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I guess the mold should be the first thing. Thinking to myself, can't do that without guitar yo trace or a plan. Ok so next step, order a plan and buy some MDF. I hate MDF.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I hate MDF. I use birch or maple plywood. I make both the outside mold and bending forms (for using a heat blanket) using the same pieces of plywood. If you don't need a bending form you can economize by segmenting the layers of the outside mold. I usually use 3 layers of 3/4 inch ply for the outside mold (gives me 6 layers - 4 1/2 inches for the bending form)

Look for low budget chinese birch plywood or ? a type of Luan from the big box stores

Problem with the Chinese birch is it has voids and soft spots. Can be a major irritation when making bending forms and trying to screw on the metal covering. If you can afford it, buy the good stuff. Don't use MDF unless you absolutely have to.

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“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

Maybe you guys could show me your molds so I can determine what's best for me. I like the segmented idea. How many layers are best for a dread?

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Hutch

Get the heck off the couch and go build a guitar!!!!

I just use whatever the cheapest plywood underpayment is at the time. It doesn’t have to be high quality for molds. You are stacking enough layers together that the odd void doesn’t make a difference. I made one mold from MDF and I won’t do it again.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

You want to have enough to just be able to glue and clamp the kerfing on the other side, top or bottom. I've used 5 laminations of 7/16" baltic birch and trued them up on a oscillating spindle sander. Baltic birch ply is about as good as you can get...

I just snapped this pic of two of my molds. I like to make the halves with alternating long and short sides so they interlock and can be pinned together through a hole. Both of these molds will do more than one size by spreading them out and pinning in a different hole.

You can see that one is 5 layers and one is 6. That was determined by the thickness of the plywood that was on sale at the borg when I decided to make each mold.



Edited to turn the picture upright.


Sent from my iPhone using Tapatalk

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Most of my molds and benders are made from MDF. That being said, as I make new molds, they get made out of Baltic birch marine plywood.

My molds are made from three layers of 3/4" Baltic birch plywood. I cut out the body outline on the first piece as accurately as possible on the band saw and then use that piece as a template to rout the other five pieces. The three pieces of each half are glued together with Titebond. The spreader blocks are made from the offcuts. Keep in mind that if you have the spreaders in place when putting the top and back on the sides, you will need to able to extract the spreader parts through the sound hole once the box is closed up. Not shown in the photo is a length-wise spreader that can come in handy to prevent chatter when driving the bus.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

As a rank amateur on my 8th instrument, I make my molds from 3/4" plywood with 2X4"s as interior spacers and they are quite easy to build.. I use what ever plywood is cheap and as void-free as I can find. This one is A/C plywood from Blowes - scroll to the right, text below, click to enlarge:

https://www.flickr.com/photos/ruby1638/8942017807/in/album-72157641029319394/

They end up 3" thick which, as Haans says, leaves you enough sticking up to clamp lining on. If it is too tall for clamping the lining, push the entire body up a bit from below. I didn't show this, but I screw it together at the "ears" sticking out at the heel and the neck to hold it together using 3" drywall screws.

You could cut one of these down to the "donut" shape that some use. I bend on a pipe, but careful cutouts still could be used on a bending machine

I Just used one for the third time and it is holding up fine, but if you are going into business, something a little more elaborate would be in order.

As always, your mileage may vary

Ed

mine are either MDF or 3/4 plywood. I bolt four pieces together and cut them out as one.



The "outies" get made into the mold, I'll put spacers in between them depending on the depth of the body, they run across the top and butt of the mold



Since I bend my sides on a Fox style bender the "innies" become the bending mold.



If you are going to bend differently you can use the innies to make a waist spreader - glue a couple of pieces together and chisel out a little divot for a turn buckle



I've tried cutting the outside of the body mold closer to the shape of the guitar - it makes it a little easier to reach clamps but I'm not sure it gains that much. Also, I like the sides to stand proud of the mold by a half inch or more - that lets me clamp as required

I just ordered the herringbone plan from stewmac. Now I need to buy some plywood and I don't have a truck. Can I get it all out of a half sheet or 1/4 sheets?

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Hutch

Get the heck off the couch and go build a guitar!!!!

My dreadnought mold is 24" long and came out of two half sheets of ply. I got four of the six layers out of one half sheet. I don't have a truck either so the half sheets were the way to go since they fit in my car.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Mine take 1/4 sheet of plywood 2 X 4 feet, and some scrap 2 X lumber. Each side of the mold is 2 X 2 feet cut in half, so 4 pieces 1 X 2 feet.

For the record, I drove over 50 miles with a sheet of custom made plywood tied on the rack on top of my Prius and still got 45 MPG.

Ed

Not the best picture, but may give an idea of what I use.
4 layers 3/4" construction ply with removeable "extras" top and bottom to enable firm clamping of the neck and tail blocks for gluing.
Located with dowels and secured with screws.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks everyone. I still haven't decided but one thing I'm pretty sure of, it will be the least expensive to make. Probably regular old plywood or the dreaded MDF just because it looks so nice. I know baltic birch would be ideal and maybe my next one will use it but for my first couple I'm going cheap. There's a lot of stuff to buy when your building your first guitar and the cost needs to be spread out, at least for me, I'm a far cry from rich.

