Tips on making large frames

[Adam Cavaliere]

I just made a 62" x 20" picture frame and have some questions for you guys.

Normally when I have long boards, I try to get them pretty flat all the way along the length, but I learned early on that if I am doing a glue up, I can't expect to get a 62" board completley flat. What I mean by that is I would have to start with probably a 6/4 board to get it completley flat down to a 3/4 board. The issue with that is that there is potential that the wood would warp over time because of all of the wood removed to get down to 3/4.

So now, I took that knowledge and decided to try making my picture frame. I used 4/4 boards that were S2S. In reality they were about 1/16 thicker than 3/4. I tried running it through the jointer and then planner, but there was still a bit of a cup in the wood. This all resulted in the frame not being completely flat, but having a slight twist in it.

What should I have done? Started with a thicker piece of wood?

[Matt Day]

It could be a lot of things, as cutting wood can release a lot of movement. Depending on how the tree stood and what part of that tree you have in your shop can have an effect. For instance, if it was a branch (unlikely I think), the bottom part of the branch was under compression it's whole life and will tend to move after cutting.

Try taking even amounts of wood off each side of the board, rather than all off one side, to try to even out the reaction.

What length jointer beds do you have on your jointer?

[Adam Cavaliere]

68" Jointer bed.

The wood was already slightly cupped before I tried straightening. I am just wondering what the course of action would be to go after approaching building a frame that large. Did I not buy thick enough wood? Or did I just pick bad wood? Is it truly reasonable to think I can find a 65" piece of wood that is completely straight?

[Peter Quinn]

To finish at 3/4" I'd start at either 4/4 if you can get it hit and miss planed to 15/16" or in the rough, and it sights pretty flat to begin with, or use 5/4. I would not start thicker than 5/4 for the reasons you noted. Planing off a lot of wood can lead to a new set of problems. When I have to start with thicker material, I will flatten, plane it down closer to my final dimension, then sticker it and wait a week or two, at least a few days if in a rush. Let it find a new resting place, then flatten it again and plane to final dimension. Then ASSEMBLE it. I don't mill wood I will not be using shortly. Letting it hang out gives it a good chance to go squirrley on you if humidity changes.

As you approach the 70" long mark, you will likely need to start with 5/4 to get flat over that length unless the boards are pretty flat to begin with. Give them a good look at the time of purchase, even lay out your lengths with a ruller and chalk if they are longer than you need. You can train your eye to spot a flat one and reject those that are cupped or twisted or bowed. Maybe a straight edge, like a rip of plywood can help too.

[Matt Day]

You should be able to get a board flat. Have you calibrated your jointer? I'm not an expert at that, but I've just followed the directions on mine and never had a problem.

I'm putting the finish on today to some large frames I made, the 2 larger ones are about 30"x30" and are 3.5" wide. I mitered the corners and used splines (about 2.5" deep).

[Adam Cavaliere]

Matt,

I have calibrated my jointer and have yet to be able to successfully flatten a 65" board without purchasing something much thicker than the stock I want to end up with. It is much easier to accomplish on 30" pieces of wood when there is less of a distance to correct a twist or cup.

Peter,

Can you explain a little bit more what you mean about the rip of the plywood? Are you suggesting applying that to the longer pieces of wood to keep them straight?

[James Baker SD]

Adam, is it really a problem? Last June I made an 80" x 36" picture frame for a really big art print my wife bought. I got the wood as close to flat as possible, but could see it was not perfect. It had enough flex in it (basswood) that I was able to force the miters to perfect fit and then pinned the corners with dowels. With glass, mats, backing, frame and art, it weighs about 50 pounds so I used rather substantial mounting hardware that forces it away from the wall slightly. When hanging, the remaining warp in the frame pieces is virtually unnoticeable to me. Our guests comment on the overall impression they get, but nobody has spotted the non perfect frame yet (maybe I just have polite guests).

James

[ian maybury]

Seems to me Adam that quite apart from the normal cupping/twisting/warping after cutting issues that at least some of the problem may be to do with the likelihood that a 60in board in 3/4 is not going to be all that rigid, and also that it's probably a bit longer than the infeed table on the jointer.

The precise nature of the twisting/bowing of the board also matters. Cupping and short humps are not too big a deal to sort out. A steady twisting/bending over the full length of the board can be more problematical.

