build thread 5-String Aria Pro II SB1000/R150-ish bass

[JayT]

Wow, such great work - I envy your skills so am taking notes.

[Prostheta]

I was hunting around for some 4-5mm plywood, and I think I have enough to make a radius sanding caul. Basically, I drill a hole at either end, countersink, fit a machine bolt and tighten it with a washer and nut. A piece of string is tied between the two (an eyelet or using more nuts to secure), then twisting a rod similar to how you tension a bow saw to bring both ends up into a radius. It's pretty simple, but great for sanding in relatively straight concave contours.

[Prostheta]

5 hours ago, ScottR said:

I can't say I've ever run across anything like that. Is it just really thin?

Your wood choices are going to look great with finish on them. What is your plan for that?

SR

 

I was thinking something a lot lighter than the poly used on the originals, preferably something thinner like an oil. The tests I've done on cutoffs haven't had the same deep wetting effect I've been after though so I might have to try a few other ideas. I might even go with shellac, which gives me a good excuse to de-dust the room after all this sanding! That would also make decal application simpler and cleaner.

[Bizman62]

@Prostheta that sanding caul is brilliant!

[Prostheta]

15 hours ago, JayT said:

Wow, such great work - I envy your skills so am taking notes.

Envy is not a good thing! Skills are meant to be conveyed, so if there's anything specific here you'd like me to expand upon and help you develop, drop the question. Happy to help float all boats. All I do is use what I was taught and developed through practice and application. This isn't a one-way street, so by all means, ask away man.

[Prostheta]

I spent a little time last night and this morning refining the heel transition contours. Having an actual SB-1000 on the bench is fantastic for comparison. They're the same as on my RSB-600 (passive SB-type bass with a 4-in-line headstock, different neck taper) anyway, but still.

The main changes are on the bass side cutaway, bringing the neck profile cross-section in closer so that it tucks away more tightly into the cutaway corner. Feeling for corners and flat spots helps bring this out into a more consistent and even contour. The same applies to the treble side cutaway, with a more gradual transition. This 0ne is most important as it's intended for use, whereas the bass side is mostly cosmetic. This transition refinement also brought the immediate body-to-contour transition angle in to the small 45° drop I mentioned earlier, which can be seen in the central laminates between the wings. This forms the basis of where the contour is "forced" and the rest is blended into that. Again, tactility is the key, so plenty of sanding with 80 to shape, 120 to smooth for checking with the fingers and repeating until you have to regrow the skin on your fingertips. I might bring back the bass-side a little bit, however this is something my fingers will tell more than my eyes.

[ScottR]

19 hours ago, Prostheta said:

I was hunting around for some 4-5mm plywood, and I think I have enough to make a radius sanding caul. Basically, I drill a hole at either end, countersink, fit a machine bolt and tighten it with a washer and nut. A piece of string is tied between the two (an eyelet or using more nuts to secure), then twisting a rod similar to how you tension a bow saw to bring both ends up into a radius. It's pretty simple, but great for sanding in relatively straight concave contours.

This is a new one to me. I like to take the foam sanding blocks that come with micromesh and adhere a flat piece of .030" polycarbonate to one side. That makes a good stiff surface on a block that can be rolled into a variety of radii merely by squeezing. It's a little trickier to hold a constant radius like yours.......but then I pretty much never use a constant radius. Another thing you mentioned that I meant to endorse was the use of the rubber spindle sanding cores as sanding blocks. I often use the sleeve as well. Extremely useful for contouring smoothly.

SR

[Prostheta]

Turns out that I don't have any Flexiply or thin plywood anyway! Oh well. I was sure there was some around here somewhere....

The thinking behind these sanding cauls is that you don't need to apply any sort of pressure or grip to maintain them in their shape. Besides them allowing you to concentrate on the sanding rather than keeping them in form, the biggest advantage is consistent pressure; a caul that is naturally trying to unspring will apply greater sanding pressure on the ends of the caul causing uneven results. Similarly, the opposite can happen if you slightly overtension it in your hand so that the apex works more than the rest of the surface.

Talking of rubber spindle sander drums....I was thinking that perhaps a modified rubber sanding block might form the basis for a new radius sanding caul, or maybe a piece of HDPE. I haven't made one for ages, and the last one just got "left" at a workplace. Talk about stealing ideas!

Another tool that I was rolling over in my head during this project was Noel Liogier's mini palm rasps. I'm sure those would appeal to yourself, Scott!

https://www.hand-stitched-rasp-riffler.com/en/rape/21-mini-rape.html

I also believe they would be perfect for the hard skin on one's feet.

[ScottR]

True on both counts....or all three or four counts.

SR

[Prostheta]

The bridge should drop in any time this week. Checking with a straightedge, the strings will ride over the pickup around the same as one would expect a bass ramp to allow. That's right on the nose, and I was super worried about that, hence the D-style bridge optioning. I've gone A-style purely as I like the large singular mass locked down to the body. In all likelihood I will look at whether I can bolt the bridge to the body using threaded inserts to guarantee strong coupling.

So I need to make myself a brass nut. From a chunk of 10mm brass, I cut a block around 7-8mm thick and got around to filing it to size using a pair of machine files. If you want a good tutorial on use of files, head over to Clickspring on YouTube whose filing is really something to behold.

 

So this is where the block is right now. The four main faces are square to each other. I started with the two faces either side of the 10mm thickness of the stock (this will be the height of the nut) and cleaned them up with by double cut file. Not to change their dimension or plane, but to smooth out. This was done with the file on the workbench and a few runs of the workpiece over its surface; pressure should be consistent and even, not to either end or side otherwise it could go lopsided. Here it only needed light pressure to cut the surface.