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Hutch

Get the heck off the couch and go build a guitar!!!!

The case for plywood versus LDF or MDF was made in a previous post, but to summarize:

- LDF is less dense than hardwood plywood, but only 1/4 to 1/3 as stiff, so more of it must be used to provide adequate stiffness in the mold to resist bending forces from the waist spreaders - this is one of the reasons why commercial LDF and MDF molds are so awkwardly shaped - it gets more material where needed, at the cost of additional weight and inability to easily clamp sides to mold.

- MDF is about half as stiff as hardwood ply, so while not as much material must be added to get an adequately stiff mold (wall thickness of 3.75"-4" for LDF and 3.25" for MDF versus 2.5" for ply), it is denser than ply...for either LDF or MDF, the weight of an equally stiff outside mold will be significantly heavier than a plywood mold (a duplicate mold in MDF would weigh about 1/3 again as much as a ply mold, but adding the additional width to the sides for equal stiffness can result in a mold that is close to twice the weight of a ply mold).

With careful layout, a single 4' x 8' sheet of 3/4" hardwood ply will make two molds, spreader ends for several more guitars, and bending forms for a guitar or two. Even Baltic or Finnish birch ply will run under $50 per mold with hardware (excluding the reduction from getting bending forms out of the sheet) and Home Depot hardwood ply closer to $25 per mold, so it makes little sense to me to save perhaps $10 to $25 per mold, but incur twice the weight every time I move that mold.

Making up a dummy ply on posterboard or other stiff cardboard and using that to optimize layout on the sheet ply material is worth considering. Also note that a 4' x 8' sheet of ply can be cut into two easier to carry/transport 2' x 8' sheets that will usually fit into compact sedans or hatchbacks with some provision to keep the trunk or hatch in place.

My own preferences:

1. As light as possible, while still being stiff enough to resist waist spreader pressure (2.5" minimum side width, and 2.75" for dreadnaughts in ply)
2. A mechanical closure at top and bottom that is a) quick to use, b) adjusts and wears well (no wood screws...quick adjustment for alignment), c) does not interfere with clamping neck or tail blocks, d) allows the mold to be clamped vertically in a repair vise for drilling neck bolt counterbores and holes, e) lies flat on a bench with reference blocks
3. Hangs from a repurposed ladder hanger with a 1/2" hanging hole on the centerline, avoiding the sort of damage possible when a rim-in-mold is hung from a point inside the body (I once asked the boss where the very cool 'section through' piece of neck block and sides came from...damage from ladder hook slipping off neck block...why every mold in the shop has a hanging hole)
4. Easily and accurately built up from a single master mold using band saw and router (one precision shaping task, versus several iterations with thicker material).
5. Outside contour of mold follows inside contour to allow easy, square clamping with smaller, lighter-weight clamps...some filleting in the waist is preferable to add stiffness without much weight increase
6. Cutaway profiles are accommodated without inserts or purpose-cut mold half (we use a single shallow slot to register a Venetian side and two slots for a Florentine cutaway).

Our preferred solution is a three ply hardwood ply contoured mold with 2" wide, 2" to 2-1/2" long 'ears' which take standard 4.5" carriage bolts and internally threaded plastic and brass star knobs as closures. Using 2-1/2" to 2-3/4" wall thickness with a fillet in waist allows adequate spreader pressure for radiusing, etc., without much in the way of distortion.





How we make molds:

- The plex or Lexan half template for the guitar is clamped 5" in from the corner of a sheet of ply and inner profile is transferred with a 0.7mm pencil
- The outer mold profile is made using an offset roller - a scrap ply disk of 2.5" or 2.75" radius - with pencil in the center hole, the disk is rolled along the outer body contour to mark the outer shape of the mold
- Use a combination square set to 2" length on the square face to mark the extension ears. For the end of the mold away from the corner of the ply, extend the master ply length out 5" beyond the end of the inner profile...this should create two 2-1/4" to 2-1/2" ears which tale the carriage bolt fasteners and also provide a square edge for clamping.
- Fillet the inside corners of the ears with a quarter or similar, and use a dinner plate to fillet the waist
- Cut out the master ply with fine tooth splinter-free blade on square-set saber saw, band saw, etc. Chipping of the surface ply can be minimized by cutting scoring the ply with a sharp knife on the cut lines.
- Carefully fair the master mold with drill press sander, spindle sander, cabinet file, or similar methods
- Lay out and rough cut five other plies using the master...these should be trimmed to within 1/8" of the finished shape
- Tack one of the rough trimmed mold pieces to the master and use a 1" cutting length bottom or top bearing flush cutting router bit in a 1-1/2" hp router (or the DeWalt trim router with a shop-made larger base) to trim off the excess material to shape
- Separate the master and copy, then glue a rough cut ply to each using a trim nailer or finishing nails and clamps to hold things together. Flush trim the rough plies. Note that the master and the first copy need to be the center ply in each mold.
- Glue and trim the remaining plies.
- Sand and lightly chamfer the outside edge of each mold half; sand the interior with P150 with a square block
- Apply three coats of shellac then wax with bowling alley or floor wax when dry (prevents glue from sticking to the mold)
- Clamp the mold halves together and mark and drill the 1/4" holes for the carriage bolts 1" in from the ends
- Fit the 4-1/2" 1/4-20 carriage bolts, 1/4" fender washer, and 1/4-20 star knob and bolts the mold halves together
- Drill a 1/2" to 5/8" hole on the join between the mold 3-1/4" in from the upper end - this is the hanging hole and will take a standard or heavy duty ladder hanger with some work to straighten the hook at the end of the hanger
- For our building system, the box geometry is referenced to the plane of the top, so we mark that reference surface with 'Top'





