Question.

When I set up a project with pieces that will fit together, the bit I specify in the cut, doesn't cut exactly.  Example.  If i have a project, lets call it a piece together dinosaur using 1/8 exact plywood, using a .0625 exact end mill, cutting on the outside of the line, it is cutting smaller the 1/8 inch.  this happens with all sizes.  1/4,1/2 etc...  when I measure the with of the notch in my program, it is exactly the width it should be.  When cut, it is always smaller.

Help?

Thanks!!

Happy New Year!!

Lots of reasons, but tool deflection is a big issue. When you conventional cut, the tool is pulled into the material, resulting in a smaller part. When you climb cut, the tool is pushed away from the material, resulting in larger parts.
It can often take some trial and error when trying to get pieces to fit tightly together.

If you're making cuts that need to be to an exact size with a machine with some flexibility you can get much closer by taking a first cut which leaves enough material for a finishing cut to exact size,

 - Nick

If you're making cuts that need to be to an exact size with a machine with some flexibility you can get much closer by taking a first cut which leaves enough material for a finishing cut to exact size,

 - Nick

how do you do that?

how do you do that?

I use the options in my CAM package to leave material for a finishing pass, another option is to lie about your cutter diameter and say it's bigger than it is, this will allow you to either leave material for a finishing pass or fine tune your setting for a correct size on the first pass.
Leaving a little for a finishing pass is always my option of choice, it tends to produce results which are more repeatable,
Regards,
Nick