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Guys perhaps you can comment on my plans for the side bending jig, currently all I can see wrong with the design is that it's only 6" wide so would have to widen it to accept a 6" blanket. Sorry John couldn't afford shipping from the US for one but I know where I'll buy my blankets.

http://www.flickr.com/photos/11224986@N ... 1/sizes/l/

http://www.flickr.com/photos/11224986@N ... 9/sizes/l/

Sorry can't seem to add pics, any hint's tips would be welcomed. A couple of things I noticed was the waist press seem shorter and sprung for some reason any clues?

Cheers

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Formerly JJH

I learn more from my mistakes than my successes

Looks fine to me, only thing might be to increase the height of the waist ram. It will make it easier to pull the bent side out. And it only needs to be 1/8" wider then the blanket and slats.



I'd use a higher wattage bulb at the waist, mind you if you're going with a blanket don't worry about it.

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Here are photos, etc. to build a good, cheap Fox Bender from my web site. Go to http://www.wellsguitars.com/Articles/BendingMachineRevised.html.

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Sylvan
http://www.wellsguitars.com

I know it's not a Fox bender, but this is the type of bender I have used for some time now, I've bent something like 60 sides or so using this type with never a failure. I like the fact that I can still feel the wood bending under my (gloved!) hands. Takes an hour or so to make and costs less than a tenner. When I want a different body shape, just make anew one, you'd have to do that with a fox bender anyway.

Oh and yes blanket and spring steel slats from John Hall.

One thing to remember, whichever type you make, is to make some sort of facility to trap the bottom steel slat when fully bent so that as you release the bent side the bottom slat isn't trying to straighten ou the wood again.





Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

If you plan on using bulbs... they may be a little low in the box. I use bulbs and have mine protude a little up inside the form. Maybe an inch or so. Your's appear to be flush. You need to get the heat close to the waist (and cutaway if you have one). That is where your most drastic bends are. They need to get the most heat. The other areas will bend under less heat.

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Joe

Well the first thing I will say is that if you use bulbs you must use ceramic fixtures. And you will need at least one 600 watt dimmer, 1 dimmer for each bulb is even better. The cost of bulbs, ceramic fixtures, and aluminum shielding, wiring and 2 600W dimmers is not but a few dollars more than a heating blanket and a router speed control.

What ever you do be sure to shield the inside of your forms and fixture. These things will catch fire when bulbs are used.

When using bulbs, control of the heat for the upper bout and waist is critical at the lease I would use a dimmer on each of those two bulbs. Be carful to not get the waist bulb too close to the bent waist.

Be sure to look up and plan for your springs properly too much spring loading can cause issues. Too little and your slats will want to gap. It is important to know the closed dimension, max extended position and the load in foot # of your springs.

6” long x 1” dia. expansion springs, depending on the wire gauge the spring is made from, is over kill. 6” inside hook to inside hook x .7/16 dia coil x .07 dia wire is a more appropriate spring

1” coil is way to big. You may want to go to leespring.com and see how extention springs are sized. You will want somthing that gives the amount of total extention you need andI suggest between 3-6 LB/in load. I also don't suggest that you try to have just ong main hook point but rather indipendent upper bout and lower bout hook points. This allows you to use shorter springs at less than their max extention to prolong life of the spring and makes accomadating multi size forms easier,

The blanket's a definate no bulbs here will add 3" in height to the ram and make the gap 6 1/2" will see if I can find a press screw easily here in the uk and will Contact John at Blue Creek for blanket and slats.

Next Question Spring or Stainless Steel Slats? I'm tending to stainless at the moment as you don't have the spring back which I think would be derimental when making bindings, unless you make a hook to hold the bottom slat in place and use spring steel. I'm 100% open to opinions

Cheers
Guys

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Formerly JJH

I learn more from my mistakes than my successes

Stainless will hold a bent shape. Can be mostly re-flattened but will hold some memory.

Spring steel will not hold the bend but will need to be cleaned and blued or painted with hi temp paint regularly to prevent rusting.

I prefer spring steel because I use many vastly different molds with different waist and cutaway configurations so I don't want memory in my slats. Also as you bend back and re-flattened stainless over and over the harder it is to keep your sandwich tight and flat which is important when bending laminated purfling and binding with laminated purfling to help prevent the laminations from separating and bulging out if they do.

