'Vintage correct' or not

John_A

I recently bought a guitar body and tried to bit my Callaham bridge and because the route for the trem block is slightly off-centre it doesnt fit.  If aligned centrally the block catched on the top edge of the block route.

Now the Callaham block is a few mm wider than a standard fender, which does 'just' fit, but if the bridge is aligned with  the centre-line of the body there is about 1mm clearance at the top and 3-4mm at the bottom, so to me, the lock route is out of alignment.

The measurements should be as follows according to a Fender blueprint, and if they were the Callaham block would fit.

Trem route length 3.125"

Top to centre 1.375"

Bottom to centre 1.75"

The manufacturer of the body is stating "Our body is taken from an actual original, most people want a copy of an original." and not taking my argument on board which is:

The Callaham trem WILL fit a vintage correct route if it is sized/aligned correctly

The Fender trem sits off-centre in your route, it shouldn't, it should have equal clearance both sides.  It does 'fit' but only just

The reasons for this is 1960's manufacturing tolerances.  The body you are copying is not quite right

With CNC you should be able to make a '60's body as-per design, not just take a copy of one that want quite right to begin with

Thoughts? 

ICBM

Are you basing the centreline of the body on the body dimensions, or where the centreline of the neck is projected to when the neck is fitted? These are not necessarily the same thing (although they should be, on a Strat) but obviously if there is a difference then the bridge needs to be aligned with the centreline of the neck, not the body.

John_A

As you say, should be the same thing, the centre-line on a strat should run from the edge of the neck pocket, all the way through the to the strap button mount.

Basically the question is what is 'correct' as per the plan, or as-per one particular 1960's body?

ICBM

Correct is as per the plan. If you copy an individual example you have no idea what part of the tolerance range any dimension is in. This is a major problem with reverse-engineering anything from a manufactured example, and is often why copies are not as accurate as the real thing, unless the copyist has access to the same calculations the original designer did when specifying the tolerances. Basically it's a sort of engineering Chinese Whispers.

My dad was a metrologist (measurement science engineer) and drummed this into me, for what it's worth!

OK, a Strat body is not exactly precision engineering... but since one of the major unknowns is the hand-sanding of the body edges, there's no guarantee that the centreline of the finished body quite matches the centreline of the machined routing any more.

Funkfingers

The blueprint is a statement of intent. It is no guarantee of the end result after a sequence of template-guided routing operations.

Another consideration is how the unfinished wood as been treated after the shaping. Moisture content variations can play havoc. Wood can warp.

Bottom line. You can always cut more wood away. You cannot easily put it back.

John_A

Funkfingers said:

The blueprint is a statement of intent. It is no guarantee of the end result after a sequence of template-guided routing operations.

Another consideration is how the unfinished wood as been treated after the shaping. Moisture content variations can play havoc. Wood can warp.

Bottom line. You can always cut more wood away. You cannot easily put it back.

Agree, but surly it's the right place to start rather than reverse engineering a body that was made from it

poopot

Where’s the body from out of interest?

Nomad

ICBM said:

Correct is as per the plan. If you copy an individual example you have no idea what part of the tolerance range any dimension is in. This is a major problem with reverse-engineering anything from a manufactured example, and is often why copies are not as accurate as the real thing, unless the copyist has access to the same calculations the original designer did when specifying the tolerances. Basically it's a sort of engineering Chinese Whispers.

You can also think like a designer and infer the intended nominal size from the measured size. it's relatively rare that something is designed with grotty nominal numbers, although they can exist as a result of geometry (like the length of one side of a triangle is nearly always grotty to multiple decimal places).

The Strat blueprint is quite interesting in that the main shape is defined in fractional inches while details like cavities are in decimal inches. The default tolerance for the fractions is +/- 1/32" (0.79375mm), but +/- 0.010" and +/- 0.005" for 2 and 3-place decimals (0.254mm and 0.127mm). So, they allow for more slop in the body outline than in the cavities. Also interesting is the rather odd size of the radius at the left-most side of the control cavity - 0.438". It's actually a rounding of 0.4375", which is exactly 7/16", indicating that the cavities were still conceived (at least in part) in fractional terms, and converted to decimal to apply the tighter default tolerances.

It's notable that the curves of the body (horns, bouts, waist) are undefined apart from some convex extremities - there are no radii, the positions of the concave extremities have no dimensions, and the distances of the extremities of the horns from the centre line are undefined. Probably hand drawn or traced and intended to be transferred onto a template directly - there's a note at bottom-left which says "[illegible] of body may be taken from dwg".

ICBM

Nomad said:

The Strat blueprint is quite interesting in that the main shape is defined in fractional inches while details like cavities are in decimal inches. The default tolerance for the fractions is +/- 1/32" (0.79375mm), but +/- 0.010" and +/- 0.005" for 2 and 3-place decimals (0.254mm and 0.127mm). So, they allow for more slop in the body outline than in the cavities.

Exactly, so it's the cavities which should be used as the reference for the bridge position, not the body outline.

Nomad said:

there's a note at bottom-left which says "[illegible] of body may be taken from dwg".

"Perimeter", I think.

Nomad

ICBM said:

Exactly, so it's the cavities which should be used as the reference for the bridge position, not the body outline.

