Having trouble finding a radius sanding block for my bass

[SC Bassboy]

Hello everyone.
Recently I purchased a used Warwick fretless and have decided I want to resurface the fingerboard. As with most things German made it has proved to be a challenge to find the tools/information I need to accomplish the work. The fingerboard has a 26" radius and I've Googled till my finger tips hurt trying to find one for purchase online. Starting to think I will have to buy a precision ground flat sanding rail and hope for the best. Does anyone know where I can buy a 26" radius sanding block?
Thanks!

 

[Gilmourisgod]

If they exist at that radius, I've never seen one. It may be possible to "cove cut" one yourself on a tablesaw, or have somebody do it for you. It's kind of a scary cut, I did it once, and it made me nervous! There are wood radius beam vendors on EBay, might be worth asking if they can make one for you, should be simple enough on a CNC.

 

[SC Bassboy]

If they exist at that radius, I've never seen one. It may be possible to "cove cut" one yourself on a tablesaw, or have somebody do it for you. It's kind of a scary cut, I did it once, and it made me nervous! There are wood radius beam vendors on EBay, might be worth asking if they can make one for you, should be simple enough on a CNC.

That's kind of where I'm at with this. Either having a machine shop make me one or do it with the flat rail. I've got multiple Warwick 5 string basses and they all have the same radius so it would probably worth my money to get a custom one machined so I can level my own frets too.

 

[Jeff Siddall]

Any single radius fingerboard with string spacing wider at the bridge than the nut is imperfect by definition. Rather than trying to create a "perfectly imperfect" radius, I recommend your second idea of using a straight sanding beam, being sure to sand along string paths. That will get you to an ideal fingerboard shape even better than what they made in the factory.

If it's hard to wrap your head around the geometry, have a look here for some good images of what happens, and why I chose to never build a single radius fingerboard:
Compound Radius: Explained | stewmac.com

 

[Bruce Johnson]

To true up the surface of a fretless fingerboard, or to level frets, you don't need a radius block, and really shouldn't be using one. Radius blocks are used for shaping the radius on a new flat fingerboard blank.

Truing the surface of a fretless fingerboard should be done with a long narrow flat sanding beam, following the string paths. We go over the geometry and procedure in mind-numbing detail in this thread:

Even fretless fingerboard levelling tips

Leveling frets is a similar process, best done with a long narrow flat beam. It can be a metal beam with sandpaper on the bottom, or a long flat grinding stone.

 

[SC Bassboy]

Any single radius fingerboard with string spacing wider at the bridge than the nut is imperfect by definition. Rather than trying to create a "perfectly imperfect" radius, I recommend your second idea of using a straight sanding beam, being sure to sand along string paths. That will get you to an ideal fingerboard shape even better than what they made in the factory.

If it's hard to wrap your head around the geometry, have a look here for some good images of what happens, and why I chose to never build a single radius fingerboard:
Compound Radius: Explained | stewmac.com

Yeah, I've read several threads about leveling the fingerboard last weekend. My wife found me in a closet mumbling craziness about hourglasses and paraboloids. The theory makes sense for sure, I'm just a little nervous about it as this is a "golden era" Warwick and I would hate to FUBAR the fingerboard. Sanding the string paths seems simple enough but most the threads I've read sort of gloss over blending everything together afterwards. For the record the local luthier is super backed up and can't get to it till the end of the year. You guys don't even want to know what it would cost to send the neck back to Germany to have Warwick do the work . Anyway, I've already bought a straight sanding beam so I'm invested.

 

[Bruce Johnson]

Yeah, I've read several threads about leveling the fingerboard last weekend. My wife found me in a closet mumbling craziness about hourglasses and paraboloids. The theory makes sense for sure, I'm just a little nervous about it as this is a "golden era" Warwick and I would hate to FUBAR the fingerboard. Sanding the string paths seems simple enough but most the threads I've read sort of gloss over blending everything together afterwards. For the record the local luthier is super backed up and can't get to it till the end of the year. You guys don't even want to know what it would cost to send the neck back to Germany to have Warwick do the work . Anyway, I've already bought a straight sanding beam so I'm invested.

