Question about Screws

[ajdragon01]

Hi

 

Is it OK to use allen head metric screws instead of the stock Tamiya screws? 

[JennyMo]

Depends on what kind of plastic you're screwing them into - to softer nylon type works reasonably well with a machine thread first time, but if the plastic is hard you'd be better off tapping them with the correct size metric tap first - makes it easier to screw them in and reduces the chance of the harder plastic chipping/splitting from the less sharp screw thread being forced in (compared to a cutting tap) - which can happen since the metric thread pitch is so much finer than stock 'wood screw' thread.

[kevinb120]

When you reinstall or the install a screw into an already threaded plastic part, slowly spin the screw anti-clockwise first. You'll feel a light thunk when the starter thread lines up and it then will screw right back into the original threads.  This works with any thread type.  Keeps you from cutting a new set of threads. This also goes for metal, particularly aluminum with a steel fastener, especially in blind installations with a screw that can easily be driven in crooked, like mounting a motor where it's easy to run out of hands.

Also never push down any harder than it takes to remain in good mechanical contact with the screwdriver or hex head, when it's all seated it should just need a good snugging down, if you're on the threads property it should tighten smoothly. Plastic is essentially a natural thread lock.  If using the screw to cut a new thread the same rule applies after the first three or so threads have formed and the screw starts mechanically cutting its path from there. A self tapper will do this in less than two turns, a machine screw needs 4 or 5 at least to reliably drive and cut. Then back off pushing and let them cut the threads. This even applies to a tapping tool.

If using a power screwdriver always start and end each screw with a manual driver. And use slow speeds 

The plastic should hold a good and proper thread for a long time if not indefinitely if you don't cut additional thread paths or over tighten. I have 10+yo dogged out powerful bashers that have been rebuilt countless times without a single bad threaded/stripped hole unless it's crash damage.

Do these things and you'll always be screwed.

 

[Wooders28]

Did that with some on my Dark Impact 

 Just don't use Stainless in aluminium, you get Galvanic corrosion and struggle to get them out.

[skom25]

6 minutes ago, Wooders28 said:

 Just don't use Stainless in aluminium, you get Galvanic corrosion and struggle to get them out.

You can use bit of grease to avoid that. I used Stainless Steel screws in bike for many years and never had any issues.

[Wooders28]

1 hour ago, skom25 said:

You can use bit of grease to avoid that. I used Stainless Steel screws in bike for many years and never had any issues.

Works on larger cap screws (M8+ etc), but on M2 & M3 it doesn't take much, to make those an issue to get out.

Most people don't use anything when they 'upgrade' to a stainless bolt kit on their RC, see it all the time at the club.

[Frog Jumper]

4 hours ago, ajdragon01 said:

Hi

 

Is it OK to use allen head metric screws instead of the stock Tamiya screws? 

In general yes, but follow the advice above.

I’ve started ordering packs of SS hex button heads on ebay.  They are usually fairly inexpensive.  I haven’t had any issues so far.

 

[skom25]

1 hour ago, Wooders28 said:

Works on larger cap screws (M8+ etc), but on M2 & M3 it doesn't take much, to make those an issue to get out.

Most people don't use anything when they 'upgrade' to a stainless bolt kit on their RC, see it all the time at the club.

There are quite a lot M3 and M4 screws in bike. Never had any issues.

Going back to topic:

I always use Tamiya Tap Tool. Stainless Steel Screws are not equal quality. I have some which are really nice and some which are awful.

If you can pay bit more, Tamiya Hex Screws are excellent.

[Wooders28]

22 minutes ago, Frog Jumper said:

 I haven’t had any issues so far.

It's only into aluminium you'll have issues, as the chemistry doesn't like each other. Stainless are also a weaker bolt than cap screws (which are usually 12.9) , so unless it's looks and the heads not rusting, you're probably better with standard high tensile cap screws.

 

2 minutes ago, skom25 said:

There are quite a lot M3 and M4 screws in bike. Never had any issues.

Might be something I'll suggest, when one of our club members insist on a stainless 'upgrade' (even though they're not an upgrade imo) 

I've normally had to drill them out on 2nd hand cars that's came with them.

[skom25]

It is good to just unscrew and screw again them from time to time. If someone leaves them untouched for few years, probably you are right.

[alvinlwh]

57 minutes ago, Wooders28 said:

Stainless are also a weaker bolt than cap screws (which are usually 12.9) ,

Someone once said to me, if there is a crash bad enough to damage SS screws, it does not matter how strong 12.9 screws are as the part the screw is holding on the car will break first. 

Here is one of my SS screwed chassis crash. The suspension holder broke before the SS screw. 

Sure, a proper 12.9 screw will be stronger than my Aliexpress "special" SS, but the part the screw is holding will still be just as broken. 

[Crucial]

8 hours ago, ajdragon01 said:

Is it OK to use allen head metric screws instead of the stock Tamiya screws? 

Yeah.

It is possible to overthink these things.   Just don't overtighten them regardless of what type.

[ajdragon01]

Hi

 

The cars that I would be using the screws on would be the Hornet Evo the Grasshopper, and the Kong Head, and I would be using black oxide steel metric screws and not SS, .  I actually have a M3 tap from another RC project that I can use to tape the hole first. 

 

I tried putting a M3 screw into one of the m3 screw holes on the evo chassis and it looks like I will have to either make the holes slightly bigger or tap them first.  The entrance side of the hole looked OK but the other side of the hole was turning  white and had cracks in it.

[Wooders28]

5 hours ago, alvinlwh said:

Sure, a proper 12.9 screw will be stronger than my Aliexpress "special" SS,

Most think Stainless to be a stronger 'upgrade' , but baring anti corrosion to the bolt heads, actually worse. 🤷‍♂️

 

[Frog Jumper]

1 hour ago, Wooders28 said:

Most think Stainless to be a stronger 'upgrade' , but baring anti corrosion to the bolt heads, actually worse. 🤷‍♂️

 

For me its was about avoiding rust.  I drive a lot at a local baseball field and for some reason the clay seems to have a high salt content.  Maybe as an anti-weed product??

And it looks cool!

[alvinlwh]

1 hour ago, Wooders28 said:

baring anti corrosion to the bolt heads, actually worse

That is the only thing I need from the SS screw. As I showed in the picture, the part it is attached to is no stronger than it and will break first making the strength of 12.9 screws pointless. 

[alvinlwh]

2 hours ago, ajdragon01 said:

The cars that I would be using the screws on would be the Hornet Evo the Grasshopper, and the Kong Head

It does not matter what you put it into. I got boxes of M3, M2.6 and M2.5 screws that I use in place of Tamiya screws. I order replacements in 50 or 100 at a time.

As @Crucial said, no need to over think things. If instructions says a 3 x 12 screw, I just grab a 3 x 13 from the box and use it.