Guitar body feeds and speeds help

gtr.c2d (874.4 KB)

What material are you cutting?

Which machine do you have?

How will you be holding the stock in place?

1 Like

It’s a hardwood. Made up of black mahogany yellow Osage and ash.

Shapeoko 4xl

Double sided adhesive on the back. Carbide3d supplied clamps and I will secure some pieces of plywood to my hybrid table.

I also have a couple of the following bits. But they are super long. I saw a video done with thick stock on a standard length bit.

I did a test run with a body made up of laminated beam. Worked pretty well. But my speeds are too fast.

If you take a look at the pic of the body, it dropped the bit right by where the neck is inserted…up to that point it was perfect.

Can’t see pics in the links and not quite sure when you say drop bit, but I cut guitar bodies regularly with no issues on my 4XL . The one thing you need to remember is that a CNC can not read the hardness of the wood or grain. What I mean by that is when routing by hand, you naturally speed up in the soft areas of the wood and if you hear the machine bog or burn you slow down etc. It’s human nature. A CNC is dumb and only does exactly what you tell it to. This means you have to make sound choices (bits, speeds and feeds) on its behalf. This may mean you make different choices based on material even if it’s for the same body shape. IE Mahogany Vs Ash. You may end up with 60ipm for softer woods and 40-45 for harder woods.

You can adjust the speed of the router RPMs while it’s moving too. Listen to how it sounds and watch how the chips are flying. If the chips are more like powder you may have the spindle too fast. If it’s bogging or working too hard, the RPMs may be too slow. It can very from wood to wood even of the same type.

For Mahogany or Korina bodies, I have the router set on about 3.5 for RPMs and run at 60 ipm with a 1/4” bit. You could go faster, but you don’t know what the grain is like which can be much harder than the other areas. You will easily hear this when cutting across the grain. Your multiply body is all end grain is likely very hard on your bits. I would go slow. Make sure you bit is about 1” into the collet and make sure it’s really tight. I use two wrenches and almost make it gorilla tight. Not completely but i tighten it until I can’t move it with reasonable force.

I bought a 4” long bit and cut 1” off of it. It’s now a 3” bit with a doc of 1.75. 1” into the collet 2” sticking out. Let’s do the math. 2” of bit, plus 1.75” of stock is 3.75” of Z travel. Now add your offset or height above work. Let’s say 1/4” above work. You are at 4” of Z travel which is just under the max Z on the Shapeoko 4. So for this job, no bit longer than 3”. Oh and because these are 1/4” shanks, you don’t want a lot of side force on them. So speed and feed is important.

Finally don’t be in a rush. Let the machine do the work. It takes me about an hour front to back to cut an explorer body out of Korina.(Limba). Could I go faster, sure but I rather have a nice quality program that runs good on similar wood types and makes a quality cut.


Here’s the result. Slowed it down quite a bit. And it worked really nicely


Looks great. Are those circle marks from surfacing? If so your machine may need to be tweaked ensure square, plumb and level compared to the spoilboard. There is another post about this same topic. In the end, the milling marks were due to the router not being square to the table.

Looking great so far. Looking at that first photo, the router is quite a ways up into the mounting block. It’s hard to tell from this angle but be sure your router is in full contact with your mounting block, if you can afford to.

1 Like

This topic was automatically closed after 30 days. New replies are no longer allowed.