Blade for PVC?

[Colin]

I need to cut a 48" circle out of a sheet of 3/4" thick PVC. Is there a particular type of Jig Saw blade which won't result in the material "welding" back together from the heat of the blade?

 

[SqueeGee]

I haven't had great experiences with jig sawing something that thick. The blade bends which ends up giving you an inconsistent beveled edge. I'd recommend having it cut on a CNC.

 

[BBworks]

There are other options. We use table saws at our shop. You can cut circles on a table saw, check it out on youtube, or you can use a composite blade for cutting acryllic if you are using a jigsaw. For an elipse we go to our router guy.

 

[fixtureman]

A router would be a better choice

 

[CanuckSigns]

Colin:

for the nicest edge possible, I would use a hand held router. there are 2 ways of doing this, depending on whither you are able to drill a hole in the centre of the circle or not.

option 1) make a circle cutting jig for your router
http://www.diynetwork.com/how-to/how-to-cut-circles-and-curves-with-a-router/index.html

option 2) cut a circle from .25" thick mdf (or something else inexpensive) sand it so it's nice and smooth and use a straight cut bit with a ball berring guide to follow the pattern in your mdf.

I don't think a jig saw is the way to go on this.

 

[visual800]

if you absolutely have no other option, cut with jigsaw using a large tooth wood blacde and then go back at slower speed and knock debris off. It is a pain and sometimes that all we got is a jigsaw.

 

[bob]

There are other options. We use table saws at our shop. You can cut circles on a table saw....

You can also drive a nail with a rock. Merely because something is possible does not mean that it's reasonable.

Cutting circles, especially large circles with anything less than CNC tackle is problematic. Using hand and even stationary tools you're essentially trying to draw a circle freehand with a power tool. Good luck.

If you opt for a router, it will leave a nice clean edge but it can get away from you in an instant and ruin your workpiece.

If you choose a jigsaw it will leave a less than ideal edge but its easy to control.

It fairly easy to rig an extension table on a band saw which will give you a better and far more perpendicular edge but it's somewhat less forgiving that a jig saw in that if you should get off course it takes longer and more effort to get back on track.

If you go for the table saw like Primitive Pete above, most likely it's because that's all you have. You need more tools.

 

[Colin]

if you absolutely have no other option, cut with jigsaw using a large tooth wood blade and then go back at slower speed and knock debris off.

As the PVC will have a laminated digital print on both sides (inset about 2") before cutting the circle, I think that I'm going to need to use a jig saw.

I guess I'll go to the store(s) and see what they have for blades, buy a few and try 'em out on a scrap piece. Perhaps there's a "carbide" type of blade? This might help with keeping the heat down? shrug

 

[rjssigns]

I've had good success with Bosch blades for everything from Acrylic to DiBond.
Don't forget to sand then flame polish the edge.

 

[TwoNine]

What helps...A little...Is if you have a jigsaw with a variable tilt on the blade - such as a high end DeWalt or similar. Set the saw so that the blade is at an angle instead of cutting straight up and down - This cuts down on the welding problem pretty significantly. Use that method with a slow blade speed and decent rate of travel and you'll have minimal sanding. But I still always recommend over-cutting them and sanding down, you have SO much more control that way IMO.

 

[Colin]

What helps...A little...Is if you have a jigsaw with a variable tilt on the blade. Set the saw so that the blade is at an angle instead of cutting straight up and down - This cuts down on the welding problem pretty significantly.

Great tip, thanks, I'll try that on a piece of scrap.

 

[weaselboogie]

I have great success with a bandsaw. Make a jig on the bottom side with a nail sticking up about 1/4" and 2' away from the blade. Make a center mark on your substrate on the backside. Feed the material in, underneath , line up the mark to the nail and spin. Once you get this setup you can cut a perfect circle in 10 seconds.

 

[Colin]

^^^ That too is a good idea. Thanks. The sign is a double-sided one, and my plan was to lay down the prints first, but I suppose could do this method as you've described, and then apply the prints, which I would have to cut by hand, cover with transfer tape and then apply after the cut using application fluid.

Hmmmm

 

[TwoNine]

Yeah - lay the print after cutting for sure. Regardless of how you cut it. Otherwise they may even be off from one another from side to side. It's just never a good idea to lay a print/vinyl prior to cutting.

 

[Colin]

It would be easier to lay the prints down first using the Big Squeegee, I could get the positioning right no problem, but putting the laminated prints down after with transfer tape & fluid would be ok too.

 

[Sign-Man Signs]

About two years ago, I had a project that required me to cut about 200, 14 inch circles out of expanded PVC, 1/2 inch thick. I made the attached jig then used a trim router to make the cuts. The router mounts on the left side as shown in the three hole position. I use a 1/4 straight flute router bit. Once set, the router won't walk on you and cuts a perfect circle. The jig is made out of a 3/8 x 8" x 30 inches long aluminum plate I got from the local junk yard for about 20 bucks. Guide marks are at 1/2 inch intervals. Mounting hole size is 1/4 inch.

 

[Colin]

For our common data bank, I just cut the 48" circle using a new 10 TPI jig saw blade. It didn't "weld" the PVC behind the cut like the used one that was originally in the saw. I also ran the saw on a medium speed.

Thanks for all the replies.

 

[bob]

I have great success with a bandsaw. Make a jig on the bottom side with a nail sticking up about 1/4" and 2' away from the blade. Make a center mark on your substrate on the backside. Feed the material in, underneath , line up the mark to the nail and spin. Once you get this setup you can cut a perfect circle in 10 seconds.

Could you expand on this? Perhaps with photos or illustrations? Your description above is somewhat less than revealing.

I've been contemplating the notion of a universal jig for cutting most any oddball shaped piece into a circle, ideally without a center pivot ala centerless grinding, and would very much like to understand your setup.