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Steam bending wood for a chair

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Steam bending wood for a chair

Postby Stargazer » 30 Oct 2017, 12:16

For a significant birthday I was given a chair making course with James Mursell at the Windsor Workshop. I thoroughly enjoyed the experience and ended up with a very comfortable chair as well. Encouraged by the process I started to set up to try and make my own chairs. First up was the purchase of a lathe and teaching myself to turn between spindles so that I could make the chair legs and my first project was a small wooden stool (effectively the lower half of a chair).

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Next I decided to refresh my memory with another course and I made a rocking chair and learnt a few different techniques for chair manufacturing.

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For my first complete home workshop made chair I am making a simple side chair with spindle back and a bent crest, so far the chair has turned and carved parts so the crest will be the first part that I have steam bent at home.

First up the construction of a steam box, a very simple double exterior grade plywood box with 50mm celotex insulation and an outer box for stiffening and protection. The inner box has dowels across the width to support the wood being steamed in the centre of the box. The steam generator is an old wallpaper steamer from a car boot sale. This is good for approx 60min of steaming.

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One end of the box has an insulated hinged door, the other has an insulated tightly fitted plug door. Both doors can be opened or removed once steaming has finished to allow the interior of the box to dry/air ready for the next time it is to be used.

Sitting on top of the steam box in the last picture is the piece of ash to be bent, it is approx 22" by 4" by 1" thick. This was placed into the box once the steam generator had come to a boil and left for about 40min.

Next to come, the bending jig.
Last edited by Stargazer on 30 Oct 2017, 12:34, edited 1 time in total.
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Re: Steam bending wood for a chair

Postby Malc2098 » 30 Oct 2017, 12:28

Brilliant! Can't wait to see it in operation!

Chair and stool look really nice.
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Re: Steam bending wood for a chair

Postby Robert » 30 Oct 2017, 13:13

I've watched a few videos lately with steam bending in them. All seem to involve having a metal strap with end stops clamped to it so the bent wood is under lengthwise compression. Look forward to seeing how you do it :)
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Re: Steam bending wood for a chair

Postby Stargazer » 30 Oct 2017, 15:12

Robert wrote:I've watched a few videos lately with steam bending in them. All seem to involve having a metal strap with end stops clamped to it so the bent wood is under lengthwise compression. Look forward to seeing how you do it :)


Robert,

I have also used the metal strap to pull the wood around a former, this is really where you are putting a serious bend in the wood for a bow back or the arm rail in the rocker above.

A chair crest is a much more gradual bend so I thought it would be within my scope as a novice. It uses a slightly different technique although the wood is much thicker/wider than an arm rail.
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Re: Steam bending wood for a chair

Postby DaveL » 30 Oct 2017, 15:35

Nice work, I am interested to see how the bend works out.
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Re: Steam bending wood for a chair

Postby Andyp » 30 Oct 2017, 15:45

Me too!
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cheers
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Re: Steam bending wood for a chair

Postby Stargazer » 30 Oct 2017, 16:15

Right, part two...sorry about the sideways pictures and the inverted one, is there an option to rotate the pictures?

The bending jig for a chair crest is a simple press using a hydraulic bottle jack. My version is a straight copy of the welded steel version I used on the chair making course. The main structure consists of 2*4 and 2*3 pine glued and screwed together. The former is a laminate of 5 pieces of 18mm plywood glued together then the former cut with a bandsaw to form the matching curves. For future chairs the former can be swapped over for a different shape if required.

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The lower horizontal rail is fixed and supports the bottle jack, the middle rail slides up and down with jack and is prevented from rotating by the uprights. This also provides a mounting point for the crest former.

The upper rail is fixed and supports the upper part of the crest former.

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After steaming for 45min the ash is removed from the steam box using gloves (reminder to self use gauntlets next time that cover the gap between glove and sleeve!) and placed between the two halves of the former lining up the centre mark. Then pump up the bottle jack (3 tonne rating). This part surprised me as the wood deformed very easily with early any effort or groaning from the wooden jig. Especially as I had earlier tested the jig with some 18mm plywood which bent easily but with some creaking from the jig.

