Archive - January 30, 2015

Building The GLS Heated Side Bender

Building The GLS Heated Side Bender

There is no doubt about it. One of the most sought-after specialty guitar tools in a guitar shop is some sort of a bending system and usually one that has a heating element of one kind or another is part of the lure of these great devices. Here at Georgia Luther Supply, our Heated Side Bending Machine is our best seller, and for good reason. Nearly everyone wants this time-saving device.

If you don’t want to go through the hassle or expense of making one of these, you can purchase one of them pre-built from our store, We also offer all of the hardware that is needed to completely assemble a bender, right down to the assembly screws, springs and attachment hardware.

Recommended Materials and Tools:
  • GLS Heated Side Bender Plans (Either Guitar or Ukulele Bender)
  • 1/2 sheet of 3/4” (19mm) birch cabinet grade plywood
  • Small Piece of 3/8″ Plywood
  • Small Piece of 1/4″ Plywood
  • GLS Hardware Package
  • Router
  • 3/8” Diameter Straight Cut Router Bit
  • 3/4” Forstner Bit
  • Table Saw
  • Drill Press
  • Band Saw
  • Portable Drill or Drill Press
  • Screw/Countersink Bit
  • Titebond Glue
  • Quick Grip Clamps

Note: You can build the jig without some of the stationary tools listed above, but the task will take much more time. For instance you can use a circular saw to cut plywood or even a hand saw. A brace and bit can be used in lieu of a drill press and assorted hand saws can be used rather than a band saw.

Part Layouts and Initial Cutting:

Start by taking the plans and laying everything out on the plywood from the template sheet. Cut the jig sides to width and length. Also cut the base, the feet, jig enclosure ends, top cap, plus all the smaller parts for the retainers.

Layout the channels for the guide bar in the sides of the bender and carefully cut out with a router and 3/8” bit. Use a fence to keep your cuts straight. A plunge router works best for this. Depending on your equipment and experience you may want to make these full depth cuts in (2) passes rather than a single pass. Also if you cut in one pass you will find that the slots will clog up with wood chips and your cuts will not be accurate.

Always clamp your work firmly to the workbench and wear proper safety glasses before using power tools. Ear protection and a dust mask are also essential for your safety!

Cutting Pockets for U-Bolts:

Next cutout the backside of the jig sides to receive the “U-bolt” attachment hardware with the router set to the proper depth – refer to the plans for these dimensions, and coordinate with your hardware.

GLS Tip: If you plan to make more than one bender for higher production guitar or ukulele building, make a template from 1/4” hardboard and carefully cut the guide slot and u-bolt recesses in the template, making allowances for a router bushing thickness. Clamp the 1/4” Hardboard to the plywood, install the bushing and router bit in the router and accurately and quickly cut out the proper opening in the plywood. You can also cut the outline of the jig sides using this template.

Cut the free-form saw cut of the jig sides on the band saw and finish sand them. Assemble the “U-Bolt” retainers on the sides of the jig and check the fit to be sure that the hardware does not extend past the inside face of the jig side. Also it is easiest to attach one end of each spring before you attach the “U-bolt” because the spring ends are closed. Tighten the nuts very securely while you have access to them.

Preparation of the Top Plate of the Bender:

In the Bender Top Plate, drill all of the screw attachment holes and countersink them as necessary. I prefer to dry fit everything before I glue the parts in place –

In the Bender Top Plate, cut the hole for the press screw to fit so you can insert the top female portion of the press screw through the plywood and attach to the underside of the plywood plate. If you use our press screws, you will need to file a registration groove at the top and bottom of this drilled opening for the hardware to fit properly. This groove shows on the template drawings.

Jig Side Assembly:

Square-Up The Bender Sides, Mark The Floor and Clamp

Place the floor of the jig on a firm work surface. Place both sides of the jig next to the floor and made sure the sides are even by checking with a try square. Measure from each end of the sides to the floor to center the sides of the floor.

Hold the side in place and plumb by placing a quick grip clamp on one end.  Drill pilot holes into the jig base to prevent plywood splitting.

Secure the side to the base with 1-5/8” screws.

Slip a 6” extension spring over one of the U-Bolts and place a nut followed by a washer on each leg of the U-Bolt. Insert the U-Bolt through your prepared holes in the jig sides. Place the backer plate on the inside of the jig side and screw it down tight with (2) nuts on the inside of the jig side.

Note that you can make slight adjustments to the extension of the U-Bolt legs by adjusting the nuts on either side of the jig side. Tighten these nuts so they will not come loose during use.

