The second moment of truth arrived. Will the hardware fit inside the holes of the printed parts? Yes.
There will be more than one moment of truth during the build of my Mostly Printed CNC machine. During the fabrication phase, there are critical points where you discover whether or not the parts and hardware fit together properly.
Previously, I described the importance of 3D printer calibration in making sure that the plastic parts print to the correct size. This is especially important for printed holes that need to accept hardware properly.
My first moment of truth involved the EMT conduit rails that need to fit properly within the clamping shapes provided by the printed parts. That went well.
After buying most of the hardware (screws, bolts, nuts) it was time for the second moment of truth. Would everything fit?
Hardware fits – Passing the second moment of truth
Things could probably not have turned out better. The first part I screwed together was the corner block and its accompanying lock structure (see top left). This is meant to hold together two lengths of steel rail at each of four corners of the frame. In addition to accommodating the #6-32 machine screws, the slot in the side of the plastic part also has to fit a captive locking nut.
The second part I screwed together was the roller assembly (middle and right pictures). These use 5/16-18 bolts to secure bearings to the rail, and also to secure the vertical stepper motor mount and, when they arrive, the idler pulley for the timing belt drive. Again, it seems to have come together like a charm. As the bearings and pulleys have not yet arrived from China, there is not much else I can test at present.
I had been prepared to do a bit of filing in case the holes were too small. But this was not necessary. It is great when things work out in practice as they were designed in theory.
You might also notice in the pictures above that I have finally found good use for my collection of old Costco pill bottles. They provide a great way to organize the hardware.