Official Luthiers Forum!

Is that a Rosewood guard on your Jointer ?

very cool !

-jd

Burton,

Any chance of see pics of your "Mario inspired" veneer/fret press?

Thanks,
Max

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Max Bishop
Brighton, Michigan

Thanks everyone! I am enjoying doing this.

JD - yes, I had some cutoffs from some boards I processed and the natural edge was just right for the guard, I couldn't resist.

Max, I took some close up shots last night and I will post them tonight along with some more stuff completed.

On a side note I had a little accident with my thickness sander getting my finger caught between a thick piece of wood and the conveyer belt. The actual injury is pretty minor but may slow progress down a bit for a week or two until I am back to full motion. Watch those fingers at all times everybody!

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Here are some close ups of the press. It was built from memory of a photo I saw once so it is probably not too much like Mario's but it does work. If I made it again I would beef up all parts of it but until it starts to fail I am going to leave it be. It does flex some and I don't mind that, it lets me know I am getting good pressure. Here is a photo:



And a close up of the rail system. I winged it here originally.



Those show it as the purfling press. To move it over to a fret press I simply unscrew the straight bars and screw in the fret press cauls that Stewmac sells. I got some from John Watkins as well but I don't believe he sells them anymore. I do need to remake the connector between the threaded rod and the caul. Right now it is the mahogany pieces with a threaded insert in top and a friction fit at the bottom. There is play in the top insert and once in a while a fret goes in a little crooked. I plan on making some improved ones soon.



I hope that helps. Let me know if you want any other close ups or anything.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Burton,

Thanks so much for the photos and info on the press. I will probably trying to come up with a version for my veneer work.

Thanks again,
Max

_________________
Max Bishop
Brighton, Michigan

I had run out of prepared bracewood just before this guitar so I had to go through the process to choose some more. This process for me starts with some nice chunks of wood. I have been getting wedges, pieces, and even boards from the people I buy my red spruce from and I have other pieces from other purchases. I don't pay too much attention to the species. Most of it is red spruce but I don't have a problem with it being a mix. I am mostly interested in the stiffness and weight. I have never used sitka that I know of. Not for any reason, I just have never purchased a billet of Sitka bracewood.

I start by rough cutting brace sized blanks from the boards. My final sizes are .3 x .7 x 18 and .5 x .7 x 18 so I cut them a bit over this dimension. If I cannot read a board from the cathedrals on the side grain I will work from a split face. I do try to be as careful as I can without being totally anal to have the grain be straight in both directions. I try to cut a bunch, at least 50-60 pieces. I cook all of these at the same time as when I cook my tops. I usually leave them in a bit longer and feel confident to take them out when I see sap oozing from all surfaces. There are some pieces that will just not ooze sap but most will, mostly from the end grain. Out of the oven I try to leave them alone for a month or two in the shop to let them re-acclimate. Once I am ready to begin the testing I will bring them down to their testing thickness. I make up bundles from these batches and set them aside for future builds and the bundles consist of (7) .3 x .7 x 18 pcs. and (3) .5 x .7 x 18 pcs so I make a bunch more thinner ones than thicker. Here is a shot of them waiting to get tested.



My deflection setup is worked into my table saw jointer jig. I made rails that slide in the t slot and lock down and a digital indicator spaced to fit between them. I use my little kitchen scale for the weight and my deflection weight is a nice piece of verawood (that smells amazing) and weighs in consistently at 1.5kg. I write the weight right on the brace and then write the deflection number next to that. I write the number as 17, or 20 but what it really means is .017, or .020. Looking back it would have been smarter to use a heavier weight to get more fine tuned deflection numbers but I have a bunch of data already behind me. I may switch at some point and do a few batches with both numbers to find where the 2 data pools correlate but for this batch I stuck with this weight.



Here is a shot of a brace on the jig. I do it from both sides just to be sure. They are almost always within .001 of each other which is fine with me.



Once everything is tested I make some piles and try to figure out how many sets I can get from what I have. I usually reject anything that deflects over .020 and anything that deflects right at .020 that weighs over 30 grams. I find that usually weight corresponds very closely to stiffness but there are outliers. In this case the pieces I had with very pronounced dark lines were much less stiff than the tight grained wood. This goes against "common" knowledge that says those stripey red spruce tops are the stiffest. All I take from that is that there are always exceptions. After factoring out all of the weaker braces I was left with a good group. Here it is organized by lowest deflection.



