Official Luthiers Forum!

I was checking out the new stuff at LMI and came across this:



I guess whom ever designed this mold did not subscribe to the building methodology that leaves the spreaders in the mold until after the top and back plates are attached.....

Not sure about the spreaders, but I like the simplicity of the mold.

Yeah me too Sam and I also like the way it opens up but remains one piece.

At $95 a pop it would not be a biggie to make one's own spreaders either. And they have 4 sizes available with one being a parlor which I have not seen available from anyone prior.

Here's a link: http://www.lmii.com/CartTwo/thirdproducts.asp?searchtext=recent&Submit=Search&NameProdHeader=Guitar+Molds

these look much better than mine, in what way aren't you sure? (i'm looking for a way to improve mine and slighly extracting info without anyone noticing)

is it the plastic wheels?

_________________
www.theguitarrepairworkshop.com

Nope it sounds like he closes the box and then pulls the spreaders out through the sound hole and with this design that would be unfeasible

_________________
Zac

Anchorage Alaska

Finshed my 1st! See #1 here

Made my new mold for $4.00 worth of nice scrap plywood from the hardware store, and some bandsaw time. But Iunderstand the consept of the body length spreader.

I also have a hole in the center spreader to align the dish through a pipe, so I can put in the back dish and top dish radii exact, this one won't do that either, and its near impossible to do perfect without center alignment of some sort.

_________________
Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I

Frei could we see a picture of it?

_________________
A higher purpose for wood.
Rich Smith
Issaquah, WA

Hesh, this mould is for guitars with very big soundholes.

I think you'd have to use a big spreader like this because the mold is so thin. If you put in a spreader at the waist if would deform too much. Pushing out the the whole side would avoid that problem.

I take my spreader off after I get the top on and before I put on the back so this would work for me. But, man, I'd be p****d off if I forgot to remove it before attaching the back!

Ah, the Clarence White D-28 replica's!

I like keeping everything in the mold until both back and top are on, so I probably won't spring for one, but I do like the way it is hinged.

_________________
Jim Howell
Charlotte, NC

It's not so bad Mike buddy - all you would have to do is loosen the knobs and presto you will have one big-arse mirraca.......... A baritone mirraca....

I honestly like the idea. Although it wouldn't work for anyone that is looking to close up the box before taking out the spreaders, those spreaders look pretty nice and I like how they fit right up against the entire side instead of just certain points. It's definitely an interesting idea...

Just a thought, but couldn't you just cut those large spreaders up into smaller ones and rethread them if you wanted smaller spreaders anyway? It doesn't seem like it'd be much work and the spreaders themselves would already be perfectly fitted to the mold.

Yes, when I get new batteries. Few days.

_________________
Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I

You'd need a big arse man to play it, too...

You need a center point for accuracy. The sides of the dish curve constantly, and change angle. Centering the mold guarantees the sides sand to the same spot on the dish IE: one inch, one inch and 1/4 etc etc in constant. Think of the center point going 1 inches from the rim. Can you keep the mold centerlines, back and front, centered exactly at one inch from the rim when you rotate it? I suppose you could get close, but I wobble.

Likewise I have seen people seem to misunderstand the dish itself for X braces. The x brace goes through the midline of the dish. One side of the dish is slanted \ the other side goes like this / It is not flat bottom across the brace -- like this.

_________________
Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I

Frei buddy think of a radius dish as being not unlike if we could use the inside of a sphere to sand our rims. No matter what part of the inside of the sphere you sanded against the radius acting on the rim would be the same. Hold it on the inside of the top, the side, where ever you sand your rim against the inside of the sphere the radius is the same.

This is why centering the rim in the dish is not necessary.

But don't you find that if you keep it centered then the you are more likely to sand it evenly as you aren't putting more pressure to one side or the other? I have to say that when I sanded the rim on my motorized dish it was pretty easy but when I added the linings and a beveled belly and a armrest and then sanded it became tricky to sand since the armrest didn't sand as fast as the kerf linings. Granted it was my first time but I can see how centering it would make it easier.
Shouldn't that mold be thicker then what looks like about 2"?

Here is my little jig for bowl sanding.

I do this first with out the linings, then again to flush them up after they have been installed. Like Todd, a 10 or 20 minute job per side.

