Center Finder needed (NOT for round objects)

What you need is something that looks like an expandable baby gate, or one of those expandable lamp contraptions - like a pantograph.

You put the outside pointers at the edges of the frame, and the center thingy is the middle.

The device pictured provides the solution. It looks far too complicated for the job. Simplify the design by reducing it to the bare minimum of parts. Fabricate it from aluminum tubing for light weight and ease of use. It could be made to be supported from overhead to keep it within easy reach and out of the way for the other operations on the frames.

I use to use an old Child safety gate that would expand to fit the doorway. I took the ends and filed them to a point and aligned these up with the edges I wanted to locate the center on and my middle point of the XX would show me where to place the hanger. This worked pretty well when hanging lots of items for a display or a gallery. Quick reference and easy for students to use. One would align and mark, the other would attach the ring or plate.

A very similar but smaller device is used in sheet metal fabrication for race cars (and other things) when locating numerous rivet holes evenly. I'm thinking that Eastwood might be the source.

Oops! I just read post 7.

Hey that's cool..

Dear Santa....(ok it's a bit early...sue me)

Would it take too long to use a chalked string?

The idea is to stretch it diagonally between 2 opposite corners, then 'ping' it to leave a chalk-line. Repeat with other pair of corners.

Very cheap - may need a 'third hand' to do the pinging.

Alternatively, do the same thing with a long straight-edge and a pencil.

To find the centre of an edge, use a (non-elastic) string for the length, then half it.

I just want to say that you guys ROCK! All are great suggestions and am I very, very, very appreciative of your quick responses. 1) I looked for the baby gate in hopes I could modify it, unfortunately all the ones I found allow the user to move the two arms asymetrically. There is one exception and I have to look at it more closely to see if it could be customized. http://shop.happymothers.com/shop/prd_GMI36_Keepsafe%2036%22%22%20Expansion%20Gate.html 2) I think the chalk idea might be a little too messy; however, creating a center point by drawing a line from corner to corner on each pair of corners and then identifying the intersecting lines seems by far the best. I would just need to figure out how to prevent occasional damage to the frames while moving around a large metal straight edge. Maybe I can soften the corners. The downside is that the center point is really far from the top of the frame where the hardware wil be mounted, so I will probably need to add a step with a carpenter's square to get the centerline to the top of the frame where it is needed. 3) The center finder tape is probably the best, because it requires the least steps and identifies the centerline where I need it (at the top of the frame). I just need to spend some time training my employees how to measure so they can find the point a second time. GREAT FIND! Thanks to all who responded. More ideas are always appreciated. FYI, one company wanted to charge me about $3,000 to create a tool from scratch with a rack and pinion guide. Worse, is that one tool probably couldn't do all the size frames we need. Probably not a bad price for a custom tool, but one of the options above should work out perfect. Thanks again.

I would like to add one to all theses good ideas. And I do believe (grin) this be the slickest one.

There is a metal ruler with a gear teeth along one edge used in linear actuators (motors moving things back and forth linearly). It is so widely used it got to be an off-the-shelf item. Take two facing to each other. Get a small gear with the same teeth, the same thickness of the ruler, center hole open, off-the-shelf again. Rivet a big washer to both side, so it has no chance to drop out of the gears, when assembled. If you want to simplify the assembly, use 3 gears to keep the rulers parallel. The central gear's center hole is always halfway from both edge of the frame.

Your local metal fabricating shop can help you to locate the stuff, and assemble them such, that the two rulers freely slide. It has the freedom of motion 1 to 2 or thereabout. It is compact, after all it is just two rulers side by side.

Checked out your tool. Looks like a mini baby gate.Probably where they got the idea. The only change would be to remove or mask off one of the linkages since it has 8 point segments. Although if he's using the long serated hangers, he would just have to position it equally between the two inner points.

Nice Find!

I remembered seeing it a few years ago and knew that Rockler was the source. Still had a heck of a time finding it on their site. I agree that it would need to be idiot proofed before sending it to the shop floor.