Springs & U-Bolts

Lower Jig U-Bolts For Ukulele Bender. Note (2) Springs On Left

Assemble the remainder of the U-Bolt/Extension Spring Assemblies and attach in a similar manner as you did above.

The photo shows a ukulele bender which uses a total of (3) U-bolts on each side, while the guitar bender only has (2).

On the Ukulele Bender place a 3-1/2” AND a 6” extension spring on the left side of the jig and on the back U-Bolt place a 3-1/2” extension spring.

One the Guitar Bender, attach (2) 6” extension springs on the second lower U-Bolt.


Interior Of Bender Side Showing U-Bolt Plates

The photo left shows the arrangement of the U-bolt backing plates and nuts placed in the recess for them in the side at the interior of the jig sides. This photo is for the ukulele bender – the guitar bender would only have one recess at this location.

Install the front closure plate between the two jig sides, carefully align them, and hold in place with a Quick Grip clamp.

Drill pilot holes for the screws and screw the closure into place.

Note that if you do not drill adequate pilot holes the closure plate will split as the screws are very close to the edge of the plywood. If you do split the plywood, work some wood glue into the plywood edge with some glue spread on your finger and back out the screw and clamp.

If you plan to make the back enclosure plate the control plate for a digital controller, you should carefully scribe all of the plug and electronics layouts on the plate and rout the openings. Next install the electronics in the plate.

For our guitar and ukulele benders I like to keep the electronic relay on a separate piece of wood, so I place that against the top of the control plate and glue and screw it into place, as shown here.

Now you can connect all the wiring to the electronics, insert the thermocouple wiring through the fitting and test the unit to make sure it is working properly. If everything checks out install the back control plate in the jig body, in a similar manner as was used from the front closure plate. For the ukulele bender it may be necessary to slightly adjust the U-bolt connectors as they may protrude into the interior of the jig sides. This is simply done by adjusting the inside and outside nuts of the U-bolts.

For the next step, remove the top portion of the press screw from the screw and place it into the top plate of the jig. Place the plate in a vice and drill pilot holes for the attachment screws. Again, note that most press screws have registration ribs and your hole in the top plate will have to allow for these ribs.


Attach Press Screw Plate To Bender Top Underside

Secure the press screw to the top plywood plate with (2) screws. Note that the photo shows the underside of the top plate.

The screws should be a minimum of #10 screws and almost the full depth of the plywood as this connection receives considerable stress during bending operations.

To prepare the installation of the jig top plate on the sides, it is best to install a spreader between the sides from a scrap piece of plywood as shown in the photo here.

Carefully measure the dimension and compare to the top plate.

Test fit the top plate on the top of the sides and make any adjustments to the plywood spreader as needed. Also this is the best time to drill the pilot holes into the jig sides from the top plate. This can be a bit tricky to drill with a hand drill, but you will find if you place the jig on the floor of your shop, this will give you a much better angle to align the drill during drilling.

It is best to glue the top plate to the jig sides as this is a joint that receives the most stress for the bender. Apply a light film of wood glue to the tops of the jig sides and place the top plate in place and screw the (2) screws at the opposite corners of the plate first (at a diagonal).


Align Top & Clamp. Glue In Place And Screw To Bender Sides

Make any adjustments by using the plywood spreader and a Quick Grip Clamp as shown in the photo. Once you are satisfied the plate is setting squarely and aligned to the sides, install the remaining (2) screws. Next tighten all screws tightly in place and do a glue cleanup from the joint.

Georgia Luthier Supply Tip: To make your bender more rugged use longer screws for this joint. Use a minimum of 2-1/2” long screws and carefully match the pilot holes to the screw. I hold the screw up to a strong light source and hole a drill bit in front of the screw threads. The proper sized drill bit will be the one that shows just the screw thread behind the drill bit.

Screw the (4) rubber feet into place on bottom side of the (2) plywood jig feet.

This is optional for some luthiers as many of us prefer to clamp our benders to the work bench or work area to prevent any movement during bending operations.

Hold each plywood jig foot on each end of the jig floor with a Quick Grip Clamp by carefully measuring and centering the foot on the floor plate. Drill the pilot holes and secure with (4) 1-5/8” screws.

End Retainers


Pieces of End Retainer Laid Out

Okay the basic jig body is now complete. Next we will need to put together the fussy parts, which are the waist and end retainers.