Summon up your courage and follow our directions! Truing up a fretless fingerboard isn't hard to do, once you understand the geometry and why it needs to be done that way. Take your time and do it right. We'll help if you have questions.

 

[Arie X]

for roughing, it's highly possible to attach psa backed sandpaper to an un-damaged portion of it (like the upper registers) and use that to duplicate the radius into a new block. depends upon how f'd up the fretboard is though. radius blocks don't need to be that long anyway. a little time consuming, but it works.

fine tune the board with a flat beam along the string paths.

 

[rudy4444]

That's kind of where I'm at with this. Either having a machine shop make me one or do it with the flat rail. I've got multiple Warwick 5 string basses and they all have the same radius so it would probably worth my money to get a custom one machined so I can level my own frets too.

If you want to make a radius board for yourself I have a photo and some instructions in post #28 here:

30” Scale Compact Semi-acoustic Fretless Bass Build

 

[Bruce Johnson]

About 25 years ago (!!) I made up a whole set of my own radius blocks, because I didn't want to pay the price for the commercial ones. Back in those days, Stew-Mac was about the only place you could buy them. They sold the cast resin blocks, and they were fairly expensive. Then, they started selling the machined maple radius blocks, which were more reasonably priced. Then along came the extruded aluminum ones, which are expensive. And now, some imported extruded aluminum ones which are cheap.

I made my set from MDF. They are made up of a stack of pieces of 3/4" MDF held together with two long bolts. I made up the first one by hand layout with a beam compass, working the radius carefully with files. Then I used that first one as a template, making up a bunch more of them with a router and a bearing bit. Then stacked them all up to make a radius block of whatever length I wanted. I made maybe 8 of them of the radiuses that I needed. They worked great. I still have them, but I don't think I've used any of them in 20 years.

Some years back someone gave me a whole box load of the Stew-Mac maple radius blocks. They work fine, but I don't use them for much of anything these days. I radius the fingerboards of my basses with a router in a special fixture, and I true them up with long flat sanding blocks. I level my frets with a long beam that I made, fitted with abrasive stones.

 

[tchristian]

I made a swinging cradle for the router. The block is laminated MDF. I move the block incrementally (between light cuts) between the spacers at the base. The aluminum side rails on the block may be redundant. A lot of effort for a single block I used on an abominable truss rod replacement job. Also, the jig would be awful tall for a 26" radius.

 

[bdplaid]

Any single radius fingerboard with string spacing wider at the bridge than the nut is imperfect by definition. Rather than trying to create a "perfectly imperfect" radius, I recommend your second idea of using a straight sanding beam, being sure to sand along string paths. That will get you to an ideal fingerboard shape even better than what they made in the factory.

If it's hard to wrap your head around the geometry, have a look here for some good images of what happens, and why I chose to never build a single radius fingerboard:
Compound Radius: Explained | stewmac.com

Brilliant!

 

[bassdude51]

I'm finding 20" with StewMac. 26"! WOW!

(20" is in this link.)

8" Radius Blocks | stewmac.com

 

[Matthijs]

Yeah, I've read several threads about leveling the fingerboard last weekend. My wife found me in a closet mumbling craziness about hourglasses and paraboloids. The theory makes sense for sure, I'm just a little nervous about it as this is a "golden era" Warwick and I would hate to FUBAR the fingerboard. Sanding the string paths seems simple enough but most the threads I've read sort of gloss over blending everything together afterwards. For the record the local luthier is super backed up and can't get to it till the end of the year. You guys don't even want to know what it would cost to send the neck back to Germany to have Warwick do the work . Anyway, I've already bought a straight sanding beam so I'm invested.

If the bass i reasonably playable now, you should be allright without the radius block. You are not going to remove a lot of wood. I’m kind of OCD in using a radius block to round off the board after I’ve done the string paths, but for a one time leveling on a good bass you should be allright.

 

[Matthijs]

And also: 26” is pretty flat. So the risk of you seriously altering the radius while sanding with a straight profile is small.

 

[smtp4me]

To true up the surface of a fretless fingerboard, or to level frets, you don't need a radius block, and really shouldn't be using one. Radius blocks are used for shaping the radius on a new flat fingerboard blank.

