Imagine a 16″ square of 4/4 Walnut from which I’d like to cut a slender “S” that will be 1¼” wide all the way. I need several of those S’s to complete a project.
I made a template out of ¾” baltic ply and intended to cut to approximate size on the bandsaw and then use a ½” trimming bit in my router table to make identicle S’s from the template and the 4/4 material. Two successive attempts have resulted in the walnut shearing along grain lines.
Is there a better way of doing this?
Should I just bandsaw and sand the legs to a line rather than the trim bit?
Any suggestion would help brighten a frustrating week-end!
Thanks
Replies
Not sure I totally understand your problem but if I do, you're going to need bent laminations or steam bent wood. Cutting the shape from a solid piece is going to result in several areas with short grain which will snap like a toothpick. If these are legs that need to support any weight I think the project will probably self destruct. A pic or sketch of how you're using these might help us understand the problem better.
If you build it he will come.
I'm real new to this forum - and a little bit computer challenged.How do i post a picture?
If you do a search of past threads there are lots of info that explain the process better than I could. I searched on 'attach files' and saw lots of threads. This one looked like it might explain everything: http://forums.taunton.com/fw-knots/messages?msg=12915.1
One of the posts in that thread also has a link to the Sandbox where you can experiment all day long until you get the hang of it.
If you build it he will come.
Well Let's give this a try!Actually these S's that I am trying to make ARE going to be table legs and I think it is the short grain breaking that might be happening on the router table.I made smaller versions of this table in Maple some time ago and although they are very fragile they have never broken. Now I am trying to make slightly larger version to use as an end table and trying a different wood and thicker material - but maybe maple is simply tighter grained and inherantly more stable?
Nice drawing! Tonight's photo editing night. Here's a smaller copy for the dial-up folks. Cropped a bit, and reduced to 25%.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Muchos gracias FG. I was going to resize last night but it was getting late. I've got cable Inet & download time isnt an issue but the pic was too big to see on the screen.
Londonlad - how are you cutting the S shape with respect to the direction the grain is running? The strongest way would be like the attached, with the grain running along the long side of the board. Since you mentioned cutting these out of a 16" square, I think you might be cutting with portions ending up with short grain, but thought I'd better ask before offering any other suggestions.
If you build it he will come.
As others have pointed out the shape of the legs is inherently fragile whichever way you orientate the grain and a laminate structure would be a great deal stronger.
However, if you really want to use solid wood and shape them, then a way to do it that will almost certainly eliminate the chance of the them breaking as you profile them is to remove the router and pattern cutting bit from the job.
Replace the router with a bobbin sander or spindle sander and use coarse grit abrasive paper for the initial shaping, 40 or sixty grit will do. To use the sander you will still need a plywod or MDF template of the exact profile required. This is attached to the solid wood blank and you trace around it. Remove the template and cut as near as you can to the marked line with a bandsaw. Re-attach the template.
Next you need to rig up the sander to do the final profiling. If you've ever used a spindle moulder (shaper) with a ring fence then you'll quickly work out how the next bit is done. Cut a piece of plywood about 250 mm long (10") X the diameter of your your sanding bobbin or spindle. Round the end of the plywood to the diameter of the bobbin or spindle, or just a tiny bit smaller. Attach this finger or leg to a block of wood so that the rounded end of the leg sits above the spindle circumference. Clamp it to the table and profile this way. Slainte.
*Edit. PS. You may need to build up the height of the spindle/bobbin sander table with layers of ply or MDF to do the job. I thought that bit was pretty obvious so didn't think to mention it before, but, on reflection I decided I perhaps ought to remark on the requirement.
Richard Jones Furniture
Edited 8/28/2006 6:17 am by SgianDubh
Sgian,
I was going to make this a separate thread but it might relate to Londonlad's issue. Last night my wife brought home the broken leg from her dad's dinning room table...split down the middle. I believe the table is a triple column Duncan Phyfe and the leg had been doweled into the column. On closer examination, it appears the leg was made with two pieces of stock (about 7/8" thickness)and has a thin piece(1/16") of something between the two pieces stock. I'm not sure if the 1/16" is for strength...or because there is beading on the top to make the two sides fit better together from a looks standpoint. As you might imagine the dowels are smack dab in the middle of the two pieces.
I'm not sure how I'm going to fix this but I thought you might have seen this construction in your travels and if it does provide strength would it work for Londonlad?
