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December 11, 2018, 05:18:47 pm
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What to use to back a cab?

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Author Topic: What to use to back a cab?  (Read 2024 times)
mdfa.ca
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« Reply #30 on: November 07, 2014, 09:40:31 am »

Had the first run at this last night... Went to the hardware store and was presented with a whole wall of JB Weld LOL. Eenie Meenie Miny Moe... I picked one that was for use in plumbing and water fixes. It's supposed to be impervious to all those bad chemicals, including water, didn't realize it was going to be white. It did set nicely though and I think it will work just fine, but I was sure someone said it's near black. Is there one specific type I should buy?

M
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Haderly
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« Reply #31 on: November 07, 2014, 10:15:20 am »

I have only used the "Original" JB Weld and it is dark gray. http://www.jbweld.com/product/j-b-weld/
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« Reply #32 on: November 07, 2014, 10:35:27 am »

Thank you, I'll get that one today.
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mirkaba
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« Reply #33 on: November 07, 2014, 11:01:04 am »

Personally I wouldn't want to apply JB Weld to a nice cab. Especially if it is someone elses cab. I would definately set the stone with a black plastic/viny or Electricians tape unattached backing. Just me though.............Good Luck!

i
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Bob

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« Reply #34 on: November 07, 2014, 11:04:08 am »

Mirkaba,

I am not attaching, I'm just creating a separate backing which will also shimmy one end of the cab. It's uneven.
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« Reply #35 on: November 10, 2014, 12:32:11 pm »

Not sure if anyone else has suggested this, but why not used the standby 303 epoxy? All you need to do to color epoxy any color you'd like is add a bit of enamel acrylic (I use Testor's brand, available at any hobby shop). A tiny bit -- like enough to coat the bottom third of a toothpick, should be more than enough to color a fair bit of resin.

Come to think of it, why not just use something like acrylic enamel paint? Blast it with a heat gun before it dries to kill any bubbles and cover it (do the same for resin if you go that way instead), and you should be good, I'd think?
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PhilNM
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« Reply #36 on: November 10, 2014, 06:56:12 pm »

Your slab is on the way! It went out yesterday.
Phil
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« Reply #37 on: November 11, 2014, 11:11:59 am »

Thanks, Phil! 

I had one of those days last night when whatever you touch just goes south really fast. Among other things I tried fusing a piece of fine silver wire, 18G. Well, now I'm wondering if it was ever FS. Not only did it not fuse but on 3 attempts scaled so badly I can't even clean it in pickle.  Hmmm, I wonder if it's sterling maybe? Or i just don't know what I'm doing LOL. Then I tried soldering a bezel and just couldn't make it work. It either evaporated too quickly or fizzed and spat, literally throwing the solder wire bits all over. I gave up on the third attempt and went to watch TV.  Maybe I'll have better luck today.

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« Reply #38 on: November 12, 2014, 11:25:47 am »

What kind of epoxy does one use for gluing the cab onto the doublet?

I realize I'm late to this topic, but I use Hyxtal to glue up doublets and triplets. It takes longer to set up, but it's easy to de-bubble and it never yellows.
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« Reply #39 on: November 13, 2014, 08:45:53 am »

I use JB weld and Devcon to make backs for uneven stones like some turquoise and carved fire agates so they can be bezel set. both clean up easily with denatured alcohol, set hard and can be sanded down as needed.
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finegemdesigns
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« Reply #40 on: November 13, 2014, 04:52:12 pm »

It occurred to me just now that there might be consequences to using different methods to back cabs that relate to expansion and contraction due to temperature changes. For example if JB Weld expands at a different rate than your turquoise it seems this could cause the weaker material (in this case the turquoise) to crack. The same could happen to a backing of black jade or basonite that is glued with a rigid substance like super glue.

So really the method that might be best is to use basonite or black jade (or similar) with an epoxy that doesn't harden totally rock hard. Answer 330 epoxy. Hardens hard but not as brittle hard as super glue. Also the glue is slightly thicker so this layer between would allow for some expansion of both backing and gemstone.
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« Reply #41 on: November 14, 2014, 06:45:44 am »

Finegemdesigns, the cab will not be "married" to JB weld. It's just something that will be slipped under the cab to lift it and give it a darker background.
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GregHiller
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« Reply #42 on: November 14, 2014, 06:58:08 am »

> For example if JB Weld expands at a different rate than your turquoise it seems this could cause the weaker material (in this case the turquoise) to crack.<

If you'd ever used it, you would know that JB weld cures to a soft semi-flexible material. While I agree that it's likely to expand/contract at a slightly different rate than whatever stone you are using, it is not going to put any significant pressure on your stone and make it likely to crack.

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« Reply #43 on: November 14, 2014, 04:09:13 pm »

> For example if JB Weld expands at a different rate than your turquoise it seems this could cause the weaker material (in this case the turquoise) to crack.<

If you'd ever used it, you would know that JB weld cures to a soft semi-flexible material. While I agree that it's likely to expand/contract at a slightly different rate than whatever stone you are using, it is not going to put any significant pressure on your stone and make it likely to crack.

You are right I never used it. I was thinking it was similar to other "metal" type epoxies that harden very hard.

But your and mdfa.ca's posts don't seem to address the idea that one point of a backing is to strengthen the stone. Especially weaker gems like turquoise.
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« Reply #44 on: November 17, 2014, 01:59:49 pm »

>But your and mdfa.ca's posts don't seem to address the idea that one point of a backing is to strengthen the stone. Especially weaker gems like turquoise. <

Backing a stone with JB weld makes the bottom surface flat.  It also could to some extent probably hold a stone together to make it less likely to crack apart.  Once the bottom of the stone is flat, when you put pressure on the stone as you are bezel setting it it is less likely to crack because the pressure will be better distributed. 

Don't know what to tell you beyond that.  I've used to for fire agate, turquoise, and malachite.  Worked great.  Try it if you like.
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