LumberJocks

my hard knock lessons in steam and heat bending

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Blog entry by Jim Sellers posted 09-28-2014 02:16 PM 1834 reads 0 times favorited 9 comments Add to Favorites Watch

Was working on a project which would require 2 strips of curved walnut so decided I needed a steam box. It had been on my bucket list for awhile so now was the time. I already had an old pressure cooker and a single burner electric stove. Only other things needed was a box and some hose.

Well, I actually made 2. The first one was made out of plywood and was a major fail. I should’ve had enough common sense to know what was wrong. After about 2 hrs of boiling with the burner on high, I put my gloves on, took the end cap off and removed the wood. To my disappointment, there was no burst of steam when I took the cap off and the wood was barely warm. I’m thinking to myself “dang! what a waste of time and electricity”.

One problem was that the box was too big and I had the strips raised only about an inch off the bottom. The other problem was that the hoses were too long and had created a p trap so the steam must have been condensing and settling in the p trap.

Oh well, let’s try again. This time using 4” pvc pipe and shorten the hoses. After 2 1/2 hrs of boiling and steaming I took them out. They were pretty hot but didn’t seem as soft and flexible as I had hoped. I clamped them in the jig and let them sit for a day and a half. When I took them out, they flexed back slightly and still didn’t have the exact curve I wanted. I had to leave it alone for awhile.

A couple days later I thought I’d try the heat gun. I clamped it in the vise, heated the area I needed to curve and to my surprise, bent and flexed with ease. And held its shape.

So my advise to anyone wanting to bend a small strip of wood, try a vise and heat gun before wasting time and energy building a steam box.

-- J.C.Sellers, Norcross, Ga. Just cut it right the first time. The best carpenters make the fewest chips.



9 comments so far

View BenhamDesign's profile

BenhamDesign

102 posts in 882 days


#1 posted 09-28-2014 03:55 PM

Good tip. I saw a guitar maker use a 150 watt light bulb inside a metal pipe to heat it up. He then pressed the wood to the pipe to make the bend. It was a youtube video but I can’t remember whose channel I saw it on, but it worked pretty well.

-- What I do in and out of the shop at http://www.BriansBenham.com

View stefang's profile

stefang

15512 posts in 2796 days


#2 posted 09-28-2014 07:37 PM

That is very interesting. How long did you have to keep heating it with the gun?

-- Mike, an American living in Norway.

View Jim Sellers's profile (online now)

Jim Sellers

397 posts in 1797 days


#3 posted 09-29-2014 01:14 AM

Mike, it took me only a minute or 2. I guess it depends on how close your gun is. I would say stop just before you char the piece. I had one corner to char black but since the piece was slightly over sized, it sanded out easily.

-- J.C.Sellers, Norcross, Ga. Just cut it right the first time. The best carpenters make the fewest chips.

View robscastle's profile

robscastle

3392 posts in 1666 days


#4 posted 09-29-2014 01:39 AM

Interesting little project with the heat gun I must say.

I will have to try it myself, because physics indicates if you heat a piece of timber on one side by default you will alter the EMC (Equailbrium Moisture Content) and it will curve towards the heat source as the timber has shrunk on that side due to moisture loss.

Steaming increases the EMC of the timber and allows the fibers to expand and in the process softening them, this effect now allows the material to be bent and upon drying in a clamp it will retain almost all of the set.

Have a look at my work bench top sitting in the sun.

-- Regards Robert

View Mike Throckmorton's profile

Mike Throckmorton

124 posts in 1127 days


#5 posted 09-29-2014 01:48 AM

I’ve resorted to a similar technique to put bends in 1/4” thick edge banding to follow curves.

Spray bottle of water in one hand, heat gun in the other and clamps in the other two to clamp to my bending form as the wood relaxed. Keeping the wood moust with the spray reduced or eliminated burning and eased the bending.

-- You are never complete, you just draw a line where done is and stop at that line.

View robscastle's profile

robscastle

3392 posts in 1666 days


#6 posted 09-29-2014 02:38 AM

Ok here are my results

I set up a piece of wood in the vice, clamped it up ready to go.

Out with the heat gun

Went up and down with little effect holding pressure on it by hand
So decided to add some additional bending effort.

Went up and down again, with very little result again.

Maybe the heat gun was not hot enough
So out with the Propane torch

That was certainly getting it hot

some minutes later, after every smoke alarm in the house was tested.

This was the result

I think there is a slight bend in it !

So a clean up was in order

I have to agree it does work to a certain extent.

Just how much is required is of opinion

So there you go eh!!

-- Regards Robert

View Jim Sellers's profile (online now)

Jim Sellers

397 posts in 1797 days


#7 posted 09-29-2014 03:07 AM

Dang Robert! don’t burn your shop down. All I can say is it worked for me. I suspect that all the steaming I did to it must have added extra moisture content to make it flex easier when heated. So maybe the steaming wasn’t such a bad idea after all.

-- J.C.Sellers, Norcross, Ga. Just cut it right the first time. The best carpenters make the fewest chips.

View robscastle's profile

robscastle

3392 posts in 1666 days


#8 posted 09-29-2014 06:46 AM

Hello Jim

Yeah I got the word from the wife as well regarding fire, so its no more inside !!

-- Regards Robert

View Roger's profile

Roger

19867 posts in 2266 days


#9 posted 10-02-2014 12:17 PM

Very interesting.

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed. Kentuk55@yahoo.com

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