Cut the blocks of solid wood for the 2 end retainers. These can be either hardwood or softwood. I prefer to use hardwood as I usually have a large supply of those scrap pieces lying around the shop and it will last much longer.

Cut the (4) end pieces of the end retainers from 3/4” (19mm) plywood. Drill the attachment screw holes and countersink in the end blocks. Also drill the holes for the spring attachment hardware and be sure to drill out the backside of the end blocks with a 3/4” Forstner bit to recess the bolt end and nut.

Assemble the End Retainers


Glue Plywood End Onto Solid Wood Block

Place a thin film of glue on each end of each of the retainer blocks (the solid wood, not the plywood). Lay the blocks flat on the workbench and slide the plywood ends into the glue to seat them.

Carefully clamp the plywood ends to the solid block with a quick grip clamp. Do the same with the second end etainer. After about 10 or 15 minutes run the 1-5/8” screws into the end block for the mechanical attachment. Now is a good time to finish sand the end retainers and knocking off all the sharp edges.

Assemble the carriage bolt/washer/nut assemblies for each side of each retainer.  There are (4) of these and they are key to the proper bending process.



Install Hardware & Tighten Securely

Follow the plans carefully and assemble them exactly as per the plans. The photo to the left also shows the correct configuration. Tighten the inside nut with a ratchet or wrench to secure each connection.

The end retainers are now complete.

The Waist Retainer

This is a much more complicated task as the retainer has an adjustable component when can form to the different curves of the assorted guitar and ukulele shapes.

Cut the solid wood block to shape and dado a channel down the center of the block to accept the 3/8” plywood guide which will fit into the 3/8” channel that were cut into the sides of the jig. Make this joint tight enough so you can use a mallet to force it into place. This block can also be built from (2) pieces of plywood stacked on top of each other.

The center spine that holds the movable plates is the next task to be completed. Start by cutting a 3/8” piece of plywood to size as per the drawings. Next the slots have to be cut into this plywood for the adjustable plywood plate attachment of either side of the spine. The easiest way to complete this is with the use of a drill press and a scroll saw or jig saw.

Mark and drill four holes for the ends of the slots. After these holes are drilled, cut the remainder of the slots with a scroll saw. or jig saw. Dry fit the plywood and place glue into the channel. Glue in place and let dry.

Alternatively you can drill only (2) holes and band-saw the waste from the slots and glue the open end of the slotted plywood into the waist block.

Place the Waist Retainer into the jig body as indicated in the photo on the left.

You can easily swing the retainer plywood through the guide bar slot from this position and make it ready for attachment of the screw press foot.

Note that any time you need to remove the waist retainer you can use this method for removal without dis-assembly of the entire bender.

Run the press screw down to the retainer block and carefully mark the location of the press screw foot and mounting holes. Remove the retainer block and screw the foot to the block using (2) 1” #10 screws.

Remove the screw press foot from the retainer block so you can again fit the retainer block into the jig.

Waist Retainer – The Adjustable Plates.

The adjustable plates of the waist retainer allow the luthier to bend viturally any instrument shape by simply adjusting the movable plates. The plates we make in our shop are on the CNC and are very easy to build. If you don’t have that luxury available, you can go about this another way, but we will cover that in another posting.

Place the plates into position on the waist retainer spine, and bolt them into place using the 5/16” carriage blots and a washer and nut on each bolt.

A Few Final Thoughts.

  • I prefer not to use glue on the jig because of the heat that is generated during jig use. (one exception is the attachment of the top plate to the jig sides.) The mechanical attachments will give and take a bit more than glue will and the glue joints will eventually fail because of the heat and expansion-contraction.
  • Also, if you choose to adapt your jig for built-in electronics for heating control (like our Georgia Luther Supply Controller) it is a simple matter of backing out a few screws and make the changes. Nothing is destroyed and the change can be made effortlessly.
  • Also many builders who do no wish to spend the time to make the most time-consuming portion of the bender, being the waist and end retainers, we offer complete assembles retainer packages for both our guitar and ukulele benders. Build the remainder of your jig to our plan specs and you can slide seamlessly incorporate these retainers in your bender.
  • Here are a few photos of a finished ukulele bender that was used for this instruction sheet. The guitar bender is very similar with a few changes other than size of course.


Ukulele Bender Side View

Ukulele Bender Side View

Ukulele Bender Cntroller

Ukulele Bender Cntrolle


The GLS Side Bending System provides you with one of the most basic tools to obtain great results every time when constructing your acoustic instrument.

Copyright © 2015 Georgia Luthier Supply