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Molds: Internal versus External for newbies

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Total Posts: 242
My LMI kit arrived and still haven't decided which style mold to go with. It was recommend I go with the Stew Mac style internal mold for my first build but I've read people have had problems with these. Also I watched part of the video that came with my kit and started wondering... is it any harder to build an external mold than an internal? I plan on building a go bar deck since it will be easy to build and I know that could be used with an external mold to close the body. Any thoughts on which to go with and why? Thanks.

Apr 03, 08 | 1:29 pm

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Total Posts: 309
Just as one person's observation: I thought it was much harder to make the exterior mold.

Apr 03, 08 | 2:51 pm
Bill Cory

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Total Posts: 3584
Jeremy -- I go along with Hugh. It is more difficult to make and external mold, especially for a first-time builder without a shop with bandsaw, etc.

Id you don't feel the internal mold will do it for you, I'd recommend contacting one of the suppliers below (both advertisers on this site) and buying a mold. Another $100 ... a better guitar. or

Both are sellers on eBay: KennethMichaelGuitars is This EBay Store and Blues Creek Guitars is This EBay Store.

You can't go wrong with either of them.


Apr 03, 08 | 3:02 pm

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Total Posts: 242
I do actually have a bandsaw but I've never done anything that requires that kind of precision.

Apr 03, 08 | 5:08 pm
blues creek guitars Authorized Martin Repair Ctr

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Total Posts: 1011
On the mold , the mold does 2 things, one is symmetry and the other is holding the neck block in position to the top for the proper neck angle. If you don't use a mold of some sort expect a lot of issues at neck set time. If you check out this bolg you can see one of the benefits of the mold

Apr 03, 08 | 8:03 pm
John B

Total Topics: 15
Total Posts: 76
If you have a bandsaw or scroll saw with a router, then an external mold is not that bad.. This is the process I took to build my external OM mold.

I made the best copy of the plan that I could (didn't want to cut up the original).. I then taped 1/2 the plan to a posterboard and cut it out very carefully. This gave me a template I could trace onto a board..

I then used the template to trace 1/2 guitar to a 1/4" piece of fiberboard. I then cut this out very carefully with a scroll saw.. I imagine you could use a bandsaw successfully also. 1/4" was thin enough to easily to sand out irregularities in the shape but thick enough to use as a bearing template guide for a router with a flush trim bit. It is also a stable long lasting template that can be used over and over again.

From here, I traced the 1/2 guitar template to a 3/4" MDF approximately 12" x 24" (MDF shelving at Lowes or HD works well) I rough cut the mdf slightly oversize then used the 1/4 inch template clamped on to it routed flush to the template using a flush trim bit. This made an exact duplicate of the template..

I then used the formed 3/4 inch as the template for the rest of the required 3/4" peices. These all will be identical and will make the mold symetrical when put together... You need a minimum of 4 for a Kinkead type form.. Or more for a solid form similar to KMG's or Blues Creek's. Mine form was after Kinkead's model with many 4" long posts separting the outside forms. I think building a solid form similar to KMG's or BC's would be easier.

This is a lot of work for a form but if you have the tools and like to build things, then you can save a bit of money too... I think mine ended up costing $15-20 or so in material for the MDF, fiberboard, etc. If your time is worth money and not therapy then it likely isn't worth the $50 bucks you might save.. For me it is therapy as I get some satisfaction with doing it myself but I probably spent 4 hours building it and at least another 4 figuring out how I was going to do it.

From my experience though, both Ken C and John H (KMG and Blues Creek) give a tremendous amount of valuable advice and help when you purchase a mold, kit, or any of their helpful tools. I think most who have used them would agree that their advice and help for a first time builder is worth much more than the purchase price of a form or a few of their helpful tools.

