Back in 2012, I tried steam bending white oak for the first time. I had a ton of trouble on this first attempt at steam bending wood. You can read about it here.
Since then, I have kept my eye out for articles on steam bending, that explain why I had so much trouble steam bending white oak. I found found the article that explains why I had so much trouble.
I don't know for sure, but I am 95% certain the white oak I tried to bend back in 2012, was kiln dried oak. Per the article above, the only way to steam bend it is to soak it at least 1 week in water and fabric softener!!
This article also suggested that one should keep the bend ends secured, versus floating in free space. My initial clock design in 2012 had one end secured, and the other end floating in free space. My guess is the bend radius changes over time on the unsecured end, with temperature and humidity changes.
Another article from Wood Magazine, has these tips, including soaking with fabric softener..........
Years of experience have taught Russ a few steam-bending secrets:
• Soften up hardwoods. Soaking air-dried hardwood parts for a week helps prepare the lignin for bending. To help the water penetrate the wood, add 1/2 cup of fabric softener as a surfactant. Add water daily so long as the wood absorbs it. Once the wood is bent and sanded, the softener won’t interfere with stains or finishes.
• Minimize wood thickness. When bending parts that will have a taper, Russ tapers the wood before steaming to reduce its resistance to bending. On parts where he’ll round over two edges along the inside face of a bend, he chamfers those edges before steaming to reduce the amount of wood to be compressed during bending.
•Learn from experiments. While steam-bending parts for a project, fill any leftover space in your steamer with various sizes of practice pieces to test their bending ability for future projects.
Old Fixture Design
I went back into Sketchup and found my old fixture design. When I used that design, I got way too much spring back. I still have the old fixture, which shows where I had to cut the angle in the bend radius fixture piece, to eliminate the springback.
In my old 2012 fixture is the piece of white oak that I steam bent. The curve is ok with respect to the right hand straight part being parallel to the left hand side straight part. I had to cut the bend radius piece with the saw at a pretty good angle. The bend radius achieved was 3.5 inches and I wanted 3.0 inches. This means you need to reduce the bend radius fixture piece by the ratio of 3.0/3.5 or 86% of the target bend radius.
Search for New Clock Design
I went on the Internet searching, and found a nice clock design........It was from 2008 and came from here.
I used Google Sketchup to come up with my version of this clock design.........
I went to Klock-it's web site and found a face and pendulum movement.........and ordered it.......
At this point, I was unsure how to package the clock movement into the clock, because no 3D drawings of the Klock-it movement and pendulum are available.
Fixture Design for the New 2016 Clock
I went back into Sketchup, and designed a new bend fixture using the process development knowledge I learned back in 2012.........
New Steam Box
Because the pieces are longer on this new clock design, I went ahead and built a whole new steam box.........versus adding onto my old steam box.......
Water Soaking Set-up
I bought a piece of 3 inch Schedule 40 PVC from my local Ace Hardware, then glued an end cap onto it. I went to Dave's Supermarket and found a small bottle of fabric softener. I put 2 cap fulls of softener into the PVC pipe, along with 6 pieces of white oak.
Then I received the clock hardware from Klock-It. I went into Sketchup and made a 3D drawing of the movement only......
Then I inserted the movement into the main clock design. I decided to use a 3/16" thick front wood piece, which will be glued to a hollow ring to hold the movement. This assembly will be slip doweled into a back round piece, for removal to change time or batteries. I may try using some permanent magnets to hold the clock assembly together.
I retrieved the shipping box for the steam generator, and got it all set up again. I can't believe it has been 4 years already since I last used it, boy time flies!
Steam bending results with new fixture
I sawed up 6 pieces to soak and then steam. When I was sawing them, I noticed one or two were really defective pieces. They had excessive splits or cracks in them. I decided to use them anyway, I could use them to verify my set-up before I tried bending the good pieces. The first piece I steamed, was a defective piece, and did split when I bent it........but I was able to verify my fixture worked ok.
On the 2nd piece, which was a good piece, I steamed it for about 35 minutes. The rule-of-thumb is 60 minutes per inch of thickness, and my pieces were 3/8" thick. Technically, it only needed 23 minutes, but I went 35 to be on the conservative side. I tried to bend it at a steady rate, not too fast and not too slow. It bent ok in the fixture......
