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How neccessary is an 18 inch metal straightedge? I do have the skill to make a wooden one but are wooden ones accurate enough for guitar making? I also have a 12 inch Starrett ruler and a 22 inch jointer plane which theoretically can be used as a straightedge.

Exactly which operations require the use of this tool?

Thanks,

-jj

The only thing I use a straightedge for is setting the neck angle. You could make one out of wood that would be close enough, but you'd need to check it against something flat before each use. It may move a little with humidity fluctuations, and there's not much wiggle room in the neck angle.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

I could not do without my precision straight edge for fret leveling.

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wah
Wah-wah-wah-wah
Wah

Thanks, I'm just going to make a wooden one and check it against the jointer plane bottom. If the tool is only used for two neck operations then there's little point in me buying one. If I get way into this then sure.

Thanks,

-jj

just get a stainless steel ruler... that is straight and doesn't warp or anything

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Jimmy: And you know the jointer plane bottom is straight because...............................................?
Tom

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

A ruler is NOT a straightedge!
Buy yourself an 18 inch piece of Starrett ground flat stock. Bought mine in the late 70's, and it will be someone elses' when I'm dead.

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"Act your age, not your shoe size" - Prince

The OP is asking if he could make himself a piece of wood to act as straight edge for various setup work. I realize a steel ruler is not a "straight edge" but it is straight enough, and if it wasn't it could be ground straight with sandpaper and a known flat surface. It would be far more trustworthy to not change in shape over time vs. the wooden stick. I have used one for years and it has not failed me for this kind of work.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

The ruler might be a reasonably accurate straight edge. There's no way of knowing unless it's checked against a reference.
I suppose he could always make 3 wooden straight edges and do the 'averaging/checking' until he ends up with a . . . straight edge!

The method for figuring out if an edge is square is to lay it on the side and draw a pencil make down the length on a piece of paper, the. Flip the edge over and draw another line. The error is magnified two-fold and is easily seen.

-jj

I'm quite happy with my inexpensive 36" iGaging straight edge with 64th inch graduations http://www.amazon.com/iGaging-Premium-36-Steel-Straightedge/dp/B005G8HEIW
I use it when flattening neck and fingerboard surfaces, measuring and marking fret slot positions, checking the arch on braces, setting the neck angle (both side-to-side and projection over the soundboard), and locating the bridge. Wouldn't do without it.

24" would also be fine. Not long enough to locate the bridge all the way from the nut, but I really measure from the 12th fret anyway since I do nut compensation these days so the nut end isn't a reliable reference point. 18" might be long enough, but I'd recommend longer.

I wouldn't be without mine- I had an aluminum one that I did as best I could to flatten without the "correct" tools (I used sandpaper on my table saw surface). When I learned more I was able to scrape in a cast iron stress relieved straight edge and it is a world of difference. I made fine guitars with the old version, it is not necessary. But now that I have the new one I won't give it up.

The thing I find it most useful for (besides the obvious - fret setups) is jointing back plates. Sometimes the grain does not respond well to the plane and a few swipes with sandpaper adhered to the straight edge makes it perfect. In that case I found a BIG difference between it being close to flat and actually flat in terms of the joints meeting up without pressure.

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

I don't use the straight edge for fretwork, it is only used for checking neck relief, straightness, bridge height vs. neck angle. If I need to level frets, I'll use the plane iron.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Chris Pile's idea regarding a Starrett flat ground stock is the best solution at $15 dollars it eliminates all the problems of agroscopy and is less than a third of the price of any other straightedge.

https://m.mscdirect.com/mobileweb/produ ... 0=76106079

No reason you couldn't make ones from wood (or metal) using the 3 straight edges method.
I used a 1000 mm SS rule which was good to better than 1 thou for a reference for a couple of years until, but being a bit bendy could be tricky to use.
But I upgraded recently - just made myself 2 straight edges from aluminium extruded bar, 75 mm x 6 mm (from the bay), flattened with abrasive on a largish granite surface plate (against a squared wooden 2" x 2" batten)
Block is flat to 0.002 mm over 635 mm, and the 26" and 9" straight edges test were checked after flattening as best I could against the plate with feeler gauges. Turned out within 1/2 a thou over the length with each.
May not be a Starrett, but good enough for me.
Flattened an old no 5 plane body for fret leveling at the same time, same way.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

P.S. agroscopy - ?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Agroscopic: the tendency for a material to absord humidity and change dimension.

Steel rulers won't do that

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

But wooden ones would.
And I think you meant hygroscopic.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I find that a flat sanding beam with PSA abrasive is the most efficient method of fret leveling.

Using my plane iron for fret leveling would make it blunt in no time ....

+1
Several ways to skin this cat, but a reliable straightedge is invaluable in a guitar shop. Mine gets used almost every day to check things like neck blank straightness, fingerboard glue surfaces, fingerboard straightness prior to radiusing, etc. Several ideas in this thread on effective, low-cost solutions, but I would say that "rulers" are generally not in that category. Certainly my 36" SS rule is not nearly straight enough, but it's invaluable on its own for locating bridges. If you can find a ruler straight to better than 0.001", well, that exceeds the spec of the purpose-built Veritas 36" straightedge that's only good to 0.0015"! Conclusion: use anything you want, even a ruler, but check it first with a "real" straightedge.
PS: mine is a 24" Veritas.

Oops, must be all the drugs I did in the eighties. Yes hydroscopic Colin.

Tim, So the ideal length of straightedge is 24" for building steel string guitars? I agree that there's a right tool for every job and the expense is worth it. I just can't afford every perfect tool for my first guitar. In the future I'll score the ideal length tool.

Steel rulers might be straight when they are laying on a flat surface, but they are thin and bend laterally making them unsuitable to use as a straight edge for fretting etc.

Hygroscopic. Stupid English language never does anything logical...

Then delay the more expensive tools. I built my first guitar without a machined straightedge -- just a 36" SS rule that was indeed crooked - but I took that into account as best I could. In fact, I built that first guitar without a lot of things I now have and appreciate in my shop. The precision of your first guitar may suffer a bit, but you'll learn just as much -- most importantly if this is something you really want to take on as a long-term activity. You may discover that straightedge would have been better if shaped like a golf club!