# How to precisely join PVC boards at 90º ?



## Paul01 (Mar 17, 2008)

I'm working on a frame for a mini CNC machine. It is made of 1/2" PVC sheet. The base is a square frame, it's 4" tall and 14" on each side. I'm trying to figure out the best way to join them very straight and secure. 

I was thinking of using a butt joint, end drilling the shorter boards and threading the holes, or cutting a notch and putting a nut in it, and then just bolting the longer boards onto the sides, then adding a gusset where I have room. But I'm not sure how to get a true end drill hole in the end of a board. I have access to a drill press, but I can't find an explanation of the proper technique. If I clamp it by one of the small edges with the length sticking up I feel like it wouldn't be that secure.

Any other advice or ideas on how to join the PVC boards at 90 degrees is welcome. Thanks.


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## cabinetman (Jul 5, 2007)

What are you referring to as "PVC boards"?












 







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## woodnthings (Jan 24, 2009)

You can butt them as you mentioned, then use these screws to fasten them at right angles: http://www.acumentnorthamerica.com/deltapt.asp They are self tapping and meant for plastic. 
The drilling operation must be precise, so I'd use a drill press. The face holes and countersinks are easy, the end holes require a jig and vertical set up fixture.
Make a jig to locate your holes on the ends by capturing the width of the 4" boards. Then use the same jig to locate the holes which are spaced the same on the ends...or you can measure accurately, but that's up to you. :blink:
The fixture to hold the boards vertically off the drill press (assuming a bench top, without enough room to stand the 14" length under the quill), can be just a hollow box that you can clamp the boards to or anything that's 90 degrees and can rest on the floor. Just clamp the bench top to the bench ( to prevent it from falling over) and rotate the head off over the edge to increase the length you can drill vertically. You can measure accurately or use the drill jig for the location and spacing.
If you can accurately drill them with a hand held drill and your jig to hold it vertically, that would be easier... :thumbsup:

If you have a solvent glue like for PVC pipes that may eliminate the need for drilling and you can use a glue block in the corners for reinforcement. I'd make a wood rectangle that's got 90 degree corners for a base the fits inside to keep all the corners square. There are self squaring clamps if you have them also.  bill


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## Improv (Aug 13, 2008)

Paul, Woodnthings suggestion of solvent welding is the best suggestion for joining PVC. If you have the room in your design, use a square rod to both give you the angle and reinforce the joint along the inside corner.
However, if possible, I would mill out the base from a thick piece so that you would only need to worry about squaring your bit to the tool surface and the single piece gives no joint for failure.
Additionally, you could make two nested square boxes out of wood gapped such that you could heat form a PVC sheet between them to a 90 deg angle. The PVC should soften at less than 100C (actual temp depends on how much plasticizer the manufactuer has added), then lay it inside the larger box and press down with the smaller box. 



cabinetman said:


> What are you referring to as "PVC boards"?


Polyvinyl chloride is PVC ... or was it the synonym of "board" with 'sheet' that was giving you trouble?

Regards,
Improv


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## cabinetman (Jul 5, 2007)

Improv said:


> Polyvinyl chloride is PVC ... or was it the synonym of "board" with 'sheet' that was giving you trouble?
> 
> Regards,
> Improv


It wasn't the PVC part. I thought the OP would clarify which or what type of "board" he was asking about. "Board" can mean any of a variety of sheet goods. 












 







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