These were enough to group into 4 sets. I use the stiffest braces for the x braces and distribute them evenly between the sets. I find that the 7 smaller bars and the 3 thicker are enough for whatever I am doing brace-wise. I really like knowing that the x braces I use on each guitar are very close in working properties to the ones I used on the last guitar. I could feel differences in some of the braces I tested when simply flexing them but I wouldn't have guessed some were stiffer by over a third or more, as some of these were. Here are the 4 groups laid out:



And then taped together for future use. 3 of these will go up on the shelf and keep me going for a few months.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

One thing I like to do is to make custom tuning buttons for each build. I think it is a nice touch and really confirms that it is a custom built guitar, not just a regular guitar made with fancier wood. In this case I used some offcuts from the back and sides and made some blackwood buttons. I had made a photobucket group a while back showing most of the steps of making the buttons and I will not go into as much depth here as I did there. If you are interested here is a link to that page:

http://s36.photobucket.com/albums/e22/b ... 20buttons/

I was not sure how the resawing of the blackwood would go so I didn't save any nicely figured pieces for one piece buttons but there were thick enough plates that it was easy to make some nice bookmatched ones. This is the stock I chose:



This stock was thicknessed to size so when they were glued together they would be the thickness I start at in the milling process. Here they are being laminated together.



From here they are cleaned up on all 4 sides and then center drilled at equal intervals along their length. The beat up aluminum jig is used for this step on the drill press.



From here the button shape is drawn onto the side of the blank registering off of the hole and the buttons are roughly cut out a bit oversize. I always make a few more than I will need, something can go wrong at any step here and it is nice to not be sweating it if you can help it.



The rough cut buttons are then placed onto the jig to cut them to the correct size. They are again registered off of the original drilled hole. This jig allows you to friction hold them tightly and use the pattern bit (again) on the router table to cut them to their exact shape.



Once cut and removed from this jig you have to clean up slightly the bottom of the button (where it slid on to the jig) because the pattern bit can't get close enough to completely cut that perfectly. After that step is done they move to a jig to sand the side to side taper on the disc sander. I made this jig with my old belt/disc combo and keep it around for this operation. Again, this registers off of the hole and will further reinforce the hole being perfectly centered on the button.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

At this point the buttons look done. I have an old 320 belt that has lost almost all of its grit and has become a perfect polishing belt and after sanding in the tapers I run them over this belt and it does a great job of slightly buffing them. They will still need, however, to be milled out to fit on the specific tuning machine shafts that we will be using. In this case we will be using the Gotoh open back machines. To get at the shafts we need to remove the stock button. I do exactly as Chris P showed in his tutorial on this and use a hammer to pry the button off. I drilled post hole sized holes in a 2x4 and added brads to lock in the machine while pulling off the button. One side is for the left hand buttons and the other for the right hand.





Once I have a look at the shaft and know what I need to mill into the button for it to fit I pack everything up and go over to my friends shop to use his milling machine and digital readout. I made a vise that holds the button tightly while I mill out an opening for the button to fit snugly onto the shaft. Here is a shot of the button held in the vise.



I lock in the position of the hole and zero the digital readout.



Then I run the little endmill to open up the button to the correct opening.



The result is a nice oval opening that will slide onto the Gotoh shaft with a nice snug fit.



After milling out all of the buttons I will choose the 6 best looking and install them onto the tuning machines. I use medium CA for this step. I first make sure that the button will fit all the way onto the shaft. Once I am confident of this I will squeeze some CA into the opening of the button and slide it down firmly onto the shaft.



The result is some fine looking tuners! I am not quite ready to put finish on them yet but I will show that step later.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

I love your deflection jig. Where did you find the digital caliper? I can never seem to find any without spending an arm and a leg.

Awesome work! Love the custom buttons. I'm may have to try that eventually.

Steve

Steve,

I got mine from Lee Valley. It wasn't a cheap one but not super high quality either. It works pretty good. I used a regular dial one for a while but for this operation being able to zero it easily is a big big plus.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Burton, How does that machine make an oval hole?

