Introduction: 4-Way Panel Clamps

Picture of 4-Way Panel Clamps

Accurately glueing up large panels can be a real challenge. As you increase the clamping pressure, the panels have a tendency to slide out of vertical alignment or even worse buckle. 4-way panel clamps are the answer to both problems but commercially made clamps are really expensive and cumbersome to use. I made 16 of these 4-way clamps out of standard 2X4's for approximately $5 each.

The special thing about these homemade clamps is the inner faces have a slight convex curve that evenly exerts pressure in all four directions. As screw pressure is applied the curves flatten with a scissor action ensuring everything in held in perfect alignment. Vertical pressure also eliminates the potential of your project buckling in the centre as you increase the clamping pressure.

I routinely glue up 30" x 11' panels for building wooden paddle board skins that are only 1/4" inch in thickness. Perfect alignment allows me to start with thinner boards and virtually eliminates the need for tedious surface planing after the glue has dried. Since these clamps excel at this task, I am confident you will love them for glueing everything from table tops to cutting boards.

Step 1: Building the Cauls...

Picture of Building the Cauls...

The curved clamping cauls are made out of standard 2 x 4 lumber. You could use expensive wood for making these cauls but it isn't necessary. If you have ever cut a piece of wood too short, you know it is very hard to stretch any species of wood. Select 2 X 4's that have straight grain and as few knots as possible. The clamps pictured are 36" long so it was easy to cut between the knots. Size your cauls to the projects you want to clamp. My cauls are 36" long as the widest paddle boards I build is 32" wide.

1.Cut your wood to the desired length.

2.Rip the 2 x 4's down to approximately 2.75" x 1.5". (You can make 1/4" thick spacers out of the cut off portion. These spacers both protect the clamps and allow you to clamp projects less than 1/2" thick.)

3.It is nice to start with straight lumber. You can either start with perfectly straight wood, joint your boards, or hand plane the board straight. As a last resort you can simply mark which way the lumber naturally curves and put the apposing curves inward. (These clamps were straighten with a jointer before adding the curves.)

4.Drill a series of holes at 2" intervals 1" in from the non-working face. (See picture) I set up a fence at my drill press and made a series of pencil marks every 2" to locate the holes. These holes are used as gross adjustment holes for different sized panels and they should match the apposing caul. If you don't have a drill press you might want to clamp both sides together and drill both holes at once. This will ensure the holes are aligned properly.

Step 2: Adding the Curve..

Picture of Adding the Curve..

The curve can be made in many ways but the easiest way is to mark the centre and use a hand plane to add the subtle curve. (The curve is so subtle that using a trammel point is not a good idea.) By taking 1 pass at each location you will end up with a subtle curve. The centre effectively gets no material removed. 3" from centre gets 1 pass of the plane. 6" from centre gets 2 passes from the the plane. 9" from centre gets 3 passes.........and so on.

1. Mark the centre of you board and make marks every 3" working from the centre to the ends.(Picture 1) It is best to mark the side of the caul and not the surface you are planning.

2. Take one pass with a hand plane working away from the centre towards the ends. One pass from 3", one pass from 6" etc... Make sure you are curving the side furthest from the holes you drilled in the last step. Flip your board and do the other half again working from the centre. You want to end up with 1 curved surface that is highest in the centre.

3. You can either curve both inner faces (2 cauls) or have 1 flat side and 1 curved caul. My clamps have 1 flat side that goes on the bottom and 1 curved caul that apposes it.

4.Lay the two boards face-to-face and put a clamp on each end and see how easily you can pull the cauls together. The amount of force you feel on the clamp is essentially the force that will be applied vertically. If you are happy with the clamping force you are done. If you feel you need more clamping pressure repeat steps 2 & 3 until you are happy with the pressure. There is no magic number as it depends on how agressive your hand plane is set and the material you plan on clamping. My clamps have about 1/16th of and inch of rocker per side.

5. Run a palm sander over the curve to make the curve fair.

6. The clamps pictured have been finished with paste wax and have a layer of packing tape protecting the working faces from glue.

Step 3: The Working End...

Picture of The Working End...

The working end of the clamp is made out of threaded rod and standard steel bar stock. The only tools required are a saw, drill, file & 7/16th tap to add the treads to the square nut. A drill press, sawzall & bench grinder make this a simple task.

Here an overview of the parts for the working end:

4 - linkage plates made from 1/8" x 3/4" bar stock.

1 - Screw - The screw is made out of a 6" length of 7/16th threaded rod.

1 - Square Nut - 1.25" x 1.5" x 1/2" piece of bar stock with a threaded a hole through the centre and two 1/4" holes for the linkage plates.

1 - Clamping Foot - The clamping foot is made from 1.5" piece of 1/2" x 1/2" bar stock. There is a hole drilled part way into the stock with treaded rod locked in place with a split pin.

1 - Speed Handles - Speed handles are simply a 1/4" steel rod bent at 90 degrees in a vice. A 7/16th nut serves as a hub with a 1/4" hole drilled through one side face.

4 - 2.5" long 1/4" 20 bolts with nylon lock nuts.

Step 4: The Non-Working End...

