Cam Levers vs Twist Knobs

The longer I use a jig or a fixture, the more likely it is that I'll find a subtle flaw or a feature that could be improved.   The Angle Clamping Fixture I have on my CNC works fine, but is a little finicky to lock in place to set the angle. I used two twist knobs to tighten the fixture position.   They worked, but would occasionally bump the fixture angle as they rotated to get tight. 

My Compound Angle Clamping Fixture

When I made the Bridges I now use for spanning my CNC bed area I chose cam levers to lock down the ends quickly.  I am extremely happy with how quickly I can loosen, reposition, then tighten down the bridges using the cam levers. 

My Bed Bridges

It took me awhile to realize again the value of cam levers.  When a jig or fixture works OK it doesn't beg for small improvements.  An email add from the company I bought the cam lever for the Bridges from provoked me to wonder if anyone sold a size I could use with the existing 5/16-18 bolts on my clamping fixture. Apparently yes. 

Cam Levers at Amazon.com

When these cam levers arrived they included 5/16-18 T-bolts that were too long. The hex bolts I'd used were too short for the cam levers.  The fix required CNC cutting a pocket for the oval head of the t-bolts, and cutting down those bolts with a hacksaw.

Improved cam locking

What used to take several turns of twist knobs to unlock then relock this fixture now takes flipping two cam levers to loosen or tighten.  

Router Fence

The fence I have on my bench mounted router is another place where cam levers make adjusting it quicker and easier.  I had some cam levers on hand that would work with the 1/4-20 T-bolts.  The bolts were too long though and had to be cut shorter with a hacksaw.  

Cam Release

Cam levers are available in many sizes. As I revisit many of my shop fixtures/jigs/tool fences that use twist knobs it is apparent that cam levers would improve the simplicity of using them all.  As I look back on the furniture projects I've done over the last several decades I realize that cam levers have been the ideal solution many times.  One example was a chair design with an adjustable seat that would slide forward or back for the user. Back then was before there was an internet and I made my own cam lever from an aluminum block using a milling machine as well as a few other shop tools. 

4D

Comments and questions are welcomed and appreciated.

 

CNC Frame Bridges as an Alternative to T-Track rows or Vacuum Beds.

I previously made a couple of frame bridges to support an assembled student project for some CNC joinery cuts: Here

Lately I've been using the bridges more often to support flat work. They have proven their worth in every case and these are the advantages they offer:

1. They are stiff and flat and remain level to each other and plane-parallel with the CNC's X/Y travel.

2. They have horizontal edges to provide clamping surface for c-clamps to hold the work down.

3. They have aligned holes for pins to set the project board against for perfect alignment with the CNC Y axis. 

4. They attach quickly into the side frame rails with one screw (or cam lever) on each end into a t-nut. 

5. They can be positioned anywhere along the side rails. 

6. With a little modification, two bridges and some all-thread turn into a bed vise that can clamp parts vertically for joinery cuts on their ends.  Link:  Bridge Vise

7. Since the bridges can slide anywhere up and down the side frame members, only three strips of 30" long t-track are needed to cover the entire X/Y cutting range of the CNC. This compares to six strips of 60" long track needed before. 

Waiting for cam levers

With cam levers to permit quick positioning

So far two have been enough, but a 3rd will be useful for long boards that may have a bow in them. The 3rd bridge could also be used to clamp a stop block on for repeated identical cuts using the same Y origin. Small C-clamps have been enough to hold work to them, but with a t-slot track embedded in their top any other t-track clamp can be used. 

My Probotix Meteor CNC has one design flaw.  The backplate that the router bracket attaches to comes down with the router.  This can collide with clamps behind where the router is at. Switching from t-track that runs up and down the bed to bridges that run side to side keeps me from clamping down anything from the front or back. Since changing to bridges I have yet to see the router bracket collide with a clamp. 

  

MDF slats between t-track on another MDF panel that span the CNC frame tend to sag in the middle over time. Plywood bridges in an L or T configuration remain stiff and straight with no deflection under the weight of projects boards or flexing when clamped to warped wood. 

So far I haven't come across any flat work I couldn't clamp securely down to these bridges.   

My strategy so far for clamping down flat cuts is to use the center of the board as the Home (start/end) point.  Then I make sure the bit won't try and pass though a clamp during cuts. I can offset the start point to the center even if zeroing the bit on the board edges.

I have some thin cork sheets I bought that might be useful as shims to protect the bridges from through-cuts. A 1.5" square to put under boards where each c-clamp ends up should be enough lift to account for router bit penetration. I'll pre-cut a stack of them and keep them stored close to the CNC.  1/8" Baltic Birch plywood scraps can also be used as shims.

I used a self-centering punch to make sure the screws for the t-track would be centered in the screw holes. Their screws go through the top plate and into the top edge of the vertical rib.  
Locking the bridges down doesn't take much time, but does require getting the Philips screwdriver out and putting it away when done. The cam levers are the magic bullet that makes the bridges easy and quick as possible to set in place and use.

Now I'm contemplating how best to accommodate thick/tall work that I could cut if I could sink it down into the frame.  The bridges could be bolted into the bottom slots of the frame to gain 78mm save for the Y-axis limit switches that protrude into the 30mm width of the rails.

The day the cam levers arrived I cut a notch in the top end of the side rails to slip t-track nuts into for them. The levers came with a stud too long but none were available the size I needed. I cut the threaded studs down to the the length needed using my metal cutting chop saw. 

So far I'm happy with this design.  The cam levers make a huge difference in the time it takes to set up for a cut. When I can't use the t-track clamps small C-clamps do a great job of holding down the work. I just have to take care when setting up a job to not run into a clamp.

The black t-track came from Amazon.com:

The cam levers came from Zoro

Comments and questions welcome.
4D