vti-chris

I striped 1 of the 4 screws that go under the car and hold the front gear box(4x18mm) on a Hyper.These screws are tapping type with big threads(Coarse threads),now hexcrews.com doesn't sell this kind of screws and told me that i can screw in a machine screw and it will hold better cause of the more threads.Can this work or will i ruin the plastic threads on the gearbox?

vti-chris

Now that i saw the manual,most of the bottom screws and servo tray are coarse(standard) thread screws.I will have to get the same?Or will the machine screws work at this?
NEED HELP!![sm=confused.gif]

Foxy

I had to do this a couple of times on my R40 due to accident damage...if the hole is not tremendously cross threaded, it will work, the extra thread does give a very secure hold, but if the machine screw continues turning after you wound it all the way in (i.e. the inside of the hole is totally chewed), then you might wanna try the plastic wood method (use a matchstick or a needle to apply plastic wood to the sides of the hole, it may need a little drilling afterwards). If that doesn't work (and it's only a temporary fix to get you through a race meeting anyway), then see if you can replace the chewed plastic part with aluminium, or simply buy a replacement part. Hope that helps...

vti-chris

I striped the head of the screws.So i need to replace the screws,BUT i can't find tapping screws,only machined screws,and i want to know if the machine screws will hold in the plastic threads of the tapping screws OR if they will ruin them!!

Foxy

The advice you were given (that they will provide as good a hold, if not better), is correct. Sorry I didn't realise you ruined the screw...how did you manage that???

You could of course buy an ofna screw bag which will have the correct ones. Probably that's the best thing to do, if the hole is definitely still in good shape.

vti-chris

I don't like these hex screws i prefer phillips but can't find anywhere!
The threads on the plastic are OK,i think i took it off only once to put diff oil in the diffs.If i use the machine screws now will i be able to put standard screws back in i find some?

What's the plastic wood???Is it that white glue for the wood???

Foxy

Yes...

Oxi...

Mallon exei onoma sta ellinika, alla den to 3erw egw. Basika, einai liquid plastic in a tube, which dries into hard plastic and usually has the colour of wood, as it is normally used to repair furniture when damaged. It's damn useful stuff. I haven't seen it in greece (but I haven't been looking either)...

scrapheep

Dont worry about finding coarse thread replacement screws, get M4x18 bugle head machine screws.
Replace all 8 of the coarse thread screws, the machine screws will hold much better.

As a matter of fact you will probably end up replacing all the coarse thread screws on the buggy at some point...and you will be glad you did.

vti-chris

So you put it in the hole,on the threads,leave it dry,and screw the screw in and it will make it's own threads...!Swstos??
It will be good as new or you need to be carefull not to screw too much??

vti-chris

Bugle head?These are the same as flat head=cone head=countersunk,right?
I think i'll just order all machine screws and finish it here,but i sure need some pushing,don't want to ruin the plastic threads...h...e...l...p...!![]

Foxy

They will hold and they won't ruin the holes, they do less damage than the tappers. Get them if they'll make you happy (I have to say I never felt the need to replace all my screws with machine screws, I only ever used them until I could get the original screws)...!!

Plastic wood is a great temporary fix. Who knows it may last years but I simply wouldn't leave a broken part on any of my cars for longer than I had to.

scrapheep

Correct...and they wont damage the plastic or back out due to vibration.
I replaced all the coarse thread screws on my Hyper7... including the pan head screws that hold the wing brace to the rear bulkhead...pesky buggers would loossen after every run.

Giles300-72

My Feedback: (2)

If you replace a course thread screw with a fine thread screw it will mess up the threads. it will work but you would never be able to put a course thread back in it. In plastic the fine threads would make their own threads and would hold. My suggestion would be to look into finding the correct screw. If you don't believe me go to the hardware store and take a course thread bolt and try and put it in a fine thread nut. It won't work. The reason you can still screw the a diff bolt into plastic is because the plastic will give. But to answer your question it will mess up the threads. You can do it, and it will hold, but if you keep going back and forth from fine to corse then eventually nothing will hold.


On the other hand if you are keeping the same thread pitch and just going from a tapping to a machine screw then no it want hurt anything. The reason a machine screw would hold better is because the threads go all the way to the bottom of the bolt versus a tapping screw the threads come to a point.

vti-chris

Thank you all for the help!!
I will be using just machine screws from now on since these are all i can find.And since they hold better,no reason for me to go back(to coarse)!!

Foxy

Having done it myself, I have to disagree...

If you try to put a fine thread bolt into a coarse thread nut it will not work either, but this is because they are metal. Because the machine screw has a finer thread (and normally fractionally less diameter of thread, as they don't need to 'tap'), it does less damage the wall of the hole, it is no problem to have both threads, but if one of them gets even a tiny bit cross threaded, then you will have problems. I used to use the machine screw for one day or two until I could get an original coarse screw back in there, and I never had any problems getting the coarse screw to hold again, because the thread is much coarser and sharper. Of course, it does have a lot to do with the elasticity and quality of the plastic.

Agreed...

An extra 1 or half mm of thread on a 6-8mm screw really does nothing, machine screws have much finer threads, therefore more threads in the hole, that's why they hold better. They are designed for threaded metal holes. The tappers are designed to dig into plastic or wood and that's why they have coarse, sharp threads, you won't find a genuine machine screw with the same thread as a tapper, it wouldn't be feasible due to the angle of the thread.

vti-chris

Are the wood coarse screws the same as plastic coarse screws that we use on our models or are they different?
If the same then i could use those if i can find some!

Foxy

They won't be radically different, but the thing to remember is that tappers are all kinds of different threads, they are not required to be a certain specific thread breadth because they tap the hole themselves. It would be quite surprising if you find a wood tapper of the same thread (using tappers of different threads will certainly destroy the hole). Also, wood tappers are totally pin sharp pointed, where as plastic tappers are only tapered.

Short answer, no, I shouldn't think so.

rcyou

Fastenere has M4 Button & Flat Head Socket Screws in stainless steel.

mzanzirc

I found on my RC that self tapping screws are mainly used when going into plastics, where the machine screws go into alu or metal.