Luthier Tips du Jour - The LMI Side Bender

Uploaded by OBrienGuitars on 10.05.2012

The process of bending sides has evolved significantly over the years.
Back in the old days I used to bend on an old pipe filled with charcoal.
When the commercial benders with heating elements in them came out I started using them.
As I built more guitars I switched to the silicone heating blanket method
as the heat source and bent on a homemade form.
This evolved into a little more sophisticated version
that uses springs to apply pressure as the sides are bent.
All of these methods and contraptions have their pros and cons.
However, if you are like me and are always looking for a better mousetrap
then let me introduce you to the newest design in side bender technology.
This cutting edge side bender made by LMI has some great new design features
including an open front cantilever design
allowing you to access the bender directly from the front,
revolutionary roller clamps
that integrate precise bending control and constant spring tension,
as well as the on board electronic temperature read out
that allows you do dial in the exact bending temp
and maintain it with the use of a thermal couple.
Yes folks, this is the Rolls Royce of side benders!
So, let me show you how it works.
When you receive the bender you will need to assemble it.
Fortunately there are some video instructions that come with it that make assembly a breeze.
The aluminum cantilever arm attaches easily to the bender base
and is adjustable to accommodate smaller projects.
The base also houses the LMI temperature controller.
The bending form is also easily assembled and rests on the base.
You can easily swap out the form for the model guitar you want to bend sides for.
LMI has forms for the most popular guitar models including my own classical model.
The machine head design incorporates waist shoes for precise bending.
The shoes quickly install on the press mechanism
and are quickly swapped out when switching to another form.
The head press screw has been upgraded for smoother operation
and a long service life.
The non slip silicone rubber roller assembly design
provides tactile feedback while bending,
you can actually feel the wood begin to relax as you bend.
To prepare for bending I first place one of the pieces of spring steel
that came with the bender on my bench.
I then place the long silicone heating blanket on top of that.
One of the thermal couples gets placed on top of the blanket
just rear of the guitar waist.
Next I lightly spritz the side with water.
I then wrap it in aluminum foil and place it on the heating blanket.
I clearly mark the waist on the aluminum foil.
Next I place the other thermal couple on top of the side just forward of the waist.
Now the small heating blanket gets placed on top of the side
and thermal couple at the waist.
And finally the second piece of spring steel gets placed over the entire sandwich.
Everything is held together with a couple of small clamps at the waist.
The entire sandwich is now placed into the bender.
The open face design allows you to do this easily.
I lightly tighten the hold down press to apply a little pressure
and adjust the shoes if needed.
I also use a small piece of spring steel placed under the entire sandwich at the waist.
This helps support the bend at the waist.
This is especially helpful when bending woods that are notoriously difficult to bend.
Since I am going to begin by bending the waist
I turn on the power to only the small heating blanket that was placed at the waist.
I have my temperature set to achieve and maintain 350 degrees.
As I arrive at this temperature
I turn the hold down press about a quarter turn every 15 seconds or so.
This gives the wood time to get thoroughly hot as it comes in contact with the blanket.
After the waist is completely bent I turn off the power to the temperature controller.
Now I install the roller clamps
which are used to actually bend the upper and lower bouts.
I then unplug the thermal couple that was used to measure the temperature
at the waist and the small heating blanket
and plug in the thermal couple that will be used
to measure the temperature to the long heating blanket.
I also plug in the long heating blanket which will heat the entire side.
As the temperature heats up I tension the roller assembly for each roller clamp.
This allows the roller assembly to stay where you leave it while bending.
When I arrive at my target temperature I start to roll the clamp along the side.
I can actually feel the wood relaxing under the heat
and pressure of the roller as it advances along the side.
You can pause at the largest radius of the bout
to allow the side to relax with the heat before continuing the bend.
Roll the clamp all the way down to the end of the form.
Do the upper bout in the same manner
taking your time around the most pronounced part of the bend.
Since the temperature controller is maintaining the temperature
there is no need to rush the bend.
Take you time and let the wood tell you when it is ready to bend.
When the side is completely bent I dial my temperature down to about 260 degrees or so
and maintain it there for about 15 minutes.
This helps to lock in the bend and reduce spring back.
I then turn it off and let it cool.
I can now remove the roller assemblies and release the tension at the waist.
I now have a perfectly bent side that matches my form exactly.
Technology is constantly changing and evolving
but I find it almost unimaginable to improve upon this latest side bender design by LMI.
Let’s see what the future holds.