Official Luthiers Forum!

Hello all i'm about to start joining 3 sitka spruce tops and i noticed that on one of them, the saw cut on the end grain did not line up when the two halves were stacked on top of each other (there are witness maks on the edge grain).To get the saw cut to line up i have to slide one half along about a 1/4 inch.How could this be,does this mean i will have to cut 1/4inch off to get a bookmatch? i,m confused as to how this could have happened, any help appreciated thanks Roby

Roby: I wonder if the quarter is off a bit and you have the wrong faces on the inside...??
Tom

_________________
A person who has never made a mistake has never made anything!!!

Thanks for the reply Tom according to the witness marks on the edge grain i have everything the correct way round.Thanks Roby

You have the wood in your hand , so look close and check out the grain lines not the witness marks . Yes sometimes you get a set where a bit may have been trimmed off . It happens sometimes . Learn to read the grain. If you surface the two faces , you should be able to read the grain better and see the match .

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Thanks John what is confusing me is why i have to slide one half along when they are stacked on top of each other to get the saw cut on the end grain to match ,the saw cut is very wavy so it is easy to match nothing has been trimmed off because both halves of the set are the same width ,thanks again Roby

Thanks John what is confusing me is why i have to slide one half along when they are stacked on top of each other to get the saw cut on the end grain to match ,the saw cut is very wavy so it is easy to match nothing has been trimmed off because both halves of the set are the same width ,thanks again Roby

Here's a theory: If the sawblade has a very wide kerf and you've taken lots of meat out while resawing the tops, you'll end up with an appearance which is less bookmatched than it would be with a woodmizer type of blade. In other words, the pattern that matched up perfectly to the other side is now sawdust. It'll get worse if you haven't yet smoothed the top, e.g the pattern will continue to migrate when you take more sawdust off while smoothing them. This has happened to me on figured back sets. Does that make sense?

thanks corky i didn't resaw this it came from a reputable supplier this is totally confusing trouble is the grain is so tight i can't seem to make a reliable match the only thing i've got to go on is the saw cut on the end grain which is very wavy so it is very easy to match,if i can iwill try to get some pictures posted thanks Roby

Hi Roby,

Can you put up a picture? That way we can give you specific advice. I have some theories but would want to see the issues you are describing before ZI commented. Personally I don't see how the saw cuts and witness marks should be offset...(I believe you when you say they are but something seems "funny" there).

Thanks

Shane

_________________
Canada

ok heres a couple of pictues the first one shows the saw cut lined up the second is with the edges lined up

OK, can you place the front one to the back and see how that lines up?

_________________
Canada

What matters is the match at the joint.

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Aaaah, I get it.....

Shane's got an interesting idea.

Also, as Howard said - it's the joint that matters, so.... if you're committed to joining that side, you'll probably have to take a 1/4 inch off to bookmatch them, but the grain lines are the determining factor. What's the joint like on the other end? Are the growth marks tighter or wider at the other end? If the other end matches up and are tighter, I'd just join that side instead.

What if these wre book matched but were much longer than necesary and they were individually lopped off to fit in the shipping box? As others said, try ignoring these edge marks and see if you can get them to match.

Another possibility is that they are slipped matched. I once received a back set that seemed like a perfect book match except for some individual curls not matching, and the two pieces were not exactly the same outer dimensions. I played with it a long time before I figured out that they were slip matched, and they fit together end to end.

You really need to show us, and focus yourself, on the bookmatch pattern with the two sides laid side by side
as you will see them on the guitar. As stated above, there are a couple of reasons why the end cuts could have
been made with an offset. I've often seen bookmatched sets where slipping one side down a fraction of an inch
made a much better looking pattern, usually because of the mis-match of the grain due to the missing saw
kerf wood. Can you get a picture of the grain on the matched faces of the slabs?

_________________
Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

Hello all sorry it took so long to get back and thanks to everyone for all your help.Shane, if i place the the front half to the back i have to slide it the other way to get the cut to match. Anyway like everyone said it's the joint that matters so i need to study the grain and see what i can make of it, i'll try and get some pictures posted.Once again thanks to you all,this place is great,you learn so much Thanks Roby

The very first thing you need to do is to cut straight off those junky sawed ends, then use a sharp plane to finish the endgrain surface. You should be able to see the pattern perfectly. Stack up the plates and align them at both ends. Cut the excess, if any, minding the final guitar width. The result top doesn't have to be 10 inches wider than the guitar, as wide or even 5mm less is manageable, since you will have to add binding anyway.
You also need to inspect the flaws of the top, so before saying "this is it" you need to smooth the face and look for defects that can be eliminated by rotating, flipping and moving the pattern around for a bit.

_________________
Build log

First of all, do not rely on saw cuts on the ends. You don't know how or when those cuts were made. At any rate, those cuts are not perpendicular to the face, and should be offset when you consider the material removed between the halves. Also, the edges could have been trimmed haphazardly in the milling process. After all, you have bought a raw material, not a precisely dimensioned product that is 'ready to go'.

A skew cut with a sharp chisel will also work. As Howard pointed out, the only place that the grains need to match is at the joint, so concentrate on surfacing the ends in that area.
If you still can't see the grain, wet the wood and use a magnifying glass. Wood grain changes when you allow for the saw kerf and surfacing, though it changes the least when the grain is perfectly vertical. Very often, the grains will line up at the joining edge, then shift a little as you move away from the edge, but that is irrelevant. What your eye is drawn to is how the grains meet at the joint.
Line up the grains on each end, then clamp or tape the two halves together to joint the edge.

_________________
John