[eforer]

I'm cracking in to my first guitar project on my cnc router. We're a display, sign, and retail fixture shop so I'm not very skilled or familiar with hardwoods. We work primarily in aluminum, plastics, fiberboards/particle boards, laminates etc.

We don't have a thickness planer and I have some new chunks of maple and African Mahogany that aren't dead flat, I also need to take a 1/4" or so off the top of the Afracan Mahogany to add the flamed maple top. The maple is a tick over 1/4" and not perfectly flat either.

I am looking for advice on tooling and methods to make these surfaces flat and ready for sanding/glue.

From what I've read a large down cut end mill seems like the hot setup.

Thoughts?

-Ed

[michiganbill]

A large down cut mill might work on the thicker stock (tiny feed or step-over).
For 1/4"stock it might not work too hot, unless you have a way to ensure that there is perfect contact to the spoiler board (vacuum set-up?).
When I have tried to surface thinner stock I generally make it worse.
I do not know the particulars of what you are doing but would you need to have the 1/4" material all that flat if gluing it to the flattened mahogany? Might be that the way you clamp the glue up would be just as if not more important.
I hope you have success, my daughter is just learning the acoustic guitar and using "daddy's machine" to make her an electric one is a constant request.
Are you using a kit? a Set of Plans?

Bill

[eforer]

Hi Bill,

We have a 20hp vacuum hold down on our multicam. The 1/4" is pretty flat and would glue up fine. What do you think about surfacing the top after it's glued to the mahogany? What do you use on the thicker woods to flatten out the surfaces?

[michiganbill]

Wow 20hp vacuum and a Multicam (beats the heck out of my shopvac and slightly modified FLA 300)
I assume that you are using some relatively thick mahogany (+0.75")
When I have surfaced hardwood it was for a few reasons -
• True up a piece of rough stock so that I could use surface 1 as a base on to the spoiler board (I used a 3/4" DC end mill with steps in the 0.0625 range) lightly sand with typical sand paper, flip and then as long as I have the stock have not surfaced the other side - just went to cutting the 3d pattern
• When I needed a glue surface - about the same just jacked the RPM up - again sanded well
As to gluing up (again I am not sure of the plan you are following - sorry) you need to ensure that "top" and "bottom" are parallel before the glue-up or the flame will not be of consistent thickness. If you plan on cutting through the maple into the mahogany parallel surfaces are even more important.
There are quite a few videos on You Tube showing all sorts of clamping and cutting techniques - for CNC guitar body's
Are you just making the body or the neck/frets as well?
Bill

[eforer]

The hold down is 20hp, the dust collector is only 7hp but it gets the job done. That said I've seen guys with home made machines make such beautiful things it, very humbling.

My plan was to flatten I side, flip and flatten the other side so I had a nice parallel block.

I'm not doing a neck. I'm making a double fat telecaster. I'm just using a mighty mite neck.

[palenn]

I've found the best method of initially flattening the first side of a piece of wood is one a large belt or disc sander. Several options then can be used for thicknessing and further machining. The advantage of sanding versus jointing or planing is elimination of tearout on figured woods. The initial flattening can be done without distorting the workpiece and leaving a non-flat surface.

[wbegg]

I use this on my DIY and never had a problem. Flatten one side, then flatten the other.

It's inexpensive, also.

http://http://www.grizzly.com/products/Bottom-Cleaning-Bit-1-2-Shank-1-1-2-Dia-/C1261

[ger21]

I wouldn't use a downcut. Upcut's will leave a better finish.

I'd probably try something like this.
Mini Insert Spoilboard Surfacing & Rabbeting Router Bit with Scorer 2 + 2 Design -Toolstoday.com- Industrial Quality

When rabiting or surfacing, I climb cut along the grain, alternating edges and working towards the center. If you take off too much at a time, the last pass may tear out, so I'd stay around .05-.09 per pass.