You mean something like in the attached sketch, BG? certainly by slightly altering the angle of the grain in a laminated structure you can spread the load and reduce the weakness that short grain can impart. Even a thin 1/16" middle laminate will help spread the weakness around.
There is an aesthetic question to be resolved of course. Do you want alternating grain showing? Is it visually acceptable to the overall design of the piece? Only the designer can make that judgement at the design stage. Customers, critics and others that look at the end result will also have an opinion. On the other hand not everyone has the most informed education or appreciation of design-- they can find it hard to understand the designers' wrestle with the conflicting requirements of bringing an idea to fruition. Slainte.
Richard Jones Furniture
Edited 8/29/2006 3:35 am by SgianDubh
At the end of the day, I think a lamination would probably be the way to go. However that might have to wait until "next time". I managed to fabricate 8 legs over the weekend and they all seem to be able to withstand being held at the top and having a substantial downward force exerted on them - no failures. I'm hoping that since the top is relatively small and the intended use is as an "end table" that the tables will see a long life - so long as nobody tries to sit on the thing or use it as a stepping stool to change the proverbial light bulb.My local woodshop only carries 4/4 versions of any hardwoods that are not Cherry or Oak and I have historically avoided re-sawing since my early attempts were disasterous! I have now gotten myself a great 1/2" blade and should perhaps try resawing.PS I'd considered switching the template/router process for the oscillating sander but I still needed the router to put a "round-over" on all four edges.
Sgian,
Yes, your design is quite close to Grandad's table leg...with the center 1/16" thick piece being formica or something like that. Only one of the two pieces of wood has the grain oriented correctly. The designer hid this feature by staining the cherry dark, putting 1/8" beads on the top and a brass slipper on the foot...so only from the underside could you see a seam.
My suspicion is that it is one of those 'nice' pieces built about 60-70 years ago...and sold by Ethan Allen Stores or the like...
London,
What douglas is trying to tell you is that you cannot use solid wood for this application of a table leg. You're very lucky that your maple legs have held, because they eventually will fail, also. Wherever your "S" cuts across the grain of the wood, it creates a 1 1/2 " fault in the wood, which a 2 month old child could break. For an end table, forget it. You'll have coffee and soda pop everywhere.
You need to either steam bend this curve, or (preferred by me) use a bent lamination technique. Ask if you need to know how.
Jeff
As douglas2cats said. Orient the grain to run diagonally so that you will minimize the short grain.
I have attached a few photos of a candle stand which is over 250 years old. The legs have a popular design of the period and are similar in theory to the ones you are making.
I tried to get a photo of the grain to show how the grain direction is running diagonal to the curves, about 45 degrees in relation to the column.
The legs on this table have not cracked or broken as far as I can see. So, eventhough such construction is a little dicey, for your application I think it will work.
Good luck.
J.P.
JP,Your advice is good that grain orientation is critical for greatest strength, but I have my doubts that the twisty table design can be robust with grain direction aloneIf you look closely at the legs of your candle stand, you'll probably find that the thickness of the leg has a continuous taper from top to bottom (thickest at the top). Some are not but they're typically heavier than 4/4. There's also a lot of depth toward the top. The leg acts as a lever and the greatest load is normally at the top. The twisty table is a cool design, but it's got a long lever acting on a narrow bend close to at the top. Looking at the picture, a grain orientation just off vertical might be better, though I doubt good enough in walnut.I wonder if another approach would be to laminate several thin plies with the grain perpendicular to each other to make up a 4/4 board. The arrangement of plies would have to be symmetrical to minimize twisting, but this might result in a stronger material.Pete
Edited 8/27/2006 10:58 am ET by PeteBradley
Pete,I agree that the twisty table design may have some flaws however with careful board selection for grain direction it appears to be workable. Laminations are most definitely stronger, however then you have lines from the plies and the difference in grain on the edges which will be more pronounced with finish. Plus you still have glue joints that may fail over time as well.The candle stand legs are the same thickness from the shoulder to the foot. With most of the shaping taking place at the ankle, which is mostly round, then the foot ends up slightly rounded or dome shaped.Most of these types of legs fail at the ankle, which is where the short grain usually falls, plus they are weakened by shaping as well.This one seems to have been well taken care of, except for the finish of course, and is one of the few examples I have seen without a broken leg.It is made from cherry so maybe that has a little something to do with it.I offered the table as an example to illustrate the point that risks taken with the material may not always end in failure, as some others have posted.J.P.
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