Thicknessing questions...

[nnickusa]

I've got my back, sides and top ready for my next try. Blackwood Back and sides, and cedar top for a dread...

I'm planning to thickness them tomorrow, and am looking for advice on thickness....Back 2.5mm, sides 2.0 mm? And top? From the book I used, the recommendation would be around 3.2mm for cedar, does all that sound right?

Thanks,
Nick

[Allen]

It's sounding in the ball park Nick, but there is nothing like having the wood in your hands and bending and flexing. I would tend to keep the cedar top a little thicker in it's initial dimensioning, as it's so soft that you will invariably take off a fair bit in the finishing stages.

Also one thing about Western Red Cedar is that it dings and scratches from just a stern glare. I've seen quite a few builders get those dings in a top that they thicknessed to it's optimum, only to try and sand those spots out latter. Making the top far too thin in some areas. Moral of the storey. Be bloody careful with a cedar top.

[Phil]

.......... be bloody careful with a cedar top.

Yesss, Take all precaution when working with cedar, like removing your wrist watch and clipping your fingernails very short.

Phil.

[woodrat]

I like cedar tops but the softness is an issue....love the stern glare illustration Allen!

3.2mm is an average thickness for WRC based on its average GPa and densities..... I wounder where I got that?

Will also benefit from a bit of edge thinning around the lower bout too Nick

John

[nnickusa]

Right. Be very careful with cedar. Got it. Might thickness that one by hand sanding then. I used my hand-held belt sander last time, and it worked fine, but with the cedar, I'll just use my big hand sander....This time I have a dial micrometer to measure the thickness. Likely that will work better for getting a consistent plate.....

No worries about the fingernails....I'm a chef, and with all the wet my hands are in, the fingernails just sort-of fall off after .5mm of growth.

I will keep my wife away from it, tho....last one, I had just sanded back for finishing, and she gave the top a great big tap with all her fingernails

Started making all the blocks and bits for the neck. I hope to glue up tomorrow morning before work...should look nice. Really highly flamed Blackwood, with a tassie oak centre strip, about 6mm....I love a laminated neck....

[woodrat]

I wounder where I got that?

John

I wounder where I learned to spill?

[nnickusa]

According to me mum, that was one of the firstest things I learned

[Trevor Gore]

I wounder where I learned to spill?

NZ?

(Sorry guys, couldn't help myself)

[woodrat]

[Nick]

I wounder where I learned to spill?

NZ?

(Sorry guys, couldn't help myself)

You spelt it wrong anyway Trev, it's Un Zud.

[nnickusa]

OK. I've spent a few hours sanding the top, back and sides. I've got the top to 3.4mm very consistently, and will ease the edges to 3mm +/- as I go, assuming I'll take off another .2mm with finish sanding and whatnot, but the back and sides are +/- .05mm, and in a couple spots + .1mm. Would you guys go with that? Every time I tried to even them up, I ended up a bit over or under in different spots....

I'm sure that they are much more consistent than my last effort, and I think theyt'll have to do. Clearly, I'm gonna need a good thickness sander if I continue this...did I say IF

Actually I'll need a few other gadgets to make it all more consistent, as I'm using whatever tools I had left over from my building days....

Thanks,
Nick

[kiwigeo]

OK. I've spent a few hours sanding the top, back and sides.

Time you got introduced to the humble cabinet scraper......it's my weapon of choice for final thicknessing of tops and backs.

[nnickusa]

Point taken. Kinkade does mention and demonstrate the use thereof, but in varying order of use vis-a-vis the sanding block.

Going to Bunnings in the morning to get some plywood, so I'll see what they've got.....

But, does .05-.1mm really make that much difference? (Ducking the subsequent barrage of scorn for the new builder... )

No, seriously, what overall effect would such variations have for the sound, given that it's the back and sides.

I'd guess that my OM sides were quite a bit thicker in the centre, as all I had to measure was an engineer's square to look at the edges, and I know I had a spot on the back that was a fair bit thinner than the rest....

[Nick]

Time you got introduced to the humble cabinet scraper......it's my weapon of choice for final thicknessing of tops and backs.

A deceptively simple looking but extremely effective tool & one that should be listed in the "must have" column in every builder's shop. Great tool for removing material in small but quick amounts Nick.

[kiwigeo]

But, does .05-.1mm really make that much difference? (Ducking the subsequent barrage of scorn for the new builder... )

No, seriously, what overall effect would such variations have for the sound, given that it's the back and sides.

I'd guess that my OM sides were quite a bit thicker in the centre, as all I had to measure was an engineer's square to look at the edges, and I know I had a spot on the back that was a fair bit thinner than the rest....

Rather than aiming for a number you should be constantly testing the stiffness of the wood and in my case I tap the wood as well and listen to pitch and sustain. With spruce Ive found it fairly easy to judge when a top is close to a thickness where its going to start going floppy on me and thats where I stop. Im not a great fan of cedar as its too easy to overdo the thicknessing and it seems to not take much to go from a stiff top to a floppy one...personal choice of course and not a reason for you to not use cedar.

[nnickusa]

Thanks Martin,

But, with all of one build under my belt, I'm trying to tap the collective wisdom of the forum, and not the wood. I honestly couldn't say what is good, and what isn't until I've done this for a while....FWIW, both the top and back ring very clearly and have a nice muscial tone....

I will grab a scraper or two tomorrow, and clean up the plates....