One more thing i did not see mentioned but could have been and I missed it. If you plan on using more than one shape bending for it is a good idea to make your forms 1" longer the the centerline of the shape. In other words add a 1" of tangent straight at the end. A couple reasons: first this allows you pull your caul all the way though the required bend area. And second if you accidently were to drop or knock the form off a shelf or table while not in use you will not damage the bending portion of the form.

My forms are [the shape of the (body less 1 blanket, less 1 slats, less typical side thickness)] with 1" in extra length at the bottom of the form.

For best bending you want your form to bend the wood in the exact finish position it will be assembled. So if you use the sandwich method with the blanket on the bottom the your form shape need to be offset to the inside by the thickness of a slat, a blanket and the thickness of the wood if you use the sandwich method with blanket on top the off set the shape to the inside by 1 slat and the thickness of the wood.

Do you have to exaggerate the bends on the forms to eliminate springback? and not 100% sure where I'm adding the extra inch on the form?

Thanks

_________________
Formerly JJH

I learn more from my mistakes than my successes

I do not over bend some do. But I cook off the side for 15 at 200-220 after the bend to get rid of any added moisture if I spritzed the wood and i leave clamped up in the bender over night, always

the extra is at the bottom of the form

I would always go for spring steel due to the lack of memory. As I said in my above post it makes life much easier if you can trap the bottom steel slat to make things easy when taking the wood off the bender. I just use bent wire 'staples' that slide into holes in the mould and keep the bottom slat tight to the mould while removing the wood, like this:



Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Right guys spring steel seems most popular as you don't need to reflatten it any stainless users wanna share opinions and any UK sources of spring too would be good may look a trampolins next

_________________
Formerly JJH

I learn more from my mistakes than my successes

A thoughts just occured to me if springs are hard to get is there anything wrong with bungee cords instead?

_________________
Formerly JJH

I learn more from my mistakes than my successes

Extention springs are easy to find anywhere. A good hardware store will have a wide sellection

Not in the UK they won't!! JJH - Do some google searching - I can't remember the name right now but somewhere in the Midlands is a specialist spring maker that does mail order (or at least there was 4 years ago).

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Hi there JJH.
Thats the same plan as from Jim william's book.

This is my system:



I went for aluminium bars in the side form because round ones messed up...or i messed them up.
Trick is to keep the edge of the bar at 90 degrees to the edge of the wood form.
I also use lots of bars because i find it gives a more uniform bend.
I used threaded rod to fit the waist clamp because the Jim williams plan juggested that i needed to weld, which i can't do and i don't have a welding kit so i needed an alternative.
I use hand pressure to feel whether a side has give to it when tightening the waist clamp using the threaded rod system.
I glued alfoil to the inside of the form because the previous form and sides scorched with heat.
I also used stainless steel slats.
Stainless does have a memory but i also use the same slats as a side laminating caul so i like that it has a bit of a memory.
A local luthier complained to me that his light coloured sides used to stain so i went for stainless as a precaution.
I don't get any staining but theres also a few other things that i do differently so i can't say that stainless is the answer but its working for me
I use baking paper between my sides and the stainless slats.
It takes the brunt of any excess heat i think, and it also tends to sweat and keep the moisture in so i don't need to spray water on the sides before bending.
I've only ever bent cypress so for other timbers you might need to experiment.
I used cement floats as end spring clamps.
Sash clamps to hold it all in place.
Ceramic light bulbs, and i lined the light box section with aluminium foil also.
Seems to have solved the scorching problem.
I got an electrician to wire it with circuit breakers etc because it works off 450 watts and i wanted a safety in the event that something shorted out.

I found the springs while i was walking around a small local harware store in a daze trying to spot things that i could use for guitar making.
I think that they are a pretty standard thing that they carry.
Thats how we spotted the cement floats as a clamping soluion They have handles and were perfect for our needs.....Bonus

As an end note, this is my new improved version.
Spend your time and look around for all the bits, do your research, don't take any shortcuts and you'll save yourself in the long run.
This thing gets REALLY hot and i wonder if octopus straps or bungee straps would melt.

Cheers,
Claire

I'm hoping that with the blanket rather than bulbs the jig will stay relatively cool as it's focused. Also found a supplier of springs now trouble is a fixed fee postage works out around £3 if I buy a set of spares.

_________________
Formerly JJH

I learn more from my mistakes than my successes