B&D Workmate Update for my CNC Bridges

Bridge Vise for Vertical Clamping

The Black and Decker Workmate is an ingenious product.  The split top serves as vise jaws along with the bench dogs to allow clamping boards of most shapes snuggly to work on. I've owned one for 4+ decades and found many uses for it. 

On my CNC I use 3 bridges rather than a t-slot or vacuum bed to hold boards in place. T-track in each bridge top let me slide wood clamps to hold down projects.  I woke up early on 2/27/2026 with the idea of modifying two of the bridges so I can also use them as clamp jaws.  (Bridges)

First step was to double up the thickness of the jaw faces. I glued another piece of 18mm Baltic Birch plywood to them to create more surface area on the mating faces. I then applied some Cat's Paw friction tape to their surfaces. 

Doubled Up

There is roughly 22" between the right side rail and the radial axis tailstock rail.  Swing room for the crank handles may eat up 1.5" on each side.

The bridges don't need to open more than 1.5" or so for what they may need to clamp vertically.  Short lengths of all-thread, a couple lock collars and Teflon washers on each side, and a couple handles.  I'm using 7/16-14 all thread.  My local True Value store had 2' lengths of 7/16-14 all thread. I bought one and cut two 9" sections from it for this project

Some blocking to bring the thread collar out flush with the edge was added.  Collars and square nuts were ordered from the Jungle store. 

Collars arrived 3/11/2026.  I drilled a recess for the collars and the Teflon washer on the inside of the front bridge using a 1.25" Forstner bit on my Nova Voyager drill press. 

I made the Teflon washers for the 7/16" all thread. I clamped down a 1/16" thick sheet of Teflon on my CNC to cut the center holes that will ease the process.  I sliced off the row, then snipped them apart before sliding them onto the all thread.   I clamped them in place with a hex nut on each side, then mounted them on my hobby lathe to turn them round.  

3/16/2026: I finished up this project this day.  I chiseled out a slot for the square nut to be able to slide under the top of the bridge, then glued a board next to the nuts so they wouldn't be able to turn when tightened down. To keep the nuts in place I added magnets next to the shafts

Square Nut. Round Magnet

First test holding a 3/4" thick section of plywood proves they work.  As with the Workmate though the pressure from each side needs to be the same for flat boards.  Best strategy is to make sure the front side is parallel to the front frame rail and locked tight to the side rails. Screw the back bridge/jaw tight, then lock it tight to the side rails.  

Handles were needed.  I drew up a design and cut them out on my CNC from a thick scrap of red oak.

Red Oak Handle

Two Hex Nuts Jammed Together

Handle slips over the outer hex nut.

This idea works well for holding boards vertically to CNC joinery on their end. Dovetails and box joints and variations are now fairly easy to cut using my CNC.  The details of this project are prototype solutions.  As I use it needed improvements will like show up. I'll append them to this blog post when/if they happen. 

In use this bridge vise has proven to be quicker/simpler to use than my compound angle clamping fixture here:  Fixture.  Clamping anything from long boards that need joinery on their end, or small parts that may need a curved surface on their top edge is quick and easy to do. 

4D

Optimizing CNC Pockets for Hex Nuts

For the closed end wrench handles I made in a previous post I needed a pocket for the hex nuts on the vise shafts.  These are the steps I used to make an optimum vector outline for the CNC cut pockets.  

1. Start by carefully measuring the size of the hex nut.  A digital caliper is preferred for that task. 

Hex Outline

2. Draw a hexagon that size.   My CNC software has a nice polygon drawing tool that makes drawing hexagons easy. 

3/16" Bit Used

3.  Choose the smallest diameter end mill that has enough length to cut a pocket as deep as the nut is thick.   Draw a circle that diameter centered on each corner of the hexagon.  

Corner to Opposite Corner

4. Now draw lines from corner to opposite corner. 

Inner bit outlines

5. Draw another circle the size of the bit centered where the initial circles cross the diagonal lines .

Almost Done!

6. You can now delete the initial circles and diagonal vectors.  

Circles Snipped

Hex Snipped

7.  Hopefully your software has a snipping tool as you need to snip away the section of the new circles that is inside the hexagon, and then snip away the section of the hexagon that is inside what is left of the circle. 

What you are left with should be a closed vector outline of the optimum hex pocket shape. 

Room for Hex Nut Corners

Again, choose an end mill the smallest diameter that is long enough to cut the pocket for the hex nut.  The example above was a 15/16" tall hexagon and the bit used was a 3/16" downcut spiral end mill.  For 1/4-20 hex nuts I use a 1/8" bit.  For even smaller nuts a 1/16" bit can be used.  

Comments always welcomed!

4D

Motorizing my Adjustable Angle CNC Clamping Fixture

Using my adjustable angle clamping fixture is relatively easy.  One nagging "flaw" it has is the ease or perhaps unease of setting the angle on it.  Projects often expect a precise setting. The action of lifting the jig and holding it in position while setting the clamps is usually an awkward ballet.  If only I could motorize it. 

Setting the Angle

The desire to motorized my clamping fixture is an old one. I've looked into stepper motors with Arduino control, drive screws and rack and pinion gear drives, long counter-balanced lever arms, magnetic repulsion, etc.. Magic had only a fleeting consideration as I found it an unreliable force.  😉

This project strives to motorize the lifting of the fixture with a linear actuator.  It is also a test to see how fine of control I can achieve with momentary toggle switch up/down button presses to control the actuator.  I hope the actuator movement can be slowed down with a variable speed controller for more precise positioning of the fixture angle.  