Several interrelated possibilities come to mind. Say the long twist or bend is to rear of the board and downwards when you start planing. When you start cutting you start to create the plane or a flat surface you now hope to have continue for the length of the board. The problem is that the downward twist/bend will tend to lever up the tail end of the board as it comes on to the infeed table. You will probably be manfully bearing down on the board to keep it flat on the outfeed table at this point, which will probably bow it - meaning that the cut surface won't be flat any longer once it's released. If the board isn't pressured enough to bend, then the board will be progressively raised up off the cutter and the plane/flat surface you thought you were cutting will become a curve anyway.

If the twist/bend is upwards, then provided you reliably keep the pressure on the outfeed table so the newly planed surface stays flat on it the result will be that as the tail of the board lifts clear the cutting will stop. Which is OK (at least in theory), just repeat the cut until the board cleans up over its full length.

The practical problem with this is that having started at one end and created a surface not ideally aligned with the board you will probably have lost much of the thickness of the board by the time it cleans up - whereas if somehow you could have tipped the board so that it was resting on the high point of the bulge with the ends at roughly equal heights it would have cleaned up with less material removed.

Some achieve this by eyeballing where the hump is, by tipping the board into the correct attitude, and then manually hold it there while planing off most of the bow/hump in short stopped passes - but it requires a good feel for what's going on and isn't strictly speaking the best practice, nor the safest. Once the (central) high part of the bow is removed though it opens the way to cleaning up with some full length passes provided the distance between the high spots is less than the length of the infeed table - meaning that the jointer can now work a intended.

An alternative is to use long infeed and outfeed table extensions (accurately leveled, and long enough to accommodate the full length of your board) to avoid the 'kick up' issue, and to machine with the board flipped over to be 'bow up'. i.e. material is removed from the low hanging ends first.

Some use the manual/eyeball/stock tables approach 'bow up' to separately remove the low hanging ends, and open the way to a full length pass as described above.

The flexing of a thin board like yours while it's machining may still be an issue though, meaning that mounting it up (with its natural bend undisturbed) in some sort of a sled in the form of a dead straight web/vertical board in MDF/ply fixed to each side is probably the ultimate fix - it eliminates the need for long table extensions as well. The boards must be set parallel to each other though.

My instinct - especially with a board thin enough to be flexy (but not flexy enough that it doesn't matter) - is to bite the bullet and go for the sled right from the start. Start with a board with enough extra width, rip straight sides on it, then screw sled strips to each side (cut away the strips with the screw holes afterwards), and plane away.

The board thickness required depends on how bowed it is, as already suggested the straighter the better as less machining is likely to result in less risk of subsequent movement - provided the moisture content is right.

It's a bit more work than the eyeball methods, but is probably safer and a lot less stressful.

The bottom line to me is that there is no one size fits all solution to this problem - every board has to be checked for exactly what sort of bend it has, and this considered with machine capability before deciding the best machining method.

ian

PS even it's flat when made there's probably a significant risk that the board could cup after the frame is made if it's wide enough. That's one for those with more specific experience, but might some quarter sawn timber, or even a switch to veneered MDF or ply be a possibility? Maybe even some lengthwise slits in the back like are used on hardwood flooring boards to stop them cupping?

[Will Blick]

I have built a lot of 60 - 120" picture frames through the years. Some as long as 20 ft.... its a nightmare :-)

First, I agree with Ian... I have a 12" Grizz Ultimate jointer with 80" beds. No matter how long the bed is, if you are trying to flatten a board longer than the length of one of the beds, its often problematic. You have to eye down the board and come up with a sensible strategy to joint the board to minimize waste, not always easy...then, as mentioned, it will move on ya after jointing, as the cuts expose fresh wood...

Its not just about the board being straight either..... the miter joint also becomes vulnerable over time to twisting, cupping, expansion contraction, etc. Bottom line, its best to use laminated MDF for long picture frames. The longer the frame, the thicker the frame. The thicker the frame, the more the movement will open the miter, or cock it in some manner, all based on how the wood decides to move. This is why 4" thick pix frame is considered VERY wide for real wood... hence why I moved to laminated concoctions :-)

Also, if you can buy moldings that are already finished, then you are starting with wood that has a better chance of surviving long term movement. Most "sticks" of moulding come in 8 ft lenghts, and joining them is not easy, unless the molding is thick. If you look at pix molding catalogs, you will see not many make thick wood mouldings, they all went MDF with laminates, mostly paper laminates...you gotta get creative with big frames, if you want long term success.