The shots show using the mold to hold the rim for work in the repair vise, the hanging method using modified ladder hangers (which gets things off the floor and safely out of the way), some simple layout tools used on a scrap of 1/4" MDF (we would mark this with a fine mechanical pencil, versus the very useful General brand 'Layout' pencils used for visibility in photographs), and a completed master ply layout with half of an L-00 mold currently in use in the shop.

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For the times they are a changin'

- Bob Dylan

Sometimes its just easier to buy a pre made mold. Just depends on your personality type.

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Another way to look at this is - that for those using the outside mold/bending form approach - making a template, a mold, and bending form is a nice warm-up for the real work. It is how all of the students here spend the first couple sessions, and they take home at least some of the infrastructure to continue building once completed.

Another issue is that we have not seen or used a commercial mold that meets our needs, but that may not be an issue for someone that is working through a first project, and does not have work flow issues to contend with re: an out-of-system fixture.

Finally, if funds are scarce, Mr. Minch's approach of upper and lower plies with spacers between, or even a one-time-use corrugated cardboard mold might be enough to get through the first project.

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For the times they are a changin'

- Bob Dylan

The four half sections shown in my last post are about 22 by 8 depending on the size of your guitar. You can easily get them out of a half sheet or smaller. I used MDF because its cheap and easy and I will never make more that a couple of guitars from one mold. I've built a total of 23 to date and almost every one is a different size and shape. If I was going into production my molds would be entirely different.

When you get your plans take them to Kinko's and get 2 or 3 copies made. Put the originals away, use the copies. You will cut some of them up to make molds and patterns, get glue and spill coffee on them. Get Cumpiano (many of us built our first several guitars with only that book). Download the free instruction PDF form StewMac for their kit (I know, you're not building a kit but it will help and its free).

Some other random thoughts:

- take the time to learn about acoustic guitar geometry before you actually start building. Keep those relationships in mind as you build. Check often.
- don't be obsessed with bracing and tap tuning and all the mumbo jumbo that you will read here and other forums. Follow a good set up plans and your guitar will work fine. Maybe post a picture of your braced soundboard - folks will tell you if you need to take more off.
- concentrate on worksmanship and good joinery. Use clamps to hold things but don't force it - if it seems like you are applying too much force you probably are.
- consider a bolted neck joint for your first build. Dovetails are elegant and can be a real joy when it all comes together, but can also be a nightmare the first time you try it.
- if you have a question stop and ask it. Listen to the answer(s) you'll get from the forumites.
- there have been several first timer build threads recently. Read them, particularly the parts where they have problems. Think about how you will approach that problem.
- there might be a few tasks that you'll want to out source - I have a friend thickness sand all my plates and I buy preslotted fretboards (I make about every scale length from mandolin to baritone and I just haven't set up to slot them all). I buy my kerfing and binding and back support material premade, and for my inlay I buy precut pearl.
- I think the most difficult parts of home building include setting the neck angle (and understanding it), doing the binding (the angle of the top and back makes it tricky), finishing (be thinking about this from the start). Shaping a neck and bending sides can be tricky but fun. Installing and leveling frets takes time and patience (and a few special tools).
- have fun

I use an open work board also known as a solera but I like to use good quality plywood for it. MDF dust... yuk! Plus if you get MDF wet it deteriorates. Good quality plywood is worth it.

For those of you who make the molds and cut it on a band saw do you use a spindle sander or something to finish up? I cannot imagine cutting the shape out so perfectly on the bandsaw and I don't think I'm bad at using a bandsaw.

Router and template.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I cut the body shape out of the first half piece on the bandsaw and then use it as a template to rout the other pieces. No sanding needed. Cutting that first one requires some pretty close focus and, for me, keeping the wood piece in constant motion with no stops goes a long way to preventing bandsaw ridges on the cut face.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I bought 1 2x4' piece of birch plywood. I'm going to use spacers in between.

So the build has begun I think.

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Hutch

Get the heck off the couch and go build a guitar!!!!