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Welded Wooden Step Stool

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Project by leonmcd posted 07-31-2007 09:08 PM 3410 views 9 times favorited 16 comments Add to Favorites Watch

My niece recently asked me to make her a step stool and Lumberjocks has a wood joinery contest. At first a complex step stool with twenty eight joints that was designed for people to stand on did not seem the ideal project to do without glues, metal nails, screws or other mechanical fasteners!

That was until I discovered “wood welding”. I’ve followed the discussion on contest rules and as far as I can tell there is no restriction on “wood welding”. This project is 100% wood (except for a little of my DNA).

The step stool has a pecan frame and the steps are honey locust. The dowels are the cheap some kind of white wood variety. Except for the steps, all the joints are lap joints “welded” in place with dowels. The steps are butt joints “welded” in place with dowels.

So what is “wood welding” you ask?

Since I’ve never created any joinery without glue, I hit the internet looking for glueless joints. I found a reference to “wood welding” which is a commercial process that uses vibration and pressure to join wood without glue or fasteners. It was discovered in 2005 by accident when a technician forgot to include the plastic sheet that they put between the two pieces of wood before welding. Seems that the wood stuck together just fine without the plastic. Just wood on wood. Some of the wood components actually melt and fuse back together to form the weld. It forms a joint in 3-4 seconds that is as strong as a glue joint after 24 hours.

The only down side for me was that the commercial process uses machines costing thousands of dollars.
Luckily I found a tiny reference that hinted that you could do the same thing with dowels and a hand drill.
Unfortunately, it did not say how. After quite a bit of experimenting, I discovered that I could use a hand
drill to put a 3/8 dowel in a 5/16 hole and it was definitely welded. Using pliers I could twist off the
dowel without breaking loose the weld.

I learned that there are some tricks to doing this and I plan to put together a video blog to demonstrate the process.

-- Leon -- Houston, TX - " I create all my own designs and it looks like it "





16 comments so far

View RobS's profile

RobS

1334 posts in 2965 days


#1 posted 07-31-2007 09:33 PM

Very interesting..Nice job.

-- Rob (A) Waxahachie,TX

View Damian Penney's profile

Damian Penney

1140 posts in 2650 days


#2 posted 07-31-2007 09:35 PM

Fascinating…

“At the very high temperatures attained by mechanical friction (higher than 180°C) the characteristics of the wood lignin and hemicellulose between the wood cell walls change, and start to flow, hence the initial phase of « melting ». The wood fibres released by this flow of materials become then entangled, and form a high density composite by being drowned in the molten material once this has cooled down. This composite constitute the bondline, or better the weldline of the timber joint. The researchers involved have also clarified some of the main chemical reactions occurring during welding. The mechanical resistance of the joints formed by welding in 2-4 seconds is comparable to what obtainable 24 hours after gluing.”

“The second process developed is high-speed rotation welding of dowels. A dowel in rapid rotation inserted by mean of a simple electric drill into a substrate welds to the substrate with a mechanical resistance 20 times greater than the traditional hammer inserted dowels, and with a strength comparable to dowels glued-in for 24 hours with PVA adhesive, all this without the use of an adhesive.”

-- I am always doing that which I can not do, in order that I may learn how to do it. - Pablo Picasso

View MsDebbieP's profile

MsDebbieP

18615 posts in 2819 days


#3 posted 07-31-2007 09:40 PM

I can’t wait to see this video.
It sounds fascinating!!
the stool is beautiful – a lovely addition to a kitchen.

-- ~ Debbie, Canada (https://www.facebook.com/DebbiePribeleENJOConsultant)

View coloradoclimber's profile

coloradoclimber

548 posts in 2726 days


#4 posted 07-31-2007 09:43 PM

now that is cool. who’d thought to do that. Back in boy scouts you learned that if you rub wood together you get fire, not glue. I suspect different woods, higher oil content, moisture, and such would have different welding characteristics and techniques.

thanks for sharing, pretty interesting.

View Mike Lingenfelter's profile

Mike Lingenfelter

501 posts in 2772 days


#5 posted 07-31-2007 11:39 PM

Yes very interesting! I’ll have to look into that process, I’ve never heard of that. I love learning something new!

View Mike Lingenfelter's profile

Mike Lingenfelter

501 posts in 2772 days


#6 posted 07-31-2007 11:47 PM

I love Google :).

