Designer dimensions vs cut dimensions

[Bob Victor]

In designer I create a carve region with dimensions. After uploading project, load board and perform the cut, the carved region is larger than the dimension I set in designer. Example in designer I want the carve region to 4.25" x 3.50", after the cut, the carved region measured 1/8" larger. I have read on calibrating the CW. Not sure if that will solve my problem. If I try to adjust designer dimensions, then my region comes smaller then I wanted. If anyone can provide information on how to correct sizing in designer vs what CW cuts, would be appreciated.

[bergerud]

The first step is to understand how Designer carves pockets. If I draw a square in Designer and assign it to be a 1/2" deep carve region, it will end up being carved larger for two reasons:

First, the tip of the carving bit is a 1/16" ball. The machine will carve out the region by sweeping the mathematical center of the bit over the area of the square. The sides of the ball will cut 1/32" over the boundaries of the square. The bottom of the pocket will be a square 1/16" oversize.

Second, the bit has tapered sides. As the center of the bit carves up to the square boundaries, the ball goes over the edge and the taper above it goes even further over the edge. The pocket will be even wider at the top. Depending on how deep the pocket is, the top of the pocket could be up to 1/4" wider.

The over carve by the ball can be compensated for. One can just make the pocket 1/16" smaller. (If one has carve regions as boundaries on top of the pocket sides, bit optimization best is another method which can be used to keep the ball inside the boundaries.)

The taper problem, however, cannot be compensated for. If one wants vertical sides, one has to use a bit with straight sides like the 3/16" carving bit. The other option is to mill the pocket with a cutting bit. One can mill out the whole pocket with a cutting bit or just make a "clean up" pass around the sides of a carve region.

Note: The Designer program is not perfect WYSIWYG for pockets. It will show the overcarve of the ball but it does not show the overcarve of the bit taper. A pocket will be displayed as 1/16" larger but with vertical sides.

[mtylerfl]

Hi Bob,

Bergerud presented an excellent explanation, along with suggestions for you.

In addition, you may find the following CarveWright tutorial videos helpful, as well. Here is the link:

Pocket Cutting Tips – Part 1 and 2

[ktjwilliams]

Sounds like Dan has figured it all out ... Thx Dan .