Stripped a hex screw while assembling my TT-02BR

[LMF5000 54]

Well, this is a first for me. I stripped the circled screw. With exactly zero miles on the chassis.

I was actually happy that the BR came with hex hardware - I thought it would be a more enjoyable build experience than the usual Philips head screws because they were less likely to cam out and strip, right?

Not so. The screws holding down the pinion/spur cover were tight, because my screwdriver uses changeable magnetic bits so it's a tad thicker than one with a fixed bit . When the screw is approaching fully tightened, the sides of the screwdriver foul against the sides of the spur cover so I had to have with the screwdriver at the slight angle for that screw and the one opposite

After first assembling it the first time, I removed the cover piece again to rotate the brushless motor to try different positions for wire clearance. Screwed all the screws in, tightened them fully... and the marked screw was feeling a bit different. At first I thought I'd stripped the plastic so I thought I'd remove it to check... but nope. The head is completely rounded.

So far I've I tried the rubber band trick, supergluing a bit to the screw (the glue just broke off), hammering in the next size up torx bit (I couldn't hammer hard enough to get it to sink in), all didn't work. What can I do? The buggy is completely driveable, but it's going to be a big problem the first time I have to remove that cover for maintenance. It's a deeply recessed screw so cutting a slot with a Dremel will definitely destroy the plastic. And this is a 3mm screw and was VERY hard to screw into the plastic.

[spankrjs 81]

If the screw originally took a metric hex tip try an imperial/SAE tip. I've had success doing this in the past, worth a shot.

[Andreas W 3163]

On my Tomahawk I have a few questionable screwheads. My cheapo tools haven't made them any better. Before I started working on it this time I got this set. What a change. Even the screws I was worried about went out just like that. So I would try good tools before trying torx in the next size. 

 

https://www.elefun.no/vare-60029/verktoy-core-rc-premium-umbraco-set-15-20-25-30mm

 

Good luck and hope this gets sorted without any damage.

[skom25 2676]

For some reason, this hole is quite tight. I noticed this when I prepared few TT-02s.

I recommend to use Tap Tool next time or just hard screw to prepare threads first.

Try Torx key. If it will not work, use dremel. Sprue with gear cover is very cheap, so you will replace it in worst scenario.

BTW: do you have good quality allen keys? With proper tool, Tamiya screws are excellent. The best I had.

[Nicadraus 6799]

Here's a tip:

CA glue, cornstarch/flour/powder & hex diver.

Insert the hex driver in the screw hole. Drop some CA glue to fill the hole while the driver is inserted and put the powder on the glued area. It should dry up quickly, 3-5 secs. Then start twisting the hex driver clockwise first. If it makes a small/minimal turn/movement, turn the driver counter-clockwise to unscrew.

The hex driver can cleaned by soaking the tip in acrylic thinner for a day. It will help disolve some of the CA glue but not completely. Just enough to pull out the glued screw and clean the driver's tip.

[Pylon80 4318]

I think the root cause is as you described, holding the tool in an angle, which wouldn't happen with a dedicated RC hex driver, so you know what to do

For now, the only way to get it out (that I can think of) is to cut a slot into the head with a thin cutting wheel on a Dremel. Then use a flat head screwdriver. That will ruin the spur cover but that's just a sprue to replace. In any case, it will be delicate work as cutting an accurate slots in an M3 head is not easy.

If everything fails, you can grind the head off completely with the same cutting wheel as above and replace the cover plus the lower deck which will then have a stub of screw stuck inside. A TT lower deck is 5$ 🤣 probably the cheapest ever made by Tamiya. Also depending on your attention to detail you might be comfortable running the car with the cover only held by 3 out of 4 screws. It would annoy me but everyone's different.

[Superluminal 4210]

Does the BR come with carbon reinforced tub? I upgraded my TT02 type S to one of these and found it pretty tough screwing into so ended up putting grease on the threads.

Ive used a pretty good screw extractor set before which had some bits that looked like drill bits that cut into the head and wound the screw out.

If its in a difficult to get to spot but you can still get some grip on the tool head then you could potentially use a soldering iron on the screw to soften the plastic and see if it will come out and then repair the thread with some CA after when fitting a new screw.

[LMF5000 54]

2 hours ago, Pylon80 said:

I think the root cause is as you described, holding the tool in an angle, which wouldn't happen with a dedicated RC hex driver, so you know what to do

For now, the only way to get it out (that I can think of) is to cut a slot into the head with a thin cutting wheel on a Dremel. Then use a flat head screwdriver. That will ruin the spur cover but that's just a sprue to replace. In any case, it will be delicate work as cutting an accurate slots in an M3 head is not easy.

If everything fails, you can grind the head off completely with the same cutting wheel as above and replace the cover plus the lower deck which will then have a stub of screw stuck inside. A TT lower deck is 5$ 🤣 probably the cheapest ever made by Tamiya. Also depending on your attention to detail you might be comfortable running the car with the cover only held by 3 out of 4 screws. It would annoy me but everyone's different.

