Introduction: CNC Hold Down
Quick, tool free, repeatable clamping system.
Step 1: CNC Hold Down Clamp
I originally built my CNC router with several t-slot rails built in for lots of clamping options. I quickly realized they were a pain in the back. I wanted something quicker and repeatable. I'm going to, soon, replace the t-slot with a vacuum hold down. So, I also wanted something that would not interfere with the work surface. I was browsing around through Harbor Freight and found these. https://m.harborfreight.com/24-in-ratcheting-bar-clampspreader-68977.html except 36" (couldn't find online)
Step 2: Modificating.
Because it is designed as a spreader and clamp one end already has a hole drilled through it. I just removed the existing screw and replaced with one of my t-slot screws and a spacer to keep it from binding. The other end I cut to the width of my deck. I drilled a hole and added another t-slot screw and a little bigger spacer, to keep the sliding clamp just off the work surface. This clamp I pretty much leave in place. This gives me a fixed Origin with a sliding clamp.
Step 3: Second Clamp
Pretty much the same as the origin clamp. Big difference here is instead of the screws I used a captured knob on the near and far side for quick, tool free adjustment.
Step 4: Awesome'ness
So far it has been great. Quick and accurate. Another great benefit is I get side clamping because the bar is a little springy. Just set the near side and tighten the far side with pressure. The clamping brackets themselves can be sacrificial if the tool runs over it. The side rails not so much. Make sure you put something between the rail for a sacrificial buffer.