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Mold Question
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=12528		 Page 1 of 1
Author:  slackkeymike [ Wed Jun 20, 2007 1:37 pm ]
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When making a plywood mold (for a special shape guitar), would it make sense to use the "cutout" part for the side bending shape?

PS: If anyone would like to make the mold (reasonable price) I am open to offers...I do not have a big enough bandsaw. Its for a Dyer Model 6 Harp.
Mike
Author:  letseatpaste [ Wed Jun 20, 2007 2:01 pm ]
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If you're good with a band saw I suppose you could, but there's not much room for error. How big is your bandsaw? I've cut form pieces on a 9" Ryobi and a 10" Craftsman. I get it close to shape on the bandsaw and then finish up with the disk and spindle sander for the first piece, and then use that as a pattern to rout the rest, which are also cut close to shape on the bandsaw.

You might consider making patterns out of 1/4" material and getting the shape exactly right and smooth, and then using a router with a pattern bit to cut your mold and/or bending form pieces. A disk sander and oscillating spindle sander are really helpful to get smooth curves, but not absolutely necessary I suppose.
Author:  Cocephus [ Wed Jun 20, 2007 2:26 pm ]
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If you find you can`t use the cutouts for your bending forms, they can be used in making your spreaders for your mold. It worked that way for me.
Author:  slackkeymike [ Wed Jun 20, 2007 3:25 pm ]
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That makes a lot of sense when I think about it!
Author:  Gary L [ Wed Jun 20, 2007 10:54 pm ]
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That is what I do. I make mine out of MDF and cut the pieces for the outside mold with a template and a 1/4" diameter flush trim bit. Since the complimentary cut-outs for the bender form is 1/4" smaller, the difference is perfectly made up by the thickness of the side, heating blanket, and flashing. Before I assemble the bending form, I further shape the bender cut-outs slightly from about the shoulders of the bouts to the ends so I can overbend. The procedure is a bit rough on the router bit, but it sure is convenient.
Author:  bob_connor [ Wed Jun 20, 2007 11:34 pm ]
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I use the cut out section of the mold like this.



I can bend two sets of sides at a time. One set goes into the mold and the other set gets clamped into the jig in the pic to hold the sides in shape.

Now for some light entertainment.

Whoever first guesses what wood is in that jig I'll send a figured Gidgee bridge blank.

I'll shift this to a new thread so I'm not hijacking Slackkeymikes thread.

Cheers
Author:  JimWomack [ Thu Jun 21, 2007 12:02 am ]
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I do something similar. I cut my forms 1/8" to 1/4" proud on the inside and use a spindle sander chucked into my drill press to finish one of the pieces, then use that piece with a flush trim bit and a template attachement to finish the other pieces.
I use the inside cutouts for my bending forms. I take 2 sides and screw them into a 2x6 base. I then screw in some 1x2 cross braces and cover the whole thing with thin aluminum stock... the kind of stuff the big box hardware stores sell as kick panels for screen rooms. Takes about 20 minutes to put the whole thing together. My heat source is a cheap HF heat gun. I drill a couple of 1/4 holes in the opposite side to prevent back pressure from ruining the gun. The whole thing works very well. The aluminum does a good job of transferring the heat. Here's what mine look like:



Different angle:



I screw the thing to a narrow plywood plate so I can clamp it to my workbench.



It's worked very well for me, FWIW.
Author:  Dave White [ Thu Jun 21, 2007 8:38 pm ]
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Mike,

This post by Ken McKay on bending double-bass sides should be of help/interest to you. For the harp guitar I am building I am using the shape of an existing guitar and for the bass side I bent the waist and lower bout in the fox bender with the guitar form, for the treble side I bent the waist, lower and upper bouts in the Fox Bender. Then I used the hot pipe, and finally used the pieces inside the mold with the heating blanket sandwiched between two bending slats to press to the final shape. You have to be VERY VERY careful doing this to have the right protective clothing so that you don't burn yourself (or set fire to the bench ). It doesn't take very long - mist the sides, press the heated sandwiched blanket against for a minute or so and the use various spreaders to hold the shape while it cools - I used thin dowel rods. Here's a few pics that might help:







Author:  charliewood [ Fri Jun 22, 2007 5:13 am ]
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Tazmanian Tiger Myrtle would be my guess!
Author:  slackkeymike [ Fri Jun 22, 2007 3:20 pm ]
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Dave, keep me posted..I am working on a Dyer Model 6.

Mike
Author:  Dave White [ Fri Jun 22, 2007 8:03 pm ]
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[QUOTE=slackkeymike] Dave, keep me posted..I am working on a Dyer Model 6.

Mike[/QUOTE]

Mike,

You can follow progress of the build here on my website.

Looking forward to seeing yours progress.
Author:  slackkeymike [ Mon Jun 25, 2007 3:22 pm ]
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Nice work!
Author:  Michael Dale Payne [ Tue Jun 26, 2007 12:00 am ]
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For the price you can't beat John Hall's molds or bending forms. He has a great supply of common forms and or can build to your needs. He is a sponsor check at Blues Creek Guitar's link at the top of the page.
Author:  Michael Dale Payne [ Tue Jun 26, 2007 12:04 am ]
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I should have added they are made from only top grade ply and hardware. None beter anywhere. He makes all of mine.
Author:  peterm [ Wed Jun 27, 2007 2:41 pm ]
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John Hall is the way to go.....give him a call!
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