Well, my plan so far is to run it until I break something that needs access to that cover. In the meantime I'm pondering what to buy. Maybe the sprue with that cover so I can Dremel a slot into the screw with reckless abandon. Maybe some extractor bits so I can try getting it out more elegantly. Pobably some longer hex bits so I can drive the screws in straight next time and avoid this problem going forwards.

[Otis311 423]

May need to just drill the head off with a ~3mm bit. Once the cover is removed there should be just enough thread to grab with some vise-grips.

[skom25 2676]

Probably idea of @Otis311 is the best. Just buy new cover.

[alvinlwh 8068]

4 hours ago, LMF5000 said:

Maybe some extractor bits 

Try something like this. 

Also, are you using long reach bits with your screwdriver? 

They allow deeper reach than standard bits. 

[LMF5000 54]

Well, it's out, but not in the intended way. I bought some extended torx bits and screw extractors from the local ironmonger. The extractors didn't have drill bits so I had to use my normal right-handed metal drill bits to drill out the screw. The extractor wouldn't bite and grab the screw head, and eventually out of frustration I applied full throttle on the drill with the extractor, which still didn't turn the screw but ate off all the flutes on the extractor (it was the only one they had and obviously not very good if the metal of the screw was harder than the metal of the extractor).

I drilled the screw some more with a 2.5mm drill bit, then I thought I'd try a hack from YouTube where they hammer in a bigger torx bit that just fits the hole. Hammered it in and it seemed to be grabbing, went to turn it with the screwdriver, and the bolt head sheared off. I had to pull the screw head from the torx bit using pliers. Then since the head was gone I removed the other screws and removed the gearbox cover (good thing too, I discovered the motor pinion had worked itself loose!). There was about 2mm of screw shaft sticking out of the plastic, so I grabbed it with vice grips and spent half an hour painstakingly unscrewing it, an eighth of a turn at a time (I removed the battery holder post for more wiggle room).

The gearbox cover is mostly undamaged and the chassis only has some light scuffing from the vice grips, which I covered with extra AW grease. Lesson learned - the new screws bviously installed with the extended bits!

[Superluminal 4210]

Great work - that does look like the hard fibre reinforced chassis tub in the last photo and these can be pretty brutal on screws unless you run a thread forming tap in them first. I tend to apply a blob of grease on the screw threads to make them easier to install and you dont need as much force on the tool bit.

[skom25 2676]

7 hours ago, LMF5000 said:

Well, it's out, but not in the intended way. I bought some extended torx bits and screw extractors from the local ironmonger. The extractors didn't have drill bits so I had to use my normal right-handed metal drill bits to drill out the screw. The extractor wouldn't bite and grab the screw head, and eventually out of frustration I applied full throttle on the drill with the extractor, which still didn't turn the screw but ate off all the flutes on the extractor (it was the only one they had and obviously not very good if the metal of the screw was harder than the metal of the extractor).

I drilled the screw some more with a 2.5mm drill bit, then I thought I'd try a hack from YouTube where they hammer in a bigger torx bit that just fits the hole. Hammered it in and it seemed to be grabbing, went to turn it with the screwdriver, and the bolt head sheared off. I had to pull the screw head from the torx bit using pliers. Then since the head was gone I removed the other screws and removed the gearbox cover (good thing too, I discovered the motor pinion had worked itself loose!). There was about 2mm of screw shaft sticking out of the plastic, so I grabbed it with vice grips and spent half an hour painstakingly unscrewing it, an eighth of a turn at a time (I removed the battery holder post for more wiggle room).

The gearbox cover is mostly undamaged and the chassis only has some light scuffing from the vice grips, which I covered with extra AW grease. Lesson learned - the new screws bviously installed with the extended bits!

I suggest to use much less grease on gears.

[LMF5000 54]

8 hours ago, Superluminal said:

Great work - that does look like the hard fibre reinforced chassis tub in the last photo and these can be pretty brutal on screws unless you run a thread forming tap in them first. I tend to apply a blob of grease on the screw threads to make them easier to install and you dont need as much force on the tool bit.

It is - the reinforced tub is one of the upgrades included in the TT-02BR.

And yes, the instructions mentioned to use the thread forming tap on them, but I ignored that bit and just used brute force and ignorance 🤣.

[LMF5000 54]

4 hours ago, skom25 said:

I suggest to use much less grease on gears.

Thanks for the suggestion. It looks worse than it is in the pic because I only greased the visible top part of the spur. Later I manually spun it to distribute the grease all along the spur. Any extra grease gets flung onto the inside of the gearbox cover so it's self-correcting to an extent.

[alvinlwh 8068]

On 3/19/2025 at 5:22 PM, LMF5000 said:

And yes, the instructions mentioned to use the thread forming tap on them, but I ignored that bit and just used brute force and ignorance

I upgraded my FT with the reinforced tub and did not tap it. I did greased the screws going in though. The only screw I had trouble with was a metal to metal screw with too much threadlock on the YR gearbox cover.