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A couple newb questions: block height and mold malfunction
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Author:  Jeremy Douglas [ Thu May 08, 2008 5:30 pm ]
Post subject:  A couple newb questions: block height and mold malfunction
First the simple one: How much extra should I leave on my head and tail blocks to account for sanding the radius in the back rim? I don't want to have to cut the blocks once they are glued in.

The big issue I possibly have is that I don't think I can put my two piece mold back together properly if I take it apart. I had to make accomodations to true it up cause it didn't go together as planned. I'll have to take the sides out once the top lining goes on so I can contour the back. The question is will I be able to take the body out of the mold and put it back in safely?
Author:  Jeremy Douglas [ Thu May 08, 2008 7:16 pm ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
So to clarify, the only sanding I'll be doing is for the purpose of radiusing only right?

regarding the mold- I'm not going to be using a dish but rather a radiused sanding jig/stick. So I planned on contouring the sides based off my LMI plans with a plane and then putting the radius on with the sanding stick. I'll have to take the sides completely out of the mold to mark the height on the sides(I think). The way I made my mold was with two 3/4" layers seperated at the ends by two 3/4" spacers. In theory the spacers would have bolts through them to hold everything together properly, it didn't work quite right and I ended up reaming out the bolt holes, getting the mold square then bolting down. If I take it apart it will be nearly impossible to get it square again with the sides in it because it is not self aligning. Here's how I was planning on contouring the sides http://web.mac.com/magads/iWeb/Site/LMI ... A1530.html
Author:  Hesh [ Thu May 08, 2008 9:56 pm ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
Jeremy my friend I use a method that shims the neck and tail block, after they are cut to the desired height as Todd suggested. With this method the blocks are glued in place outside of the mold using radiused cauls for clamping. Then the rim is returned to the mold for the dish sanding.

The advantage is that as you sand the rim in the dish you are not sanding the blocks until the rim is almost completely profiled and sanded. This is much easier but does not give the love handles as much of a work-out..... :D

Now on to the subject of placing a rim back in a mold and having it be properly aligned. Not knowing what your mold looks like I am not sure if this will work for you - but it may. Frank Finichio teaches his students to run a 2 1/2" screw right through the center joint of the mold into the tail block and the neck block. These screws not only secure the rim at the top and bottom but act as registration points when removing and returning the rim to the mold. All my molds are retrofitted with these holes in them and my molds were purchased from John Hall at Blues creek.

Here is a toot that shows the neck and tail block shimming method: http://luthiersforum.3element.com/forum/forum_posts.asp?TID=9528&%20amp;KW=%28pics%29#forumTop

Also I profile the back edge of my sides prior to bending but leave the front edge perfectly straight to aid in gluing in the blocks on a flat surface outside of the mold.

Colin has an excellent method of marking a bent side for the proper profile that uses a very simple make-it-yourself guide to transfer the actual profile of the dish directly onto the sides. Once the sides are planed to the indicated radius the amount of dish sanding required is very minimal.

If you are interested in that I m sure we can find the link and post it for you.
Author:  Jeremy Douglas [ Thu May 08, 2008 9:59 pm ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
ToddStock wrote:
Guess I'd need to see the mold; however, never too late to do one that will work a bit better...use the current mold as a template.


I already cut my sides to length. I might would buy a mold if I knew it would work. I don't want to build another one though.
Author:  Jeremy Douglas [ Thu May 08, 2008 10:14 pm ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
Hesh, I don't have a pic of the mold but here's the design I copied.

Image

The problem I had is it would not go together correctly, so I enlarged those bolt holes, aligned everything according to the full size planes then tighted the bolts. The problem is if I take the mold apart to remove the guitar, I'm pretty sure I won't be able to get the mold back to its proper shape. Can I remove the body and put it back in with the mold still together? Or to simplify things, lets pretend my mold is one piece and doesn't come apart - can I remove and replace the guitar body?
Author:  Hesh [ Thu May 08, 2008 10:34 pm ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
Jeremy one of the potential problems that I see with this mold is that the spreader blocks are not pressing against solid wood on the mold. If the spreader blocks are not wide enough to span to the two outer plates (front and back) of the mold they could damage the guitar sides.

Also, and I know this is just a pic of the style of mold that you made and not yours, you will want spreader blocks on the lower bout and upper bout too. I don't use waist blocks but it is a good idea and I probably should.

I see what you mean about not being able to reliably connect the two mold halves in the same position every time.

When I remove a rim from the mold I unlatch the mold and spread it. Some designs permit you to simply insert something like a screw driver to spread the mold. I am able to place the rim back in the mold because I can open the mold. It's probably possible to place the rim in the mold without opening the mold if the kerfed linings are not yet installed but I probably would not recommend this not knowing if what I am saying here is possible and also not wanting to steer you in the wrong direction.

Here is a picture of a Blues Creek mold that I use. If you look closely you can see the screw that goes right through the center point where the mold is closed. These molds are excellent quality and with the addition of the center screw for both blocks it's a piece of came to remove the rim from the mold and place it back in the mold always in the same spot. The additional holes that you see around the mold are from my pre-go-bar deck days when I used spool clamps.
Attachment:
DSC01317.jpg


What is the possibility that you could rework your existing mold to split in in the center, provide a registration system like a dowel on it's side that mates with a carved out area on the other side, and then add holes for the center screw. It seems to me that if you just filled in the ends with solid wood, cut it down the middle, added a latch system, you would be good to go and this would be easier then scrapping what you have done so far.
Author:  Heath Blair [ Fri May 09, 2008 12:07 am ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
personally my mold splits in half for easy removal of the rims, but if i recall correctly from the mayes dvd's, john uses a one peice mold and just slides the rims in and out. sorry john if i am wrong. feel free to openly humiliate me.

but i like hesh's idea about cutting the mold in half and adding an indexing pin. wouldnt be that difficult (at least it doesnt seem like it would be).
Author:  Jeremy Douglas [ Fri May 09, 2008 5:07 am ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
Thanks, I didn't think of an 'aftermarket' latch. I might try it without the latch then if I can't get the sides back in easily, I'll make a latch.

And my spreader blocks do span the two plates [:Y:]
Author:  John Mayes [ Fri May 09, 2008 8:58 am ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
hblair wrote:
personally my mold splits in half for easy removal of the rims, but if i recall correctly from the mayes dvd's, john uses a one peice mold and just slides the rims in and out. sorry john if i am wrong. feel free to openly humiliate me.

but i like hesh's idea about cutting the mold in half and adding an indexing pin. wouldnt be that difficult (at least it doesnt seem like it would be).


Mine are two piece molds. I just have them screwed together most of the time and slide the rim out, but after it's boxed up I have to take it apart to get it out as the top and back overhang wouldn't allow me to slide it out.
Author:  Heath Blair [ Fri May 09, 2008 6:27 pm ]
Post subject:  Re: A couple newb questions: block height and mold malfunction
thanks for the clarification john. i wasnt positive.
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