I’m working on a CNC project where I need to cut and fit an acrylic panel inside a pocket on another panel.
•Pocket size: 60.00 mm × 110.00 mm × 5.6 mm deep
•Insert panel: cut separately and needs to fit flush inside the pocket
•Goal: insert should drop in smoothly by hand (snug, no hammering, no visible gap on the edges and flush)
I ran some test cuts:
• 59.95 × 109.95 mm → too tight, wouldn’t go in
• 59.90 × 109.90 mm → still too tight
• 59.85 × 109.85 mm → still to tight
• 59.80 × 109.80 mm → still to tight, fit flush, but I still had to tap it in with a hammers not sure if I cracked the outside
Clearly my machine is cutting slightly undersize on the pocket, because even at -0.20 mm per side it’s still tight.
My question:
How much smaller would you recommend going on all sides for acrylic inserts like this?
Should I be aiming for -0.25 mm, -0.30 mm per side, or is there a general rule of thumb for clearance when press-fitting panels into CNC-cut recesses?
Any advice on best practices (toolpath offsets, finishing passes, sanding, etc.) would be greatly appreciated.
Check your bit diameters and see if they are exactly as sold, a small variance will give you these results when assigned to tool paths that expect a 0.25” bit for example.
Edit: Also remember to provide a small amount of expansion/contraction if different materials and the difference of humidity where you are machining vs where it will reside as a finished product.
I used the Amana 51404k for the pocketing on the panel. Then used it again but made it smaller by -0.20mm on all sides to do a cutout and tried to fit it in the cutout but of course I hammered it in
For wood → wood, I typically shoot for a 0.010" (0.25mm) clearance on each side.
With acrylic you might get away with a slightly smaller gap for a slip fit.
You went down to a 0.2mm (0.1 per side). So keep nudging it down until you get the fit you want.
Did you measure the Amana bit for dimension? The point of my reply is that not all bits are exactly 0.125” or 0.25” etc. and this could be part of your deviation your seeing.
My question: