[TTalma]

I got my cnc up and running (based on a G1006), and have started making some test parts. I am planning to make some stuff where a brass piece is inlayed into wood. I cut out some parts, and when I tried to insert the brass cutout into the wood part that was machined out it didn't fit. I got my calipers out and measured a bunch of points and they all came out the same. I had to do about 10 min of filing here and there on the brass part to make it fit in place. I plan to make a lot of these, and don't want to spend 10 min on each piece.

I am using ball screws with 150lbs of preload on them, and when I cut out a circle it measure out perfect. This was the 3rd part I cut so there is no wear in the ways that I can measure. How should I change my parts so I can just drop the brass part in place and still have a tight looking fit?

[LeeWay]

A few pictures would help, but generally, you need to account for tool size and inside and outside corners. If using Mach 3, there is also on of two modes. Incremental and exact stop. Depending on what type of geometry they are, one mode may be better than the other. Speed will play a roll too with incremental mode.

[TTalma]

Thanks I'll get some pictures tonight. But it's basically a square with a circle inside it. I am using mach 3 and am using an 1/8th" bit so I made all of the corner diameters 1/8". I am not sure what the difference is between incremental and exact stop are. I am using meshcam to generate the g-code and it seems to work fine.

[dogmeatk]

Sounds like you aren't accounting for cutter deflection. The SX3 is not the most rigid of mills, even then, a 1/8" endmill is a spindly bit and you have to account for it's deflection when cutting.

Need to fit your cylinder into a 1" hole? Have you measured the OD of the machined cylinder? Is it exactly 1" or bigger?

To account for deflection in machining, I usually under size my insert diameters in my CAM software. For instance, instead of programming it to cut a 1" OD cylinder, try programming .99 or .98 and see if your parts fit together better.