I like it!

You just think that up?

Spur of the moment stuff!

I was thinking much the same with o-rings attached at the ends

"How about 2 plastic hooks joined by a piece of elastic! Mark the elastic with a pen at the center! As long as the elastic is stretched, the mark is in the center!"

True. There used to be a commercial device that had multiple divisions, with (I think) every fifth one a different color, like tick marks on a regular ruler, but variable in length. The marks were actually one side of a triangular extension spring inside a transparent plastic housing. It was made by Gerber Scientific; here's a quote:

He [H. Joseph Gerber] started making his mark on the world of science in the 1940s as an aeronautical engineering student at Rensselaer Polytechnic Institute. He discovered a way to reduce the time-consuming nature of plotting points for his math homework. The result was an "expandable ruler" created from the elastic waistband of his pajama bottoms. Gerber's creation was not only a sensation on campus; it gave birth to the renowned Gerber Variable Scale and later, The Gerber Scientific Instrument Company. Here is a photo, showing three different "stretches":

http://www.nzeldes.com/HOC/images/Gerber02.jpg.

Mr Truman Brain, you're in good company! I'm giving you a GA rating.

And a long extension spring with a low spring rate might be better than elastic for longer term use, but the principle is unchanged.

I have some made with two gear racks opposing each other with gears between. The two gears are mounted in a block in the middle. Dowel pins press into the free ends of the rack. As you move the ends with the dowel pin together block moves to center.

Block could even hold drill bushings to drill the holes for your hardware.

Mechanic and Truman.

In the face of greatness I bow my head.

The common method used in most framing shops I know of to locate the center of a saw tooth type hanger is by using a string or long and narrow piece of paper to measure the edge then fold it in half and use it to mark the center. This method is also used to locate a photo for placement in the center of a mat. You place the photo in the corner and use a paper sliver to measure from the edge of the mat to the edge of the photo. Fold the paper in half and measure in from the sided to mark where the edges of the photo should be so it's in the center of the mat. Accepted practice has the top and the 2 sides at the same dimension with the bottom somewhat larger. There is usually a paper cutter in a framing shop so long narrow strips of paper for this purpose are usually at hand. Hope I didn't confuse you.

Hi Seth

I have read through the suggestions and wonder what quantities you are talking about? How many sizes do you deal with? Make a jig (a flat band of stainless steel) for each size with a center point were it belongs.

Hand them out in the morning when the workers get the daily routine and supply them with a centre point, included in the jig, and off they go. If you have 10 sizes have 10 jigs. You could always add other important measurements to the jig as required. If I would be there you would have them in the evening and you would have no complaints about missing the center. Who ever does the job. Hope this helps. Ky.

What about a triangular template. I have drawn a single slot for marking the centre line, but you could include several sets of holes for marking screw positions accurately.

Not nearly as clever as Truman's piece of elastic.

Our factory does custom framing on a medium scale. Our orders are typically over 40 pieces but less than 150 and each frame is typically a different size. The hardware we use is the kind you find (but are not able to see) in hotel guest rooms. It consists of two brackets at the top of the frame (approx 4" in from each corner) and one bracket at the bottom of the frame in the center. The brackets are 2" wide and 1/2" high and protrude from the back of the artwork about 1/8". Each bracket is secured by 2 screws.

We currently use a homemade carpenters square that identifies a point which is 4.25" from the top right and left corners along the top edge of the frame. The assembly line worker installs the brackets at these points along the top and estimates the center point along the bottom. On a large hotel project where there are 100-500 pieces of the same size we, of course, use a template.

There are at least two problems with measuring 4.25" in from the corners...1) the operator can place each of the brackets at different heights, so the installer has to correct for this onsite to insure the art is level and 2) there are nearly an infinite number of distance between the two brackets so the installer cannot use a template

My thought was to create 5 or so standard templates that would have rectangle cutouts at predetermined distance and a centerline so the line worker can center the template and align with the top of the frame (keeps the hardware at same height). This would allow the installer to look at the back of the art, see a sticker and know the hardware is 15" on center or whatever. The installer can then use a 48" level with predetermined marks for 15" on-center, etc. to locate the holes for the wall clips that get paired with the hardware at the top of the frame.

