Bending wood


JFII
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I have been able to bend 1/4" - 3/8" oak pretty easily. I don't have access to anything other than kiln dried. In this case I am stepping up and trying to bend  1" x 3" oak for edging for a counter peninsula. (24" cab so 12" radius) . I am using hot water and bought a steamer that will give about 20-25 minutes of steam. I also have a hand held steamer and that worked with just soaking and then heating with it.

But now I am using a 4" pvc pipe (and it has only deflected very little). So My water heater is on HOT and I empty the pipe with wood every 20 minutes and refill 3 or 4 times I have an endcap with a hole large enough for the nozzle of the steamer and open a small vent at the other end put the nozzle in and lock it on. The bigger steamer produces 5 bars or 65psi of steam. which is good right?

I made using roof flashing with the ends wrapped around a block screwed to a 10" piece if 1x3  that been adjusted for the length of the board and when the board is finished steaming o put the ends on and screw them into the board so that the flashing is very tight.. I don't have a press but marked the sides of the board for center. I center the board on the form clamp the center and work on one side with clamps. I have tried fabric softener and ammonia (the latter leaving a dark skin on the wood) after i have it clamped i can see the splits forming on the edges or the flashing snaps I see it directly it always looks skin deep until the next morning when you can see its gone most of the way through the wood has what i am calling shredded (wood just pulls apart)and splits 

I am trying to select boards with the least run off of grain on the edges but after 4-5 fails I took 2 - 1"x3"s planned them down to 3/8"  then without the steamer (just the hand held) bent one on the form waited a day or so then bent the second on top without an issue. Except I would rather it not have a seam.

Any tips - maybe i should be selecting a different grain?  other than to build a real steam box I don't even know how i would heat it

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On 10/17/2021 at 2:46 AM, JFII said:

The bigger steamer produces 5 bars or 65psi of steam. which is good right?

I have been reading up on this for a possible future project. Another way of saying that is that I have no real knowledge, so perhaps someone else can comment on this. My first reaction though, is that this is a bad (possibly dangerous) idea. I don't see why pressure would be needed at all, and 5 bar seems a lot of pressure. Even if nothing explodes, something could break or come loose and shoot high pressure steam right at you. Personally I would re-think that aspect of your design.

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3 hours ago, Wood Basher said:

I have been reading up on this for a possible future project. Another way of saying that is that I have no real knowledge, so perhaps someone else can comment on this. My first reaction though, is that this is a bad (possibly dangerous) idea. I don't see why pressure would be needed at all, and 5 bar seems a lot of pressure. Even if nothing explodes, something could break or come loose and shoot high pressure steam right at you. Personally I would re-think that aspect of your design.

Most boxes are vented. Steam production is constant and the first steam has the heat pulled out of it by the wood. I am not sure I have ever seen a pressurized box, but I have seen pressure vessels generating the steam. I think just because the machine produces it, does not mean you try to contain it. 

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That's a right radius for almost any bending of KD wood.

If it were me I'd personally use bent lamination for something like this. If you don't want to do many thin plies find the thickness that you can bend with steam and then laminate them together to get the thickness you need.

Or find some air dried wood. That can't be too hard in PA there are a lot of trees in that state.

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  • 2 weeks later...

Yes Vented,

I have had 2 boards soak for more than a week. Actual thickness 3/4"   6-8  hours before I bend. I empty the tube and fill it with 160 F water allow drop to 130F then refill with last fill I only allow drop to 150F. before I pull and try.

2x 3/8" - successful, allowed to dry for a 9 days* in the form, glued together and fitted. Although I planed both boards from 3/4" the line down the center is noticeable.

IMHO the issue is time and equipment. The tin flashing would tear so I need something that wont. The time it takes to clamp down by hand. I will need to enlist an assistant.

Any ideas on a profile that would be good all things considered. I try some on the fails which are piling up but they do smell nice from the fabric softener I used on earlier attempts. (I was hoping for scratch and sniff countertop trim - oh -well)

*first set of bends I only allowed to dry for 2 days before I glued and glue failed.

20211023_045040.jpg

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You need a bending form with a more extreme bend to allow for spring back this guy uses kiln dried lumber for steam bending he has a huge shop with, lots of equipment and ingenuity he also uses a flexible steel backer hooked to a hydraulic stretcher thing-a-ma-bob dohicky ( official name ). He also uses ammonia in the water for steaming 

 

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We just laminate wood for counter tops. If you buy a 8/4 board and make numerous rips you will be fine. Just put the board back as it was  ripped. 

If you bend a board it has to want to stay in that position. As mentioned, over bending with springback.

 

lami3.JPG.2462edcbc4f201b9b470ab650591af77 (1).jpeg

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I have watched both and many more video in both cases these guys are in the business of bending wood. 

The second video they are layering and I do have a workable piece made up of 2 x 3/8" boards. I am just not happy with the glue line. Considering i need to put a profile on it I was wondering how i should take into account the glue line when choosing a profile. Both boards were bend then glue the first board I let dry for a couple of day leaving in the form and bent the next right on top of it.  Left them there to dry out the pull them out of the form glued them the clamped them back in the form. For at least a week.

The guy at the top (uses ammonia which i tried - turn the outer layer dark he isn't really bending for show) he said something i didn't understand when he was inspecting and sorting the boards for bending. 

He mentioned about grain running off and don't think i fully understand is he talking rift sawn but the lines should be straight and not move to and off the edge? 

Anyone get a fresh turkey and deep fry it on thanksgiving? Yum!

John

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I have to put more effort into sourcing. Being in the city the woodshops covet there sources - they don't want to be cut out. yes the first guy guy has the press and makes the whole thing look like a cake walk. He goes as far as to only use coal to fire his steamer

I have noticed tiny black spots after soaking or raising the grain using city treated water. started using distilled water to raise the the grain. 

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On 10/27/2021 at 10:51 AM, JFII said:

Yes Vented,

I have had 2 boards soak for more than a week. Actual thickness 3/4"   6-8  hours before I bend. I empty the tube and fill it with 160 F water allow drop to 130F then refill with last fill I only allow drop to 150F. before I pull and try.

2x 3/8" - successful, allowed to dry for a 9 days* in the form, glued together and fitted. Although I planed both boards from 3/4" the line down the center is noticeable.

IMHO the issue is time and equipment. The tin flashing would tear so I need something that wont. The time it takes to clamp down by hand. I will need to enlist an assistant.

Any ideas on a profile that would be good all things considered. I try some on the fails which are piling up but they do smell nice from the fabric softener I used on earlier attempts. (I was hoping for scratch and sniff countertop trim - oh -well)

*first set of bends I only allowed to dry for 2 days before I glued and glue failed.

20211023_045040.jpg

 

This is about 1-2 hours work in the shop...

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  • 2 weeks later...

Yes about that.

Another failure, For now I am just not equipped to bend 3/4" 

I moved forward with my two pieces of 3/8" glued together. 

Learned: Some consideration needs to be placed on the form being the same width as the board and on even pressure and distribution of the clamps otherwise the board will twist or deform.

Question: is there any safe way to trim the curved board down to size on a table saw? I didn't feel comfortable to attempt it so I trimmed it down with a jig saw, sander then hand sanding knowing if it wasn't pretty straight it will show up when the profile is cut.  I attached backer blocks to the ends before cutting the profile.

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