"Bend gage" Would this work?

I have been trying to come up with a bend gage that didn’t require me to write down a series of numbers that were carefully taken from a dial indicator. We presenly use a pencil inserted through a 6" block of wood then adjusted to find the lowest or highest points. This is pretty good and works well when doing a circle or even radiused bend. The bends I work with increase and decrease. Ideally I will have a smooth transition as the radius of the bend changes.

My idea is to insert an air brush into the sliding block with a spring loaded needle valve that changed the pattern it layed down based on how far the needle valve was depressed. Could this be done to actually lay out the current bend I have to deal with? The correct pattern would be drawn out ahead of time and the reader pattern could be compared to it.

Maybe I’m just dense, but I can’t figure out what’s being bent or the configuration of your device.

Anything you might bend, such as an archery bow or the curvature of an art project whatever.

the configuration is, lay a 6" piece of wood on a curved flat piece of wood, in the center of the curve the gap is widest, if an area is flatter the gap will be narrower. We simply insert a pencil down the center of this 6" pice of wood to mark where the curve is the flattest.

 I think what I want might be able to be accomplished just using a sprayer with a fan nozzle, the width of the fan would increase the further it was from the object with the curve.

I’m officially lost.

Are you are trying to measure/mark and existing curve or are you laying out a new curve?

Are you using an existing device as some sort of pattern or gauge?

For finding high/low along a vertical curved piece, a water level (clear tubing with (preferably colored for easy sighting) water)

What I primarily work on is all wood archery bows. We achieve the desired bending shape by removing wood. 99% of the time this is done strictly by eye but some lack the eye to achieve this and end up destroying the bow by removing too much wood in the wrong places. So looking to make a tool that would aid in marking the bow limbs as to where wood needs to be removed. Bend gages have existed for a long time using dial indicators but they don’t do a quick mark on the limbs, a pencil can be inserted in a bend gage and mark the stiff spots which is ok for accomplishing a circular limb.
I am looking for a way to mark the limbs in such a way where I know how much more or less an area is bending instead of just not enough bend. This would open it up for me to use the gage in progressive type bends. A smooth steady transitional bend is normaly what I like to do by eye.

Well were I to come up with some kind of device, for starters I would use a pen rather than a pencil. I’d set the gauge up so that the pen makes a mark when the bend is ‘under’ the prescribed breaking point and that the ink spot lets you know everything is o.k.

Put too much pressure on what you’re working with and the pen would lose contact and the user would know that “Bend Over – Ink Off”


Every time I try to visualize a means, it comes down to knowing, essentially, the line the string would follow if it were a finished bow.
Think a wide drawer with the bow parallel to the front - as the drawer is opened, the lowest point would be the first exposed.
Unless the limbs are made individually - and I can’t image they are.

The problem is knowing exactly how to align the bow on the drawer.

Things that indicate a line:
water/ink/thin oil level
taut string viewed from above or below (horizontal orientatio) or top/bottom for vertical orintation.
laser beam

I’m also assuming that each bow will be slightly different - one may be a bit thicker/thinner at any given point due to variations in the wood, so a conventional go/no go gauge would be useless.

A brilliant inspiration may come, but they’re getting rare these days…

I get it.

Suppose he has an archery bow in front of him.
He’s run the device along the bow, and
and then the spray would be narrow where its not bending much, and wider where its bending most.
I fear a spray is too inaccurate and blurry … the sides would wobble on their own.

Perhaps in a block of wood, drill two holes just big enough for pencils, but angled to the tips come together.

Now the pencils are mounted into the holes, and pushed downward with elastic. Simply tie the elastic to nails or hooks in the hood…

So now the gap between the pencils represents height of the pencils and hence the curvature of the wood in that area.

Some pics would help greatly.

Thats a good idea!! I will have to think about how to do it but I feel like it would work. Actually thast an excellent idea! If I get it working right I will name it after you.

Now you have me thinking if I could insert some kind of wedge between the two pencils with a fulcrum to help exagerate the space between the pencils a bit. The gap between good and bad will usually be about 1/16" of an inch, if the fulcrum worked off of maybe a 6 to one advantage I might be able to get a more distinctive pattern.

If the pencils could be adjusted in such a way that 1/2" wide tracks would represent a flat piece of wood and 1/8" wide tracks would represent a space of about 1/8" in the middle of the block to the bow limb. This would be about perfect.

You are wanting to measure the sagitta. You might research spherometers as used in optics. There are various types, and something you see may spark a light.

Thanks, I will look into that right now.

Based on the two pencils I think I have the perfect low tec easy to make solution that does exactly what I want. Thanks for a great sugestion. I will draw it up and post it tomorrow.