This forum has given me some good idea to help the operator place the jig in the right place, since measuring is not a skill that is widely available in the employees I have in this area of the operation.

I purchased a 36" stainless steel center-finder ruler from McMaster Carr (item 2346A33) to handle frame widths up to 36" and a center tape measure from another website to handle anything larger. We have a mat cutting machine that can whip out templates in the short term until I am ready to commit to metal ones. One interesting thing to note, frames have different thicknesses at the edges where the hardware is being installed, so in the case where a frame is thin at its edges the template would need to be moved away from the edge of the frame towards a beefier area of the frame.

Using the aforementioned tools would take a little longer on the table, but would help installations go a whole lot quicker.

The string/paper (fold in half) idea is pretty good and we might incorporate that as well, since precision is not as important as speed.

Thanks for all the ideas.

P.S. If you want to see the hanging system...http://www.mmdistributors.com/Merchant2/merchant.mv?Screen=CTGY&Store_Code=mmdist&Category_Code=T-Screw+Security+Hanging+System

I am imagining a tool with two arms and a wheel in the middle between the arms.

Suppose a circular piece of plastic or wood were designed having labeled holes through it designating the center for various sized frames. The worker could push the disc into any corner and then mark the center through the hole corresponding to the frame size.

Oops! I did forget two flats are needed on the circumference to reference the corner and center point. Essentially the shape could be a thin flat arrow point with and extension along which the differently spaced holes would designate the center point for each respective frame size.

No moving parts, simple to replicate, inexpensive materials.

get your hands on a pair of trammell points used for finding centres in weld fabricator shiops they can be as accurate as you want over 10' square circle or just about any other shape that can be created.

'da ber

Here's a jig to make sure it actually hangs square:

The frame (A) is attached by temporary clips to a thread (B) passing over a peg (C) in an upright support (D).

A line (E) is attached to peg (C), and has a plumb-bob (F) at the bottom.

The spirit level (G) is used to get the frame hanging square.

When it's square, mark where the plumb-line crosses the top of the frame.

Actually JohnDG, That is a great way to find the center of gravity for a box frame! So I'll vote it on topic! For those who don't know what a box frame is, it's a frame with depth which you can mount objects like model car collections, tops of wedding cakes, ballet shoes, etc! These can be a right git to get level if the weight distribution is uneven! (Unless you use keyhole hangers of course!)

To rout a slot centered on a piece of wood I use a base plate for the router that has one pin on either side of the router bit so all three (pin, router bit and the other pin) are in a straight line. If the board is 3" wide I set the pins in the holes that place them 3 1/4" or 3 1/2" inside to inside. I place the router on the board and then twist the router so the pins are snug against the edges of the board. This places the router bit right in the middle.

You could do the same with the width of the frames. You would just have a jig that has the pins a bit wider than the frame. Set the jig on the frame and give it a twist. Now you have a pencil or witness mark at the center and then place your mark. If the span is such that you can't get the center of the jig over the piece you need to mark you can transfer the location with a square.

You could have the jig so you move the pins to the correct holes for each width of frame. Or just make a jig for each size or similar size frames. It is possible to use one jig for several frame sizes.

Travis

Perhaps you could mark out a rule ( in cms might be easier ) with the normal measurement on one side and double the measurement on the other side. to find the center simply read the width of the frame on the doubled up side, e.g. 25.6 and then the center will be at the true 25.6 cm mark.

True. You can also buy center-finding rules with "0" at the center, and marks going both directions from there, so that when the two edges have same reading, you're centered. For your method, acquiring a ruler used for planning flights (http://www.aircraftspruce.com/catalog/pspages/pgVFRchartRuler.php) gives a two-sided scale and 2:1 ratio of markings.