I love the way you do your deflection testing and how you choose your braces. Thanks again for the incredible journey! Beth

Beth,

The machine is a milling machine and has beds that you can control very precisely in 2 axis'. The machine doesn't cut the oval hole in one go, rather I lower the spinning bit into the button and move the table (the vise for the button is clamped to the table) to make the oval hole. The digital readout I showed tracks the movement of the tables so I can be sure that I am being as precise as I need to be. does that make sense?

If you are familiar with a milling machine then I apologize for repeating this but if not it is like this machine ( a machine of mine but not the exact one I used for that process):



The handwheels on the side move the table side to side and the wheel in the front moves it in and out. It is a very handy machine! The handle coming off diagonally moves the table up and down.

Hope that helps.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

I spend a bit of time on the neck block, I feel like it is the central area of the guitar and as such deserves some attention. I make mine a bit differently than most people. I like to make them very wide, currently they are about 7 inches wide. My reasoning for this is for structure. I designed all of my guitar shapes to have a curve all the way through the upper bout, it doesn't go flat ant any point. I believe that this increases a resistance to bending in that area. By making my neck block longer I feel it further reinforces that. I also run a foot piece all the way to the first back brace. I have been using a compound radius along my backs meaning that from the neck to the second waist brace it is mostly flat and then the third and fourth braces are heavily radiused. I can get away with this with a pronounced taper in the rims, the flat plane continues up to meet the peak of the third braces' taper. I will be able to show more of this when I taper the sides and join the back but for now I like to keep that heel piece to strengthen the flat plane in the upper bout back plate. My reasoning behind the flat upper bout is to remove the collapsing dome of that area from contributing to a loss of neck angle. I feel that this is a major cause of needing a neck reset and that if that plane is flat it has nowhere to go that can let the bottom of the heel move outward. I have been using this method for my last few guitars and it has been working very well for me. There are a few bugs I had to work out (and a few to still work on) but overall it has been successful.

In beginning the neck block for this guitar I had to look closely at where my buttresses would fit. I have been using ball joints for the buttresses and they need to fit tightly and not interfere with either the extended tenon of the neck or the bevel cutaway. I made detailed drawings of the upper bout from the top and side and was able to fit everything in. The specifics I needed to find were the angles that the buttresses will come in at and how deep to make the openings for the balls in the neck block. These were the drawings I was working from:





Once I had those things locked in I could begin to construct the block. I begin with a laminated piece. It is a 1" piece of Spanish Cedar with the grain running with the sides, 1/8 (or so) piece of rosewood (ideally a light piece to match the cedar) and another piece of Cedar on top of that. Total thickness should be about 1 5/16. Also there is a 5/16 thick piece of QS spanish cedar and a 3/4 thick piece of QS mahogany. These can be laminated as they need to be fairly wide. The mahogany piece is short as this guitar will have the buttresses and I want to keep the upper bout somewhat loose. If there was no floating FB then it would also butt up to the UTB like the foot on the back. As it is now it will extend 2 3/8 or so into the body to anchor the neck extension part that does touch the top.



The large block is cut to thickness including a cut for the taper of the back on the table saw.



Then all 3 pieces are glued up together.



Once the glue has cured and I have all 3 pieces locked together as one I flush trim the sides (on the table saw and then the disc sander) and make sure the top and front are at a perfect 90 degrees to each other. There is a slight chance to change the angle of what will be the foot for the back when sanding everything flush but as long as I am careful and do not rush I can get it done cleanly.

Once these steps are complete I want to cut the opening for the tenon of the neck. I have been using a 5/8" tenon and I cut this on the table saw registering off of both sides and slowly opening up the cut until it is at exactly 5/8. Working from both sides ensures that it will be centered. The results are:

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

With the neck block flushed and with the tenon opening cut I am ready to drill for the neck bolt holes. To do this I draw my centerlines on the front of the block and use a forstner bit which is just a bit bigger than the heads of the neck bolts I will use. I try to space out the 2 holes as much as I can and still leave them able to be locked into the tenon. I have to remember the pronounced taper of the rims on the back when doing this, I have drilled it too low before and it gets dangerously close to the bottom of the tenon on the actual neck.



I drill with the forstner bit until I hit the rosewood and I stop there. I want the bolts to pull against that harder wood and not the softer cedar. Also, I know that with the thicknesses I used that means that the bolts will extend through the tenon but not into the meat of the heel, which is what I want.



