How do you square up acrylic for 90 degree joints?

[Vincerama2]

Hi guys, I've been having some issues with squaring up my acrylic joints. Like, say I want to make a box, how can I make sure that I have a 90 degree joint before I capillary solvent bond a vertical piece to a horizontal piece?

I tried using "speed squares" (metal triangles) but these require space and fit only on the inside of the joint (so if you were making that said box, you might not be able to use the speed square.

I found a plastic thing that is used for fence post levelling, so it has 90 degree part that fits around a fence post, I tried using it, but the plastic dissolved a bit, also it has gaps in it. I suppose I could place some wood in there and put the acrylic on the wood. (?)

Anyway, I was wondering how you experts get nice 90 degree joints! I was thinking that if I had a V trough set at 90 degrees, I could nestle the acrylic in this jog and it would work, but I don't know how to go about making one!

I was thinking that if I could get a flat piece of metal and put a square metal block on it, I could get an L shape that I could rest the acrylic sheet against.

I also considered that I could scrape the silicon off the inside of an old 10g aquarium and use it's corner as a guide...

But there must be some easier way! Is there some tool already around for doing this? (You can see my woodworking/acrylic skills are still in the learning phase)


Thanks!

V

[H20ENG]

What most people do is make jigs. Simply a couple pieces of plywood or MDF set @ 90 degrees. You need to trim the edge that sits directly on the joint or add shims so that no glue wicks through and contacts the jig. I used to use acrylic jigs til I glued one in place!:rolleyes:
I also made some jigs for weighting the top edge of a panel after gluing. I just glue it, pull the pins, add the weight, and reset the clamps.
Hope this helps,
Chris

http://reefcentral.com/gallery/data/500/14095glue_jig.jpg

http://reefcentral.com/gallery/data/500/140951.jpg

http://reefcentral.com/gallery/data/500/14095glue_ig_in_use.jpg

http://reefcentral.com/gallery/data/500/14095weight_jig_in_use.jpg

[Vincerama2]

I see cool. I was looking for something like your L shaped bracket to put the piece on the inside (rather than outside). I like your use of the shims.

I found this thing http://www.rockler.com/ecom7/product_details.cfm?&cookietest=1&&sku=10112 that looks handy as well. It's basically just an L shape.

V

[fitti69]

If you can find one , they make clamps to hold 90's . Cabinet makers use them . An old guy I work with has a few sets , bought them a long time ago . To date I have yet to find them .

[holry7778]

right angle clamps are easy to come by try rockler.com they sell wood working tools

[bshumake]

I found some 90 deg vice type things at Lowes. Its a set 90 deg that has a thumb screw at both sides. Just get it set and tighten the screws. I'm still in the process of testing them but they look solid, and their $8 or so.

[bkwudzjeep]

I have used those magnets that are used in welding to hold the pieces while glueing...Harbor Frieght has them cheap.
You just have to make sure to leave the paper on the acrylic, as they will scratch it.

I have also used a plastic speed square and cut the corner off of it.....you can make it almost as small as you want too....

The clamp-its are great for woodworking though, never used them on plastic....

[Vincerama2]

Ah, yeah, I had bought some harbor freight "corner clamps" and tried to use it on something. I don't think the HF stuff is good for this type of thing, there was too much play in the clamps. I forgot I had them, maybe I can make a wooden L thing from them. Maybe better quality ones would work better.

I think I remember seeing those magnetic welding block things. I'll look at that too. Right now, I'm leaning towards Rockler's Clamp-its. I think when I was making my canopy, they would have saved me MUCH MUCH headache!

Thanks for the tips, this is great! Some things I've thought about, and some that are so simple that I'm amazed I missed them (like cutting the corner off a plastic speed square!)

V

[raskal311]

squar clamps, I just bought 4 of them for $7 on sale.

[Vincerama2]

Where? Are they called "Square clamps?"

V

[raskal311]

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=1852

I didnt get it on line because they have a store near my house but it was like $1.65 each. And they call it a corner clamps

[Vincerama2]

Ah, those things, I have a set from HF, but they were too awkward to use with the acrylic I was using (the pieces were too short, plus too much play in the clamps I got) though I suppose I could use them to make a set of wooden "clamp-its". Most likely, I'll just buy Rockler's Clamp-it thing, since it seems easier.

V

[raskal311]

I havent used it yet but the lfs that i know that makes their own acrylic sump use those and their tanks comes out pritty nice. I'v seen them make 20-180gal sump with those.

[Vincerama2]

Cool...but the question is...did they use the ones from Harbor Freight? I'm cynical about HF stuff, even though I own many MANY things from them. Actually,the problem I had was that I was building smaller things that the corner clamps just couldn't grab onto.

V

[bkwudzjeep]

I actually returned my corner clamps from HF....they just seemed flimsy, and didn't seem like they held too well....it just felt awkward. Can't beat the price though!!

