Working with Plastic

[aucran]

Hi, I'm sorry, I couldn't find a good place to post this really.

I want to make some plastic covers, which should be pretty easy, but I'm not really sure how to get good straight edges.

I cut the plastic from a large 4'x8' sheet with a jigsaw so none of the sides are really anything close to straight. I have a mill that I will use to cut the plastic covers to size and drill holes in, but I'm stuck on how to start this.

Since none of the sides are straight to begin with, then I don't have a decent reference point to place the plastic in my vise and square the first edge. It's only about 1/8" thk so its pretty flexible.

Any help on this is much appreciated.

Thank you,
Aucran

[christinandavid]

Can you sandwich the covers together and clamp the lot in the vise, machining the top edge flat - or clamp the sandwich directly to the bed up against two stops for alignment and end mill the edges square?

DP

[aucran]

Unfortunately, I'm making three covers, but they are different sizes.

I think what I will do is just cut some more peices and leave myself plenty of extra room. Then I can have it floating in my vise while I cut one edge, then flip it over to the "straight" side and square up the opposite side.

Thank you though.

[christinandavid]

If the covers have bolt holes in them you could put the holes in first and clamp them to a sacrificial plate, then cut the profile out with an end mill.

Cut the profiles and tap the holes in the sacrificial plate first to guide you when you initially clamp the roughed out part.

DP

I'm assuming your machine can travel over the length of the cover...

[Shane123]

vise it down on top of scrap plastic or wood, make your thru holes, then use the holes to strap it down when you need to make the profile cuts.