Once those were clean, I started on one face of the nut. This has to be established exactly square to both adjoining faces. In my case, this was the cut end of the stock which was already fairly flat and square. All I had to do was to clean and adjust it slightly, checking with a mini machinist's square and that the reflection when laid on a mirror shows straight parallel edges.

The next step is to take a measurement from the inside of the nut slot. I use an old pair of digital calipers with a position lock knob for this. Using the internal measurement jaws to take the slot width, I lock off the measurement and use the external jaws as a scribe from either side of the block. Before scribing, I use a permanent marker as a poor man's Dykem to highlight the scribe line. The block is locked off in the vise, and I draw file the face down to these scribe lines.

[Prostheta]

A few trips from the bench to the bass, and the block was brought down to a perfect fit. There's a little waste burr from filing the nut slot square, but otherwise this is on.

[Prostheta]

I cleaned it up. The nut isn't sitting straight in this photo (I'm an idiot for leaving it like that and not noticing) but you can get the idea.

[Prostheta]

Getting the exact placement for the bridge bolt inserts is crucial for the bolts to lay correctly within the countersinking. Even though it's only a visual point for the most part, it's best practice to treat it with the same precision as critical work.

I struck a line at 90° to the centreline, dry fitted the bridge and made pencil marks through the mounting holes. Ignoring the first marks, I redrew the centre points of the three mounting holes at 36mm distant from the centreline. This shows that dry fitting the bridge was lightly offset to the bass side by a fraction of a mm. If I can make my starting points for the drill within this sort of tolerance, we're golden (just like all the hardware, @RestorationAD).

[RonMay]

@Prostheta, Precision is as precision does.

I have found in many things that making sure all the small details are as good as you can ;make them, the rest will follow.

In target shooting, if you aim small you miss small. I think it's the difference between a guitar builder and a master guitar builder.

Ron

[Prostheta]

The threaded inserts I'm using are intended for light metals and plastics, with a self-tapping slots that will drive nicely into hard woods like Maple mostly by cutting rather than displacing material. The outer thread is near as damnit a 1/4" whilst the internal diameter of the body is (as best as I can read it with calipers) 6mm.

After marking the locations with a machinist's carbide scribe (better and cheaper than an awl), the holes were drilled out to 6mm using a lip and spur bit to ensure they're clean. I have a three entirely separate sets of drill bits for this sort of work, which sounds excessive, but one is for general hole making where accuracy and cleanliness are not a priority. These are also used if the material is less than ideal and will wear the bits prematurely such as plywood. My second set (Würth Zebra HSCo) is for clean and accurate hole making in materials that might wear the bit. My "best" set are M2 HSS with a modified flute geometry that works better in pillar drills because of the rake causing the likelihood of self-feeding and wallering drilling by hand. I digress.

Three holes drilled to 15mm depth.

 

Lightly countersunk to give the threaded inserts an easy start on centre.

 

Loading up one insert backed up with a second on a bolt, locked finger tight. The slot in the insert is intended to allow any waste material from the self-cutting threads to clear. The whole thing was advanced into the hole slowly using a hand drill on low speed. The weight of the drill does all the advancement work, something like 1/2 - 1 revolution per second. You only get to do this once, so being able to move your eyes from one place to the other to do checks instead of letting the work get ahead of you is vital.

 

Like that.

[Prostheta]

Infinitely better than wood screws. I've got some gold hex screws on the way, so I'll take a view on whether I prefer the black ones or those. I'm liking these as they are though.

[Prostheta]

29 minutes ago, RonMay said:

@Prostheta, Precision is as precision does.

I have found in many things that making sure all the small details are as good as you can ;make them, the rest will follow.

In target shooting, if you aim small you miss small. I think it's the difference between a guitar builder and a master guitar builder.

Ron

 

I'm no master, and I don't expect that I will ever be one, Ron! For me it's enough to be a guitar builder and to know the fact that there's always more to learn and to enjoy the learning experience. But hey, thanks man. I appreciate it.

[Prostheta]

I've got the option of through-body stringing with the A-style bridge. This was never an aspect of the original SB basses, however I'm tempted to throw in a set of five gold Hipshot ferrules on the back just to have the option. Bridge retention is perfectly adequate, however I know I can't not do ferrules now I've thought about it.

[Prostheta]

Okay, time to work on the nut a little. Since I last discussed this, I added a light angle to either end to match up with the neck taper, so now the nut sites correctly, is the correct length and needs bringing down to height.

This is a zero fret anyway, so there's less requirement on the nut's operation beyond maintaining string spacing. I established roughly where I wanted to bring the nut down to, locked in my calipers as I did previously and scratched in at the ends on both faces. Using the same brass fret pressing insert radius as used for the fingerboard, I scribed a radius on both sides. Time to get filing!

[Bizman62]

1 hour ago, Prostheta said:

Loading up one insert backed up with a second on a bolt, locked finger tight. The slot in the insert is intended to allow any waste material from the self-cutting threads to clear.

That's clever! I would have used a flat screwdriver on the slot, your method has two advantages.

[Prostheta]

Focus, you faaaa....ohwait, wrong place. Anyway, five minutes and we're there.

[Prostheta]

6 minutes ago, Bizman62 said:

That's clever! I would have used a flat screwdriver on the slot, your method has two advantages.

That's by design, not cleverness on my behalf  

[ScottR]

1 hour ago, Prostheta said:

I prefer the black ones

Me too. It adds just enough black to balance the black springs and rollers.

SR

[Bizman62]

1 hour ago, Prostheta said:

not cleverness on my behalf

Shh...

[Prostheta]

Quick update, installed inserts for the pickup also. Same size, same process.