Arched Fret Slots on compound radius

[jfortenbery]

I'm pretty skilled w/ Partworks (Cut 2D). I'm brand new to Partworks 3D. I'm trying to project curves or arcs onto a 3D model. I then want to cut them like pockets, in that they don't extend from edge to edge and they will be cut the exact width of my end mill (.023 in).

Is there a function in Partworks 3D to do this ... or must I make the change in my model (Rhino). The problem there is it took me FOREVER to make the model. It would take me FOREVER and a day to figure out how to make the pockets.

I'm cutting fret slots in a fingerboard which is tapered and has a compound radius on the top surface.

Thanks in advance,
Jeff

[cmjohnson]

Why not take the simplest and most direct approach?

Cut the fret slots straight across. No need to arch the slot! In fact, you want a little
excess slot depth anyway as it gives room for any little shavings to fall into as you press the frets in. A slot that's the exact depth of the tang will often cause the frets to sit a bid high off the fingerboard.

Just cut the slots straight across. No Z axis movement required.

Another thing to consider is to cut the fret slots clean across the fingerboard, and then
laminate a thin strip of the same fingerboard wood to the ends to make your pockets.

I've done this, on ebony fingerboards, and the results are beautiful and perfect. I really
like the look and feel of a fretjob that takes the fret all the way to the edges of the fingerboard but the tangs are recessed and invisible, like with a bound fretjob.

CJ

[jfortenbery]

Thanks, CJ for the ideas. I've made fingerboards using these traditional methods, but I'm hoping to find improvements to the traditional way of doing things.

My thinking is that:

Flat slots in a radiused fingerboard weaken the fingerboard by removing more wood that necessary.

Binding a fingerboard is much more labor intensive than cutting pockets with a CNC. When I used a saw to cut slots, I didn't have any options but to bind or leave the tangs exposed.

Now that I have a CNC, I want to use it as a productivity tool and reduce the amount of labor in each guitar I build ... while maintaining or enhancing quality.

[cmjohnson]

When have you ever seen a fingerboard break at a fret slot? I submit that this rare (virtually non-existent) event is proof that a straight across slot is perfectly reasonable. It always has been. I've been building and working on guitars since 1986 and I've never yet seen a broken fingerboard.


Extra effort for no benefit = waste.


Binding just the sides of a fingerboard with a strip of excess fingerboard material is hardly what I'd call labor intensive. Once the strips are prepped, you glue them on the sides of the boards and trim them flush later after the glue is dried. It's a couple of minute's worth of work to do by hand at most.


CJ

Calculating 22 separate Z axis pathways will take much longer than all of this put together.

[jfortenbery]

CJ,

My concern about fingerboard strength ... which directly relates to neck strength ... isn't an issue of potential breakage. It has to do with neck integrity and stability ... same reason truss rods (adjustable or non-adjustable), carbon fiber inserts, laminations and the like are typically used in guitar necks.

It takes me a lot longer that two minutes to bind a fretboard. Maybe I'm just slow - actually, I KNOW I'm slow.

If I can program my router to start .0625 later, plunge .095, and stop .0625 early and thereby eliminate binding entirely ... that's a win for me.

A wise man once said ... Extra effort for no benefit = waste

[cmjohnson]

Well, I think that you are overthinking this a bit. The minimal material loss in the bottom of a straight fret channel on a radiused fingerboard still doesn't seem to be any sort of factor in overall neck stability.

I've seen quite a few 25 year old Ibanez guitars with very thin necks, made with
conventional slots, single truss rods, and no additional reinforcement, that are as stable
now as the day that they were made, and there really isn't a thinner neck design on
the market than those Ibanez guitars from the early 80s. If they're stable, and they are, then really there's no basis for stability concerns with any neck that is made from
good quality, well seasoned woods.

On the other hand, I've seen some really beefy, solidly made necks that warped, even though perfectly cared for, simply because wood will do what wood will do. If it's going to warp, you won't stop it from warping.

CJ

[RandK]

I don't know anything about Partmaker but surely it has something akin to 3d engrave or cut/follow a 3d profile.

The 3d geometry can be made by projecting 2d lines indicating the slots onto your 3d compound radius surface and then moving them down .080 etc (in Z for slot bottom) to accomodate your tang and sanding of the FB surface. For blind slots your lines would be trimmed short before projecting. I wouldn't recommend plunging to depth with blind slots so if your cam won't allow a depth of cut setting on this kind of toolpath just make another set of 3d profiles at -040 or something.

Radiused slots are a good thing.

[ger21]

I don't know anything about Partmaker but surely it has something akin to 3d engrave or cut/follow a 3d profile.

No, it doesn't.

[seansear]

the humidity changes and the wood swells. It's going to push the fret up. Trust me on this one. There's a reason the factories do not radius thier fret slots. Also, you need to have room for your glue to go. Or don't you glue your frets in ?

B

[RandK]

Neither of my CAM programs will post to Shopbot. That's what the OP has right ? If you can use G-code I'll be happy to program that if you send me or post the profiles, it's a few minutes of work. Maybe you could post the profiles on the Shopbot forum and ask somebody with Vectric or whatever to program that for you. They had a great forum.

Lots of guitars have radiused fret slots, some starting over 50's years ago where the gang-saw rode the radius of the board and the frets were pushed in from the side . Of course there is a few thousandths clearance at the bottom. It's a free country, build them the way you think works best.

[jfortenbery]

Thanks RandK!

I don't think my ShopBot will run straight G-code. I'll check that option out with the ShopBot Forum.

I appreciate the idea about utilizing the Vectric forum. That MAY work. I understand the only problem is Vectric only has one program that will do this ... called Aspire ... and I don't have it. (There are approx. 1,995 reasons I don't have it).

As to building guitars the way I want ... thanks for the encouraging words. If I wanted a perpetuate mediocrity, I'd buy a mediocre guitar built in a factory. There's a reason that I want to do things a little differently.

I'm new to CNC. I'm not new to lutherie.

[Mkroe]

With Vectric Vcarve Pro or Aspire you would only have to select "project toolpath on to model" when using the profile cut on the line for the fret slot to follow the radius at the depth of cut that is determined.

MK