Picture of The Non-Working End...

The non-working end of the clamp is made from 1 block and 2 linkage plates per side.

Parts list for the non-working end:

4 - linkage plates made from 1/8" x 3/4" bar stock.

1- Stop Block - 2.5" x 1.5" x 1/2" piece of bar stock with a hole through the centre

2 - Hardware - 2.5" 1/4" 20 bolts with nylon lock nuts.

2 - washers as a spacer for the linkage plates.

1 - 3.5" 1/4" 20 bolt with the treads removed and edge chamfered as a pin.

Step 5: Linkage Plates...

Picture of Linkage Plates...

The 8 linkage plates are made out of 4" lengths of .75 x .125 steel bar stock.

1. Cut stock to length.

2. Drill a .25" hole .375" from the edges.

Note: The easiest way to make the holes perfectly spaced is to use a indexing pin. Attach a piece of scrap to your drill press table. Drill the first hole. Slide your stock 3.25" and use a handheld drill to drill a hole through the first .25" hole into your table. Insert .25" bolt in the hole in the top while you drill the second hole.

3. Chamfer the edges.

Step 6: Stop Block...

Picture of Stop Block...

The stop block is made from 1.25" x .5" bar stock. The length was chosen so that it sticks out past the linkage plates when clamping thin panels.

1. Cut a 2.5" length of stock.

2. Drill a .25" hole through the centre of the .5" edge.

3. Chamfer edges.

Step 7: Square Nut...

Picture of Square Nut...

The Square Nut is made from a 1.5" length of 1.25" x .5" bar stock.

1. Scribe lines corner to corner to locate the centre of a flat side.

2. Drill and tap for 7/16 coarse thread.

3. Drill two .25" holes in the .5" face for the linkage plates.

4. Chamfer edges.

Step 8: Clamping Shoe...

Picture of Clamping Shoe...

The clamping shoe is made from a 1.5" length of .5" x .5" bar stock.

1. Drill a small hole all the way through for a split pin. This pin locks the shoe to the screw and allows it to rotate. Drill about 1/8" down from the top of your stock intersecting the edge of the larger hole (as pictured) you are drilling in step 2. If you drill these holes in the other order you will probably break the smaller drill bit.

2. Drill a 7/16th hole 3/4 of the way through the stock at right angles to the small hole form step 1.

Step 9: Treaded Rod...

Picture of Treaded Rod...

The screw is made from a 6" length of 7/16th threaded rod. The 7/16th screw diameter works well with the 1/2" thick material. The speed handle is simply a 7/16th nut cross drilled for a length of 1/4" rod.

1. Mount the screw in a drill press and rotate your stock. Hold a file to the rotating stock to add a chamfer that roughly matches you drill bit angle.

2. Insert the chamfered screw into the clamping foot and drill into threaded rod enough to mark the location of the notch.

3. Rotate the stock in the drill press again and make a notch around the circumfrence of the screw. This notch allows the screw to turn freely inside the clamping foot.

Step 10: Assembly..

Picture of Assembly..

The clamps are assembled with standard 2.5" 1/4" 20 hardware with nylon locknuts. A 1/4" pin is used to quickly open and close the clamps. The 1/4" pin is made out of a 3.5" 1/4 20 bolt with the treads cut off and the edges chamfered. It simply slides in the required hole and clamping pressure holds it in place. Store the pin in one of the unused holes when not in use.

I prefer these homemade clamps to commercially available 4-way clamps I have used. Many of the commercial clamps require assembly during use and are not as quick to tighten. Since I use 16 of these clamps at once the speed handles are really appreciated when glue is setting.


sliver paddleboards made it! (author)2016-01-22

Here is a better picture of how I hang the clamps.

GemmaM13 (author)2016-04-11

Thanks for making this, really helpful! What are the metal hinged parts the parts the boards are attached to?

GemmaM13 (author)2016-04-11

Thanks for making this, really helpful! What are the metal hinged parts the parts the boards are attached to?

GemmaM13 (author)2016-04-11

Thanks for making this, really helpful! What are the metal hinged parts the parts the boards are attached to?

GemmaM13 (author)2016-04-11

Thanks for making this, really helpful! What are the metal hinged parts the parts the boards are attached to?

GemmaM13 (author)2016-04-11

Thanks for making this, really helpful! What are the metal hinged parts the parts the boards are attached to?

itsmescotty (author)2016-01-28

junkyard and scissor jacks??

mickeypop (author)2016-01-19

been using these clams for years

Quick Note

instead of having to bolt the clamps together each time you size them to the work, i leave the passive end together and simply use clevis pins to quickly assemble the nut end.

it only takes about 4 seconds to setup them up this way

tacomamactech (author)mickeypop2016-01-19

Nice build, inexpensive, but not original.

As I stated in my write-up, "commercially made clamps are really expensive and cumbersome to use." I found the Shopsmith clamps painful to use because the springs kept popping out of the notches as you are getting them set. They work well once tensioned but on an 11' panel it is a deal breaker with 15+ clamps. There are other commercial clamps that function better than the Shopsmith's but they are hundreds of dollars each and the cauls are straight.

