OT - Slightly machining plastic sheets

12" | X .25") that I simply need a contour cut around the perimeter.Since this | client tends to think Home Depot has everything I fear that I'm getting a | bunch of blanks from some low quality material to machine. | | Any suggestions on tooling etc.. to machine the typical sheet plastic found | at HD? | | no problem on HP / speed (10K) or coolant. | | Pedroman

In the phone book look for plastics suppliers. Signmakers use gobs of it. Standard routers and bits work fine, but you have to go quickly or it will overheat the plastic. A template or bearing bit helps.

Make a vacuum fixture to hold the parts and use a 'down cut' router type bit. It will be a right hand cut with a left hand spiral so cutting action pushes the piece downward rathwer than pulling it up. I use an air blast from a micro mist applicator with the fluid turned off. A .250 diameter cutter I usually run approx 7k rpm and 25-30 ipm when cutting

3mm thick parts. These are odd shapes cut from blanks that are a portion of a spere (usually) with no seal installed near the part boundary. I make the conforming fixture smooth enough to be adequate for sealing, with channels cut to apply the vacuum to a signifigant area. If you wish to email me for more details, put vacuum fixture in subject. Flat parts with a seal installed would allow a much faster cutting rate.

michael

Home Depot toolroom wood router, a pilot bearing equipped router bit, and a template. Fast, cheap, and effective. For a more production oriented run, I'd upgrade the router to a table router or an overhead pin router.

Cheers Trevor Jones

Most likely it will be polycarbonate (Lexan). Machines easily. Get a piece of MDF to use as a sacrificial underlayment and simply bond the Lexan to this with 3M 77 spray adhesive. Use a couple of clamps also. You might want to take 2 passes on the first one and see how it goes . Any router bit will work fine and you don't need coolant.