Workholding - Long square bar to mill bed

Hello,

Thank you for taking the time to read my post.

I need to hold a piece of aluminium bar to my machine bed for milling. This bar is ~50mm x 50mm x 700mm. This would seem like a common problem so I'm probably over-looking an obvious solution.

I need to machine all of the top face so I can't clamp it down on top. If I do this in a vice then I figure I may need at least 3 vices to give the required rigidity. I only have a single vice and am keen to avoid the expense of buying more.

I think I need some sort of edge-clamping method ideally and I've been looking at edge-clamps/toe-clamps/mitee-bite type fixings but for some reason there doesn't seem to be much availability of those in the UK or at least they are very expensive. The other issue with them is that they seem to clamp parallel with the bed-slots where as I would need them to apply pressure perpendicular to the slot (because the bar will run parallel with the slots).

Thanks for reading and I'd welcome all suggestions!!

Cheers

Is breaking a code into divided parts an option? then I guess a simple bolt and nut can work for you, code first the upper part then cut with the bolt and nut hold down on the middle part and the lower part, after cutting the upper part, transfer the hold down bolts and nuts to the upper part then start cutting the middle part and so on and so fourth :)

http://www.cnczone.com/forums/attach...d=381418&stc=1

http://www.cnczone.com/forums/attach...d=381420&stc=1

clamp swapping is the way i would go too, depending on flatness requirements and tolerance. at 700mm you'll probably need several clamps evenly distributed. you can mill the areas between the clamps then shift them one at a time to the already milled bits and mill the rest.
things to consider with this method are,
how flat is the other side? is the material bowed? how many clamps do i need to hold it flat successfully? how flat do i need it to be and at what tolerance?

if you want maximum flatness and the best shot at a tight tolerance you can split the cut into smaller amounts and flip the part one or more times. this will create a successively more flat surface to clamp against against the bed.

when swapping clamps loosen one clamp, re position it, and tighten it before loosening the next.