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Gluing acrylic/plexiglass
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=36581		 Page 1 of 1
Author:  Tai Fu [ Thu May 24, 2012 8:54 am ]
Post subject:  Gluing acrylic/plexiglass
I am trying to re-make a Wells Karol jig out of Acrylic (no luck trying to find UHMW plastic, plus I prefer a clear router jig for obvious reason) and I find myself needing to glue the acrylic pieces together.

I went around chemical shops looking for acrylic cement but they do not have the right stuff (it seems the right stuff is chloroform or methylene chloride, but I am told that those substances are illegal in Taiwan) and all they provided is some MEK.

The problem is MEK takes a LONG time to dissolve acrylic and the bond seems kinda weak, or perhaps I am not doing it right. I do not know how all those sign shop do it, but they told me they're not allowed to sell me any acrylic glue.
Author:  John A [ Thu May 24, 2012 9:06 am ]
Post subject:  Re: Gluing acrylic/plexiglass
can the sign shop glue the jig for you ?
Author:  Tai Fu [ Thu May 24, 2012 9:09 am ]
Post subject:  Re: Gluing acrylic/plexiglass
John A wrote:
can the sign shop glue the jig for you ?


I guess they could, for a price.

About MEK, I was wrong about the stuff not forming a strong bond. I just glued a test piece and went back (30 minutes later) to pull it off, I couldn't. I actually had to use a hammer to break the joint, mind you the stuff isn't at its strongest at the 30 minute mark...

I found someone selling Weld On #16 and #3 but they are quite expensive.
Author:  Robert Renick [ Thu May 24, 2012 9:28 am ]
Post subject:  Re: Gluing acrylic/plexiglass
I have used CA glue on acrylic, worked for what I needed, seemed to be pretty strong, but I imagine that the right stuff can really melt it together.
Author:  Bob Garrish [ Thu May 24, 2012 11:37 am ]
Post subject:  Re: Gluing acrylic/plexiglass
The best acrylic glue is...acetone. If you have two pieces with a good clean contact, you can just put a puddle of acetone down and clamp them together. It also leaves a nice clear joint, which is why people use it for cosmetic joints. If you don't have good contact, though, you'll get a big nothing with pure acetone.

If you need to fill some space, then grind up some acrylic and dissolve it in acetone to make cement. Make sure to keep it in an airtight container, as the acetone will gas off otherwise. CA works pretty well on acrylic, they're both acrylates after all, but it's a few orders of magnitude more expensive than acetone and the bond isn't quite as good.
Author:  John Killin [ Thu May 24, 2012 1:00 pm ]
Post subject:  Re: Gluing acrylic/plexiglass
Bob,

Do you scuff sand between pieces or just brush with acetone and clamp together?

I have plans to build up a couple of layers to make a vacuum bridge clamp.

John
Author:  B. Howard [ Thu May 24, 2012 6:48 pm ]
Post subject:  Re: Gluing acrylic/plexiglass
Ive made lots of acrylic templates for cabinet hardware over the years, all were done with PVC pipe cement.
Author:  Bob Garrish [ Thu May 24, 2012 8:10 pm ]
Post subject:  Re: Gluing acrylic/plexiglass
John Killin wrote:
Bob,

Do you scuff sand between pieces or just brush with acetone and clamp together?

I have plans to build up a couple of layers to make a vacuum bridge clamp.

John


John,

No need for surface prep besides making sure there's no oil or anything like that on there. Using a solvent like this is actually welding the material together rather than bonding it; the acetone makes the acrylic mobile and what you get in the end is chemically a single piece of acrylic with no boundary layer. So I guess the answer is it's not actually gluing so the rules for gluing don't apply :)

There are certain types of acrylic sheet that have coatings put on them for UV or chemical resistance and there's a chance that those might mess with your bond but I've yet to run into that problem.
Author:  Billy T [ Fri May 25, 2012 1:37 am ]
Post subject:  Re: Gluing acrylic/plexiglass
B. Howard wrote:
Ive made lots of acrylic templates for cabinet hardware over the years, all were done with PVC pipe cement.


Pretty sure the main active ingredient in PVC cement is acetone. I use acetone all the time to bend PVC. Softens it up pretty good then sets up just about as hard as it started.
Author:  Tai Fu [ Fri May 25, 2012 2:05 am ]
Post subject:  Re: Gluing acrylic/plexiglass
Thanks for your advise. I used MEK and finished the Wells and Karol jig, here it is:

Image

Image

It looks so much more professional than plywood and it works better too, I got the knob from the router base and simply cut a few notches in the knob, and used it as a single use tap to cut some threads into the acrylic, negating the need for threaded insert.
Author:  Tai Fu [ Fri May 25, 2012 9:16 am ]
Post subject:  Re: Gluing acrylic/plexiglass
An update: after spending hours outside looking for sign shops that would not provide any acrylic cement, they told me to go to an art store. I did not think art stores would sell acrylic cement but they do.

It's a small bottle of liquid (about an ounce or so) and the storekeeper says to apply it with a syringe, Not sure what it was but glued a test piece and the stuff grabbed almost instantly unlike MEK which would allow the part to slide around for several minutes. It's not CA (because it would instantly cloud up everything it touches) but it does fog up the acrylic if it touches the stuff. It doesn't fog up the bond though.

I don't know what it is as it doesn't say but the bottle says its toxic. I am thinking it must either be methylene chloride or chloroform (it seems that's what sign shops use)
Author:  Tai Fu [ Mon May 28, 2012 12:10 pm ]
Post subject:  Re: Gluing acrylic/plexiglass
I just got some more of these "acrylic adhesive" but seriously these things evaporate kinda fast... in fact I can see a positive pressure in the bottle when I open it (I hear air rushing out when the bottle is opened).

So the question is, is it possible to retard its evaporation rate, like add cellusolve to make it not evaporate so fast?
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