I will take a few picts and post in the tools section over the weekend.
John Butler

Apr 03, 08 | 8:29 pm

Total Topics: 27
Total Posts: 668
If you have a band saw then don't even consider an internal mold. Make a copy of the plans (find an engineering office with a 36" copier), cut out 1/2 half the body profile. Trace that onto a piece of 1/2 or 3/4 MDF or particle board. Clamp 4 pieces together (I used flathead carriage bolt with the heads countersunk so I could slide it around my band saw.

Cut out 4 pieces toether and sand the internal shape (save the cutout to make the waist expander). I used some scrapes of 3/4 MDF and more flathead carriage bolts to hold it all together. Here is the proceedure

Over my years of building "stuff" I have made racing powerboats, racing bicycle frames and now musical instruments. In all cases I have learned that the tooling - jigs, molds, fixtures - are the key to the final product being anywhere close to alignment. Take the time to build a good mold.

Apr 04, 08 | 6:42 am
John S.

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Total Posts: 94
After searching OLF and other sites for a "how to" on making an external mold I came up with a procedure pretty close to that used by John B. I used acrylic for my template, which made tracing the outline from the plan easier, and used 3/4" birch plywood instead of MDF. Like John B., I made the best first wood template that I could. I cut close to the line with a jigsaw, then squared up the edges with a drum sander on a drill press. I checked the fit against the acrylic template, then made 5 identical copies by routing with a flush cut bit. I drilled alignment holes at each end to hold 3/8" dowels, and used simple draw hasps for closing the mold. My experience is obviously limited, but the ability to use spreaders to hold the sides and blocks flush against the mold is a big plus IMHO. It took me a couple of days to build it, but a lot of that time was spent waiting for glue to dry. As a bonus, I used the excess that I cut off (about 3-4" x 2') to make sanding bars for radiusing the sides. Here are a couple of pix:

Apr 04, 08 | 7:10 am

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Total Posts: 242
Thanks guys.
Freeman, Freeman did you cut right along the line or leave some wood then sand down to it? I may use your method since I don't have a router yet.

Apr 04, 08 | 8:57 am

Total Topics: 22
Total Posts: 158
On my last build I used a self invented hybrid set up. I used a craft board which is slightly more rigid than the Stewmac cardboard. The plan was to make the internal support as Stewmac do and then also cut out and external mold – to push the outer edges against the internal mold.

Don’t bother trying this, I’ve learnt the lesson for you. I ended up with rods and clamps working to keep the end blocks square. Appears that the internal form is sifficent to hold the shape but any pressure from the otherside can push everything out of wack.

If I paid myself an imaginary $20 an hour labor, the time I spent fiddling would have well paid for a band saw or the external mold. This time I am building my own.

Apr 04, 08 | 5:57 pm

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Total Posts: 242
Also Freeman (or anyone), would that gap you have between the two boards cause any adverse effects?

Apr 04, 08 | 7:24 pm

Total Topics: 27
Total Posts: 668

1) I cut close to the line, then sanded the last little bit (MDF sands very easily). It won't fit perfectly but it will be close enough.

2) The two cutouts are spaced apart to try to make the mold almost as thick as the guitar and provides a convenient way to tie everything together. I used a square to make sure they are square - the gap doesn't hurt a thing. It also makes it easy to take apart - just pull the carriage bolt out and bingo!

Apr 07, 08 | 8:14 am

Total Topics: 29
Total Posts: 242
Thanks Freeman, I think I'll use your design but probably go with 3/4" plywood since thats what's out in the garage.

Apr 07, 08 | 1:03 pm
Ken Hundley

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Total Posts: 2169
Freeman, beautiful guitar in the posts in the other forum, and I absolutely love the quote at the bottom of your posts. Priceless.

Apr 07, 08 | 7:35 pm

Total Topics: 27
Total Posts: 668
Thank you Ken. Are you refering to the link to the Annex (the pink thing)?

Apr 09, 08 | 6:10 am
Ken Hundley

Total Topics: 40
Total Posts: 2169
Nah, the one about namin the horse. I love the song it refers to, and that just cracked me up.

Apr 09, 08 | 10:25 pm

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