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I'm still working on designing and building my bending jig. I'm wondering if I need to be concerned about what type of plywood or particle board I use to build the forms, with regard to the possibility of heat causing the glue in the material to let go. Has anyone had a problem with this? Any suggestions as to what type of material to use, or to avoid?

Thanks!

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

don't use particle board. high grade birch or other hardwood hardwood ply is preferred. and if you use light bulbs line the interior surface with aluminum foil or flashing.

Hi Todd:

I don't think you'll have a problem with delamination. If you are using light bulbs as a heat source, line the inside of the jig/form with some heavy duty aluminum foil to prevent scorching, and reflect heat. If you are using a heat blanket this isn't a problem. I prefer baltic birch for all my jigs/molds, etc. because of its stability. This is the stuff that comes in the 5x5 sheets.

Regards,

-Mark

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I lined my first with aluminum flashing

i used 1" thick MDF from an old computer desk that someone threw out and covered the interior with aluminum, that's for the form, for the box with the light bulbs, i used 3/4" plywood.

[QUOTE=crazymanmichael] don't use particle board. high grade birch or other hardwood hardwood ply is preferred. and if you use light bulbs line the interior surface with aluminum foil or flashing. [/QUOTE]

What is the problem with particle board? I have at least one particle board form that I use in my bender (which is made of Baltic ply and heated with light bulbs), and it has not given me any trouble. It is lined with aluminium foil.Arnt38779.3883796296

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Rian Gitar og Mandolin

Here is a few though based on someone that has been there in more than one direction.

I built my first out of MDF it was a form type not a fox and used light bulbs It did the job and held up through two years of use. Then I bought Lance's old Fox style from him when he upgraded. It is Birch ply and I rigged it for bulbs for a while. I have since converted it to take a cutaway press and now use a blanket. I highly recommend you convert to blankets If you stay at this.

I recommend that you build out of the best material you can to make it last and be upgradeable. Even if you do not plan to use a cutaway press right now, allow for it.

While you use bulbs I really recommend that you use 3-200W bulbs and wire each with its own dimmer. You will find that the waist and upper bout gets much hotter than the lower bout and controlling each bulb will help to equalize and prevent waist scorching.

That is the beauty of blankets even controllable and quick heat-up.

You're going to get as many opinions here as there are builders, so here's mine:

Get the heat blanket. Don't waste time with light bulbs that will heat unevenly.
I use plywood for my forms, but I have a good friend who uses mdf. I'm not sure it really matters. I use plywood because mdf is nasty to cut and route. The dust is awful. That said...my friend's forms always come out nicer than mine.

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Like they said, buy the blanket. I've never done bulbs, but the blanket is very, very easy to use. Lovely stuff.

I use MDF for my forms, because its cheap, I machine outside anyway (and yes, it has nasty dust, but it machines very evenly, no grain to tear out), and did I mention its cheaper than good quality ply? I don't see why it wouldn't last at least as long, either; bending forms are hardly put under a great deal of stress, and MDF building molds work well as well.

[QUOTE=Arnt]
What is the problem with particle board? I have at least one particle
board form that I use in my bender (which is made of Baltic ply and
heated with light bulbs), and it has not given me any trouble. It is lined
with aluminium foil.[/QUOTE]

Most of my forms are foil lined MDF as well and I havent had any
problems.

Cheers Martin

I've got heat blankets. I'm not planning on using light bulbs. I'm building a double-wide bender to bend both sides at once. The design I'm working on is based on Mike Doolin's (in AL #74), but his is not double wide. I've also been inspired by the Taylor bending machines, and my bender may incorporate some aspects of theirs. No nifty automation, though...

My forms will not be hollow like the Fox-style bender forms with light bulbs inside. There may be some spacers between sheets of plywood/MDF/particle board, but not just two sheets with metal bars between like the Fox style.

So far, no one is warning me against any of these materials as far as heat causing delamination or breakdown of the material, so unless anyone chimes in with a warning about that, I'll make my decision on the basis of stability and durability, also considering cost... and then there's the "what do I have on hand?" factor...

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

I'm using MDF for my forms with foil lining. No problems so far. The only one I foresee is screwing hardware through the MDF. Even using bolts instead of wood screws, the MDF probably won't hold up as long as ply. But, like Mattia said, it's cheap!

Todd I have one form that is solid ply thru & thru, 6" wide and I have the same form from John Hall at Blues Creek that is the typical fox style. The only difference in the bending is picking the dang thing up. If you use the blanket or bulbs you want to use either spring steel or stainless steel slats top and bottom of your side wood and these slats support the wood to the form shape. So all the extra ply or mdf in the middle of your form is doing nothing for you but adding weight. I don't think it will make your sides any truer

MDF here in my home grown bender. I sandwich the sides with a blanket between SS slats and bend away. Never had a problem with the uncoated MDF. (and it's very cheap! Like me.)

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Joe Beaver
Maker of Sawdust

After working with light bulbs I came to the conclusion that a small investment for the heat blanket is well worth it!

Good luck building!

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

I'm currently building one with particle board. Why, cause its easier to machine then plywood. Built my template with MFD to get it smooth and perfect with the plans. Then I am making many of the cores hollow with a big fostner bit to bring down the weight. I too am building one like Doolins. But am trying to use something other then the toggle latches he uses. They are very expensive. Any thoughts there??? By the way in a note from Mike he told me he is still using the one shown in GAL article without any mods, so its holding up in his shop..
Mike

I use cam clamps to apply the pressure. Just pull it around the mold good and tight then clamp. No springs or screws. Just the basics.

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Joe Beaver
Maker of Sawdust

Mike, you can use those big yellow quick clamps. Check out Mario's site here are some pics of his bender. Very simple, uses a blanket.

Thank's Mario

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joe, I would need some really long cam clamps to go around the lenght of the body.. no seriously after I read Rods answer and waded through all of Marios wood it hit me.. cam clamps, or bar clamps, with anchors mounted in the main frame. Not sure if the guide post are needed in Marios bender. I was too tired to think about it after I made my way through the wood pile. But now I think maybe they would help as you pull in the waist to keep it aligned. Thanks guys tons of help there..

I like to keep mine very simple, remembering it's just a shape to bend wood around and keep it that shape until it cools. So I use simple 18mm plywood, good quality but not birch, some 3x2" timber and a few eye bolts. Studding through screw inserts hold the whole thing rigid. I think we can overcomplicate things at times especially for the guy that builds 3 or 4 a year.







Colin

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Thanks for all the input. Sounds like nobody's having trouble with the heat causing delamination or breakdown of the various materials.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/