[Vincerama2]

So I've discovered that there are things called "Angle Plates" that is used in modelling hobbies tomake right angles. Typically aluminum. Similar to "clamp-its".

I copied H2OENG and made some acrylic "angle plates" with spacers. It was hard to get these at a 90 degree angle, but using 2 speed squares and using the store cut edge (which I assumed was mostly square) I think I succeeded.

I might still go buy some clamp-its though!

Thanks!

Oh, also here's a trick to NOT gluing the work pieces to acrylic angle plates/jigs.... line the jig with tinfoil before puttint the piece on it! The tinfoil is thin and compliant enough to not interfere, but the solvent can't get though it either to weld your work to the jig!

V

[bkwudzjeep]

Originally posted by Vincerama2

Oh, also here's a trick to NOT gluing the work pieces to acrylic angle plates/jigs.... line the jig with tinfoil before puttint the piece on it! The tinfoil is thin and compliant enough to not interfere, but the solvent can't get though it either to weld your work to the jig!

V

Good idea!! Not sneezing while applying the glue helps too....

Did the project come out alright? If so, post some pics if you get the chance.....

[Vincerama2]

So far, all I've done is make the 90 degree things. They are pretty much 90 degrees. Probably "90 degrees enough" for my purposes.

A few projects I have in mind (just for fun, of course!)

1) Square calcium reactor. I actually already have a round one, but it mostly sucks. So for fun I thought I'd make a DJ88-design square one. The trick is that I found a local Tap Plastic that cuts it's scrap to 8.5" by 8.5" squares. I was wondering if I could edge bond two pieces together to make a 17 inch x 8.5 inch piece. I don't think edge bond strength would be too much of an issue.

2) A knock off CPR Aquafuge. I actually have a fuge in my sump, but I think it would make a neat project.

3) A "vacuum cleaner" for the main tank. I've actually worked around this because I built a hose holder that clamps to an old HOB filter. I hang the filter on the sump (not running) put the hose holder into the back of the filter, then start a siphon on the hose so that I can siphon/vacuum flatworms and algae into the back of the HOB which then filters the water. I'd like to make a HOB Box to replace the HOB filter...just for fun.

What I have done is make a small acrylic line holder to hold my drip like from my kalkwasser reactor/mixer. I also made a table to sit under my skimmer inside my sump to raise it up.

Plus I keep thinking of "just cuz it's fun" projects...part of the fun is trying to make it with scrap pieces of acrylic. It's less of a challenge if Tap Plastic makes it for you and you just glue it together. Plus I'm cheap.

V

[AZDesertRat]

I have seen people use plastic speed squares and cut the edge off where they intersect so nothing touches right at the joint. They cut it back about an inch or so.

[Vincerama2]

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=1938

Now this looks good and cheap! Not worth the shipping though, but if you are near a harbour freight store, they are 99 cents in the latest flyer.

It's a magnetic holder for welding. It's 4 inches (not sure what dimension! LOL!) and it has the cut-out at the corner. Anyway, if I were near a HF store, I'd pick up 4 of these.

Online, they are $1.59 on sale (regularly 5 bucks) but they look like they would work great with acrylic. And since they are magnetic, you can put a magnet on the other side of the acrylic to clamp it, even in places where a regular clamp could not be used.

V

[BeanAnimal]

Just as an FYI... I have yet to find a plastic speed square that was even close to square...

For that matter Most of the metal ones arent that square anymore. Don't even get me started about carpenters squares and levels. I went through about 2 dozen stanley and similar levels from Home depot... not a damn one of them was truley level... not the 4 footers or 6 footers. not the torpedos.. nuthn.

Good acurate tools are hard to find these days. I will purchase a few expensive machinests squares and a cabinent makers or engineers level next time around... no matter what they cost. A 1/16 or worse over four feet is pretty sucky. The stanley "specs" state much better but just don't tell the truth.

Bean

[bkwudzjeep]

Vincerama--those are what I tried...they worked pretty well for me.

Bean--I know!! It's getting hard to find good tools these days!! I was workig with some of my students and I checked some measurements before cutting, and they were almost a 1/4" off....they said, "it's close enough"...needless to say we had a long discussion on that! I hope that is not what we have to look forward to in the future.

[BeanAnimal]

I called stanley regarding the issue.. they in "spin mode"said I must have got an item that represented an anomale. I explained that I tried dozens of items from several different vendors at several different times (over 2 years) and that the majority were horribly innacurate. They then tried to tell me that I must be introducing the error. Matching a square to a machinists square leaves little room for error! Swapping a level end for end and marking the bubble, leaves little room for error.

The next spin was that the tools were accurate within the price range in the industry and they recieve very few if any complaints.

Sad to say the least.

Bean

[bkwudzjeep]

Originally posted by BeanAnimal


The next spin was that the tools were accurate within the price range in the industry and they recieve very few if any complaints.


:rolleye1: unbelievable.....