Official Luthiers Forum!

I went shopping for a level at lowe's yesterday and the only ones they had, had ridges in them, or a hole in the side, to view the bubbly thing. so i bought a piece of mdf for $7 and had them rip it for me, too. i applied sandpaper and screwed the small strip to the factory edge. i joined tops and backs over the weekend and it worked like a dream. i get it close with my plane and make a few swipes on the shooting board.

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"...you have to get over your strict adherence to your largely imagined notion of absolute perfection..."

Waddy: Dead flat is a tall order. First of all,compared to what...? In order to insure the level is close to being flat you need three of them to check against each other. If you use two and they appear to be flat,you may have one that is concave and another that is equally convex. They fit together perfectly but neither is flat. With three levels you can check to see if they all fit perfectly ie they are flat or you will see discrepancies when all the levels are cross checked against each other. Most folks are not aware of this unless they have had some sort of machinist or mechanical fitting training.
Tom

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

I'll put it this way, I check things against each other, also against my "precision" straight edge, and against my ground granite counter top section, which I've found is really flat. Maybe "dead" was a poor choice of words.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Waddy : We could go on for a while discussing this I'm sure but I'll just ask you a couple of questions. How do you know your precision straight edge is in fact straight..? How have you checked you ground counter section to ensure it is flat...? Just trying to point out to the crowd that it is easy to fall into a trap with measurement facts.
Tom

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

I am very curious why no one has mentioned using a jointer? You can pick them up used for less than the price of a good plane and it really makes quick work of jointing a top or back.

Try a homebrew try plane about 18-20 in long , they are also inexpensive on e bay about a stanley number 6 plane . Properly sharpened and with some practice , it will pay dividends in the long run. Sandpapered levels , work, but planes IMHO leave a much smoother gluing surface, and besides you will be proud you did it, once you master the skills needed to flatten of backs , tops or sides , a very useful skill,

+1

Truer words were never spoken.

The only practical way to check whether a surface is straight, and flat, is to test it on a certified surface plate with marking blue, and see what the results are.

I can guarantee 110% that any level bought off the shelf, is not going to come up to scratch.

Flatness and straightness can only be achieved by lapping after surface grinding (or milling) and that just doesn't happen in the case of store-bought levels. Why would manufacturers bother making their levels dead straight ?

Lance, if this is contravening the rules, feel free to delete, but in the circumstances I feel this link is relevant to the discussion ...

I think all this concern about the flatness of straight edges etc., which is an interesting topic in itself, is side track in this discussion. The tried and true (!) methods, involving hand planes and shooting boards, give great results, and require only minimal skill. I think a lot of folks would be better off if they took the time to learn this technique, instead of looking for alternatives.

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Rian Gitar og Mandolin

Looking for short cuts in luthiery, leads to too many shortened pieces of firewood

If properly set-up and with sharp blades a 6" or even 4" jointer will work just fine. I jointed 100's of tops and backs at Pantheon with a 6" jointer. Generally the jointer tends to take more material in the middle of the run, so pressure must be adjusted accordingly. The opposite is true when using a hand plane: we tend to take more material at the beginning and end on the run, so again pressure must be adjusted accordingly at the butt of the plane's sole.
In my shop I use a 4" jointer to get close and a #4 Stanley with a shooting board to joint the plates. I have a #5 and #6, but I find the #4 more than adequate and much easier to handle.
It's easy, takes 5 minutes and very seldom do I have to use a jointed beam with PSA sandpaper (some hardwoods, especially if there is grain going in different directions, can be extremely stubborn with the plane).
I highly recommend building a light box to candle the joint, it must be perfect and close without tension or force, especially for the top.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

IMO, it really doesn't matter how you do it,
as long as it comes out right.
I join weiss tops and backs, which are 32" long.
I get them close on a tablesaw, then stack them on top of each other,
the one being sanded 1/4" beyond the lower one,
on a flat surface,
using a CHEAP 5 foot level, with 80 grit glued on,
and get perfect results in 5 minutes.
Straight is straight.
You could buy extruded aluminum for cheap.
It usually is straight.
If it isn't,
don't use it.
Ha!

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Theoretically it should since there would be more gluing surface. However for thin guitar plates I'd think it makes no difference. The downside is that a skewed (or scarf) joint will move the glue line across the grain as the plate gets sanded down which is too bad if you really worked your joint to be invisible (i.e. between 2 grain lines on a spruce top).

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/