The ability to make a workbench mobile is a necessity in a small workshop.
See how to add wheels to 4×4 bench legs in a sturdier way than simply drilling into the end grain.
Also see this post:
How to Choose the Right Casters for Your Workbench for even more tips!
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Transcript and photos below the video.
Why Not Just Screw Directly Into the End Grain?
When you insert a screw into the end grain, the thread of the screw is running directly parallel to the grain of the wood.
That means it’s a LOT easier to knock out of the wood!!
And since these screws are holding casters, they will take a lot more side-to-side stress.
That’s especially true if you hit a bump when doing things like rolling the bench outside your garage shop. There may be a lip or dip between the garage floor and the drive, and the wheel, and the screws holding it, take that full impact.
Once an end grain screw becomes loose, it just starts eating out a bigger hole until it falls out of the wood because it has nothing to hold onto.
Insert the Screw Across the Grain
Pocket holes on opposite sides of the leg are a super easy, and sturdy way to attach a plywood square to the bottom of your bench leg. And you’ll screw the caster bolts to that square.
The screws are cutting across the grain of the leg.
And, the screws are pointing inward, at an angle.
This eliminates the side-to-side sheering, even if you hit a bump now and then.
Use a Plywood Square
Instead of mounting the caster directly to the end of the 4×4 post, mount a piece of plywood to the post.
And then mount the caster to the plywood square.
Cut Your Plywood Squares
A 4×4 post is actually 3.5 x 3.5 inches.
That means you’ll need a strip of plywood that is 3.5” wide by at least 14” long.
I would actually cut one at least 24” long, and here’s why.
I had a scrap piece of plywood that was 17” long that I ripped down to 3.5” wide.
Then I put it on my mitre saw and started cutting off 3.5” at a time.
When I got to the last one, I had this problem.
The board was so short that there was no safe place for me to hold it down with the material clamp, and certainly not my hand!!!!
Even if I could have held it, there is too much danger of kick out from the saw.
And boy, do those little pieces of wood go flying!!!!!!!!
So, I used longer boards and clamps to hold the short plywood strip in place while I cut. And yes, I stood off to the side a bit, just in case.
If you start with a longer strip in the first place, you won’t have this problem.
Plan Where Your Screws Hit
You don’t want the screws for the casters to hit the pocket hole screws for the legs.
And, you can only get just so close to the edge of the leg with the pocket holes.
So, you may need to do a bit of planning even before you drill the pocket holes.
SEE: Kreg Jig K3 and K4: How to, Cheat Sheet, and Tips for details on how to align a K3 jig so it is in the outermost position you can place a pocket hole.
I’ll give you a hint. It’s 9/16”. And lining up the gray edge of the K3 with the edge of the leg puts the hole exactly 9/16” from the edge.
Test Caster Placement
Below is an edge-on shot of the bottom of my 4×4 bench leg, after it has been cut to size and notched for the rails.
The left side of the Kreg K3 is where I’m drilling the hole to attach the plywood square.
I’ll move the K3 over and do the same on the right.
And then flip over the leg and drill two more pocket holes in the same places.
Here you can see the orientation of the 2” caster I’ll be using on my bench.
The caster mounting holes are clearly to the inside of where the pocket holes will hit.
So, it’s safe to mount it this way and the two screws will never touch.
You’ll also notice that the caster mount is rectangular.
So, if I turned the mount 90 degrees either way, it would likely still be safe to mount that way.
If you’re using bigger wheels, then you’ll need to pay very close attention to the orientation of that mounting bracket rectangle.
Drill the Pocket Holes
I’m using the edge of my mitre saw station material support shelf to clamp down the bench leg.
SEE: Easy DIY Mitre Saw Station Build Plans https://heartwoodart.com/easy-diy-mitre-saw-station-build-plans/ for details on how and why I built the support shelf to double as a pocket hole making station.
ALSO SEE: Easy DIY Notched 4×4 Workbench Legs for how I cut the notches on my mitre saw. It was SO much easier than using a circular saw and chisel!
Here I’m drilling into the left hole, which is 9/16” from the edge of the leg.
Set the K3 the same as you would for drilling into a 2×4, which is actually 1-1/2”.
(See that Kreg Jig tips post for details on jig and drill bit settings, including a cheat sheet chart.)
Attach the Plywood
I could have attached the plywood squares right after I drilled the pocket holes.
But I chose to wait until I was building the bench frame.
I used my handy Kreg right angle clamp on the top, and the floor on the bottom, to hold the plywood square to the leg.
That sure made it a lot easier to attach evenly.
Mark for the Caster
Having the frame built also meant that it would stand up on its own for attaching the caster.
(During the frame build I have it flipped upside down anyway. So this was a time saver too.)
Be sure to check your caster mounting bracket orientation!
You want the screw holes to be inside the pocket holes.
At this point I just drew the outline of the caster mounting bracket and holes.
Drill the Pilot Holes
The lag screws that fit these casters is 1/4” x 1”.
The drill bit I used for the pilot hole was 12/64”. You could also use 7/32”.
And you can see my quick and dirty method for marking my bit so that I don’t drill too deep.
SEE: Pilot Holes: Why to Use the Right Drill Bit and Countersink for how to determine what size bit to use.
Mount the Caster
This is how my dad taught me to bolt something down.
- Put the screws in diagonally.
- Ensure all are well started before tightening any of them down fully.
- Tighten the up, meaning thumb tight, diagonally.
- Tighten all down, meaning wrench tight, diagonally.
Now you have a rolling workbench!!
You can use the same method for doubled 2×4 legs, like I did for my mitre saw station too.
SEE: Easy DIY Mitre Saw Station Build Plans for details on the way I doubled 2x4s for the legs, and why I used bigger 3” wheels.