I let this first piece dry overnight in the fixture. The only potential issue I noticed was that on the bend radius, the piece bulged above and below the 3/4" wide plumber's strap I used. The piece is 1.5 inches wide, so there is 3/8" above and 3/8" below the plumber's strap. Once the piece is dried, I will see how significant the bulges are. I could add a 2nd piece of plumber's strap, so the height of 2 of them would match the thickness of the wood.
1st Steam Bent Piece
Over-all, this wasn't too bad for the 1st attempt. If anything, I over-compensated for the spring back, in that I have to gently bend the side so it is parallel to the other side.....
I have a little cracking on the bend radius, but I think I can sand it out ok.
The other surprising finding is the bend did bulge above and below the 3/4" wide plumber's strap!
On the left hand side, you can see the bulging above and below the mark left by the 3/4" wide plumbers strap. I guess I will have to use 2 pieces of plumber's strap, so they are the same thickness as the 1.5" wide board, or try a piece of 1.5" wide aluminum or tin. I can probably sand out most of the bulges on this piece.
Getting Rid of the Bulge
I decided to try using 2 widths of 3/4" inch wide plumber's strap, to result in it being the same width as the piece being steam bent, at 1.5".
The tough part is trying to get the 2 pieces at exactly the same length or tension. I pulled on the end wood block to try to make them exactly the same.
In the photo above, I am using a wet piece of the 1.5" wide oak, to test out the fit of the upgraded fixture. It will be interesting to see if it works!!
Depth of Water Penetration after 7 Days of Water and Fabric Softener
The photo below shows the piece after I sawed it to the desired 28.5 inch length. It looks like about 1/16" of soaking penetration. My digital camera doesn't photograph small cross sections very well. The piece is 3/8 x 1.5 inches in cross section, and 28.5 inches long. The most critical part of the board being bent, is the outside of the bend radius.
Leg Length not Identical after Steam Bending
In theory, both legs should have come out the same length........but they did not. Fortunately, my clock design doesn't really care what the final height of the 2 bent legs are, just that the 2 bent pieces should be the same height. I took the piece to the table saw and made the legs the same. I used a 5.5 inch long spacer block to keep both sides parallel. The final bend diameter was supposed to be 5.25 inches, but it ended up at 5.50 inches..........not too bad given the nature of the process!!
2nd Steamed Piece with 1.5" wide double plumber's strap
I went 45 minutes steaming time on this one. I'm not sure if it makes any difference, but I would rather be on the safe side. It bent fine. After soaking for 7 days in water and fabric softener, the web boards are are a little wider than the 1.5 inches I sawed them dry at. I got a little check mark on this 2nd piece on the outer edge......because the plumber's strap is just a smidgeon narrower than the piece being bent.
1/8" Round-Over on Router Table
I put this round-over on using the router table. I started it about 2 inches from the bottom ends. I want a square bottom to fit into the base plate, versus rounded edges.
Tenon on Ends
My design calls for the ends to be tenoned into the base place. The base plate will have 1/4" wide rectangular holes. Since the bent piece is 3/8" wide, this means 1/16" must be removed all around the ends. I was able to use the router table to remove the material on 3 sides. On the 4th side, I sawed with a dovetail straight saw, then hand chiseled it.
When I bought this Sears router table almost 40 years ago, the sliding miter gage came with it.............and I'll bet I haven't used it for almost 40 years...........but it still works ok.
I had to glue and clamp up quite a few boards to make the rest of the parts on the clock. Including the base, 3/16" thick front circle, 1" thick inner ring, and 9/16" thick back ring. I made enough boards to make parts for 2 clocks.
Making the Base
I glued up the boards, then planed them to 1" thickness.
I glued the paper pattern onto the boards, printed from Sketchup......using White Elmer's glue......so I could wash it off when done with a wet sponge.
I used my Delta mortiser to put in the 1/4" wide by 1-3/8" rectangular holes in the base. I had to free hand the location, because of the angles.
I made patterns for the round front face..........which is the same basic pattern for the inner ring..........then a 2nd pattern of the back round piece. I glued these onto 3/16" luan. I cut them oversize by 1/8" on the bandsaw, then sanded them exactly to the round edge using the vertical disc sander from Harbor Freight, which worked well. I then tried out the look of the design by holding the front pattern in rough final position........
I cut the back round piece oversize on the bandsaw, then air nailed the pattern to it with 4 nails. I went to the router and used the follower-bit to make an exact copy of the pattern.
