Machining a flat surface

[Rrobson]

@Arc Tourist depends what your doing. If you are only machining one face then your vice could be 10mm out of square and on the wonk and provided the bed, ways, tool and bearings are all bang on it’ll produce on flat machined face, which is all the op is looking for.
If you want the part to have a pair of parallel faces then that’s a different matter.

As for a flat surface, second hand straight edges are cheap enough and should easily be accurate to within a thou or two over its length. Graded ones and those that have been looked after will be better than this.

One on Facebook, 6’ straight edge for £50!!! You could cut it down if needed (though I can’t believe I’ve just suggested that… )

Engineering straight edge

6.6ft engineering straight edge, with wooden box. Collection Billericay

www.facebook.com

 

[KemppiFrog]

I think part of this maybe is that Guitar bloke has no experience outside of his field, whereas anybody involved in engineering knows assorted solutions.

 

[bricol]

I still remember a rather scary run from a factory in Italy to a well known maker of cams in the bosses fast car, driven by an employee who fancied himself as the next Miki Biasion - he seemed to forget at one point the road we were on at that point was not a dual carriageway . . . I sat in the back on the return trip, making a colleague sit closer to the scene of the accident

Anyway - relative thin compared to diameter steel disc that needed to be flat - it could be off compared the centre line it rotated about, but it had to be pretty damn flat on the face to seal. It had been ground but was "wavy" to put it simply.

It had been done an mag table - which simply pulled it down against it, ground "flat" - when released, the internal stress popped back into a slightly distorted shape.

The road trip to the cam maker was because they would glue the disc down - it wasn't pulled flat against the table. Ground flat, really flat, while we wandered their facility. Worked perfectly.

 

[Arc Tourist]

@Arc Tourist depends what your doing. If you are only machining one face then your vice could be 10mm out of square and on the wonk and provided the bed, ways, tool and bearings are all bang on it’ll produce on flat machined face, which is all the op is looking for.
If you want the part to have a pair of parallel faces then that’s a different matter.

....................................

Fair enough.

 

[Erie Fred]

OK, it is for fret clearances, around .2 mm tolerence. The one he bought was SS tube to the dimensions above. Quite pricey..
We have found a machine shop that can deal with it,

One thing about this, I am getting to meet a whole new bunch of people.... One yesterday is a very respected Prof at four local music colleges and plays in a jazz band.

I wonder if Jimmy Page, Jimmy Hendrix, David Gilmore, Terry Cath, Eric Clapton, et all needed such accuracy ?

 

[smashweld]

guitar string are measured in thou, the difference between 8 thou and 9 thou string is noticeable, the difference between an 8 and a 12 is HUGE!

ok I know it's to do with higher tension for the same note on a thicker string that make's a lot of the difference, but still!

 

[KemppiFrog]

I wonder if Jimmy Page, Jimmy Hendrix, David Gilmore, Terry Cath, Eric Clapton, et all needed such accuracy ?

That they use(d) certain makes of guitar might be an answer..

 

[Misterg]

I wonder if Jimmy Page, Jimmy Hendrix, David Gilmore, Terry Cath, Eric Clapton, et all needed such accuracy ?

The accuracy that [I think] were talking about here is in tooling used to check or level the frets. The requirement isn't for accuracy per-se, but for absolute uniformity.

A fret board needs a subtle curve along its length so that you can hold a string down onto any fret without it touching any further along (and causing buzzing, etc). One way to achieve this is to straighten the neck and then lap the top surface of the frets to a smooth cylinder or cone (to take into account the curve of the frets across the fretboard). This matches all of the frets to each other, but also creates a flat on the top of each fret which is no good either (you don't get a clean note). So each fret then needs to be restored to a rounded profile without changing the height established in the first stage. The curvature of the neck is then adjusted to have a slight forward bow (typically 0.006" from straight over the length of the neck for an electric guitar - more for an acoustic) which gives enough 'relief' for all notes to play without the string hitting higher frets as it vibrates.

Certain players / playing styles favour a low 'action' (the height of the string above the fret) - Jimmy Page famously does. This can only be achieved if the process above has been carried out meticulously - so Yes, his guitar will have been set up to levels of accuracy that I would expect to exceed the figures here.

Yes, somebody has mechanised the process:

The Plek Station - Plek

The Plek Station - a highly flexible, high-accuracy machine designed for work with the entire range of fretted (and fretless!) stringed instruments...

plek.com

 

[Erie Fred]

That they use(d) certain makes of guitar might be an answer..

Made in a temp controlled tool & die shop to 20 millions accuracy ?