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After leaving to cool down for 10min a sash clamp was installed across the extreme ends of the ash to maintain the curve and it was removed from the former and is now in a warm airing cupboard for a week drying out. Once dry the shaping of the bent crest can start then it will be fitted to the chair as the last step.
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Re: Steam bending wood for a chair

Postby Malc2098 » 30 Oct 2017, 16:20

Tasty!

Although, I got a neck ache; but I'll leave that to the Mods!
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Re: Steam bending wood for a chair

Postby tracerman » 30 Oct 2017, 16:28

Ian - I love the trouble you have gone to to suss it out , the steamer box and the jig .

I was watching telly at 0600 on Saturday morning , like we do , and found three programmes ( on catch-up) on BBC 4 called " Handmade " . A glassblower , a blacksmith making a knife , and a guy making a chair involving steam bending and an old poll lathe . Well worth watching if you can find them .
Watching you with interest . I feel you might have to strengthen your bottle-jack jig as you proceed and perhaps made mods .
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Re: Steam bending wood for a chair

Postby Malc2098 » 30 Oct 2017, 16:32

BTW, anyone watching Tips from a Shipwright might have seen Lou try this method to bend a gunwale onto a skiff.

He used a plastic bag and let the steam come out each end for about 45 minutes or so before bending it to the skiff.

https://www.youtube.com/watch?v=--iPQIwSEJM&list=PLzlN3A2DLgNwlLzXqTj7F6ITulv5jRt5Y
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Re: Steam bending wood for a chair

Postby Rod » 30 Oct 2017, 17:14

There’s been a series recently on TV called “Handmade” , one featured a Windsor chair maker. 3 parts for it were steamed bent.

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Re: Steam bending wood for a chair

Postby DaveL » 30 Oct 2017, 19:00

Oh well done that worked a treat, I hope there is not to much spring back.
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Re: Steam bending wood for a chair

Postby Andyp » 30 Oct 2017, 19:20

Brilliant. Well done
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Re: Steam bending wood for a chair

Postby MJ80 » 30 Oct 2017, 20:02

I used the poly sheet last time I did some steam bending (180 degree oak twists), I was really impressed with how simple, flexible it was using the sheet. I couldn't find any of the endless bags, but I have loads of sheeting knocking about in the barn and I cut a length to suit, folded it over the oak with some pony clamps and put the wallpaper stripper into the middle.
I think it works well for random bits, but the box is better if you are doing a couple of different things at the same time.
Love the bottle jack jig
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Re: Steam bending wood for a chair

Postby RogerM » 07 Nov 2017, 18:45

Ingenious jig, and I like the insulated double skinnned box. Thanks for all the detail. Did you get much springback when the workpiece came out?
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Re: Steam bending wood for a chair

Postby Stargazer » 07 Nov 2017, 22:10

RogerM wrote:Ingenious jig, and I like the insulated double skinnned box. Thanks for all the detail. Did you get much springback when the workpiece came out?


All the ideas and inspiration come from the jigs used on the course

The total springbuck was a few mm. Although I have removed it from the jig it is still clamped and in the airing cupboard. I will try and get another photo at the weekend.

This crest is quite shallow, only 40mm front to back bending, the rocking chair is more like 100mm. I might have to get a steel bending jig made to replicate the wooden one for something like that.

Thinking about the arm bow on the rocking chair, the wood is much smaller section so steams and bends much more easily. As was mentioned previously it is bent using a steel backing strap but once bent, clamped and cooled for a few minutes the two ends are tied together and the bow is removed from the jig. At this point the string is very tight, but as the wood dries out the bow tightens up and the string goes slack.

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Re: Steam bending wood for a chair

Postby Stargazer » 29 Nov 2017, 22:40

Finally got some pictures off the phone. Firstly a picture of the 4*7/8 *20 inch blank still in the sash cramp.
Together with a 3mm mdd template for the final shape of the chair crest.

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Then cut out and shaped (tapered, corners rounded over.

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And the holes for the spindles drilled.

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And finally fitted

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Re: Steam bending wood for a chair

Postby Malc2098 » 29 Nov 2017, 22:49

Really tasty!
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Re: Steam bending wood for a chair

Postby RogerS » 30 Nov 2017, 17:46

Many thanks for posting this, Ian. I've always been intrigued with steam-bending. You make it look so easy !
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