Hey, I'm having a slot milled that will accept a piece of aluminum bar that is nominally 0.5" wide. How wide should I have the slot milled in order to ensure that the bar can be easily removed? I'm not sure what the tolerances are on aluminum bar and not really sure what extra width to account for that doesn't require a hammer to (re)move the piece.

I would guess that 1/64" over would be plenty large enough. Not sure what that is in mm., but in SAE it'd be 33/64".

If it doesn't matter if the slot is a bit oversized I'd go with 9/16" just to be safe.

yeah, I was thinking 1/64" as well, assuming exactly 1/2" bar. However, I have no idea what the tolerances on aluminum bar are.

mcmaster carr has dimensional tolerances for most of their bar stock.

A quick check of the 1/2"X?? got +/-0.014" as a worst case on the 1/2" dimension which is just under 1/64" (0.015625").

Is it just the end of the bar that's going into the slot or are you sliding half the bar through the slot? If it's the former than it doesn't really matter since aluminum's pretty soft and it shouldn't be hard at all to file or grind down the end of the bar if needed.

CNC milling tolerances are typically +/- 0.005 unless you ask for better than that

What you need to consider is this. If the bar is nominally .5" (