Guide Body Filler Tutorial

[fibbef]

I don't remember if I shared this on BitBuilt before, but this is exactly why I made this video:
And yes, Bondo STINKS! Whenever I work with it, it has to be out in my garage. Otherwise the smell doesn't get out of my basement for about 24 hours.

 

[cheese]

And yes, Bondo STINKS!

Bondo you STINKY Ｍｅｍｅ

 

[Nick]

What kind of bondo is best to use?

 

[fibbef]

@Nick you mean in terms of brand? I doubt it matters. If you're in a region that doesn't sell Bondo brand, any type of automotive body filler would probably work. The thing I didn't cover in the video is glazing/spot putty, which Bondo (as well as others) makes as well. It's not so much a body filler as it is a finishing tool. If there's interest, I could probably piece together a glazing putty vid, even though it's really easy to work with.

 

[Nick]

Just ment I typed in bondo on eBay and there's acouple different kinds? Didn't Know if the numbers 261 or 267 reffered to anything in the titles or if they just refer to can size or what as I've never used it before?
http://m.ebay.com/itm/NEW-Bondo-261...%3A592fd3eb15b0a357ebae3028fffc47ed%7Ciid%3A3

http://m.ebay.com/itm/Bondo-267-Lig...064afab8ea4cea2b1260df&pid=100465&rk=1&rkt=1&

 

[fibbef]

Different sizes. Those appear to be the exact same product.

 

[Nick]

Ok that's what I thought but wanted to make sure thank you.

 

[jefflongo]

What would be the best choice for say, frankencasing a GC controller shell into a plastic case (ZN-40 for my situation)?

 

[fibbef]

@jefflongo melted ABS, epoxy, or epoxy putty (personal preference in that order). I'm an ABS convert because it's cheap, easy to make more, and you're recycling plastic that you'd otherwise be throwing away. I have used 2-part epoxy for frankencasing and it turned out well, so I'm not knocking it. I've seen the work of others who have frankencased with epoxy putty and that can turn out awesome as well. Personally, I just don't like having to knead it manually and I feel it's a bit heavier than the other options once cured.

 

[Vonn]

Not a great technique when craftsmanship is in mind, but there's a quick trick I picked up from repairing plastics on motorcycles with spare plastic, optional wire, and optional additional plastic (like a zip tie). You use a soldering iron to heat up the plastic and basically weld pieces together. Could be useful for tacking frankencase-things into place as an alternative to glue.

Here's a long-winded video:

 

[GingerOfOz]

Not a great technique when craftsmanship is in mind, but there's a quick trick I picked up from repairing plastics on motorcycles with spare plastic, optional wire, and optional additional plastic (like a zip tie). You use a soldering iron to heat up the plastic and basically weld pieces together. Could be useful for tacking frankencase-things into place as an alternative to glue.

Here's a long-winded video:

The smell though...

 

[Madmorda]

I haven't tried melted ABS, I usually use epoxy. I have used epoxy putty as well and while it did hold, I wouldn't recommend it unless it's somehow better for your situation than ABS or regular epoxy. It's just a pain. I will say though that I've been working my way through different brands of epoxy, and many of them that are "resealable" are not. So while epoxy is quick and easy, if you plan on using it for small things over a long period of time, melted ABS might be overall better since it won't drool on your table.

Edit: just wanted to add, clear epoxy does have a dual purpose for me since I use it to protect delicate soldering points. Since I'm buying it anyways, it's my go to.

 

[jefflongo]

I haven't tried melted ABS, I usually use epoxy. I have used epoxy putty as well and while it did hold, I wouldn't recommend it unless it's somehow better for your situation than ABS or regular epoxy. It's just a pain. I will say though that I've been working my way through different brands of epoxy, and many of them that are "resealable" are not. So while epoxy is quick and easy, if you plan on using it for small things over a long period of time, melted ABS might be overall better since it won't drool on your table.

Edit: just wanted to add, clear epoxy does have a dual purpose for me since I use it to protect delicate soldering points. Since I'm buying it anyways, it's my go to.

So if you're frankencasing, how effective is using epoxy? Seems like it would be a challenge to get enough in the gaps. I'm just inexperienced though.

 

[Madmorda]

So if you're frankencasing, how effective is using epoxy? Seems like it would be a challenge to get enough in the gaps. I'm just inexperienced though.

