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Hi,

If this topic has been beat to death, I apoloizise in advance. I did a search and just too many articles poped up that didn't answer my questions.

Having said,

-What is the advantage and disadvantage of using Spring versus Stainless steel?

-What are you currently using?

-When you say "solid form" in reference to bending machine, what does this refer to? and what would be non-solid?

Thanks, David

Hi David,

Spring steel doesn't have memory in that when you bend your sides with it, the slats will just go back to being straight, were as Stainless steel doesn't do this, it has some memory in that when you bend your sides, it will hold much of the shape bent.

Stainless steel will not rust (much) over time and it also will not oxidize the wood if you use water to bend (or even if you don't). Spring steel will rust over time and it will cause some oxidization on the wood because of the moisture used to bend.

Most people who use spring steel slats will wrap their sides in either craft paper (same stuff they make paper grocery bags from) or aluminum foil that way the steel is not in direct contact with the wood.

I use spring steel. I use to use aluminum flashing material (cheap at Home Depot) but it has memory and doesn't work well if you go from one guitar shape/size to another because of the memory.

Bending forms:

Here is a picture of one of my bending forms, this is considered to be an open form (not solid) in that it is hollow between the outside pieces. Sorry this isn't a great picture.



I don't have a picture of a solid bending form for you, maybe someone else will have one to show. Basically you make it out of multiple pieces of plywood or other material to reach the width of the bending form.

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David hopefully this will help:

Stainless slats will not stain your wood except that Koa and some blackwood, related to Koa, has been known to get a great tint if directly in contact with the stainless slats. This can be avoided with the use of craft paper between the wood and slats.

Spring steel can stain your wood even leaving blue spots on the wood.

Stainless does not return to an entirely flat state after bending but I store mine flat and have marked the slats so the waist is in the waist area for every bend.

Spring steel will return to a flat state after every bend.

I use both with the wood never coming in direct contact with either of the two slat varieties. In fact I use 3 slats and my stack looks like this from bottom to top.

stainless slat
wood covered on both sides and spritzed lightly with distilled water craft paper
stainless slat
blanket
spring steel slat over the blanket to help redirect the heat from the blanket down into the stack

A solid form is exactly that - solid over the entire bending surface much like a plug.

A non-solid form has two sides and wood or metal tubes located as cross members connecting the two sides of the forms.

I personally use the non-solid forms, as sold by John Hall at Blues Creek, and I believe that the advantage is that a solid form will wick the heat from the stack to some degree making higher bending temps more difficult to attain.

An advantage of a solid form is that it can also be used as a gluing caul for those who use/make double/laminated sides.

spring steel is a medium carbon steel that exhibits high yield strength. this means you can bend it a bunch and it will return to it's original shape.

stainless steel has different alloying elements which give it it's anti-corrosive properties. It does not typically have as high of a yield limit and therefore will not be able to bend as much and still return to it's original shape (think overstretched slinky).

I use stainless, but i do not have to do any sharp cutaway shapes.

a solid form for bending is one that is made solid all the way thru (these are usually plywood). some folks don't feel the need to make them solid and will make spacers out of pipe sections or pieces of wood.

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Hi,

Could you tell me what sharp cutaway has to do with using stainless? Can you not or would it be difficult to do a Sharp cutaway if you use stainless?

Thanks, David

I've used both and like spring a lot better. I wrap the slats themselves in foil, and the sides between layers of moist craft paper. That seems to have solved the staining problem. The lower spring steel will tend to push the sides straight when you release pressure on the bender so I put a spring clamp on each end of the lower slat and tie them together with something while clamped up. Then the lower slat won't put any unwanted pressure on your side.
Terry

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David I think that stainless, since it gives more, would be better for cut-aways since it will spring back considerably less when removing the bent side from the bender reducing the risk of the slat spring back cracking your just bent side.

My forms look like this. The center form adds support. If you are using light bulbs for heat, you can't use the center one.

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John Ressler

The problem, and the solution, are the opposite. The problem is cracking the side or binding when bending, and the stainless slat is more likely to do it by applying pressure to the unsupported inside curve while bending down the outside "horn" of the cutaway. To avoid the bottom spring slat pushing the inner curve of the cutaway out when removing the side (thereby cracking the horn), you can release the outer slats first and remove the side while keeping the bottom slat(s) held down. Also, you don't need to use thick spring steel slats that would generate that much force.

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Howard how are you riged to keep the inner slat in place in the inner horn of the cutaway. I have been working on this issue for a while. Not that it has been a big problem but some high quilt figured woods I have had this problem and I am curious to your method.

Michael, I've learned some things about this recently and soon will be rebuilding my bender for cutaways.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I use spring stainless that I get from McMaster-Carr. Works great...