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Just curious what you all shoot for with top thickness's in general. I'm sure I'll experiment with different ones down the road but I'm kind of looking for a general measurement to shoot for for my first few acoustics.

I generally start the gradual thinning of the top from around 0.130 thick. Final thicknesses have been in the range of 0.101" to 0.117". That said, I don't aim for a thickness. The thickness is what I end up with after thinning the top until it passes the sheet metal test and deflection measurements.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Exactly. The thickness is a byproduct, not a target.

I can tell you though the .110 for Sitka spruce is almost certainly a safe number to start with, which is basically factory standard.

Then, if you make a deflection jig and measure it, you’ll have somewhere plausible as a reference for the future when you adjudicate the guitar once done.

Classical guitar builders will go quite a bit thinner - 2mm or about .080 inch.

What kind of guitar are you building?

My version of a jumbo. 17.5 wide OM inspired shape.

Wood species generally, and the particular top's qualities specifically, also is a factor to be considered.

Yes, like everybody says, you don’t want to hold any specific measurement as proscriptive. But you do need somewhere to start. For spruce species it would be 0.110 inches in Texas, or 2.8mm in the rest of the world. A bit more for cedar, a bit less for a hardwood like mahogany. But every piece is different, so you then hold it in your hands and feel if it is starting to get a little bit floppy. If so, it is time to brace it. If it is still stiff and resistant to wobbling - thin it a bit more. You can go a bit thinner on a small instrument, but err on the side of thicker for your jumbo.

That's a bigun. I'd start at .125 and go from there.

I have gravitated towards a little thicker tops over the years. Partly from player feedback, and advice from my friend Hans Brentrup who used to post here. I seem to recall reading an article in the Guild journal where some prominent builders including Linda Manzer said the same.

The deflection that equates to the sound that I am after and has been well received usually results in an OM top of 0.114-0.118 for Sitka and Lutz. More on the lower range for Adi. Around .125 for a dred and in the 90’s for a parlor.

This is with pretty conventional Martin style scalloped X bracing.

Many different paths to a good outcome eh?

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It's not what you don't know that hurts you, it's what you do know that's wrong.

The top tells you what thickness to make it, if you ask nicely. This is mostly based on stiffness along the grain, and you will need to come up with some measurement of that. There are folks who can do that by feel, but I'm told that when the experiments are done it turns out that very few people are as good at it as they think they are. There are fairly easy ways to measure this, and doing so will go along way toward making your work consistent.