Wood Welding

View Don's profile

Don

2599 posts in 2835 days


#7 posted 08-01-2007 01:30 AM

Most interesting. Thanks for bring this method of joinery to our attention.

Best wishes.

-- CanuckDon "I just love small wooden boxes!" http://dpb-photography.me/

View mot's profile

mot

4911 posts in 2695 days


#8 posted 08-01-2007 06:12 AM

When I was searching glueless joinery, I came up on wood welding, but just kept on going. I’m glad you stopped to take a look around. Nice project!

-- You can discover more about a person in an hour of play than in a year of conversation. (Plato)

View Joel Tille's profile

Joel Tille

213 posts in 2902 days


#9 posted 08-01-2007 02:01 PM

I guess we can’t pull the old trick of sending someone to go get the wood welder anymore. fascinating story and nice step stool for your niece. thanks for the link

-- Joel Tille

View PanamaJack's profile

PanamaJack

4473 posts in 2736 days


#10 posted 08-01-2007 02:28 PM

Cool stool Leon! Interesting joinery method as Don says.

Thank you Mike for the article.

-- Carpe Lignum; Tornare Lignum (Seize the wood, to Turn the wood)

View leonmcd's profile

leonmcd

204 posts in 2630 days


#11 posted 08-06-2007 08:57 PM

Didn’t get around to making my video this weekend. Something about plumbing. Hopefully soon.

As I was thinking about the video, I started asking myself why would you want to use wood welding when you could just glue things to together like you always have. All the joints I welded together could have been glued. I only used wood welding for this project because of the contest. The contest is also the only reason I learned about wood welding.

As I thought about it, It occured to me that this step stool is pretty complex with 28 joints. The glue up could have been quite complex and could easily have used more clamps than I have ( “you can never have too many clamps” ). If I don’t have enough clamps then I glue it up in assemblies and then glue those assemblies together. Lots of time waiting on glue to dry. Even with enough clamps this would have been tricky to get everything in place and clamped ( by myself ).

With the wood welding, I only used two clamps. There is no waiting for glue to dry. As soon as a joint was welded, I could move to the next.

Now that I think about it, I might just use wood welding on a future project.

-- Leon -- Houston, TX - " I create all my own designs and it looks like it "

View Karson's profile

Karson

34878 posts in 3059 days


#12 posted 08-06-2007 09:09 PM

Leon:

I’m interested in your wood welding. If you attach two pieces together as a joint is the connector piece (Dowell) spun through both pieces of wood?

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware karson_morrison@bigfoot.com †

View leonmcd's profile

leonmcd

204 posts in 2630 days


#13 posted 08-06-2007 09:58 PM

Yes. I drilled a 5/16” hole through the top piece into or through the second piece. I then chucked 3/8” dowel into my drill. Then pressed and spun the dowel through both pieces.

I never found any information on the Internet on how to do this so the following is the technique I developed

The pieces to be joined need to be well secured with clamps to something solid ( bench, table, etc) ( You need to apply a lot of pressure and you don’t want it moving around )
I used a corded 7amp 1/2” drill. ( Need lots of speed and horsepower and don’t think a battery drill would work in the long run )
I beveled the leading edge of the dowel to help it find the 5/16” hole
I bottomed out the dowel in the chuck ( you need to apply a lot of pressure and I didn’t want it to slip)
I used a keyed chuck so I could really tighten it ( didn’t want it to spin out and I don’t think a keyless chuck would work)
I align the dowel with the hole and get the drill up to full speed before I start pressing
Once I start pressing, I don’t stop until I hit bottom
As soon as I hit bottom I stop spinning and pressing but I leave the drill/dowel in place ( the process needs 3-4 seconds to cool and solidify the joint )
I use the key to open the chuck and release the drill so I can remove the drill
I then cut the dowel off using a flush cutting saw

Hopefully I can find time to do the video. If a picture is worth a thousand words, what is a video worth?

BTW – It does smell like it’s burning when you are inserting the dowel but so far no flames

-- Leon -- Houston, TX - " I create all my own designs and it looks like it "

View Buckskin's profile

Buckskin

486 posts in 2646 days


#14 posted 08-06-2007 10:19 PM

Interesting concept. I may have to give it “spin” on a project also.

View itsme_timd's profile

itsme_timd

688 posts in 2489 days


#15 posted 11-30-2007 06:23 PM

Very cool! I’ll have to check into that – I’m a fan of “no nail / no screw” projects.

-- Tim D. - Woodstock, GA

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