Machining a flat surface

[KemppiFrog]

While I have done some lathe work, on my cranky old Sphere, very little experience on flat work.
Guitar friend is interested in duplication a gauge for measuring how flat things are.
Essential a bit of 300 x (50 x 25 x 3) mm SS tube with one side machined.
I assume a surface grinder would be the most accurate machine to use? Rather than a mill?

I have been surprised quite how close the tolerances are when fettling electric axes...
Any thoughts welcome.

KF

 

[hotponyshoes]

Tube is probably a bad starting point.
One reason is stainless won't stick to the magnetic bed on a surface grinder so you'll have to clamp it which will distort it..

Any reason why it can't be solid?
If it can then you'll find a ready made one easily enough.
Price will depend on exactly how flat you want

 

[KemppiFrog]

Thanks. The one he has is 3mm tube and looks stiff enough. Surely surface grinders also have vices?

Might visit an outfit locally that did some work for me a while back. The are amiable and often do stuff on classic car mechanics.

 

[Ali]

What are they trying to measure exactly? A picture of the existing one in use would be helpful.

 

[KemppiFrog]

I check this PM and get later.

 

[Porkypine]

I'd assume its some kind of fret level bar or gauge to see how straight the neck is ?

 

[voipio]

How about something like HSS Steel Flat Bar Strip Metal Plate Lathe Turning Tool? A piece 14 x 50 x 300mm will weigh about 1.6kg, and cost around £60:

www.ebay.co.uk/itm/196730288849

 

[Brad93]

Just buy a straight edge.

Tube is no where near straight to begin with, internal stresses and lack of rigidity will mean any machining causes it to walk all over the place

 

[BrokenBiker]

Tube won't really be straight, and even if you grind it, it won't really stay straight...straight edges are readily available and accurate

 

[Pete.]

Is the requirement simply for a flat face? Does it have to be super light weight?

 

[Arc Tourist]

I would also surmise that the flat surface required is for checking fret work.

 

[oldbikedavey]

Cerromatrix is your friend.....

 

[6ply]

Thanks. The one he has is 3mm tube and looks stiff enough. Surely surface grinders also have vices?

Might visit an outfit locally that did some work for me a while back. The are amiable and often do stuff on classic car mechanics.

I mostly use a magnetic vice / chuck in the surface grinder. Occasionally, I clamp a part in a steel vice and place this onto the magnetic chuck.

 

[Arc Tourist]

I mostly use a magnetic vice / chuck in the surface grinder. Occasionally, I clamp a part in a steel vice and place this onto the magnetic chuck.

Yes, but has the steel vice and its internal bed been ground for accuracy?

 

[6ply]

Yes, but has the steel vice and its internal bed been ground for accuracy?

Yes

 

[Pete.]

Yes, but has the steel vice and its internal bed been ground for accuracy?

That matters not at all. If the vice is holding the part the only thing that affects the work is clamping stresses and how good a condition the grinder bed is.

 

[KemppiFrog]

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.

 

[Talk]

300mm will harldy cover all the frets in one sweep, ragardless, a steel rule would even
do for this kind of thing, it is not critical and heights will be easily spotted.
In any event, the person cutting the frets and the slots for them will hold the key
to getting them right, else they should be in a different job.

 

[Misterg]

OK, it is for fret clearances, around .2 mm tolerence. The one he bought was SS tube to the dimensions above. Quite pricey..

It may be that, at the dimensions requested, it's for holding abrasive paper for leveling the frets (it sounds far too bulky to use it to check clearances).

For checking straightness, I use a straightedge from Wilko (RIP) that cost about £4!

This sort of thing, but ~450mm long:

https://www.amazon.co.uk/Faithfull-RULE1000-Aluminium-Rule-39-inch/dp/B000C750F6?th=1

0.1mm is enough to cause 'issues' if it's in the wrong place.

I know you've got it sorted now, but you could have considered fly cutting it on the mill if you wanted to go down that route.

 

[Arc Tourist]

That matters not at all. If the vice is holding the part the only thing that affects the work is clamping stresses and how good a condition the grinder bed is.

I would disagree. Having the bed of the vice as close to parallel as possible with the surface grinder bed, will provide a repeatable reference point if the part has to flipped or relocated in the vice; at least that's been my experience.