Re: Cedar, I've never had a cedar top guitar, and thought I'd try it out. Looks nice, and complements the blackwood well. I'm hoping, again, for a decent player, but with better fit and finish this time. I'd hate to waste the back, as it's come up really nice with a sand down to 120. Nice figure, and the bookmatch is almost perfect, and the B/S set was only $75.

And so it goes....

[Allen]

.05 to .1mm can make a fair bit of difference in a top. I wouldn't expect a huge difference in a back. On a dread it may make bugger all difference in a top too. I think the larger the instrument, the more leeway you get without really stuffing things up.

It will make the sides easier, or more difficult to bend. But Blackwood is probably one of the easiest woods you'll ever find to bend.

Most important part of a cabinet scraper besides how good the steel is, is knowing how to sharpen them. Get that down and you'll wonder why it's the best kept secret around.

[nnickusa]

Thanks, Allen.

The top is easy. It's all within a bee's dick of the same thickness, and I've left it a bit oversize, for later sanding, so I think I'm right there....If nothing else, a bit of scraping, and this one will certainly be much more consistent than the OM, which sounds just fine to me....

Right now everything is in the "workroom" for a week(?) in a controlled environment, or should it be longer? It's all nice old dry timber. Oh yeah the braces are in there too....trying to learn

[Allen]

Really depends on how controlled the room is. If it's a consistent 40 - 45% RH then a week is good.

You can install a rosette at any time. It's just those cross braces that are going to give you problems if the RH is not in your favour.

You can also bend the sides at pretty much any time if you want. Just so long as you have a method to hold them in shape once they are bent. It depends on your building method, but if you are using a outside mould with a bolt on neck then the sides can be bent. Install linings and blocks while the top and back are resting in the controlled RH. That would keep you busy for a bit. When I build with that method I have the rims all ready and then get both back and top ready to go, so I can glue them both on in one day. I really don't like to give the body any chance on changing shape with swings in RH, even if they are small it can change the body geometry. Top or back can expand or shrink and the sides will flare. Once the box is fully closed you are pretty much home free.

And things like slotting fret boards and tapering them can happen at any time. Even getting that neck pretty much finished is not out of the question. It's gotta be done sooner or later, so if you are antsy about waiting there is lots of things to putter about at.

[woodrat]

I have to agree with what the learned gentlemen have said regarding the humble cabinet scraper. It has so many uses in lutherie and when the technique of preparing the hooked cutting edge is mastered it is a sublimely delicate tool to use. Allen is very right about the quality of the steel. My favorite one is a Sheffield steel Marples branded one. When you go to buy one if it says stainless steel on it dont even consider it. I bought the SSteel one from Stewmac and it was rubbish. Having said that I would be surprised if a general hardware store would keep a good cabinet scraper these days...probably better to get it through Carbatec of similar...but if they have a stack of Marples cabinet scrapers there somewhere on the north coast of NSW...buy the lot!

Anyway Nick well done on becoming a guitar maker !.....as the ad says..."bet you cant stop at one"

John

[nnickusa]

How about these? Looked around after reading the last few posts...Would take a while, but I'm trying to be patient this build...

http://www.ebay.com.au/itm/140605953021 ... 1423.l2649

Should there be nothing tomorrow, and the plywood is for a semi-solid mold. One thing I liked about kinkade's book was the use of the mold throughout the build process...

[Nick]

But, with all of one build under my belt, I'm trying to tap the collective wisdom of the forum, and not the wood. I honestly couldn't say what is good, and what isn't until I've done this for a while....FWIW, both the top and back ring very clearly and have a nice muscial tone....

Tap, flex,feel & run the wood between your fingers after every 'sizing' step or operation you make Nick (sounds kinky I know! ). I know you say you don't know what you are listening to or feeling at the moment but with every build you are building up a knowledge base and after a while you'll have a better feel for what the wood's telling you. As a prominant Archtop builder (Bob Bennedetto) explained on his DVD, even listening to noise the hand tools make as they cut or remove wood can tell you something. It's a very 'organic' experience & the reason why I love this building lark!

A decent Cabinet scraper will last you for years & pay you back the purchase price in bucket loads over the years so purchase your first well, it's not a tool you really want to skimp on. I bought (as well as some decent ones) some cheapo's from LMI (their various shaped ones), these are Ok for small amounts of scraping & do need re-sharpening more regularly.

[woodrat]

Nick, I think the Crown Tools ones should be good....

John

[woodrat]

BTW, Nick, if you dont have a thickness sander and you want to make your own bindings. Rip them a couple of tenths oversize and then scrape them to thickness on your bench with them ganged together so the scraper doesn't tip and your bindings stay true. If you make 2 sets (8 bindings) then it means that it is even easier to keep them consistent. Thats a good technique for people starting off if they have not yet delved into buying a Thickie Sander...

John

[Lillian]

I started with cheap, nasty so called hand scrapers. I ended up using them for glue scrapers.

I have an Bahco (formerly Sandvik) scraper and a Sandvik scraper that I've had for years. I also have several of various thicknesses from Lee Valley and from Lie Nielsen. I use them interchangeable depending on if I want a thicker steel or thinner. But usually what it comes down to is which is already sharpened and ready for use. I have about a dozen or so. I tend to use them until they need to be sharpened and then do the whole bunch at once.

I also use the Veritas Scraper Holder. I need it because my hands aren't what they used to be.


Lee Valley has some super-thin milled scrapers that I think need to join the herd.