[Stephen Tashiro]

.. hence why I moved to laminated concoctions :-)
...If you look at pix molding catalogs, you will see not many make thick wood mouldings, they all went MDF with laminates, mostly paper laminates...you gotta get creative with big frames, if you want long term success.

I find it possible to get reasonably straight pieces of lumber by a combination of cutting groves down and/or across the boards to weaken their ability to hold their shape and laminating boards together so that their defects cancel each other. For example, two bowed 1x3x3/4 boards glued together so their bows cancel can produce a reasonably straight piece of lumber. (Of course, some passes through the jointer makes it even better.) Cupped boards that have groves cut down them lengthwise into the sides that formed the peaks of the cups can be clamped and glued together so the grooves are hidden and the cups cancel each other. Twisted is lumber is interesting because boards have either a left hand or right hand twist. You can't join two boards with the same handed twist together to cancel the twists, no matter how you orient them. (So you can't cut a twisted board in half and glue the two pieces back together so the twists fight each other. You can find two completely different boards with opposite handed twists and join them to cancel.) I think lamination is an excellent thing! - even if it is done by a non-industrial process.

By the way, for those that have made large picture frames, how are such pictures hung? Where are the support points on the frame and does the design of the frame take these into account?

[Will Blick]

I hear ya....but my problem with all these techniques are.... if the wood is reactive enough, it will break the glue joints holding them together. Or, the reactive board will influence the non reactive board. So this becomes a "wait n see" proposition. If the frame is for yourself, sure its worth the risk, but not if you are selling them. IMO, it's a tough gamble on a costly picture frame.


Of course wood choice and how the wood has dried seems to be the two biggest influencing factors for long term stability. I used a lot of basswood, as its relatively stable, but not at 10ft+, small errors magnify into noticeable errors. Often the frame is still usable, its just not very nice.

Another poster made a great point about knowing what part of the tree the wood came from. This makes perfect sense....but not everyone has the luxury of finding such wood. I would think the closer to the center of the main trunk, the least chance of movement? Anyone confirm this?

As for hanging heavy picture frames...I only hang them from the sides, using z clips. if you hang from the top, the weight of the entire contraption will will stress out the top miter joints, adding to the risk of an open miter.

[glenn bradley]

I am in the "too thin for that span" group. If you are after the look of thin material but require some more rigidity, there are probably ways that I can't think of to do that. Ways I can think of is to use thicker material and then profile it like . . . well a picture frame, to get the lighter look you are after.

If you really want to keep the appearance of the frame light, make it an appliqué. Make a backer, or substrate if you will, out of 1/4" ply or hardboard with battens glued for rigidity. Position the art and "apply" the frame pieces over it screwing it down from the back.

I'm obviously pulling these ideas out of my ear ;-)

[johnny means]

Sounds like your lumber may be the problem 3/4" from 4/4 is pretty much standard yield in any production shop. 60" is in no way to much to expect from properly cut and seasoned lumber. Of course, we are talking about wood here and one expects to see the odd board with a little more twist, cup or bow, but if your boards are regularly too warped to get 3/4 from 4/4 you should look for a new source.

[Adam Cavaliere]

Bottom line, its best to use laminated MDF for long picture frames.
...
If you look at pix molding catalogs, you will see not many make thick wood mouldings, they all went MDF with laminates, mostly paper laminates...you gotta get creative with big frames, if you want long term success.

Will - I am not completley familiar with the process I would need to accomplish this. With the frames I build, I tend to route them to put my particular look and feel on them. If I were to route Laminated MDF / Ply, it wouldn't look pretty. I am guessing you mean that they laminate after the routing is done. How is that accomplished?

[Jim King]

I have made several frames for a local artist and as his work sells for big $$ I laminated three species in several cases to be sure of no future problems with twist or warp in the larger frames up to 5 feet long.

The wood was kiln dried to 8 % and the mitered corners were fastened with dowels.