Best straight edge size for tuning up guitars

[Keith Walden]

I've lost my old Starrett 24", and am looking online for a good but cheap straight edge to tune up fretboards etc so to speak. There is a 30" I was also looking at but Im just getting one. This is for 25" scales, electric, dreds etc,

Will 24" do it or should I go for the 30"?

[Glenn Cummings]

You probably made your decision.
I would have said 24" to allow it to be used between nut and bridge and other protuberances.

Starrett is a 'go-to' name, other manufactures may provide a cost effective 30" to add to your collection.

[Pat Foster]

I find the 24" from igaging useful for truing necks and fretboards. For setups I use the straightedge from a T-square at the big-box office supply store. I'm much more comfortable with plastic around a spruce top.

[Barry Daniels]

I have an 18" machinest's straight edge that I think is perfect for fretboards.

[David King]

A straight edge is only as good as it is stiff and flat. For my money I bought a thick, 4' aluminum straight edge at the hardware store (after looking through the stack and finding one that was also flat) and cut it into a 28" and a 20" section for bass and guitar fretboards. I have three Starrett rules, a 12, 18 and 24" which are OK and longer steel straight edges with a ground beveled edge but those are just too heavy and aren't perfectly flat so not great for accurate fretwork.

[David King]

Of course a real machinist's straight edge is thick cast iron that's seasoned, ground and then hand scraped. They run in the many hundreds of dollars and weigh a lot more than you'd want them to on the bench. https://www.subtool.com/st/se-ci_cast_i ... edges.html

[Rick Milliken]

similar idea to David's, I took an aluminum framing square (cheap). Cut it into two pieces then using my machined straight edge (expensive) as a reference, sanded the edges flat.

[Freeman Keller]

I have a couple of 24 inchers that I use most of the time - its nice to have two to put along side the fretboard when I'm trying to find the centerline at the bridge. They are good for laying on the fretboard of an acoustic when checking the neck angle. I also have a 36 inch that is very handy for laying out the scale length - I can shove it against the nut or a block in the nut slot and measure 24.75 or 24.9 or 25.4 or 25.5 or 26.5 or whatever scale I am using. Mine are all cheap ones from one of the box hardware stores - I'd guess they were ten or twelve dollars.

[Peter Wilcox]

This is the one I have - straight as far as my eye can tell, and scales are inches and cm/mm. If I need s short one I use the 12 incher from my combination square.

https://smile.amazon.com/gp/product/B00 ... UTF8&psc=1

[Mike Spector]

I use a Starrett 24" also, but found a 36" that reads in hundredth's of an inch for setting string lengths to position the bridge on acoustics.
It was a "blemished" on E-Bay for about $30. I still don't see why they called it "blemished". It looks fine to me.

try Taylor Tool Works: Blem Cosmetic Second PEC 36" Rigid 5R (1/10,1/100,1/32,1/64) machinist ruler
Item# 131333527033
$27.99 USD