_________________
Support the OLF! Bookmark our STEWMAC link Today!
Lance@LuthiersForum.com

There have been several threads in the past on the issue of whether you have to keep the rims centered on the dish. Often the discussion degrades to a bunch of "What?" or "Sure you do" and "No you don't". I think the confusion stems from different definitions of "up". Look at the attached image. On the top drawing the guitar is centered on the dish. If you get off center and still keep the rims pointing in the same direction, you will sand your rims to different heights as shown in the middle drawing.

However, if you let the guitar follow the contour of the dish, (which is what you do naturally when you do this free-hand), you get the situation illustrated in the third drawing. The rims are on a line perpendicular to the tangent of the curve of the dish and this is true regardless of where the guitar is placed on the dish.

Ok, the second drawing is what I'm talking about, if you want your "center" or high point to be in the bridge area, then you have to do it like #2 drawing. For the back I guess it doesn't matter. For the top, you may want the peak of the dish at the bridge and not before it in the center of the guitar.

Also, I have never checked the radius of the dish to see how accurate it was, I am so used to having to sand vertical with braces and keep them over one spot anyway.

So the new question is do you want your bridge at the peak of the dish, or the peak of the dish before the bridge... ???:mrgreen:

_________________
Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I

I built a simple rig that uses a shaft, assembly mold a simple bushing in the center of my sanding dish (requires a 1" hole to be drilled through the center of the dish) that allows me to keep the body centered and in proper plane to sand the back's spherical radius by hand with no worries of getting out of plane form one side to the other. I just hold the dish sides a rotate the dish around the shaft, the shaft is 3/4" diameter sugar maple dowel and the bushing is made for UHMW. I have several bases that hold the at the proper angle and indexes the mold to proper location. One for dreds, one for SJs and Oms and one for the MJ. They all use the same shaft and bushing.

Oh goody, I get to draw some more pictures. The three pictures show and exaggerated radiused top on a completely flat backed guitar. The first picture the top with a peak in the center of the guitar. The second picture shows the same arch with the neck block smaller. This has the effect of moving the high point of the arch back toward the bridge. If I rotate the guitar so that the arch is in the same position as the first guitar, we see that the rims are not straight up and down but the peak of the arch has moved back to its original position. The effective peak of the arch can be adjusted by the amount of neck set

The profile of the rims should be set during the building process and not when the final sanding is taking place. That means that the guitar can be put anywhere on the disk with the same results. However, the taper for a 25' radius is very small and it would be very easy to get it out of spec just by pushing too hard or soft on the head block.

Many neck setting procedures compensate for errors in this area because they measure the height of a straight edge that is resting on the neck, right above the bridge position and adjust the angle of the neck accordingly.

True dependent on a few issues like the pressure applied by the builder during sanding and the accuracy of the initial profile and the way the builder set the top of the lining. many builders set the linings height above the profiled rim at 1/8" or so proud. Many do this by eye so it is possible to have an inconsistent height above the profiled rim that could lead to lopsided sanding. also the neck block being square bottend. If the approx. taper formed by the dome is not pre cut into the neck or tail block this can cause the dome to contact at the wrong plane in the early stages of sanding that can thow some misalignment into hand sanding the dome. I have dome this unitentionally in my early days of building.

Also some builders rough profile the sides (+or- 1/32 to1/16 to perfect profile) and allow the sanding to square and smooth out all.

Putting the linings a little high wasn't really a problem but when adding the cherry blocking for the armrest and ribrest made it difficult as it was about 1/16" above the side so it would be profiled also for gluing. I had to actually hold the mold up and apply pressure to the side with the rest and try to keep it level. You can imagine how much faster the side without the blocking would sand.

I think if someone wanted to use this new mold from LMI, there might be a way to do it.. Probably not
worth the effort but I think it would allow assembly of the guitar and removal of the supports through
the soundhole with top and back in place. It's a really poor photoshop job, maybe you can get the idea.
Just section the pieces as I've shown, install one more turnbuckle and you should have something
that could be removed through the soundhole.
Or, make your own. I just did for an OM and I think it will work. This LMI version does have some
merits, however.
http://www.redshift.com/~gibson/BENDING ... dMOLD3.jpg

_________________
Bruce Herrmann
"What lies behind us and what lies before us are tiny matters compared to what lies within us."