Bending Mahogany Trim
A furniture-maker gets tips on making tight curves with Magohany. October 2, 2005
Question
I am currently building a corner entertainment center. In the design are several shelves with round ends. The curve is roughly a 6 inch radius. The shelf material is a 1 inch particle core mahogany veneer plywood. The design calls for a reeded edge on the shelf. I've attempted to bend a trim that I made of solid mahogany with a triple reeded edge, 1/4 inch thick by 1 inch wide without much success. Some of the methods I've used are as follows: steaming, soaking for several days and then steaming. I'm running out of ideas and now it is the only thing left to do on this project, so I need help.
Forum Responses
(Furniture Making Forum)
From contributor F:
Make a clamping jig with the same radius as the shelf, cut strips of wood 3/32 to 1/8" (keep in sequence) and glue and clamp. When dry, trim and apply to shelf and reed.
From contributor R:
What type of failure did you have while steaming 1/4" thick mahogany?
From the original questioner:
I steamed it for 15 to 20 minutes in a steamer I built for this project. Whenever I tried to form it, it would split out along the reeds on the outside of the radius. I had hoped to be able to form the edge before attaching it to the shelves, but since I've found no success that way, I will have to laminate it like suggested, attach it to the shelf, and then form the reeded edge.
From contributor G:
There is a limit to how pliable you can get wood, even with steaming. That is why, with severe bends (which is what you have), we always use end pressure. The end pressure applies compression, and so there is less tension force, which is what is causing the breaks. It is very hard to apply compression for small pieces. So, you must use ammonia bending (see archives here) or laminated solids, etc.
From contributor B:
I would think you should be able to bend a 1/4" x 1" piece of mahogany to a 6" radius with steambending even without steel straps to force compression.
My guess is that you did not get the wood up to temperature. The wood needs to reach 195 to 200 degrees to bend. You can drill a 1/4" hole in your steam box and insert an oven meat thermometer to monitor temperature inside the box. If you bring the box up to temperature with the reeeded strips inside, when it reaches 195 degrees you should be able to make the bend. Make the strips at least 6" overlong each end for the bending process and trim them back after they have set in position. There will be some springback, but it should be within the tolerance needed to reapply the bend as the strips are attached to the shelf.
From contributor R:
I agree with the post above, and will add that it might work better if you work the reeds onto the edgebanding after you make the bend.
From contributor D:
A different tack is to:
1. Make the molding out of solid wood. You don't state the amount of curve, but 90 degrees is easy, and can be done in one piece at a 6" radius. Calculate the outer radius, swing a router or just bandsaw it, reed it as needed, then use a curved fence on the bandsaw or swing the router again to cut it loose. This will clamp easily to the shelf with no fussing or cussing, as in bending a piece. Sawn solid also lets you work the ends - butt, miter, lap - easily without wrestling the bent stuff. Think of the curves as a whole and swing the router to cut out the shelves, then the same setup to make the molding.
2. It may be simpler to use solid wood for the shelves and profile it - if the design allows.
3. We regularly turn small curves on the lathe, then cut them up into curved segments. We would turn and reed a disc mounted on the faceplate, then part off the molding at its 1/4" thickness.
There are more ways to skin that cat, but these will keep you busy for a while.
From contributor R:
I am definitely with the post above on trammeling routers. It's a blast! I have a large workspace and one of my trammels is 14 feet long, for doing those slight radiuses.
Wouldn't the piece in question be fairly weak due to short grain in a thickness of
1/4"?
From contributor D:
Yes, it would be a bit weak, as it is cut loose from the blank - especially with a router. Around here, we would bandsaw with our circulator jig, and handle the parts carefully. Once they are glued and clamped (no pins!) to the shelves, then they will be fine. Or do the reeding after the application to the shelves. So many choices.
From contributor A:
One thing you don't mention is the type of mahogany. If you are using pattern grade Honduran (scarce as hen's teeth, nowadays), you might be okay. But any African, Philippine, etc. mahogany that shows a grain pattern would most likely not work in steaming. The issue is that you get grain run out and since kiln dried wood is not the best for steaming anyway, you start getting grain fractures. I've done a bunch of steaming and mahogany (other than pattern grade) is a poor candidate. If you are pre-reeding it... then your grain breakout issue becomes even greater and totally unpredictable. I'd build up laminate sections or do some of the solid machining already discussed here.
From the original questioner:
Thank you for all your suggestions. I ended up laminating strips and gluing in a jig and reeding the edge after applying it to the shelf. If I was to do this again, I would definitely try cutting solid wood radiuses as suggested, as I think it would give an added appearance to the piece.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor E:
African mahogany is three times harder to bend than American mahogany. But the best you can generally get with American is a 12" radius. The advice to laminate thinner strips in your curve could work. I would suggest that you try using a bending strip of metal to take the stress off of the outer curve.