Then, with a 1/4" drill bit I will drill through the block using the center point from the forstner bit as my centering guide. If my lines were drawn correctly I should have nicely centered holes in the tenon opening.



The tricky part of this neck block is cutting the openings for the ball joints for the buttresses. I have done it a number of ways and while they have all worked they have not been as clean as I would have liked. I was able to find a monster old milling vise that has 2 separate tilt options for cheap on craigslist and purchased it mostly to make these cuts. Until I get my own milling machine fit into my shop (which requires a little remodeling) I am again using the bridgeport at my friends shop for this. I made a simple table that anchors the block in the tenon and against the flat end face. It is important to do this step before sanding the block to fit the curve of the sides, I need that flat face to lock it in. I set both angles on the vise based on what I concluded I needed from my drawings.



I set my depth of cut again based upon my drawings and I am ready to make the openings.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

The tail block is much easier to make than the neck block. I start with a nice block of mahogany. I don't mind using a slightly heavier piece for the tail block, I think it helps balance out the guitar a bit on your lap.



I will resaw this piece to end up with a 1/2" piece and a 1/8" piece. I shoot for a 5/8" thick tail block. Once I have those 2 pieces thicknessed I will cut 2 slices down the length of the main piece. I see these as further crack protection. While it may be overkill with the double sides and the outer block lamination it only takes a second to do. 2 thin pieces are sanded to fit snugly in these openings and then glued in.



Once these are flushed I glue the 1/8 lamination over the entire piece. I do run the grain at 90 degrees to the main block. The main block is more or less parallel to the sides' grain.



Out of the glue up I flush everything up and have my nice clean end block. I try to make it a bit over my side thickness so I don't have to be so perfect gluing it on. 3/16 or so taller than it needs to be is what I shoot for.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

I used to dread sanding the blocks to fit the curve of the rims. I made some guitars that were flat on the ends but I didn't at all like how that looked. I was at my friend Walter's place one day and saw a simple jig he had come up with and had the aha moment and came home and built this jig right away, it has made what was a painful process much more easy and exact.

It starts with an added table for the disc sander. On the front is a small piece of angle aluminum locked in from underneath. That aluminum piece should be as close to touching the disc as it can.



The other part of the jig is a piece of wood with the curve of the top and back copied onto opposite sides. Once I have those perfect I rout the offset of the rims and that aluminum piece into them so they are cut back by about .14 or so. Those little stewmac bits are very helpful here again. One run with the .06 and another with the .09 get you about as close as you need to be. Here is a shot with the master piece with the prepared neck and tail blocks.



The blocks must be offset a bit from the wooden master piece to make full contact with the sanding disc. I usually get the double stick tape ready and press the block to the disc and then insert the master piece under it until it hits the aluminum piece. I line up my center lines and press it down. It may seem a little inexact but it works very well.



Now I am ready to go to it on the sander.



The result is a perfect curve and a perfect fit to the sides. It also leaves the tenon opening centered as well.



The tail block is done the same way except that it needs a separate piece to keep it locked at 90 degrees, it does not have the extension to tape down. This piece rides in the centerline of the master piece. Once the tail block is taped to the 90 degree piece everything else is done the same way as the neck block.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Now that the curves are sanded in I can finish up the rest of the blocks. The neck block especially is very blocky at this stage and I want to make it a little more elegant looking. I made a curve that i like and I will draw this onto the top and bottom of the block. While it does make it more attractive to look at it also eliminates any straight lines, especially any that could follow a grain line and make it easier for a crack to form.



Once these lines are drawn I cut and then sand these tapers into the block



As it is now it looks fine but is still a little more massive than it should be. The last step here is to drill some holes down through the main body to try to lighten it up a bit. I run 2 all the way through on either side of the tenon opening. These will be reinforced with CF tubes later. The flanking holes are drilled almost all the way through from the back. I want full gluing surface for the softer top wood. After drilling these holes the weight is still on the heavy side but I feel the added stability is worth the extra grams.



And a shot of the 2 finished blocks sanded and ready to glue in:

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Wow!!

This thread is both awesome to look at and haunting....cuz I HATE making jigs!

Great stuff Burton!