Truing the surface of a fretless fingerboard should be done with a long narrow flat sanding beam, following the string paths. We go over the geometry and procedure in mind-numbing detail in this thread:

Even fretless fingerboard levelling tips

Leveling frets is a similar process, best done with a long narrow flat beam. It can be a metal beam with sandpaper on the bottom, or a long flat grinding stone.

I read the first several pages in the thread you linked to. Great stuff! I put a CA glue finish on my fretless and started sanding with a matching radius block. I realized (completely by accident) that the block was taking more off the finish towards the middle of the fingerboard than towards the edges, as I moved up higher towards the body. Wound up using a straight edge.

It all makes sense - the fingerboards of stringed instruments do not require a radius, the radius just makes playing more comfortable. To get the most consistent leveling is to sand along the path of each string. You could even say that since each string has it's own slot in the nut, and if the bridge allows separate height adjustment for each string, then balancing the level from string to string is not really necessary, especially in the case of a fretless where vibrato is done by rocking the fingers instead of bending the strings.

 

[dwizum]

Part of the challenge of being "new" to some things is that you miscalculate the parts of the process that are important, and/or you get nervous or anxious about the "wrong" parts.

I think that's what you're doing here. I'm paraphrasing here, but you seem to be OK with the string paths part but you're worried about blending everything afterwards.

Getting the string paths perfect (with a flat sanding block or beam) is the important part. Blending everything together afterwards is not really that important!

In other words, it sounds like you are already comfortable in understanding how to do the important part, and you're getting nervous about not understanding the part that's easier and doesn't even really matter all that much.

Go re-read the threads, ask specific questions if you are really stuck, and have at it. All you need is a flat beam. Don't get hung up on a radius block. The flat beam will get your string paths perfect and it can also be used to knock off the hard corners between the facets to smooth things out afterwards.

 

[Neill Graham]

Hello everyone.
Recently I purchased a used Warwick fretless and have decided I want to resurface the fingerboard. As with most things German made it has proved to be a challenge to find the tools/information I need to accomplish the work. The fingerboard has a 26" radius and I've Googled till my finger tips hurt trying to find one for purchase online. Starting to think I will have to buy a precision ground flat sanding rail and hope for the best. Does anyone know where I can buy a 26" radius sanding block?
Thanks!

If you really need a sanding block to resurface a ready made fingerboard, I think you could just make one yourself out of a piece of softwood like pine or spruce. I made an electric upright bass last year and rounding the fingerboard was actually one of the more pleasing tasks. It would be easy enough to take a 6 inch long piece of spruce 2 x 4 and cut in your concave curvature along the length with a rasp or file since your radius is so flat. You can copy the correct radius from your guitar with a contour gauge onto a piece of cardboard making a convex curve, cut it out and use this to check your concave radius as you are shaping the channel in the wood block. When you are satisfied with the channel, place a larger 6x6 piece of sandpaper onto the block over the curved channel holding it lightly on the sides while you press it down on the fingerboard and run it up and down using the paper grit of your choice. It can be very satisfying.

 

[Gilmourisgod]

I've hand-radiused two boards now, and it's a workout on hard woods like Bubinga. Even with a stiff radius beam, it's really hard to avoid "dishing" the center of the fretboard. I don't know if that's just because as you move the beam back and forth, the middle get exposed to more length of sanding strip, or just the mechanics of the human body imperceptibly applying more pressure at the middle of a stroke. On the second build, I kept reversing direction of the strokes, alternating between straight beam along the string paths and then "blending" the resulting flats with the radius beam, but never really settled on the perfect technique. My current build, I just cheated and had LMI radius the Ebano board for me. I'm still using the radius beam to rough radius my MOP inlays and black CA glue gap filler, not sure how you would do that accurately with a straight beam.

 

[rudy4444]

I plane off some of the fretboard surface at each side to pre-form the "radius" and eliminate a lot of the hand sanding grunt work. Keeping track of exactly what your surface looks like is easy to do by adding pencil squiggles along the face of the board. You can instantly see where you're removing material and how far you need to go before you've reached your target radius.