Introduction: 3D Push Block for Woodworking
This is a tool that can help to make sure you have the same number of fingers after using your table saw as you had when you started. I won't say it's the perfect push block for all occasions, but it is a great addition to your safety arsenal. It really shines in some specific situations - such as ripping thin pieces from stock that is already pretty small. Like when you are trying to get that last little useful piece from some expensive, exotic hardwood.
This shop-made push block is called a 3D Push Block because it gives you control on the stock in three dimensions: it holds stock firmly down to the table, firmly sideways against the fence, and pushes it forward through the cut. All while keeping your hands a safe distance from the blade and preventing pieces from rocketing out the back into you or surrounding objects.
This push block was inspired by the GRR-Ripper by Micro Jig, a very popular woodworking accessory that has surely prevented a lot of injuries over the years. In my opinion, it is a good value and money well spent just buying one. This Instructable shows how the more...frugal, among us can make one at lower cost.
I found even more inspiration on YouTube by others making their own versions. Here is one of the best examples.
Step 1: Tools and Materials
I made this out of Baltic Birch. I used some 3/4" (which is really 18mm) and 1/4" (6mm). I love working with real Baltic Birch. It is very consistent and stable, with few or no voids in the lamination.
Materials and Supplies:
- 3/4" Baltic Birch, or similar plywood
- 1/4" Baltic Birch, or similar plywood
- (4) 1/4"-20 EZ-Lok threaded inserts
- (4) 1/4"-20 Star Stud Knobs
- Gripping material (can substitute rubber mat and adhesive)
- #6x1" Wood screws
- Wood glue
Step 2: Cut and Prepare Assembly Pieces
Cut plywood to the following dimensions for the various parts:
- (1) 8"x3-3/4"x3/4" for the top or main body
- (2) 8"x2"x3/4" for the left and center legs
- (1) 8"x2-3/4"x1/4" for right leg
- (2) 8"x3"x3/4" for handle (used in step 4, not shown in pic)
- (1) 8"x3-1/2"x1/4" for balance support upright
- (1) 8"x2"x1/4" for balance support foot
Mark layout for 1/4" slots in top. Slots are 2-1/4" in from ends. Slots end 1/2" from right side and 1" from left side. These slots will allow for adjustment of the center foot. Cut the slots using your preferred method. I like to predrill the ends of the slots and use the router table to cut the remaining part. Setting up a fence on your drill press table really helps here. It is not critical that the slots are exactly 2-1/4" from each end - but it is critical that the spacing of the slots and holes for the threaded inserts be the same. Leaving the drill press fence in place and using it for all of the holes aids in this.
Do similar slots for the balance support upright. These are again 2-1/4" from each end, so you can use the existing fence setup on both your drill press and your router table (if that's how you made your slots). These end 1/2" from the top and bottom of the support upright.
Mark and drill holes on the edge of the center leg. The holes should be 2-1/4" in from the ends (to match the distance between slots in last step) and centered on the width of the leg. For the 1/4"-20 EZ-Loks listed, I find 11/32" holes work well. If you use another brand of threaded insert, drill your holes to the size required. It may be a little fussy, but I like to counterbore the holes just a bit with a 1/2" drill bit to allow the heads to sit flush, or slightly below, the surface. Go slow and steady so the drill doesn't grab and go too deep. Drill the same holes in the center of one side of the left leg (use your fence again). These will hold threaded inserts that allow the balance support foot to be adjusted.
Insert 1/4"-20 threaded inserts into these holes. I like to use a dab of general purpose glue like Elmer's ProBond Advanced to help secure the inserts over time. If you use a polyurethane glue like Gorilla Glue, use it very sparingly so that it doesn't expand over the top or into the threads.
Sand all the pieces as desired, but especially the surfaces that will be sliding against each other during adjustment. If you didn't counterbore the holes for the threaded inserts, you may want to do your sanding before you install them (now he tells me!)
Step 3: Assembly
Start assembling the balance support by cutting a couple of triangular gussets from some scrap 3/4" plywood, or whatever you have on hand. Glue the balance support foot to the upright using the gussets as shown in the pictures. This is a really nice place to use a pin nailer. You can even pin through the side of the foot into the edge of the 1/4" upright if you are careful. Without one, you may have to glue it up in stages and clamp carefully.
Attach the right leg (fence side) to the side of the main body by clamping, drilling countersunk screw holes, and driving in #6x1" wood screws as shown in the pics. Do not use glue here. This leg is attached like this because it is one of the most likely to be damaged, so needs to be replaceable. Also, the horizontal screws into the main body won't be in the path of the blade if you do accidentally cut into it.
Glue and clamp the left leg and secure with screws, brad nails, or pins. This leg is a lot less likely to get inadvertently cut, but you could skip the glue and use wood screws alone if you want it to be replaceable too.
Step 4: Making the Handle
I saved the handle for last because it has to be made to provide clearance for the center leg adjustment knobs. If your knobs are different than what I used here, you may have to modify the design somewhat. You may want to modify it regardless - I don't seem to have much luck making handles that look good. If you make this and come up with an attractive handle, please post it!
My handle was made from two pieces of 3/4" material glued together. I layed it out to be 1-1/4" from the outer to inner edges. Holes were drilled for the inside and the remaining waste cut out on a bandsaw. I used a combination square to mark where to cut off the corners for rough shaping. Glue these pieces together and clamp or fasten with brad nails.
Filing and sanding got the handle to the final shape. I routed the edges with a roundover bit for comfort. Once you're happy with it, drill holes in the top of the main body 5/8" in from the edges and centered. Countersink the holes from the bottom. Start #6x1" screws from the bottom far enough that the points stick just slightly above the top surface. Place the handle in position and press down to mark for predrilled holes in the handle. Attach the handle with glue and the screws.
Step 5: Final Assembly
Attach the center leg using two of the star knobs and adjust it right next to the left leg. Set the push block assembly on a flat surface and check for level from side to side. You will likely have to trim or sand the bottoms so all line up nicely. A disc or belt sander with an attached table at 90 degrees works well, if you have one. Once finished, adjust the center leg to the middle and recheck. Fine tune until you are happy with it.
Some gripping material needs to be added to the bottoms of the legs. I listed some really nice 3M material in the materials list, but it is a bit pricey. Well, actually, it just doesn't come in small quantities. There are a number of alternatives. One that worked well for me was to attach some tool drawer liner with contact cement and trim with a razor blade. I applied the contact cement to both surfaces and let it dry a few minutes as per the instructions. Then I clamped it as shown in the picture. A similar option might be non-slip drawer liner.
Lastly, I applied some paste wax to the bottom of the balance support foot and all of the surfaces that slide against each other. Be careful not get it on the gripping material - some denatured alcohol will clean it off if you do. The balance support can be attached or removed as needed.
Second Prize in the