Handles in wood how much weight

[TheRic]

Was talking to the wife about making a couple of things. When we started talking about handles in the side (holes cut thru the wood, not attached to the side) and how much weight it would hold. Is there a rule of thumb or a calculator that would tell me? I'm sure it would vary on the type of wood, the thickness of wood, the thickness of the wood above the handle, etc.

Any and all help would be appreciated.

[cabinetman]

If you could be more specific it would help. I'm envisioning a cutout like for a tray or tool chest. The sketch below is for a stool I made many years ago, and there is a cutout in the top, is this close or similar to what your talking about?
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[RAFlorida]

Handles

I think in this case you will be working in the abstract. Most noteworthy is common sense, weight verse wood density, screw/nail size, how close to edge the fastners are, etc. I don't think you'll find a calculation for such stress issues, but just try to keep in mind how much weight verse density of the wood, etc.

[TheRic]

Thanks for the responses. Guess I should have explained a little better.

The cut out handles I'm talking about is tray with sides and/or a box with handles cut out on the sides.

I know it matters on how the box is put together makes a difference with it breaking apart, bottom falling out, etc. What I was asking is more the handle area itself. How much could a handle hold before the wood would split / break away.

I would think the thickness above the cut out (from top of hole to top of piece, not thickness of wood) would matter to a certain point. After it got so thick it would not matter much.

I'm not holding my breath for a actual formula, but it would be nice. A general rule of thumb or past personal experience would be helpful.

[steve-norrell]

I routinely cut hand holds into the sides and/or back of cabinet drawers. I usually make the cut so the top of the 'handle' is about 3/4 inch below the top of the drawer side or back. See picture. I have no weight data, but these are tool drawers and are somewhat heavier than, say, kitchen drawers or dresser drawers.

Regards, Steve

[JimD]

It is possible to calculate but I do not have the constants for wood handy. The stress you would be concerned about is a shear stress at the edges of the opening - for a design like the pictures above. The cross section to resist failure is the cross section of the material at both ends of the opening. If you have an inch above the opening and it's 3/4 material then you have 1x.75= .75 square inches to resist the stress times the two ends = 1.5 square inches. Next you need to know what the species of wood will resist in shear. You may be able to google that information. To make it stronger, you would increase the material over the hand-hold and/or increase the thickness. Wood shears much more easily with the grain, of course, but normally you would have the grain running the long way and the stress would be across the grain where wood is stronger.

The other thing to check is the strength along the grain for the material at the ends of the cutout. For instance, if the piece is 12 inches long and has a 4 inch cutout and is 3/4, you have 4 inches on either end of the cutout where, with solid wood, you have a shear stress along the grain of the wood where it is weaker. Even though the area is relatively large (4x.75x2 or 6 square inches) the lower strength across the grain could make the strength less than the smaller cross section above the cutout. This also assumes the end is not rigidly connected to the front and back. If it is, then their cross section would also resist the stress and this is unlikely to be the weak point.

I have also made things this way. I would not use less than 3/4 material if any weight is involved because it will be uncomforable for your hands. It is also important to run a router bit around the open (with a 1/4 radius) so it will not dig into your hand too much. I never calculated the stresses, I just made things so they seemed sturdy enough and that was always true. Another way to look at it is to think of a square handle the same cross section as the material above your cutout. If you can lift the load with such a handle, your cut-out handle will also be strong enough.

Jim

[LCHIEN]

I once made some cedar planting boxes. I put handles on the ends. I routed a pattern 4" long from end to end with round ends 1.25" high in a 6" wide board with the grain running parallel to the top edge. MY habd fit comfortably in this opening.

That leaves about an inch on the ends. Did I say it was 5/8" thick cedar from fence boards? After about 6 months of weathering, all the handles had broken, along the grain that ran 1" into the ends of the handle. So take that experience, there's not much strength along the grain. Maybe a harder wood, and not being weathered, would have made a difference, but it surely exposed a weak point in my design. Basically I cut out 2/3 of the strength along this grain and thru the handles.

[TheRic]

Thanks everyone for the replies.

Steve, would you say that you have about 50+ lbs in the drawers. I do like that idea of having handles in the drawers. I can see where that would come in handy, specially for heavy drawers.

Is MDF better or worse then hard wood in the stress area?

Would I be safe to say that hand holds about 3/4 down, in 3/4 wood, with a good several inch's to each side of the hand hold be able to lift 50 lbs. in most hard woods?

If I'm talking 2 handles, would that then be 25 lbs per handle (assume evenly distributed) or doesn't it work that way for some reason?

[crokett]

I think MDF would be worse. If you are worried what you can do is route mortises on either side of the handle and glue in plywood inserts, then cover them with hardwood. The handles will never fail.

Another option would be constrasting wood inserted before you cut the handles out so the grain runs perpendicular to the tray sides. This puts the stress on the long grain and the handles will be plenty strong then.

[steve-norrell]

Thanks everyone for the replies.

Steve, would you say that you have about 50+ lbs in the drawers. I do like that idea of having handles in the drawers. I can see where that would come in handy, specially for heavy drawers.

Is MDF better or worse then hard wood in the stress area?

If I'm talking 2 handles, would that then be 25 lbs per handle (assume evenly distributed) or doesn't it work that way for some reason?

Ric,

Sorry for taking so long to get back to you.

The drawers do not contain 50 lbs, probably more like 25 - 30. I would think that wood or plywood would be better than MDF for real heavy stuff but I have no real experience with it. Also, taking the drawers completely out is a very rare event; so rare that I can't recall the last time I did so.

I guess if I were really concerned about the handles pulling out, I would screw in a metal strip across the outside of the drawer, just above the 'handle'. That, however, would be a very extreme condition.

I believe the weight would be evenly distributed to both 'handles' only if the drawer contents were evenly distributed.

Regards, Steve

[TheRic]

When Steve mentioned heavier than kitchen drawers, and that they are tool drawers I pictured in my head HEAVY. Started to think MDF might be better in this case for some reason.

I am talking about making it out of wood (not MDF or plywood). I'm a little concerned, but not as worried about the handles breaking away as SWMBO. I guess in some ways looking for backup.

[steve-norrell]

Ric (and others):

As coincidence would have it, I am building some wide cabinets for the LOML's project room. The drawers are about 20 inches deep and 40 inches wide. Questions arose as to where to put the 'handles'.

At about 36 inches or so, handles on the side become too far apart for the LOML and so I cut the handles into the back of the drawer. When the drawer is removed, we would use the drawer pull and the back handle to lift the drawer. Drawers less than about 36 inches wide get the handles on the sides.

For the most part, I use those 50# rated "Euro-style" slides that go across the bottom corner of the drawer, which, IMHO gives some support to the bottom. I usually cut the drawer bottom to the full drawer size and rabbet the sides on to it with glue and nails/screws. For deeper and/or larger drawers I use 100# rated sliders that allow 100% opening (http://www.rockler.com/product.cfm?p...rawer%20slides).

Our kitchen drawers were installed by the remodelling contractor and do not have 'handles' cut into them.

I should add that both of us are retired so lifting heavy drawers is not something we would look forward to. For our purposes, the handles are to make it easier to lift out the empty, or almost empty, drawer.

Regards, Steve