The gaps really shouldn't be huge. Epoxy is pretty viscous so it goes in decent sized gaps, but if it's too runny to stay you can wait like a minute and try again. When drilling your hole, try to not make it too big. The ideal goal is to get the new piece to hold itself in the hole somewhat firmly so you don't have to worry about it shifting while drying. Failing this, I use superglue to hold it before epoxying.

Here's an example of me using epoxy. I just epoxied these squares in. Before and after sanding and bondo:


It basically becomes part of the plastic and is maybe a little easier to sand, but not by much.

You can always do more than one layer if it doesn't fill the gap completely

 

[jefflongo]

The gaps really shouldn't be huge. Epoxy is pretty viscous so it goes in decent sized gaps, but if it's too runny to stay you can wait like a minute and try again. When drilling your hole, try to not make it too big. The ideal goal is to get the new piece to hold itself in the hole somewhat firmly so you don't have to worry about it shifting while drying. Failing this, I use superglue to hold it before epoxying.

Here's an example of me using epoxy. I just epoxied these squares in. Before and after sanding and bondo:
View attachment 2317 View attachment 2319

It basically becomes part of the plastic and is maybe a little easier to sand, but not by much.

You can always do more than one layer if it doesn't fill the gap completely

Do you just coat the sides of the piece you're frankencasing in with epoxy and then insert it into the hole?

 

[Madmorda]

Do you just coat the sides of the piece you're frankencasing in with epoxy and then insert it into the hole?

I just insert the piece the way I want it to be, make sure it won't move, mix my epoxy, then use a toothpick to dribble / wipe it in the gap between the two pieces. It's okay to not get enough the first time, you can always do a second layer. Just make sure that it isn't drooling out of the gap from the other side. If it is, you can use your toothpick to keep pulling it back into place until it gets more viscous. (Usually only a minute or two)

 

[jefflongo]

I just insert the piece the way I want it to be, make sure it won't move, mix my epoxy, then use a toothpick to dribble / wipe it in the gap between the two pieces. It's okay to not get enough the first time, you can always do a second layer. Just make sure that it isn't drooling out of the gap from the other side. If it is, you can use your toothpick to keep pulling it back into place until it gets more viscous. (Usually only a minute or two)

So after you epoxy you use bondo to fill the rest of the gaps and sand to smooth the surface? I imagine you don't use a ton of bondo.

 

[Madmorda]

So after you epoxy you use bondo to fill the rest of the gaps and sand to smooth the surface? I imagine you don't use a ton of bondo.

Yeah, you use epoxy to fill the gap. Bondo body filler can be used to fill in uneven spots or "dents". Then you can use bondo glazing and spot putty to fill in super tiny uneven parts, like minor scratches or pinholes / air bubbles, whatever. I actually get away with using just epoxy as both the epoxy and the body filler on small projects because I hate the smell. Then I finish up with spot putty. For larger jobs though I recommend the Bondo body filler for sure. The spot putty is really soft though, make sure you don't fill in anything but the smallest spots with it. It's more of a smoother than a filler.

 

[DeoNaught]

Thank you, thats the first time I have heard of ABS cement, Thank you.

 

[fibbef]

Not a great technique when craftsmanship is in mind, but there's a quick trick I picked up from repairing plastics on motorcycles with spare plastic, optional wire, and optional additional plastic (like a zip tie). You use a soldering iron to heat up the plastic and basically weld pieces together. Could be useful for tacking frankencase-things into place as an alternative to glue.

I've heard of this method but never dared to try it because I was afraid I'd get melted plastic stuck to my iron.

Here's a pic from my first finished portable that shows off a few of my techniques. I used bits of plexiglass to cover openings, held them in place from the inside with duct tape (comes off fairly easily no matter what filler you use), and epoxied them into place. The tape helps eliminate drooling through the cracks. I used a liberal amount of bondo to fill other gaps, although I would use ABS now if I were to do that again. @Madmorda ABS will drool if you make it too runny, but if that's the case, you just leave it open to the air for a little bit and the acetone will start to evaporate, thickening up the mixture.

See spoiler if you want to see how this case progressed.

Spoiler: filler progress

Switched to bondo over the epoxied spots to add contour and smoothing (I find it's much easier to sand).

Lots of glazing putty (the darker pink).

Sanded and primed.

Painted.