Actuator Placement

The tough challenge was finding an actuator that could work with the geometry of my fixture and how it is mounted on the CNC relative to the base the CNC sits on. Position of one end of the actuator needed to be "exactly" where the end limits of a specific actuator would line up in both horizontal and vertical positions of the fixture.  An actuator with eight inches of travel would only work if mounted in a very specific position.

As the fixture rotates from vertical to horizontal, the actuator had to be entirely behind the vertical position.  Geometry dictates exactly where it could be mounted. Ideally the push of the actuator would be 90 degrees from the fixture plate, but that is impossible given the arcing transition from vertical to horizontal.

The actuator I ordered has 8" of travel.  It has built in limits to not go past 8" or under 0" when closed. In the diagram above I had to find a position under the bed of the fixture where when mounted the actuator moves exactly 8" from vertical to horizontal positions.  You can see that I've come very very close.  Within a few 1/1000ths from 8" .

Mounting brackets that came with the actuator are represented in the drawing.   

I took the fixture off the front rail and clamped the bed of it to my CNC so I could cut pockets and holes for the nuts and bolts needed to mount the actuator end brackets

I've now got one end bracket bolted to the underside of the fixture bed.  I've at least momentarily mounted the other end bracket on the CNC base.  I'm waiting for a variable speed control to arrive before wiring up the actuator to see if where it is mounted works.

Wiring the speed control took some contemplation.  The control box is a simple toggle relay that switches the current depending on which control button is hit.  It suggested the speed control should be between the power supply and the control relay box.

The speed controller arrived.

Speed Controller

The lead from the power supply needed to be cut off and wires stripped to attach to the speed controller. Done. The wires from the control box to the actuator need to be soldered together.   

I'd hoped the speed controller came with a way to bolt/screw it down, but that appears to be another puzzle to solve. I want to affixed it to CNC frame so it is secure and won't move when I raise or lower the actuator speed.  It appears to be an aluminum extrusion, capped with plastic ends and a front frame for a metal plate that has the speed dial and markings on it. There are a couple of screws on one end, but not the other end although there are holes for screws there. There are also two screws on one side of the extrusion. In line but not equally spaced from the ends.  I suspect I'll need to open it up to see if I can drill a couple holes in the bottom to put screws through for attaching to the CNC frame.

Soldering the actuator cable to the control box cable is done.  A system check verified that the speed control and remote control all work as expected.  Installed on my CNC it looks like it will do the job.  There is a bit of flex in the fixture, but with the speed control and a magnetic digital angle gauge attached to the metal blade of a tri-square it only took a few second to set the angle on the fixture.  Tightening the cam levers momentarily wiggles the CNC and make the angle on the gauge vary, but once done and settled down the angle returns to what the actuator set it to. 

Actuator in Place

The controller came with a wireless switch.  That is nice as finding a place to mount a wired switch would be a challenge.  I can keep the wireless control in the drawer of the work station. 

In practice I'll never need to bring the fixture to a horizontal position as I have a better setup on the bed for horizontal work.   For now though this linear actuator should do fine handling any or of he future angled or compound angle CNC jobs. 

One small shortcoming is that when beginning at the vertical position and actuator retracted, starting out the actuator force applied is at a shallow angle relative to the fixture bed. Due to play in the connection points precise setting of angles from 80 to 89 are best done manually.   The ideal angle between fixture and actuator would have been 45 degrees at both starting (vertical) and ending (horizontal) positions of the fixture. Unfortunately no such mounting point for the actuator exists. If I could mount the base of the actuator 45 degrees from the bracket when vertical I'd need a bit more than 8.5" of travel to push it to horizontal position. 

A revision to make it work at 45 degrees would require a new mounting platform for the bottom of the actuator, and new positions for both end brackets. The bottom end would extend much farther away from the CNC base. I'm looking for an indirect mechanical approach/solution, but complicating the mechanism is contrary to my personal design philosophy. A better strategy might be to start from scratch and design a new fixture that includes motorized control from the beginning.  

Questions? Suggestions?  Leave a comment.

4D

 

Rotary Cut Radius Box Corners

You can cut a rounded corner for a box as a two sided job on your CNC as shown in a previous post:  HERE

You can also cut the rounded corner on the rotary axis of your CNC from the same rectangular starting block. 

16" Long 90 Degree Rounded Corner

What the CNC thinks it is cutting

Actual ends shown in the first image

The centers on the block ends must be a little lower than actual when mounting the block on the radial axis. The profile shape must be placed so all parts of the inner curve can be reached by the bit as it rotates around the center. Very little material is taken off the rectangular block compared to what would need to be removed from a cylinder of wood for the same result. No roughing pass is needed given the small stepover taken by the bit when cutting this shape from a block. For this example I used a 1/4" diameter ball nosed bit. 

Vectors Used

The starting block for a rounded corner with a 1" internal radius and 1.75" external radius is 2.5" wide and 1.0625" thick. Adjust the starting block size to encompass different sizes of rounded corners.  I recommend making the block 2" longer than the final part you need to keep the router/spindle chuck away from the rotary axis chuck and tailstock. 

An example Aspire CRV3D file for this specific project can be found on Vectric's forum here:  Forum.Vectric.com

The actual vector used for the final cut was created with the "Unwraps selected Object" tool you can only access while in a rotary job. 

I helped students with rounded corners for their cabinet projects several times over my teaching career. This is one creative application for the rotary axis of the CNC. 

Question, critiques, and comments are as always encouraged.

4D