Over the last ~year, 1086 has been working on streamlining our machining process for machining aluminum box tube. Our new tube vise is able to hold tube in both the 1" and 2" orientations, allows for machining all the way through the tubes, and streamlines the work coordinate system.
The clamp is cut from 1x3 6061 bar from Xometry and uses a set of Eccentric Hex Clamps. They’re definitely a bit overkill, but we had them on hand. Some small changes could make any of the other sizes on McMaster work fairly well.
Clamp in 2" orientation: When machining the 2" wide faces, the tube rests on the upper “shelf” of the vise. This allows the lower area (highlighted in blue) to serve as a relief so that you can drill/mill all the way through the part without cutting the fixture.
Clamp in 1" orientation: When machining the 1" wide faces, the tube rests on the lower “shelf” of the vise. This allows the lower area (highlighted in red) to serve as a relief so that you can drill/mill all the way through the part without cutting the fixture.
WCS: In both orientations, the clamp provides an end stop in X and a fixed Y position. Because of this, we can avoid re-zeroing in between different operations, and even between entirely different parts
While the clamp was designed for 1" and 2" tubes, it can accomadate anything smaller than those sizes using parallels to shim the gap between the clamp and tube. Pictured above is a 1.5x1.5 tube shimmed with a 1/2" parallel.
Strength: So far, I’ve had no issues with it. I’ve only pushed a 1/4" end mill to around 100 IPM (.075 radial, .125 axial), so I certainly wouldn’t expect to, but the clamps are rated for 2k lbs, so I expect to be able to push pretty hard on this in the future.
Tube Ends: Prior to making this, I generally machined tube ends using a 3/4" end mill full depth through the end of the tubes hanging over the vise. Because there’s now material directly under and next to (on the X- edge), this is no longer possible. In order to cut the edge all the way, I cut the top .800" in the first op, then flipped the part over for op 2 and slip the now-finished shoulder (red edge) into the hard stop so that I could cut the remaining saw-cut edge (blue). This ended up working extremely well, and there’s hardly any cusp from the overlap.
Price: One of (in my opinion) the biggest strengths to this design is the price. We paid $32 for a 30" piece of material and cut a 20" version and 9" modified version (see photos below for modified version). Even if we purchased 10 clamps instead of using ones on hand, we be spending right around $100, which ends up being pretty cheap compared to some of the COTs options.
CAM: When programming parts, I imported the clamp body into Fusion360, mated it to the part, and set the origin based off of that. It’s an unnecessary step, but I find it to be quick and a good way to double check my WCS.
CAD release: The STEP file in GrabCAD works, but has every single clamp in both the open and closed position for a 20" version. The Solidworks files are set up parametrically; edit the “Length” variable in the “Parametric Body” file and the assembly will automatically update. I chose to cut a 20" one due to machine travel distances, but it could easily be extended to suit whatever length you want.
Holding the clamp: Originally, I was planning on boring holes for 1/2-13 holes to bolt to the bed of the mill. However, because the mill belongs to our sponsor, it makes more sense to put the tube vise into the mill vises than to remove their vises every time we have to machine tube. It wasn’t the solution I had hoped for, but we lose no noticeable rigidity (the 1" bar is plenty stiff for the forces involved in cutting tube, even when mildly cantilevered). Additionally, the WCS is still constant between operations, so even if I take it out at the end of every day, I’m still only edge finding once per day, a massive improvement over our old tube system. I have CAD with the 1/2-13 holes if anyone is interested.