I have a need to put a 1/8" slot/channel through a 1/2" aluminum rod across a 90 degree arc. I need downward pressure on the rod to rotate the rod 90 degrees, so a pin holds the rod through this slot such that as the rod slides down, the rod will spin. Picture drilling a hole through the rod from 0 degrees to 180 degrees, then moving down the rod a distance equal to 1/4 the circumference, rotating the rod and drilling a second hole. Now picture connecting the two holes to make a slot/channel.

I proto'd this with wood, and did this by marking at 0 and 90 degrees as outlined above, drawing a line between the marks, and using the drill press with a wood bit, then slowly walking the rod through that line. With metal, I'm assuming I'll need to make multiple shallow cuts, like you'd do when making a channel with a router through a piece of wood. Also, I'll need to make more than one of these cuts, so with that in mind, I am looking for some mechanism to make the travel of these cuts repeatable.

I am thinking to use a drill press with a machining bit, but how to hold and move the rod?

What would be really great would be a cross-slide vise that not only moved the work in the horizontal, but rotated the rod at the same time with a 1:1 ratio. Anyone heard of such a thing?

The other option would be to build something custom. My first thought is to take a page from a lathe, and using a drill or lathe chuck that holds the 1/2" rod, put a fin on the shaft at 45 degrees to run against a rigid guide, then use a screw on the end to replicate the motion of the cross-slide. Another possibility might be to put threads at 45 degrees on a rod that can couple to the 1/2" project, then screw those threads through a matching nut. Anyone heard of anything with threads that course? Some sort of clamp assembly maybe?

Hmm, I wonder if a corkscrew would work? Thinking out loud, clamp a piece of cork, run the cork screw into it, and use that to guide and repeat the movement and rotation on the rod for the cut. It wouldn't be too hard to increase the angle as needed by bending the coils in the screw... I don't love it, I think it'll need to be more rigid, but it feels like it could lead to other ideas...

There is some wiggle room in this project:
I don't need to stick with aluminum, but it is for a marine application, so it needs to resist corrosion like stainless steel.
The diameter of the rod can be different, though it needs to stay under 1".
The 45 degree cut is arbitrary, but it does need to travel the 90 degree rotation of the rod. I am taking advantage of incidental downward pressure on the rod to allow 90 degree rotation at a point governed by another guide. But, a 0 degree cut, essentially nearly cutting the rod in two, not only doesn't allow reaction to the downward travel, and makes the rod too fragile. Also, if the angle's too large, the rod has to travel too far to get to the 90 degree rotation.

Thanks for anything you can suggest! Either in design or in the tools to use for the project. Note that I'm DIY on a budget. Something like a CNC is out of bounds unless I just break down and hire out to a shop.


Read the full thread at metalworkforums.com...