_________________
There is no difference between the man that thinks he can....and the man that thinks he cannot.

Wonderful job on all accounts, the building and the recording. Very helpful to me. You are teaching me a lot.

Burton, I do have a question. When you weigh and measure the deflection of the brace wood, why don't you ratio the two numbers so that you are more easily comparing each piece with only one number, say the ratio of deflection per gram?

Thank you for this effort! Please keep at it.

Ed

Hey Ed,

For the braces it is the deflection number I am really the most interested in. All of the braces I have measured have lined up more or less with the heavier ones being stiffer. As long as it is on that curve I will always choose the stiffest ones first, the differences are usually only 1-2 grams for an oversize brace so in the brace shaping the difference is much smaller. I do like to see the weights to eliminate braces that fall outside of the curve. There were a few heavier ones in the last batch that were much less stiff than they "should" have been based on what I have been seeing in my data from the last few years. Those got tossed. If I found one that was much lighter then the others and still as stiff it would be very interesting. I may set it aside and re-test it the next batch just to make sure it really was an outlier. If it was it may get used for an UTB or maybe the second back brace, braces that almost can't be stiff enough.

In reality I probably could ratio the numbers and maybe I will do that alongside what I have been doing to see how it all correlates but choosing based on the stiffness is really what I am shooting for.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Greetings.

I just wanted to chime in and express my appreciation for the care, detail, and painstaking effort that Mr. LeGeyt applies to his craft. I am the fortunate recipient of this guitar–it is a 10th anniversary gift from my wife and I couldn't be more grateful.

What makes Burton's approach more interesting is that he initially came to my home, listened and watched as I played my acoustic guitars, he had me play guitars he had previously built, and played those guitars himself so I could hear them from a different perspective. He counseled me on tone, woods, appointments, and everything else that truly confounds most of the guitar-playing public.

As I watch this build I am in awe of the process. AND THEN I remember that this will one day be a piece of art that I will have the privilge to hand down for (hopefully) generations to come. I just hope I can do this guitar justice. Might be time to take up lessons again.

Thank you Danielle, and thank you Burton.

Lucky, dude! It is an awesome process Burton seems to have. Beth

Gavin, nice to see you here! It will be nice to have this detailed a document for your guitar.

I have been a little slow getting these up, they take a while to photograph and load up. I am a bit ahead of my posts but I will try to catch up some here.

I made the neck block with the openings for the buttress ball joints and now I need to make something for the other end. In the past I have used simple wood pieces glued on the side that the buttress presses into and this will be similar to that but I wanted to make it a little more robust and give it a larger gluing surface and wrap it around the waist a bit if I could.

I wanted these to be laminated as they will take quite a bit of force and I wanted to minimize the chance for splitting. I would rather risk the glue line here than a split support. I started with 2 pieces each with 3 laminations:



Then I glued these up with the middle piece oriented at 90 degrees to the other 2:



Once these were glued and the edges all cleaned up I wanted to be sure of where they would eventually be on the sides. I used my lining side (there will be more on this later) to mark where a vertical brace will be on the rim. This side support will butt up against that vertical brace when it is installed.



Once I know where the side support should be I can mark the curve I need to sand into it onto the bottom of the support:



From here I go to the bandsaw and then the sander and rough in as close as I can that shape into the blank. From there I go back to to the same form I used to laminate the sides and use one of the sides clamped down and some PSA sandpaper on that to finish the sanding and to get my perfect fit.



Here is a finished support against the side. You can see the pencil line showing where the vertical brace will be. There is some extra to the side support in case the vertical brace is off by a bit, I will fit it to that brace later:



These 2 supports will be set aside for now. Eventually they will be machined with the correct shaft opening to anchor the buttresses.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

After all this time getting pieces together and prepping parts for later it is nice to actually get started working on the plates. The back wood has been resawn and rough surfaced and now we want to get everything glued up and begin to work towards braces.

I start with the plates and look for exactly where I want my pattern to fall. In this case my plates were well oversize and I had a lot of room to choose from. The best curl was on the outside of the plate and to show that off best I will need to move my center seam from where it is currently. I will need to trim some wood from what is shown here as the center seam:



To cut out some of the center portion I used my table saw jointing board again. This worked quickly to give me a mostly straight edge to work from while perfecting my joint.



