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foz75

Reducing hole diameter in plastic parts?

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So I've been building my novafox slowly over the last couple of weeks. Today I'm assembling the front steering knuckles, and on one of the F1 arms, one of the holes for the 8mm ball stud is too large. The threaded part of the stud just pushes right in, no threading required. So I guess I need a new F parts tree, but what can I use to fill the hole, or at least reduce it in size? 

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Try filling the hole with epoxy just prior to screwing in the ball stud.  Wipe off an extra.

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The epoxy method sounds easier... Can the ball stud be removed later on of needed? A new parts tree is 10 euros at tamico, postage is 13 euros... 

Are the any other compatible options? Will try the fix, but just in case...

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22 minutes ago, foz75 said:

So I've been building my novafox slowly over the last couple of weeks. Today I'm assembling the front steering knuckles, and on one of the F1 arms, one of the holes for the 8mm ball stud is too large. The threaded part of the stud just pushes right in, no threading required. So I guess I need a new F parts tree, but what can I use to fill the hole, or at least reduce it in size? 

I assume the plastick is ABS. You may get ABS studs for plastick soldering, dissolve a bit with acetone this will get the ABS into paste, fill in the hole and drill again once dry.

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I'm not sure on the type of plastic. The marking on the tree is >PC< which I think is the type of material? I don't have access to a drill press, would have to use a vice and hand drill so can't guarantee the results... Which makes me prefer the "glue and screw" method. 

 

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2 hours ago, foz75 said:

The epoxy method sounds easier... Can the ball stud be removed later on of needed? A new parts tree is 10 euros at tamico, postage is 13 euros... 

 

I don't know if you can remove without pulling out the epoxy.  I suppose you could always re-epoxy it if you needed to remove it.

If anything, it will hold together until the new parts tree gets delivered...

Terry

 

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Epoxy is the right way to go. Gluing in some of the plastic off the tree would be good but as you say not having a drill stand makes it almost impossible to drill accurately without the drill wandering.

You will need to rough up the inside of the hole to get good adhesion. Once glued in it will be very difficult to get apart again.

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If I am not mistaken, the plastic is ABS.  ABS pipe cement for plumbing can be used to build up the material.  I had repaired my childhood Hornet several times using ABS pipe cement by adding pipe shavings to the cement and filling the damaged parts with the mix...

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4 hours ago, foz75 said:

The epoxy method sounds easier... Can the ball stud be removed later on of needed? A new parts tree is 10 euros at tamico, postage is 13 euros... 

Are the any other compatible options? Will try the fix, but just in case...

Yep epoxy is easy, and if you want to keep the ball stud removable later on (so you can use it again on the new F parts, I assume), just coat the ball stud threads with some kind of thin lubricant: Tri-Flow, 3-in-1 oil, etc. (possibly WD40 too) before installing the ball stud.

The lube layer itself doesn't need to be very thick, but you want to make sure the threads are evenly and fully coated, otherwise you'll get "sticky" spots that could hinder removal. The lube keeps the epoxy from sticking to the ball stud, while still allowing the epoxy to form into its threads. With no lube, the epoxy binds everything together and makes it difficult or impossible to fully clean the threads for reuse.

So my suggestion is to oil the ball stud, mix your epoxy and fill the hole, then screw the ball stud in and clean up the excess. That should hold you over until the new F parts arrives, and you should still be able to back out the ball stud for installation in the new arm once the epoxy is dry. With the new epoxy threads formed in the old arm, you should even be able to unscrew/rescrew the ball stud like normal (once the epoxy is dry, of course!)

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19 minutes ago, SupraChrgd82 said:

If I am not mistaken, the plastic is ABS.  ABS pipe cement for plumbing can be used to build up the material.  I had repaired my childhood Hornet several times using ABS pipe cement by adding pipe shavings to the cement and filling the damaged parts with the mix...

No, if it is marked as PC, it is polycarbonate. 

https://en.m.wikipedia.org/wiki/Polycarbonate

ABS is a different type of plastic. 

https://en.m.wikipedia.org/wiki/Acrylonitrile_butadiene_styrene

 

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Thanks for all the help! Being polycarbonate, is epoxy still the best glue to use?

I will order a new parts tree anyway, but I do wonder how my F2 part has been made with one of the holes too large? There must be more out there from the same mold which I imagine have the same dimensions...

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Just to play devil's advocate here... are you sure you've got the right ball joints going in there? The large ones with the hex hole in the end?

 

79155930_ScreenShot2022-01-20at2_15_16PM.png.9e2ecfa88fa4a1602b225c413601eb7d.png

 

The only raeson I bring it up is that it would be very strange to have one hole in an injection-molded part be the wrong size. And if it is, that's a problem Tamiya (or their distributor) should make right for you. You shouldn't have to order a new parts tree to correct their mistake.

But double-check to make sure you grabbed the right part, and are putting it in the right hole, first...

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Yep, definitely the right part. I bought the kit nearly two years ago and have had it waiting until then, so don't think the shop or Tamiya will be too interested. Might try anyway

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6 hours ago, foz75 said:

So I've been building my novafox slowly over the last couple of weeks. Today I'm assembling the front steering knuckles, and on one of the F1 arms, one of the holes for the 8mm ball stud is too large. The threaded part of the stud just pushes right in, no threading required. So I guess I need a new F parts tree, but what can I use to fill the hole, or at least reduce it in size? 

For the time being, I would use superglue if the hole isn't too loose.  GL with what you decide and hope you get the correct part soon!

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quick update...  after ordering a new F parts tree along with a few other bits to make the shipping worthwhile, this afternoon I decided to have a go at sorting the hole. I took everything apart as I didn't want to risk gettin gglue on anything other than where I wanted it. I had a good look at both the holes in F2, and both the 8mm ball connectors. The holes do appear to be slightly different sizes (I haven't measured), and the ball connectors appear to be exactly the same (again, I haven't measured). I figured I might as well try the ball connectors in the opposite holes, and what do you know, the ball connector that had screwed in fine as it was supposed to, did the same in the hole that is "too large". And is tight, all OK. the ball connector that wouldn't screw in, as threaded in to the other side, in the threads already tapped by the first ball connector, and while it isn't as tight as I'd like it, it is in and I think it will be OK. I don't want to risk tightening any more in case I strip the threads. So the problem seems to be double - a slightly (but not too much) oversized hole, and a slightly (but not too much) undersized ball connector thread. Either one on it's own would be OK, both together just don't work! I have a new parts tree and more ball connectors on their way anyway (will be useful for spares), but it makes me wonder about the tolerances in Tamiya parts!

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