hello cnczone,

this is my first post. it looks like this is an active, deep site with lots of pros and veterans. glad to be here.

i'm the teaching assistant in the digital fabrication lab at columbia university's graduate school of architecture. we have a small lab: a waterjet, two 3 axis mills and we just got a new mill for metal. it's a Techno LC 3024. it has a 30x24x5 bed and an oil coolant system. http://www.techno-isel.com/CNC_Routers/3024LC_TableTop.htm

me, i'm not a pro and milling metal is new to me and everyone else at school. it's definitely not a pro shop situation. We have lots of students with varying skill levels. we want to train them to use the mill. typical things that students will do: contour cutting aluminum, mild steel and stainless sheets; surfacing thicker aluminum block.

i need to know: what kind of sacrificial layer should go below a piece of metal that is being cut all the way through? aluminum? mdf? plywood? does it matter?

my idea is to put on a sacrificial layer and then mount toggle clamps on it. At first we'll require that students conform to a standard width (18") with their material so that the jig will work for everyone. thinking about using these toggle clamps that i read about in another post. http://www.bosstoolsupply.com/index.asp?PageAction=VIEWPROD&ProdID=2932

any feedback on the sac layer, jigs etc? Sorry for the long post.

thanks,
josh draper