is there a formula for cauls?

[Steven Lee, NC]

Need to make some and am wondering for x length, how much curve to put in there. I'll get them CNC'd.

Is QS white oak or Ash suitable woods. I have some extra.

Thanks

[Thomas Eustis]

Need to make some and am wondering for x length, how much curve to put in there. I'll get them CNC'd.

Is QS white oak or Ash suitable woods. I have some extra.

Thanks

Personally, I would go with ash. It’s cheap, has little tannins (less bleed), has great- but gentle- bending, and takes tooling pretty well. Can’t miss.

[Prashun Patel]

Oak or ash will make fine cauls. The bending ability of cauls is largely moot; the bend is so small, and that the curve is cut across the grain.

The only possible reason not to use oak or ash, IMHO is that they are harder than a lot of boards you may be trying to bring together, and could mar delicate edges.

I have had the best luck with 2x4's. They are the perfect thickness and width for most 4/4 or 8/4 glue ups, and soft enough to protect the edges, and cheap enough that you can make them the exact length you need.

The best article I've found on cauls is Mike Henderson's. You'll find it on Highland WW's article site. You'll know the curve is perfect if slips of paper are held tight when the cauls are brought together face to face.

I hate when people do this but I'll do it anyway: I wouldn't get them CNC'd. They're easy to make in almost any way: a hand plane, a bandsaw, or my favorite: A power jointer. The curve does not have to be perfect; A faceted taper every 3 - 4 inches is fine. In fact, this is another argument for a softer wood; a faceted taper will conform more evenly (in theory) than a harder wood to the clamped board edge.

[Mark e Kessler]

i have always used Ash, Maple, Poplar, and usually find 1/8" - 1/4" taper from center works, I use the jointer and maybe clean up a little with edge sander of belt sander, no rocket science required....

Mark

[Prashun Patel]

Depends how long they are.

[Jared Sankovich]

Bend them the reverse direction with a jig and run through a table saw. It takes maybe 30 seconds to cut a 4' caul with a perfect curve.

[Mark e Kessler]

Sure ok, 1/8" for short, 1/4" for long...

Depends how long they are.

[Steven Lee, NC]

great article, thanks

https://www.highlandwoodworking.com/...ril/cauls.html

[Roger Feeley]

Bend them the reverse direction with a jig and run through a table saw. It takes maybe 30 seconds to cut a 4' caul with a perfect curve.

Ha! Genius idea. Just screw the center of the caul to a much bigger board and then wedge the ends to whatever curve you like. Cut straight on the table saw and away you go. Whatever pressure you used to create the curve before the cut is what it's going to take at the ends to bring the ends in.

I had never thought of this idea. Heck, it's so easy, you could almost custom make cauls as needed.

[Jared Sankovich]

Ha! Genius idea. Just screw the center of the caul to a much bigger board and then wedge the ends to whatever curve you like. Cut straight on the table saw and away you go. Whatever pressure you used to create the curve before the cut is what it's going to take at the ends to bring the ends in.

I had never thought of this idea. Heck, it's so easy, you could almost custom make cauls as needed.

Absolutely adjustable on the fly to whatever total curve you want (from nothing to the max allowable on the jig.)

I like washer head spax screws for the pulling in center.

[Steven Lee, NC]

interesting, I'll give it a go.

Absolutely adjustable on the fly to whatever total curve you want (from nothing to the max allowable on the jig.)

I like washer head spax screws for the pulling in center.

[Jared Sankovich]

Some pics, screwing directly to a board would be easier
IMG_20171211_215942_096.jpg
IMG_20171211_215942_095.jpg
IMG_20171211_215942_100.jpg

[David Hawxhurst]

The curve would be based on the length and species of wood used to make the caul. Bowclamps uses maple for their cauls. But I guess it would depend on what your using the cauls for? Keeping a panel flat during glue up? Provide even pressure along a glue joint? To me these would be two different requirements and curves.

[Edwin Santos]

Interesting caul making methods, thanks for sharing.

My way seems primitive compared to what's been shown, but here goes: Take the jointed caul stock to your flat workbench, place a shim underneath it in the center. I usually use a 1/8" shim. clamp the two ends down. So you've now created a concave bow where the caul meets the workbench. Scribe a straight line across the bottom maybe 1/4" up. Release the clamps, walk over to the bandsaw and saw to the scribed line. This entire operation should take 3-5 minutes. I tend to use KD 2x4 studs.

If you're a hand plane fan, you could use a hand plane and the scribed line as your guidepost. But now we're talking more than 3-5 minutes.

I suppose you could also use a stationary jointer and take off facets as has been described, using the line as a guide but I've never tried it mainly because the bandsaw is standing there like a young Sophia Loren just begging for attention and who am I to argue?

Edwin