I have tried using 2-sided tape several times, and it always comes loose in the middle of the job. So, I'm using little air nails instead. They are so small, you can't see them when you are done.
I went to the scroll saw to cut the ID of the center ring. I usually only do fine work on the scroll saw, so I don't keep any blades for thick work, like this 1" thick white oak. I smoked the little blade, so I went to Ace Hardware to get a better blade..........and it worked much better!!!!!!!
I glued the middle hollow ring to the 3/16" thick front round face and clamped it up. After it dries, I will use the router follower-bit to make the piece for the front face and middle ring.....
Notch for Pendulum
The bottom of the front/middle ring needs the bottom notched for pendulum clearance. I decided to use a 2 inch Forstner bit to remove this material. I did clamp the piece in the drill press, because a 2" bit can really grab sometimes and swing the piece violently. This method worked rather well, and fairly accurately and quickly.
Flush Trim Router Bit
I initially used the router bit, shown below, not in the collet.........to flush trim the round pieces to the pattern. On the 1 inch thick pieces, the middle piece, the cutting area was just a little too short......and I had to take to the disc sander and sand off the little pieces it missed. I also got quite a burn on the white oak, which I had to sand out on the drill press drum sander.
I switched to the brand new blue Rockler, flush trim bit..............and wow.............did it cut nicely. I cut all the way around first, then just moved it up in the table, to finish the cuts. Wow, no grinder burn to have to sand out!!!!!! Maybe my old bit is dull, or wasn't that good to start with, I don't know.
I put two 1/4" diameter dowels between the middle section and back face. I will glue the dowels into the back face only. This will allow the front to be removed to change the time, or change batteries.
At this point, the big challenge was how to glue the 2 small 45 degree blocks to the back face and the 2 bent pieces. I could not see an easy way to do this. I decided to mortise the two pieces into the back face. They are 1/2" thick, and I have a 1/2" wide mortising tool. Once the two pieces are mortised in, I should be able to clamp them to the 2 bent pieces using the string and nail method.
I have a 1/4", 3/8", and 1/2" wide mortise sets. I got out the never used 1/2" wide set, and went to install it in my Delta mortising tool............and it won't fit!!!!! The large diameter is about 9/16", too big for this tool............and too big for my drill press.......darn!
So, I put the 1/4" set back in, and mortised the back piece with it.
I am not sure my length of the short 45 degree pieces is long enough. I decided to go ahead and try it. I used a large rubber band to hold the back piece in rough position, then air nailed it to the bent pieces. If I did not own an air nailer, I'm not sure how I could have done this final assembly. Possibly, an option might be to dowel the 45 degree short pieces to the 2 steam bent pieces.
Testing Pendulum Fit
I wanted to make sure the short pendulum had enough swing, and did not hit the bottom base. It works ok, but on the next clock, I should increase the length of the short 45 degree pieces by 1/2" to 1" to give some more clearance.
I think this clock is going to be a pretty one when completed !!
I like the teak stain that I have used on past white oak projects before. I had to use an artist's brush with the stain, to get in between the round back face and 2 steam bent legs. I used satin versus pure gloss polyurethane on this project.
Ooooops, Almost made big mistake
I bent the last 2 pieces of white oak, to make a 2nd clock. I wanted them to dry faster, so I stuck them in the oven at 100F. That was a very bad plan!!!! I checked on them after 10 minutes, and they were starting to spread apart. I quickly clamped them parallel again, and I think they will be ok. There must be a ton of residual stress left in the bent pieces, for 100F to cause them to bend!!
View Inside the Clock
The photo below shows what the inside of the clock looks like, including where I used the 2" Forstner bit in 2 places......to give clearance for the pendulum......
Finished Clock on the Work Bench
I nailed the face onto the front using the little brass nails that came with the face........
Closing Thoughts on This Project
This was one of the hardest projects I have ever done, because of the process development required to learn how to steam bend white oak. The soaking of the white oak boards in water and Downy fabric softener worked!! I successfully bent about 6 pieces of white oak. I still got some check marks at the top of the bent piece, because my double-wide plumbers strap was just a little thinner than the water soaked wood. I was able to glue back the check, or sand it out.
A definite thing I learned was not to put the steam bent piece into the oven at 100F to dry out the wood quicker!!!!!!
Google Sketchup Warehouse
I put my design on the Sketchup Warehouse. It includes the fixture design for bending the wood as well......