Woodpeckers has paid for some email eyeballs for a new 'one time product', phenolic cauls. Here is a link to them on Woodcraft.com. I have to begin with a disclaimer: I have no problem with someone trying to make an honest buck. This is one of those times where I can't get a point across without some negativity.
Woodpeckers makes decent useful aids for woodworking. However, I don't like their 'one time tool' schtick. If I buy a tool and integrate into my work regularly, I need to know where I can get it repaired or replaced when the inevitable adverse event happens (lost, stolen, broken, lent, random act of God). Production environment tools have an even greater need for consistency. I'm pragmatic before woodworker; the one time tool schtick simply doesn't make sense to me. Sorry.
Those folks out there who don't mind the schtick can continue to patronize Woodpeckers without fear of ostracization from me. After all, the tools are pretty darn good. I'm just sayin they ain't for me.
The real reason for this post is the cauls, not to be a Woodpeckers hater. The full set of Woodpeckers cauls retails for just over $200.00. That's two bones, two Benjamins, two C-notes--to hold one stick to another.
Today, for the first time, I'm going to reveal my secret for making cauls. As usual, the pragmatic approach begins at the hardware (or home and garden center, whatever) store. The secret is garden tool handles. Any will do, but I find the post hole digger handles work the best because they are beefy and have minimal diameter changes along their length. Tool handles are already made from straight grain flexible wood, most often hickory. All that is needed is a planer or jointer.
Tool handles almost always have a natural curve that is apparent If you sight down the length. The trick is to exploit this natural curve. What you want in the end are flat edges following the curve on opposite sides. The flat edge is easily made with your jointer or planer.
Begin by marking the crown as the up side with chalk or pencil. Then cut the caul to the desired length plus several inches. Maintain the 'up' erasable marking on each caul you cut. Set them aside in the shop for about a week. I also sand the handle slightly to break the lacquer finish. You would be surprised how many cauls change their 'up' side after being cut and acclimatizing to your shop space. Change your 'up' marking if necessary.
I believe the planer is the simpler tool to create the flats on the tool handle. A simple MDF jig to keep the handle oriented during two or three passes is all that is needed. Making the first flat is the most difficult. I don't have an example jig to offer because handles bought infrequently are never the same; I make a new jig every time. My rule of thumb is to hold the handle from the side with screws or plastic clamps (screw much preferred--trust me). I don't bother knocking off the rounding on the other two edges of the caul. By all means offer a better way in the comments below.
Using the jointer to make cauls works, but you have to break the rules of jointing to do it. Remember, the caul needs to preserve the curve to be effective. The jointer is superb if you have a straight piece of wood that you want to make into a caul. Set the jointer for a shallow cut. Keep all pressure on the back of the material and run it through the jointer to the half way mark. Carefully pick up the wood and repeat the halfway run from the other side. Quite soon you will have a camber in the wood. I find that the point of the camber has to be softened with a block plane or sand paper to make the caul useful.
I use the jointer method to make expedient cauls from cheap white wood 2 X 4's. I make the camber with the whole board for safety then cut off the caul at the table saw.
As always, if you have a better way please offer it below.