# Fretboard Flatness - Precision

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When I build a neck, I always try to ensure that the fretboard surface on the neck is flat to within 0.001" before fretting, same thing with the fretted neckwhen checking the fret tops.

This seems to give good results but I still occasionally need the odd fret that needs to be adjusted.

What do you guys do in terms of precision?

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Oh man,I would never accept less than .0001" flatness..I don't know how you can live with yourself.

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Oh man,I would never accept less than .0001" flatness..I don't know how you can live with yourself.

Are you serious or joking?

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Oh man,I would never accept less than .0001" flatness..I don't know how you can live with yourself.

Are you serious or joking?

Oh I think he is quite serious. 0.001" is way too much play for a fretboard. I would at least try for 0.0005" across the board.

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What I do is I take a human hair,I split it into quarters,then I take the most uniform piece and cut it into 10...then I put my stewmac straightedge on the fretboard and if I can insert the piece of hair anywhere along the length of the fretboard I throw the fretboard away and start over..

Obviously you have to properly thickness your sheets of sandpaper to achieve this level of precision...

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I find this kinda funny, unless I'm somehow misunderstanding the question. However, I will preface this statement by saying I've never measured this like ya'll apparently have, nor have I had a problem that has led me to think I need to. That said: Stewmac's medium/higher fretwire (the "Dan Erlewine favorite" one) is .048" high on the crown, and we can all visualize how tall fretwire is in our head. So, the variance he's talking out is 1/48th of the height of the fretwire. I would put MONEY on the fact that over the thousands of feet of fretwire made for/by Stewmac there is more variance than that. Not to mention, when dealing with softer boards I'd be hard pressed to believe there aren't bigger variances than that caused by different pressure when seating different frets. Also, lets take Stewmac's fret-rocker tool, a tool designed to locate problem frets so you can level better. Their site says it is, "precision-machined for accuracy to .0015" per foot." The tools SPECIFICALLY designed to locate any problems that would be big enough to cause buzzing isn't even as accurate as this guy's fretboard level. Stewmac touts .0015" over a FOOT. This guy's saying he has less than that over his ENTIRE BOARD.

Secondly, he's asking about flatness BEFORE fretting... there are probably going to be changes larger than .001" to the level after fretting. If we're getting to the nitty gritty and someone goes "yes, but each fret will push ever so slightly on each slot, and any change should be even and correctable by the truss rod" we once again have a problem. Frets get progressively smaller as they go up, so there isn't an even amount of pressure on each slot, the pressure (as minute as it should be with properly cut slots) is more concentrated towards the body. The truss rod also does not know this when it counters any changes.

Dude, if you've got .001" down the entire board's length you're fine. Go ahead and fret!

Chris

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Well obviously you have to precision grind the fretwire,duh...I use a belt sander...this one

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Oh man,I would never accept less than .0001" flatness..I don't know how you can live with yourself.

Are you serious or joking?

Oh I think he is quite serious. 0.001" is way too much play for a fretboard. I would at least try for 0.0005" across the board.

dont ya just hate it when you finaly get your board down to .0005" and then a front moves in and the humidity changes and you have to start all over.

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OK - thatnks for the sarcasm. I know that some of you have ultra low action, which is why I asked.

As soon as the neck is fretted, all bets are off and I'll have to re-level but I like to start with a good base. I have the most accurate tools I can find but you are correct in saying that even my Lee Valley straightedge does not have 0.001 accuracy. I do check for flatness with said straightdge and some feeler gauges.

So what kind of accuracy do you guys strive for?

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In all honesty,just flat,man...I use my radius blocks and just sand until flat..then I press my frets in and level and crown them,then polish them with a dremel buffer...then I string up,adjust the truss rod,adjust the nut,and adjust the bridge..and that is it.

You just waste your time with all of that overthinking,which is why all the poking fun....

My action is set up at 1.5 mm at the 12th fret,2 mm at the 24th...no buzzing....ever.I could go lower,but I like it right there

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My radius blocks are made of moonrock though,and have been blessed by a voodoo priestess...

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My voodoo priestess

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What I do is I take a human hair,I split it into quarters,then I take the most uniform piece and cut it into 10...then I put my stewmac straightedge on the fretboard and if I can insert the piece of hair anywhere along the length of the fretboard I throw the fretboard away and start over..

Obviously you have to properly thickness your sheets of sandpaper to achieve this level of precision...

I had to throw out my Stew Mac straight edge as it was not precise enough...

I ordered a better straight edge. It is accurate to .00000000000000000000000000000000000001 . It cost a lot. I lay the newer better straight edge on the board and if light comes through I burn the board in a very large bon fire.

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My voodoo priestess

+1 I will take one of that.

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In all honesty,just flat,man...I use my radius blocks and just sand until flat..then I press my frets in and level and crown them,then polish them with a dremel buffer...then I string up,adjust the truss rod,adjust the nut,and adjust the bridge..and that is it.

You just waste your time with all of that overthinking,which is why all the poking fun....

My action is set up at 1.5 mm at the 12th fret,2 mm at the 24th...no buzzing....ever.I could go lower,but I like it right there

Just make sure no light shows under your straight edge. Watch out for the radius blocks. It is very easy to rock as you sand and cause low spots at the 1-3 fret or 15-24....

Another issue is with very hard boards. Even when straight a perfectly straight ebony board can develop back bow do to fret tangs that are larger than the fret slots.

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You just waste your time with all of that overthinking.

+1.000000001

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You just waste your time with all of that overthinking,which is why all the poking fun....

Sorry for piling on. But it was funny for a few.... then the whole priestess thing happened.

Anyway... I think you got it.

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i just try to get the FB as flat as I can. I utilize a radius block to get the initial surface and use a straight edge with sandpaper on it once its blocked to insure the flatness down the length. a seperate straightedge is kept nearby to check progress. I work up to 600 grit and thats the extent of it.

I think we need adjustments due to the board being flat under no tension, then adding it into the balancing act of the neck wood, string tension and truss rod. Thats a 3-way tango thats sure to put some odd pressures on your previously perfectly flat surface.

I know I always need to adjust some of the frets during the setup and I try to wait for the neck to settle in a bit, 2 or 3 weeks if I can help it.

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