Continuous hinge strength?

[Roland Coppens]

Hello chaps,

I'm installing an extension wing on a rolling cart, which I'd like to be able to fold down. I was considering using a continuous hinge (aka piano hinge) for this but wanted to be sure this'd be the right hardware for the application. The wing, worst case scenario would be in the neighborhood of 40-60 lbs (if all the attachments were left affixed). In the movie playing in my head, the hinge would be mounted on the underside of the wing and cart top, being flat (open fully to 180*) when the wing is in the 'up' position, and folded to 90* when with the wing in the 'down' position. The wing will have its own legs, which will fold down. The cart's top and the wing are of solid beech, 1" thick.

Would a continuous hinge and screws support this weight? The hinges I have on hand have screw holes about every 3 inches, being offset from one another on opposite sides of the hinge. The hinges are of some fairly soft metal (brass?), as they are easily bent along the long axis with just my hands.

Is this typical of continuous hinges, or have I just been seeing lightweight ones? (The local BORGs have pretty much the same thing.) Any better solutions that come to mind?

Thanks as always for the guidance and advice!

[Harry]

What are you intending to use the cart for?

[router-jim]

Roland, could you also tell us the length and width of the wing.

Thank you.

Jim

[Roland Coppens]

Originally Posted by Harry

What are you intending to use the cart for?

Originally Posted by router-jim

Roland, could you also tell us the length and width of the wing.

Principally, this cart will be my CMS workstation. It ties into the modular tool system I've been designing to be the backbone of my shop. The system is kind of reminiscent of the one that appeared in WOOD last fall, though the work on my design actually predated that article and has some notable divergences from it. The basic design philosophy, however, is much the same: bench tools fastened on bases that can be mounted to workbenches or carts and stored away on a shelf system when not in use. I have a number of workstations in various stages of planning, each having its own primary function but able to flexibly serve in other capacities as the need arises.

So, while this will be my compound mitering station, sitting next to and offer mutual support to my RAS station (still being planned), I'd like it to serve as a station for my lunchbox planer, an infeed table for my TS, an assembly & glue up table and as a general workbench. The cart stands 36" high and has a 21" x 24" top. In actual fact there will be two wings (though my original message suggests just one), each 24" wide and 28" long. The top and wings are of 1" beech.

When in mitering station configuration, my CMS on its base will be mounted to the cart's top. The wings will have removable risers and fence system much like these ones from the Online Extra for the miter saw station in Issue 98 of ShopNotes.

In planer mode, my lunchbox planer will be mounted on the cart's top and make use of the same risers (miter fences removed) as infeed and outfeed extension tables. As a TS infeed table, a glue-up/assembly table or as a general workbench the riser fixtures will be removed. The cart has double locking casters but will soon also have feet that screw down, lifting the cart off the wheels. The legs for each wing will be similarly height-adjustable. This way, the planarity of the top and wings can all be adjusted as needed for the current role at hand.

As a general workbench, I of course don't expect to be able to hew out dovetails, pound large assemblies together, or scrub plane rough stock. I do, however, want it to be reasonably sturdy and robust.

That's all I can think of at the moment in terms of information you might need but please let me know if there's anything else I can tell you.

Thanks again!

[JoeSpackle]

Roland:

Continuous hinges are actually quite common for uses like this. While they may not look as robust as other types of hinges, their benefit comes in how the load is spread across the hinge. For instance, in your 24" length of hinge, the 60lb maximum weight that you stated would be spread out to about 2.5lbs per 1" of hinge. The other factor is the fasteners. Most continuous hinges provide a screw hole every 2". If you were to use a screw every 2", each screw would hold a load of only about 2.5lbs each.

Based on the use and potential for some extra weight factors based on the use you propose, consider this hinge instead of brass http://www.rockler.com/product.cfm?p...ous%20hingethe 1 1/2" would be our first choice.

These are easily cut to length for the use you described, just make sure to work it so the maximum amount of screws are utilized to spread the load out as much as possible. We would also recommend using a pan head type of screw to provide a more solid contact with the hinge material.

Bobo and Joe