DXF wrong size

I’m working with spur gears. There are a few websites that will help produce gears that you can down load after putting in the size of gear you need. My problem is the DXF file I get are downloading in to shaper3d are to large and I have to reduce their size to 17.75% to match my drawing. My question is this a problem of shaper3d or the websight? Here is the websight evolventdesign.com

You can download a variety of gears from McMaster here- McMaster-Carr
Download in STEP format for use in Shapr3D. I do it all the time.

Yes I do that all the time McMaster Carr is the first place I go for 3D models, but they don’t have the sizes I need for this project.