The vast majority of my use with a CNC router (once I rebuild it....)

The vast majority of my use with a CNC router (once I rebuild it…) Will be for PCBs. But in rebuilding it I’ve found I need to mill some precision holes in order to mount the new ball screws and bearings.

I’ve tried drilling these by hand and up just making a pig’s ear. So am going to mill them out of 10mm acrylic or perhaps polycarbonate.

What is the easiest to use (lowest curve) free/shareware software for Windows that people would recommend?

I have SketchUp but seemingly whatever I do I cannot get it to recognise the model as a solid. So I’ve given up with that.


Fusion 360 is my favorite and free

Autodesk Fusion 360.
If you just want to do the drilling and simple outlines you can do that with Eagle and Eagle BRD widget, might sound strange but it’s possible, I recently drilled and cut a piece of wood this way. There are no limitations in eagle for dimensions and drill holes, you can go as big as you want … I guess.

Thanks both.
Unfortunately I have to send these drawings off to a fabhouse (my mill is in bits…). So eagle probably would not work. Need cad drawings in the end.

Although maybe I could find someone local with a CNC router. There is a makerlab about 30 mins away.

If it is just holes hand coding gcode is very accurate and not very hard.

Sure. But I need cad drawings! @Steve_Anken ​. Thanks though.

I find the simplest and most basic solution generally works the best. For exact drilling, ensure you have a steel ruler (tape measures suck for this), a scribe (fine point scratchy thing) and a center punch. All 3 of those things can be picked up at Home Depot for less than 15 bucks total. Just take your time, X scribe your points, and then center punch. Take your time. Then pilot drill the hole, followed by your final size. Measure everything at least twice. Also, get some clamps, clamping things when drilling eliminates all the headache!

You’re right @Daniel_Chote ​. Unfortunately no home depot near me in France and you’d think these things would be easy to source, and they probably would be. I don’t have a drill press and have a condition that means I can’t hold things steadily. So never manage to saw in straight lines nor drill in the same plane etc.

@Justin_Adie even in France you should have a hardware store that would carry such things. You don’t need a drill press if you clamp your work to something secure. In terms of tremors, as long as you’re drill isn’t too large, rest your elbow on the work surface as much as you can, I find that doing that while sitting helps me when I have a tremor.

Onshape ( is another great free one. Nothing to install as it runs in a browser.

@Daniel_Chote ​. Question for you re the manual method you outline.

In the mill elements that I am changing there are already holes for 8mm bearings. I am moving to 12mm ball screws so need to enlarge the holes (fine) but also need to make sure that the ball nuts and pillow bearings are perfectly centred to the existing holes.

Normally (were I able to do it manually) I would use compasses and scribers as you referred. But in this case there seems no easy way of manually being certain that you’re at the centre point (and on the precise same plane) as the existing hole.

Or am i missing something obvious?

@Justin_Adie I would either use very gradual increases in bit size, or, screw to a piece of wood and use that for the center point. If thickness is an issue, you could try a wooden dowel in the hole first.

I think one would still have the problem of not knowing the centre point, even if you covered it with wood. Likewise even with a dowel unless it was precisely accurately the same width. Plane is important with compasses.

I’m thinking the solution is to fill the existing holes with resin and start again. Or mill the entire piece from fresh material.

Currently the mill is made of 20mm PCB. I’ve no idea where to source that from in France!

There are big reams available that you could use to expand the hole and then there is no need to center anything.