The Vacuum Push Block

Though I'm calling this a push block, it's really a double-purpose jig. And that's what I like about it.

You can use it as a pusher, provided the workpiece is wide enough to provide a light seal to the vacuum chamber. It's useful in doing edge-forming work on smallish workpieces, meaning pieces that are bigger than the shoe but smaller than you want to maneuver around a piloted bit wilh your fingers. Suck that workpiccc to the pusher, and you can work all around the edge with your hand on the jig's handle, up away from the cutter.

But where it's really useful is damped in a vise. There it serves as a small clamping plate.

Put a handle on your workpiece by using the vacuum push block. Here I'm profiling all four edges of a small board on the router table. With the vacuum push block. I have complete control of the work, even to the extent of lifting it clear of the tabletop. And my hand is always well clear of the bit.

Clamp the vacuum push block in a vise, with its bottom up, to create a quick-release work-holder. As you can see, the work will be held above the bench and vise, clear of the vacuum line, so you have unobstructed access to the upper surface as well as all four edges.

Making the Push Block

I made this push block fairly large. That's good for its secondary application—as a vise-held clamp plate—but I admit it limits the jig's utility as a pusher. A narrow base—or a narrow vacuum chamber on the same base—might increase its usefulness. As you gain experience with vacuum work, you'll develop a sense of how small you can make a pusher and still have enough holding force to do useful work.

1. Cut the parts. For this jig. I used Apple Ply because of its plywood strength and its low porosity. It has a great many thin plies and no voids.You can make the base of plastic, and use a wood handle. Or you can make the entire jig of wood.

Choose your material, and cut the parts to the dimcn-.-»ions specified by the Cutting List. Radius the corners of the base, either by routing them using the templates described in the chapter "Boring Templates" on page 6 or by sanding them on a belt sandcr.

VACUUM PUSH BLOCK PLAN

TOP VIEW

I Vi

I square =

I square =

Brass barbed hose connector

BOTTOM VIEW

BOTTOM VIEW

Vacuum tape

2. Shape the hand grip. To be truthful, I shaped a prototype handle by bonding a paper layout to a block of wood with spray adhesive and then cutting it on the band saw. Then I sanded to the pattern's lines on an oscillating spindle sander. And having done that. 1 could confirm that the handle was properly sized for my hand and was comfortable to grip. But I also determined that the handle should Ik taller, with the hand grip a hole, rather than a cutout.

To make the handle on the push block shown in the photos, I made a template in hardboard and used a plunge router with a template guide to rough out the shape.

To make the template, enlarge and apply the pattern to the template stock. As you do this, pull the cut edge back xAt, inch to allow for the offset between the guide bushing and the bit. Bit/guide bushing combinations that will yield lA(, inch of offset include (but are not limited to):

VACUUM PUSH BLOCK

Cutting List

Part

Qty. Dimensions

Material

Sole

1 X 3" x

Apple Ply

Handle

l K"x3"x6"

2 drywall screws. #6 x

Brass barbed hose connector, male

-inch bit with a ^inch-O.IX bushing

Form the hand grip opening in the template by drilling some starting holes, then cut out the waste with a saber saw. Cut the radii on the top corners with the saber saw, loo. Then refine the shape and smooth the edges with files and sandpaper.

To cut the handle itself, bond the blank lo a large piece of scrap that's dogged or clamped to the workbench. Use carpet tape for this, and to bond the template to the scrap. Set up the router with the bit and bushing, and rout out the handles. Pry the template off the handle. Switch to the roundover bit. and radius the exposed edges of the handle. Pry it from ihe scrap, turn it over, and radius the edges on the other side. Sand the finished handle.

3. Assemble the push block. Glue the handle to the base. Drill pilot holes and drive drywall screws through the base into the handle.To prevent air leaks, apply a little silicone sealer to the screws before driving them.

4. Drill the vacuum port. The vacuum port is located at the end of the handle so it won't be in the way n

5" to

when the push block is clamped by its handle in a vise. Determine the diameter of the pilot hole needed for the fitting you'll use, and drill through the base.

5. Seal the jig. Use shellac or a varnish to seal the entire jig. Apply two or three coats. While it's good to try to seal the inner surface of the vacuum port, you don't want to clog die port.

6. Install the vacuum connector. If you use a plastic quick-disconnect fitting, use the male. Apply a bit of silicone sealer to the barbs, and press the fitting into the hole.

I used a brass connector, which has a threaded body to turn into the port. File a notch across the threads so the fitting can cut its own threads, and turn the fitting into the port. A bit of silicone scaler on the threads will ensure a good seal.

7. Apply the vacuum tape. Lay out the vacuum area on the bottom of the jig, and apply vacuum tape around the perimeter.

Using the Vacuum Push Block

To use the vacuum push block, you have to adjust your work habits somewhat. You can't start a cut. bring in the pusher,and complete the cut exactly the way you can with an ordinary push stick. If you touch the pusher to the work and pull the vacuum in mid-cut, you may jerk the work enough to botch the cut (depending on just what manner of cut you arc making). Moreover, the act of pulling the vacuum will distract you from the business of making die cut if you are using a stop cock or pinch clamp to open the vacuum line.

This leg template for a five-board bench is used with a router set up with a pattern bit. I clamp the work to a workbench with a clamp plate, then suck the template to the work. With the hoses extending away from the top edge of the work, as shown here, I can rout both side contours and the foot cutout in one pass.

A template that doubles as a clamp plate minimizes the vacuum piping and thus much of the hassle. In the setup being used here, the vacuum fitting has been inserted in one of the bench's dog holes, while the other dog holes have been covered with common packing tape. Pulling the vacuum clamps the work to the template and the template to the bench. The edges are clear, and I can run a flush-trimming bit completely around the perimeter without stopping.

When using the vacuum pusher, make it a habit to suck j the jig to the work before beginning the cut. even before! turning on the router. And if you can afford the equipment, use a pedal-actuated vacuum pump.

Was this article helpful?

0 0
Woodworking Tools and Installation Tips

Woodworking Tools and Installation Tips

There are a lot of things that either needs to be repaired, or put together when youre a homeowner. If youre a new homeowner, and have just gotten out of apartment style living, you might want to take this list with you to the hardware store. From remolding jobs to putting together furniture you can use these 5 power tools to get your stuff together. Dont forget too that youll need a few extra tools for other jobs around the house.

Get My Free Ebook


Post a comment