I’m making a blade guard for my crosscut sled and managed to get my hands on some Lexan scraps (I think thy’re actually petg, but that shouldn’t matter much). Now I need to glue up three pieces 90 degrees to one another. Anyone have any experience doing this? What’s the best adhesive to use?
Norman
Replies
I'd probably scratch up the bonding surfaces a mite and epoxy them.
There are solvents made specifically for gluing plastics.
Some answers here: http://www.acrylic-designs.com/plastic_FAQ's.htm
Some solvents here: http://www.rplastics.com/plac.html
ASK
Thanks. That website suggests I might be able to form the pieces by heating them in the oven. Have you ever tried this?
I got some rectangular plexiglas scraps once, I don't think Lexan, and used a heat gun to heat a line about 1" from each edge. It became soft and I was able to bend up each edge to make a tray. The bend is a curve but it satisfied my needs. Pieces were about 12" X 18".
If you try this, practice first. Once you heat it enough and bend it, it will still be flexible enough to move so hold it in place until it gets cool enough not to move.
ASK
Thanks again. I was thinking of forming it around a 2x4 scrap. The size & shape should be just about right.
I was working with 1/8" plexi. What thickness are you using?
Probably doesn't matter if its thicker, just more heat. If I remember it took about 4-5 minutes to get it soft enough to bend. Make sure it's really flexible befor you bend or it will crack.
ASK
1/4"Were there any fumes?
Lexan (polycarbonate) is heat-formable, but it's not nearly so easy as with Plexiglas (acrylic, PMMA). The temperature at which it softens is much higher.
-Steve
Streve, the material I'm using is actually PETG. Do you know where that falls on the continuum?
Norman,
Sorry, not following you around, just seems that way.
http://www.multicraftplastics.com/access_supplies/index.html
Weldon makes numerous adhesives for various mediums.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Hi, Bob. I did pick up some Weld-On in case the heating plan doesn't work out.
Norman,
Are you making the floating guard for your crosscut sled? Let us know how you make out.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Yes, Bob, that's the one. I'm more or less modeling it on the one that Highland Hardware sells as part of its crosscut sled.
Norman,
So it's like the one I was describing to you in the other discussion. Does Highlands slide up and down? It doesn't look like it in the pic on their WEBsite.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Bob, the HH version does slide up and down, but it also has a clever way of setting it at the right height for 3/4" and 2" stock. The design is very close to the one in Kelly Mehler's Table Saw Book, with this nifty modification.Here's the link to the plans for the Highland Hardware sled and blade guard:http://www.highlandwoodworking.com/index.asp?PageAction=Custom&ID=86
Edited 2/1/2008 3:55 pm ET by nboucher
Norman,
Thanks for the link. I printed it to a PDF for later perusal. Sorry for the late reply, your reply just showed up in the Unread Msgs. (strange).
I like that handle for the sled. Mine is very similar but sans handle; guess I'll have to make one along with the blade enclosure on the back of the front fence. So ya gonna make one? Looks lke a good one. Lining up the runners to be 90° to the fence is the tricky part. I used UHMW from LV for the runners.
Slikker'n a trout.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Bob--Maybe I'm being censored.…I worked on the crosscut sled last weekend, using some scraps I had around. I found some straight-grained hard maple for the runners and some red oak and cherry for the fences. I used ideas from a bunch of articles and Web sites, but the whole thing's pretty simple. That handle looks like overkill to me, but I may make one just for the fun of it.I recommended that link mostly because I liked that dado layout. One dado stops an inch above the sled platform, and the other stops two inches above the platform. With a corresponding one-inch notch in the blade cover, this gives you two handy positions for it. For wood thicker than two inches, the cover, still in the dadoes, just sits on the board.By the way, forming the PETG went really well, though it took three trips to the oven to get it just right. I made a form using a 2x4 scrap that I planed smooth and square, then after softening the plastic in the oven for about 10 minutes, I clamped the plastic around the 2x4—also warmed in the oven—to get flat sides and decent 90 degree bends. Much better than cementing up pieces with 90 degree butt joints, I think. Fits the dadoes nicely.I may not get much shop time this weekend, but I still need to cut the kerf in the platform and square the fence to it. Maybe I'll send you a photo once it's done.Norman
Thanks, that's awesome. Sounds like your well on your way and having fun too.
It has finally warmed up enough so I can get in some woodshop time for a bit. Gotta get that DC finished as forestgirl wants to see some pics.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Bob, where are you in NH? I grew up in Nashua and went to school in Durham. Spent many years scrambling in the White Mountains . . .Good luck with the DC.
I don't have any personal experience with it. Looking at the data sheets, it appears to be similar to PETE (the stuff that plastic bottles are made of), but is optimized for thermoforming, and has a very low melting point. So it looks like formability is good (probably better than PMMA), but you might have to be careful to avoid overheating it.
-Steve
Pardon the intrusion.
If it is PETG then it is thermoformable but it is only a little better than acrylic in impact resistance. It needs a much lower temperature than polycarbonate. You only want to heat the area that you want to form the bend. Using a heat gun is problematic since it only heats a single spot. even if you move it fast you get uneven heating. The best way to bend plastic is to use a single line heating element.
View Image Tap plastics sells them but you may not want to spend $65 on one. (Price has gone up from when I bought mine 25 years ago.)
I've also had success bending plastic by heating it in the oven. It stinks so make sure the wife is out and the windows are open. (My mom nearly killed me for doing it when I was a kid.) Make a jig to hold the plastic and protect the areas you don't want to heat. Think of it as two pockets with an exposed strip in the middle. Heat the oven up slowly. Testing by lifting one edge. When it starts to bend, it's going to soften quickly so move fast.
Polycarbonate (Lexan) is superior in impact resistance. ie. Bullet proof windows are made from polycarbonate. You can cold bend polycarbonate. I do it all time with thickness 1/8 or less. Use a sheet metal brake.
Hope this helps.
Len
Thanks, Len. I will experiment tomorrow with a small piece of PETG in the oven. Once I get the heating time right, my plan is to bend a piece around a 2x4 scrap and let it cool. Do you think that'll work?
You might want to try drape forming.
Here's an article. http://www.palram.com/htmls/article.aspx?C2004=13362
Any imperfection in you form will telegraph into your part. So you may want to clean and sand the 2x4.
Len
Len, thanks for the article. It helps me visualize what I'm doing. We'll see how it goes over the weekend.Norman
Edited 2/1/2008 2:02 pm ET by nboucher
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