STL carve came off by five degrees.

Greetings,

I drew up a pepper mill using Sketchup version 8 and exported it as a STL file using a free plugin for Sketchup. I then imported the file using the Carvewright STL add on. To make the pepper mill from a flat board I cut the STL in half and then sliced that half again to end up with a quarter slice of my original STL file. Since it is cut into a quarter the corners are beveled at 45 degrees. (think of a box with an X drawn across it from corner to corner.) The pepper mill has a couple of precise holes down the center to allow me to install the grinder mechanics. I made patterns to represent the inside and the outside of my quarter slice. On my project I placed 4 copies of my outside pattern on the front and 4 copies of the inside pattern on the back of the board. I also drew a couple of lines through each pattern to use as cutout tabs. I tied all the points to the center axis to allow for board size changes down the road. My pattern depths were chose to keep from having under cuts and to allow for the entire part to be cut out. I realize with the 7 degree taper of the 1/16" carve bit that I'm going to have some taper on the top and bottom of my pepper mill but those sections are not critical in my design. I ran my project through my Carvewright with quality set the highest allowed. The first thing I noticed was the cut was not all the way through. I used the end of my calipers and figured I had about .050 thousandths of material left. Not bad, I can sand a little to remove the excess. I cut my parts free of the board with a scroll saw and tried to put the 4 quarters together with my grinder in the middle. It looks very close to being the right size center hole and clearance hole but the edges don't line up quite right. I grabbed my adjustable head square and lined it up with the center hole and noticed the angle on all 4 sections is 40 degrees instead of the 45 degrees needed to make it all fit together. Whats up? I went back to Sketchup and opened up my quarter STL file and using the measuring tools within Sketchup I checked my angles. 45 degrees just like I thought! I'll include the files if someone would like to check for mistakes. Since I set things for 45 degrees and got 40 I know it's not as simple as changing my pattern by 5 degrees to make it carve correctly. This is just the bottom section of the pepper mill. I figured I'd try the critical part first and if it worked I'd then do the matching top section. I'm glad I did as I'm not fond of making anymore firewood than I have to. I think you can extract my patterns from the included file as I did it all with the basic version of Designer. If not, let me know and I can include the two patterns I created.

Have a great day,
Brad