be more like 90something in reality but a lot of stuff is way less like 30 or 50% so there's less actual plastic surrounding the insert.

They use the same kind of thing in devices such as laptops. Either inserted with heat, ultrasonic tools or even placed inside the molds when the parts are injection molded.




It can be nerve wracking but isn't too hard really. Most importantly, you need to work out if enough plastic will be left around the perimeter of the insert after you have drilled the hole out large enough. If there's enough material, you just need to drill the hole to the specified size, put the insert in place and introduce a soldering iron and wait a little while and with just a small amount of pressure, the insert will begin to sink into the hole.

The easiest way I've found of getting the insert level is to just press it against a flat surface while it is still hot, that seems to get it near enough to perfect as could be needed. If the part shape prohibits this, another kind of flat object can be used such as the flat end on the shank of a drill bit or something similar, as long as it's larger than the insert so the surrounding plastic can be used to get the object, and hence the insert, flat.

It works wonders for those pesky TL01/WT01/WT02/GF01/G601 style knuckles where the step screws always seem to come loose even if you tighten them gently and avoid stripping the threads. I find those screws tend to start working their way out especially when you drive on dirt and sand as some gets in between the should part of the screw and plastic and helps it to unscrew itself.




I've also use the same method on some old Nikko models such as the Dictator which uses a very similar knuckle but a unique size step screw which I've never been able to find a substitute for. When those things fall out it's a real nightmare. But with the inserts you can get a much more secure fit and I've found you can even use a little dash of blue threadlock and the inserts will hold just fine when you undo the screw again. 

I tend to use the type that is slightly tapered which makes it easier to initially insert. There are several variations of the theme available. I usually get them on ebay.

[Nicadraus 6748]

7 hours ago, El Gecko said:

Thank you for reiterating your previous message. I understood it the first time. They don't recommend it because they are the ones who spec the hardware. If a Traxxas calls for a machine screw into plastic, that's what goes there and usually nothing else. You're not starting from the same initial conditions.

OP has already put self-tappers in, so even with the correct tap, there will still be voids in the material. The superglue (I use Gorilla brand superglue which is actually a CA type glue) helps fill those voids and provide more thread surface for the screw to mate with, as if it was done that way originally. It's not rocket science.

Whoa there buddy. I never said I was better than anyone. You are the one claiming you have So.Much.Experience. and insisting it's "silly" to use superglue. Got any actual facts to back this up, or just "people are saying"? That sounds pretty silly to me.

Yikes. Icing on the fart cake.

Now that's a lot of statements from a pro builder. Says a lot about your builds. 🤔

[mtbkym01 4710]

Superglue does work, the key is to place a small amount in the hole, let it dry, then cut the new thread, works wonders. If you don’t want to do it fine, but don’t say with fact that it’s a joke or doesn’t work, when it does and has been done by plenty of modellers/builders previously.

[alvinlwh 7687]

.

[Nikko85 4156]

Does superglue also work for self tapping screws that are backing out, or does it really just work for going from ST to MS?

 

[El Gecko 1631]

1 hour ago, Nikko85 said:

Does superglue also work for self tapping screws that are backing out, or does it really just work for going from ST to MS?

 

Yes it does, same idea. You're just filling cavities in the screw hole so more of the threads make contact with more of the plastic base. The additional material also helps stabilize the hole so everything has less chance of flexing and undoing itself in the first place, and the initial stickiness acts as threadlock. I started using it awhile back on the Grasshopper/Hornet lower suspension mounts as extra insurance. Haven't had one back out since, unless I unscrewed it myself.

[InsaneJim69 1587]

As regards to super glue, I have used it when the hole is just too far gone and the machine screw just spins and doesn't grip. I found after putting some glue in the hole apply a super thin layer of vaseline to the machine screw and screw it in while the glue is wet. Once dry the screw can be removed (due to the vaseline not curing to the glue) and give ready set threads made of the super glue. It actually works quite well, but does often than not give some white fogging, but that's easy removed with a light rub of fine steel wool. But I still prefer just to go from self tapping to machine screws with no glue if I can and never had any issues. 

James.