Ooohoho-ho,,, True dat! Or they slip a notch, and you're trying to figure out WHY it's not lining up right. I think the nicest thing about your instructable is that you can hang the entire clamp up & out the way when not in use. Good Job!

sliver paddleboards made it! (author)ZoltanM122016-01-19

Thank-you!! I hang the clamps 3 deep on 1/2" x 6" posts. They hang nicely by the working ends, this allows 1 handed hanging and I usually grab 4 at a time by the speed handles. I leave the dumb ends open as shown with the pin stored in one of the extra holes.

All of my paddle boards are within the range of the screw so I have 3 fixed and one bolt (Threads removed) as a pin. I never have to change my clamping range but added the extra holes just in case. There is no problems have two pins on the non-screw end if you have to clamp different sized projects.

ljubve made it! (author)2015-12-27

thanks fir the idea.
I spend arround 5 hours on this build.

fran=1 (author)ljubve2016-01-19

are those roller chain links? if so what size idea

goykhman (author)2016-01-19

How do you prevent wooden cauls from getting glued to a panel?

I use packing tape on the clamping surfaces to prevent things from sticking. It works great and can be easily replaced when needed. I also use parchment paper to protect benches, etc. in the shop but prefer tape on things I use over and over as it is one less step.

dollarseed (author)goykhman2016-01-19

He applied packaging tape to the cauls so that glue will not stick to them. This could be done with waxed paper or parchment to achieve the same results though.

dollarseed (author)2016-01-19

Very cool project. Thanks for sharing.

VORTA5 (author)2016-01-19

Do you sell them?

jonnmero (author)2015-12-22

Excellent idea, but would use a more obtuse angle to get more force on the planks, i.e. shorter legs on the steel brackets.

sliver paddleboards made it! (author)jonnmero2015-12-22

The angle changes with the material thickness. This is a nice feature as you get more vertical force when it is needed. I wouldn't recommend going too short or you will limit the maximum thickness you can clamp. The picture shows a 2" thick board being clamped to illustrate this principal better.

Appreciate that, but I will have a selection of legs for the clamps. And as I said, the basic idea is excellent :-)
Guess it is also a matter of trying for what is best for the different jobs. Saves a lot on sash clamps, plus giving better control.

MerlinTheGreat (author)jonnmero2016-01-19

You could also use long legs with multiple holes in them so you can reposition the screws for shorter or longer lengths of the legs. That way you only need one set of clamp legs which can't get misplaced not to be found when you need them. Yes, it happens... when kids use dad's equipment.

Kreat0r (author)2016-01-09

You are an Inventor and a genius!Voted!

sliver paddleboards (author)2016-01-08

Thank-you for the votes in the 2x4 Challenge and the positive comments :)

buck2217 (author)2016-01-08

Have voted for you, looking at your design, I reckon you could make the end pieces out of cheap 2 leg bearing pullers (the kind you can pick up for peanuts at dollar stores- or if you are lucky enough to live in the US one of the DIY stores) I found a couple for about $5 each here

Mr. Noack (author)2016-01-08

Excellent! Voted! Winner!

Bverysharp (author)2015-12-30

This is a really useful tool, and a well written instructable. Thanks heaps! This might be something that my local Men's shed would be interested in....

kooler (author)2015-12-26

this is a very nice version of a 4 way clamp using 2x4's got my vote dude..

Tones Shed (author)2015-12-23

great project, thanjs for sharing

TheCoffeeDude (author)2015-12-22

This is exactly what I need for a project I'm starting, I just couldn't visualize it. Great ible!

BobF6 (author)2015-12-22

I have been using a caul and clamp setup that is cumbersome to say the least. Then where to store it. Will be building yours as soon as shop is set up next week.

ken820 (author)2015-12-22

Really like this idea can't wait to get in the shop to make a set

bricabracwizard (author)2015-12-21

Fantastic instructable! Very clear, I can't wait to make these!

Kreat0r (author)2015-12-21

very good idea. i will be building it soon.
although as a version 2.0 I will add a "Rail"on the side on one of the 4x2 so i could push the wooden plates against it before i clamp them. this way they will also be aligned horizontally too if you know what I mean.

fzumrk (author)2015-12-21

Excellent design and execution. Also, good tips for acomplishing basic machining tasks with minimal equipment.

I could have used these on a project I did recently. I will put these on my list of things I need to build for my shop.

ernstp (author)2015-12-20

Very nice solution. I like the minimal tools aproach for the metal working. I think every woodworker should be able to build this clamps.

ZombieWorkshop (author)2015-12-20

I have seen rockwell clamps but to expensive for my budget, I'm gonna try yours they look great thanks for sharing

rhpraino (author)2015-12-20

I never knew there was such a device. I could have used these many times and will definitely build a set. Thanks for the cad drawings. They are very helpful as well as the tip to drill the pin hole first.

trustmefada (author)2015-12-20

This is brilliant. I haven't seen anything like this sold commercially.

About This Instructable



Bio: I am a professional builder of hollow wood paddle board kits. "The beauty of a Sliver Paddleboard makes it easy to forget you're paddling ... More »
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