Monday, January 30, 2012

Hofner Colorama II restoration project (part 16) - making a new bridge

In the last blog post, we made a new nut for our vintage Hofner Colorama II. Also needing doing is an improved bridge.

The original one should've looked like this:

However, here's the (replacement) one I got on THIS guitar:

Apart from looking wrong (not necessarily a big problem), it has the wrong radius, wrong string spacing, and is not compensated in any way for proper string intonation.

The base is almost correct, dimension- and look-wise, so I'm going to keep it and make a new top.

First I get a brass bar:

Cut it to length to match the base:

Mark the position of the holes and hit them with a punch:

Now the tricky part for me, since I don't have a drill press - drilling the holes perfectly straight:

Holes done:

Now turned over to check how close I got. Not bad.

Quick check with the base before taking this any further:

Sides are now marked with a 9.5 radius gauge to match the neck:

The brass is now filed to shape, checking constantly with the radius gauge to make sure nothing is going horribly wrong.

And here's the bridge after that:

The guitar is then quickly strung up (I've been doing a few things in parallel here, so the guitar finish is done now - I'll do a post about that part soon), in order to determine how to shape the top of the bridge to intonate the strings correctly.

First, I put some little pieces of copper under each string. These are actually little cutoffs of thick copper wiring:

Then I check with a tuner and move the copper wires forwards or backwards until the strings are intonating properly, then mark the position with a pen.

After that, I remove the bridge from the guitar and mark it with a couple of lines that will more or less cut through the six marked positions. There's a certain amount of compromising going on here, but it should still end up giving acceptable results.

After that, I start to shape the bridge using fairly fine files:

Giving us this basic shape:

Then I start finishing it, starting with 400 grit sandpaper and going up to 2000 grit:

Finally I hit it with rubbing compound:

For the sides and back, I put the sandpaper on a flat surface and move the bridge itself. Other than that, it's the same finishing process, from 400 grit to rubbing compound.

And here's how it looks after that:

Finally some slots are added to keep the strings in place:

The aim was to follow a similar style to the bridge that would've come with the guitar originally, while correctly compensating it for an unwound G string (the original would've been shaped for a wound G string). I think it came out OK.

Sunday, January 15, 2012

Hofner Colorama II restoration project (part 15) - making a new nut

The old nut on our Hofner Colorama II was in a terrible state. It was too shallow and had a piece of card underneath it in order to raise it up. Additionally the bottom was not flat.

Here it is:

I have no reason to trust this nut at all, so I'm not going to use it as a template for the new one.

So here I am sanding a new piece of bone down to the right thickness using a piece of coarse sandpaper set on a flat surface:

Then cutting the bone to length:

Here I’m checking it fits nicely into the nut slot:

Before I can continue, I need to make up a new half pencil, since I appear to have misplaced my old one.

So we take a normal pencil:

Slice it down the middle (watch your fingers):

Superglue the lead into place (optional, but I find it a good idea, since there’s nothing really holding the lead in place at this stage):

Remove superglued finger from pencil (again, optional):

Sand pencil flat:

And then I usually put some Sellotape (Scotch tape) along the bottom of the pencil to stop from getting carbon all over everything.

Next I draw a line along the new nut, using the frets as a guide:

I like to then draw a second line a little higher as a kind of secondary guide, so I fit something nice and slim under the pencil and draw another line, as follows:

Then I sand the nut down to very close to the higher line:

Mark the position of the slots using my nut slot guide template thingy:

Then file the nut slots using nut files. I file down to somewhere between the two lines, trying to make sure I end up with the same distance from the BOTTOM of the slots to the lower line. Also I file at a slight downward angle so that the slots will be lower at the end closer to the tuners. This ensures that the strings make contact at the very front of the nut.

The idea is to get them as close as possible to the lower line without going over. Once you do that, you’ve gone too far. I prefer a little bit of a buffer, since I can always remove more material from the bottom of the nut if it’s too high, but once I go too low, it’s time to make a new nut.

I then round off the back of the nut a little and polish it up using various grades of sandpaper. And here’s the final result:

Compared to the old nut, I’m sure you’ll agree it’s a bit of an improvement:

Sunday, January 8, 2012

Hofner Colorama II restoration project (part 14) - leveling and crowning the frets

The neck on this Hofner Colorama was originally quite badly back bowed, as shown here:

In an effort to rectify this, we’ve tried three different approaches, as follows:

1. While re-radiusing the fretboard, more pressure was applied towards the middle of the neck in order to remove more fretboard material in that area. This would not straighten the neck, per se, but it would reshape the top of the fretboard in such a way that its top would end up being flatter.

2. When refretting, the fret slots were widened. When frets are forced into narrower slots, this has a tendency to force the neck to back bow, so we wanted to avoid this at all costs. The slots are still narrow enough to grip the new frets, but are certainly not overly-tight.

3. Obviously the truss rod nut was slackened as much as possible. In fact, even with the nut removed, the neck still maintained a back-bowed shape. It was noticed that the washer under the nut was wedged into place, and it was suspected that it might be preventing the truss rod from properly slacking off. In other words, when the truss rod nut was tightened, the truss rod threads would pass through the washer, but when the nut was loosened, the threads might get stuck in the washer, leaving the truss rod in a tensioned state.

After some time, the neck appears to have straightened out enough that we can consider doing a fret level and crown.

First, we tape off the fretboard, leaving the frets themselves exposed:

Then we find something nice and straight with a flat bottom. Don’t assume straight tools are actually straight, by the way. This spirit level has been confirmed as being straight enough for this job, and 400 grit sandpaper has been stuck along the bottom edge.

We then mark the frets with a “Sharpie” pen or similar:

Then we run the leveling tool up and down the fretboard, parallel to the neck, making sure to keep it straight, and giving each area (left to right) the same amount of attention.

It soon becomes evident which frets are sitting high/low compared to others. We need to keep doing this until the top (center line) of the black marks is gone on every fret:

Next, we make the frets black again, and run a radius sanding block up and down a few times until the tops of the black marks are gone on every fret again. This is to ensure we haven’t inadvertently reshaped the curvature of the frets in the previous step.

Now we blacken the frets for the last time and use a needle file to file the edges. Here I’m using a fretboard protector for a little bit of extra protection:

What we are doing here is rounding the edges of the frets again. However, we need to make sure that we don’t affect the heights of any of the frets, so we leave a thin black line along the center of the frets, as follows:

Next we run some thinner sandpaper up and down the frets briefly to help round the frets just a little more. I’m actually using a 1600 grit Micro-Mesh Soft Touch Finishing Pad from Stewart MacDonald (

Finally, some steel wool is used to polish up the frets a bit (I’m using 000 here, although 0000 would give you an even shinier finish):

And here’s the end result. A super-flat, shiny fretboard. I can’t wait to use it.