It looks much better matched up like this.



I set up a work table that I made for the jointing process. The light table is great for showing how perfect the center seam is. I have never been completely happy with the hold down system on this jig, the plastic capped hardware needs to be more robust. It does work but needs to be monitored.



Things were moving along well, the plane was cutting good and I was feeling good. I would love to say that this next photo was the final cut before I candled myself a perfect joint but it was not.



I felt good with the plane but kept getting a joint that was open in the middle. I have been having good luck with the plane recently but am not near an expert and have only begun to use it in the past year with any success. In this case I pulled out my sanding straight edge and gave it a few good swipes. This got me very close and one more good plane shaving and the joint was tight.



I usually join the centerseam as a full sized piece instead of inlaying it and I wanted to do that here. I do not have a sure fire system of perfecting that thin a piece. Any method of sanding or planing the joint has been unsuccessful for me and it has centered around how best to secure the thin piece of wood as I work one edge. I have ideas on how I might do it but have not invested the work into a dedicated jig. In this case I had it very close from cutting it down and worked slowly from the light table marking where I was flush and slowly perfecting the fit. Eventually it came together nicely and I was ready to move onto the gluing jig.

I use the same table setup for gluing up the back plates. 2 in line clamps lock down in the T slots and push against some cauls to press the 2 plates and the center seam together. It gives a great amount of pressure and the in line clamps can be positioned in many different ways. It is especially useful for odd shaped back plates. The angle on the clamps and the cauls make sure they keep the force down instead of popping up as they want to do sometimes.



Once the clamps were in place I locked everything down as best I could (and cursed those plastic handled hold downs again) and set to work with the glue. I used the Smith's all wood epoxy here. I don't have a good reason why, I have gotten into the habit of using it on the back seams where there is a solid centerseam, especially a rosewood one. I would not hesitate to use hide glue here either but I went with the epoxy. Once all the surfaces were wetted with the epoxy and the clamps were locked tight I added some good weight over the seam and let it sit overnight.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Once the back is out of the joining jig it gets run through the sander until the faces are clean of any glue residue or slight mismatch from joining. The next step is to rout for the purfling strips that will flank the center strip. I got a good tip from Sylvan once about this step. It seems like common sense now but I didn't know it before. I use a clamped down fence to rout for the purfling lines and he told me to always have this fence to the left of your laminate trimmer. The trimmer will want to bite in that direction and the fence will always stop it. I take that a step further and always have the possibility of a bite be towards the darker wood. The thought being that if it did make a slight bite it would be easier to fill and hide. With using the fence on the left however, I haven't had this happen. Here is a shot of the setup for the first purfling channel:



After the first channel is cut I will flip it around and rout the second channel. I find it gives a cleaner channel to move forward with the trimmer about 2-3 inches and then come back. It cleans it out for you. I used to just go straight down the line and have to dig everything out with a blade. It could get pretty compacted in there. Going back and forth does leave the possibility of inadvertently widening the slot so I have to be careful that my fence is strong and my pressure towards it is even. Here is a shot with both channels cut:



The purflings I made at the beginning are sized just right for my 1/16 end mill and only need a slight tap from the hammer to be seated in the slots.



Once they are in they get flooded with thin CA and then placed under weight for a few minutes. I prefer this to accelerator after having some cause the white build up which can lodge in pores and be a real pain to get out. Running a scraper or even a sanding block down the purfs also helps speed it up.





A quick job with a scraper and then a clean up in the sander and our back plate is looking great. Before the profile gets cut out I want to take this chance to do some deflection testing and get some data. I run my initial back tests at .1 so i will take the (mostly) rectangular plate down to thickness and then set it up on the deflection jig.



The data I am after in this case is g/cu" (yes, I know) and the ratio of long grain to cross grain stiffness. I am collecting this data mostly in an attempt to understand as much as I can about what the plate will do once it is glued to the rims. I always shoot for the back plate to be tuned exactly to the top plate before finishing begins but knowing how it will change from the free plate to a closed plate is at this point a total mystery. The more data I keep, though, the better chance I have of either seeing some correlations or at least finding different data to focus on. It also helps with determining the size of the longitudinal brace, there will be more on that later.

Once I have my measurements I can cut out the final shape and be psyched that things are starting to look like a guitar.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.