Yes, I'd probably draw lines from the ends of the neck and bridge cavities and find the mid-point (they're good to within 5 thou). If they're all parallel, and if the derived centre line results in the bridge being better placed in the cavity, that would be a good sign. I'd be tempted to then fit the neck and see how that all matches up as well.

ICBM said:

  Nomad said:

there's a note at bottom-left which says "[illegible] of body may be taken from dwg".

"Perimeter", I think.

Aye, that's it.

ICBM

Nomad said:

Yes, I'd probably draw lines from the ends of the neck and bridge cavities and find the mid-point (they're good to within 5 thou). If they're all parallel, and if the derived centre line results in the bridge being better placed in the cavity, that would be a good sign. I'd be tempted to then fit the neck and see how that all matches up as well.

I would fit the neck - probably just a with a clamp for now - and use a straightedge to extend the sides of it to the bridge position, and see whether centring the bridge on those lines fits the cavity correctly.

Because at the end of the day, it's the alignment of the bridge to the neck that really matters, nothing else. The only other thing of any real importance is whether the pickup polepieces line up with the strings, and there will be a little leeway in the position of the pickguard to achieve that.

John_A

Here's some pics that highlight the issue.

First pic shows centre-line of body, which aligns correctly with the pre-drilled bridge mounding holes

The next pic shows the block in position



You can see the problem seems to be that the trem block route in the body is of-centre, as-per the original '60's body 

My argument is this is wrong and should have been corrected, the manufacturer argues that it's 'vintage correct' and this is how people want them

ICBM

John_A said:

You can see the problem seems to be that the trem block route in the body is of-centre, as-per the original '60's body 

My argument is this is wrong and should have been corrected, the manufacturer argues that it's 'vintage correct' and this is how people want them

The tremolo cavity is not aligned correctly with the bridge screw holes and the pickup routs, and thus (I expect, since the front routing will be done at one go) the neck pocket. It means that if it was accurately copied from an original, that body was mis-routed.

I didn't realise the pivot screw holes were pre-drilled. If they're in the right place relative to the neck, you definitely don't want to plug and redrill them - even if that was really a good idea at all. The only sensible solution here is to enlarge the end of the cavity by just enough that the block clears it. The problem then may be that the cavity is slightly visible at the arm end, which it shouldn't be.

John_A

Yes gone for the option of enlarging the cavity very slightly.  The pivot screw holes are only pilots, but they are in the right position relative to the neck pocket, and everything else is apart from the block route.

I agree that if the original is like this it's wrong too, however the manufacturer won't move from the position of 'that's how people want them, and exact copy of an original'

They are charging me to enlarge the route because of my 'non-standard part'  

As I said, a genuine Fender blockwill just about squeezes in there but its clearly off-centre, here it is with a Fender block

ICBM

Doh. My mistake, there's an easier way - file down the end of the block slightly. If you've got a bench vice and a large file it shouldn't take too long - it doesn't need to be pretty, since you won't see it when it's in the body!

John_A

ICBM said:

Doh. My mistake, there's an easier way - file down the end of the block slightly. If you've got a bench vice and a large file it shouldn't take too long - it doesn't need to be pretty, since you won't see it when it's in the body!

I thought of that already   the pic above is the Fender block, the Callaham would need even more material removed and it would be getting too close to the string hole for my liking.  I'm getting the body routed professionally so should be a neat job after a bit of touch-up paint.

poopot

@John_A  have you measured the depth of the neck pocket yet? The body I got from them for the swampy build had too shallow a neck pocket... they’re not in “spec” at all tbh!!!!

John_A

poopot said:

@John_A  have you measured the depth of the neck pocket yet? The body I got from them for the swampy build had too shallow a neck pocket... they’re not in “spec” at all tbh!!!!

Yes I have, the neck pocket seems fine, how do you know who I'm talking about

Just actually got the body back from them, they charged me £35 to "adjust the trem route to accommodate a non-standard trem"  To be fair they made a very good job of it, and strangely enough I've had the calipers on there and the trem route is within a hair of the 3.125" it should be according to the blueprint

poopot

John_A said:

poopot said:

@John_A  have you measured the depth of the neck pocket yet? The body I got from them for the swampy build had too shallow a neck pocket... they’re not in “spec” at all tbh!!!!

Yes I have, the neck pocket seems fine, how do you know who I'm talking about

Seen your other post with the candy paint job

In addition to the swampy body issue, i had another body from them where the neck pocket was 2mm too deep... http://a67.tinypic.com/21mx7xt.jpg
end of the board should have a gap under it!... USA neck!...

John_A

Ouch - did you complain about that?  and did you get anywhere?

DrBob

John_A said:

poopot said:

@John_A  have you measured the depth of the neck pocket yet? The body I got from them for the swampy build had too shallow a neck pocket... they’re not in “spec” at all tbh!!!!

Yes I have, the neck pocket seems fine, how do you know who I'm talking about

Just actually got the body back from them, they charged me £35 to "adjust the trem route to accommodate a non-standard trem"  To be fair they made a very good job of it, and strangely enough I've had the calipers on there and the trem route is within a hair of the 3.125" it should be according to the blueprint

I'm not sure if I've weighed in on this matter before if we're talking about who I think we're talking about I've had Two La Cab bodies and now a Strat body from them all of which needed the neck pocket deepening to bring the neck down to a level where it would work without having the bridge set so high that the adjustment screws are maxed out