Official Luthiers Forum!

Trying to finish up my bender today and tomorrow and have a couple questions.

1) On the face of the spring blocks that contact the stainless sheet, the plans show a 1/2" wide and 1/4" deep routed slot. Anyone know what the purpose of this is? Is it necessary?

2) Is it necessary to build the waist press out of aluminum? I can't see that it's going to take all that much pressure so wouldn't a waist press made out of 1/4" ply pieces to match the aluminum be just as functional and easier to make considering the sizes and slots required?

3) Wiring. 14/3 appropriate? Nothing anywhere that I can see about electrical wiring recommendations either from the control box timer or to the porcelain lamp holders. (yeah I know, get the blankets. I will order them from John @ bluescreek as soon as I can get the money but for now bulbs will have to do)

4) Lastly, do you trace your bending patterns from the insides of your molds or from acrylic templates? I can't see where it would matter, but thought I'd ask anyway.

I'm way behind on my progress the past 3 weeks. Holidays nonwithstanding, I have spent a ton of time getting my table saw motor back to operational. Finally got it going yesterday so working on the bender, then my fretboard radius jig and then back to working on building a thickness sander. (got a new motor just waiting to make some sawdust!)

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Bobby Masten

What's a LCT bender?
I make my forms about 1/8" smaller then the finish size to make up for the thickness of the side and the thickness of the slat and I'll add or minus the thickness of a blanket if used on the bottom. I also make the waist about a 1/4" more radius and pull the ends in 1/4" so they are a bit over bent . There's a youtube on modifying a form in the tutorial section.
My guess on the blocks is to give the block 2 bearing points going around the curved bouts.
Every press I've seen so far has a wooden waist caul on the press. I'm sure some use pieces of emt or pipe if they have some that will fit the curve. I know one who uses a rolling pin.
Yes 14-2 with a ground will be fine as long as you don't use more then 15 amps. or use over 1800 watts of lamps.(120v X 15 amp. = 1800 watts)
You might try holding off on jig building until you need them or you might not ever get started on the guitar.

Thanks,
Personally I like the LMI plans better. Well, at least the block design.

I should have taken pics of the pieces last night for reference. Let me see if I can describe the spring blocks. They are 2 1/2" tall x 1 5/8" thick x 7 1/4" long (going from memory) . Eye hooks on the sides of course to accept the springs. The portion that contacts the stainless slat has a 1/4" deep cutout across the 1 5/8" face, 9/16" from each end. On the plans the face has an additional routing of 1/4" deep by 1/2" wide, centered in the face between the 9/16" ends. It's this 1/4" x 1/2" route that I don't understand the function of. I guess I could call Rick and ask him it's purpose.

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Bobby Masten

It's to create two bearing surfaces just like mine has a valley running down the center. It's a little hard to see in the picture but you can see the high sections where the wood is a tad burnt. It also helps to keep the clamp from slipping because it conforms to the curve of the bouts and won't rock if there was just one bearing point. I wouldn't loose any sleep over it. Once you use the bender it may become more clear to you.

ahhh... it always helps when blowing the pic up to a viewable size. Thanks Chris!

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Bobby Masten

I just shaped that face on my stationary 6 X 24 belt sander.

1.)Not absolutely required but I do recommend that you create and use it. It draws the sandwich tight to the waist caul which keeps the wood supported on both sides during the bend. A greatly reduces faceting or stress fracturing in the waist bend. With out this spring loaded bar the bottom slat of the sandwich wants to open up slightly leaving the bottom of the waist bend unsupported during the bend. Being spring loaded; the bar prevents the bottom slat for moving away from the wood in waist during the bend. I have bent many sets with out it but always dealt with occasional waist bend faceting. Once I started using it I reduced the incidence of waist faceting to pretty much zero.

2.)Aluminum waist caul is not absolutely needed but is a good idea for long life. Remember wood changes dimensionally with exposure to heating cycles. Not enough to worry about in the short term but aluminum will out last a wood caul.


3.)14-3 is fine. I will suggest you use a 600W dimmer for each bulb so that you can control the heat in the LB, Waist and UB independently

4.)I make my bending forms match the inside of my molds less the thickness of the side wood and one slat and heating blanket thickness. This is really close to half the width of a #2 pencil So I use a #2 pencil held flush against the inside of my mold to trace the form boundary. Remember the bending form controls the inside rim shape. So if you put a slat and or a blanket under the wood the form should account for that thickness + the thickness of the wood being bent. Bending fractioally tighter than the true shape is not a bad idea because the wood will spring back some after being bent. So if you plan on using a blanket in the future and plan on using it on the bottom of your wood go ahead and acount for the thickness of a blanket now eve if you will be using bulbs at first.