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I'm making a ukulele side bending machine and don't know where to get the metal slats from. I've seen people mostly using stainless steel slats, but aluminium is much easier to find and cheaper so would it do instead? Also what thickness do I need? 0.5mm?

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

All our production benders (KMG) have aluminum covered forms and all our outer slats are aluminum except for the cutaway machine which uses two slats made of .008" SS shim stock. Our aluminum is purchased from MacMaster Carr .023"

I should add that Aluminum is better at both, conducting heat and retaining heat.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Thanks! Just what I needed to know

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

I bought a 50' x 6" roll of aluminum roof flashing for $26. Easy to straighten them on the edge of a bench.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

If you are talking about sandwiching your blanket and sides between two slats then sticking them in your bending form set up than you wan to use blued spring steel slats. Stainless will not work as well with the tight bends and aluminum is too wimpy.

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Michael F Smith
Goat Rock Ukulele
http://goatrockukulele.com

I use the same thing..............!
Tom

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A person who has never made a mistake has never made anything!!!

......because I got the idea from you, Tom!

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

I used the aluminum flashing and galvanized steel with sides in craft paper.

Why do you guys like Al or stainless so much? I've been using blue tempered spring steel shim stock for over 10 years and love that it conforms well to the sides and does not deform after use. It has always worked great. Somewheres around 0.010.
Cover with Al foil and sides in paper.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Guess I've been lying because I told folks I got it from you........! Hope it was of some help Alex.
Tom

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A person who has never made a mistake has never made anything!!!

The first few sides I did I used aluminum flashing material I got from Home Depot. It sort of did the job but, as Michael said, it really is too wimpy to provide support to the wood. I switched to the spring steel and have never looked back. So my advice would be that if your intention is to build than a couple of instruments, do it right and get the spring steel.

Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

I use three slats.

Why three?

I like to use stainless under the bent side because it will not spring back like spring steel and there is some risk with spring steel of when taking the bent side out of the bender that spring back of the spring steel can crack a side as the slat tries to straighten when the cauls are raised and removed.

My stack looks like this from bottom to top: Stainless slat, wood wrapped in craft paper, stainless slat, blanket, spring steel slat. The top or third slat is to help direct the blanket's heat into the slat containing to some degree the heat rising off the blanket. The spring steel slat is on the top so it's spring back won't damage the work. Works great for me.

I also added a 4th caul to my bender for pesky sides that wanna cup.

As mentioned above our slats (KMG) are made from .023" aluminum - but I see no reason flashing would not work. We bend sides almost daily, and I know the "different stroke for different folks" rules applies but I ditched stiff SS and blue steel slats years ago. I view the pliability of aluminum as a plus as it helps with easy alignment during the process. Now I should add that our process is different since our forms are internally heated and the waist curve is pre-bent like the factories do it. The blanket, slat, side, paper, foil etc. "sandwich" method is too time consuming for our operation. That said, I'd have to concede in my case I am not comparing apples to apples process-wise.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Pat: Not sure what type of support is needed that can't be provided by AL flashing. I use a solid form and bungee cords on the ends of the top slat and have not had one bit of trouble. Sorry to hear that the Al flashing gave you problems.
Tom

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A person who has never made a mistake has never made anything!!!

I notice that your in the UK Cromwell Tools sell steel shim https://www.cromwell.co.uk/PCN4152350E may be what your looking for

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Formerly JJH

I learn more from my mistakes than my successes

I've seen pics of Tom's set up clever, simple and makes good sense.

I think the OP was asking can one use aluminum for bending slats -- not what is your favorite or current bending method.

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Ken Cierp

http://www.kennethmichaelguitars.com/

The spring back issue with a spring steel lower slat can be easily addressed by putting spring clamps on the ends of the lower slat and running a couple of strips of tape between them to retain the slat before releasing tension.
Cutaways are a little different but a retainer is easy to make.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Again as been said, there's more than one way to skin a cat (what ever that means) -- but I simply hate the sandwich method of bending sides, our forms are internally heated -- yes with blankets and some with bulbs. Using the factory method of applying heat to the inside of the curve, the compression side, the process is simplified. We pre-bend the waist curve heat on the compression side as well. The sides are profiled before bending and this system allows alignment of the inner waist apex all through the process. Plus the side is supported along the entire form minimizing cupping. And of course there is none of the spring back concerns or prevention methods needed to combat the above issues.

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Ken Cierp

http://www.kennethmichaelguitars.com/

That's slick Ken. The sandwich approach certainly does not lend itself to a production setting as well.

What would be your approach to bending a tight cutaway as in an archtop Venetian cutaway with your method?

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Tom,

I feel that it is important to use something that provides some resistance to the bend when doing the waist and cutaway areas. I think it reduces the chance of the wood cracking. That's why I like the spring steel - because it presses back on the wood and provides support. Same principle as those that use some sheet metal to provide support to the outside of their bend while bending on a hot pipe.

Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Terrence the cutaway bender works a little different, there is a sandwich so to speak but all the parts (blanket, and two .008 SS shim stock slats) are attached to the machine, the pre-cut pre-profiled side is simply loaded and the LB end clamped. In addition to the upper blanket the form itself is also internally heated. The slat are fastened to an adjustable tensioning system which is tightened or loosened as the compression caul/s are moved along the profile. This is a refined redesign of a unit I once saw on YouTube. The device must be fastened to the bench. The system is proprietary so this is all that can be posted -- thank you for understanding.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Here's where I first saw the inspiration for our cutaway bender

https://www.youtube.com/watch?v=y1K-PgNmhj8

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Ken Cierp

http://www.kennethmichaelguitars.com/

Nice jig Ken and thanks for the link.

I guess I'm not the only one who builds guitars while rocking out in my pj's! @lovelutherie

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Pat

OK I'm getting what you mean now.
Tom

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A person who has never made a mistake has never made anything!!!

Didn't they show that pic in the film 50 shades of grey?

Very nice Ken!