My modest spindle, has several collet sizes up to 6mm, but frankly swapping collets is quite time consuming (n comparison to just swapping a cutter out)

99% of the time, I use a 3.175mm (1/8") collet....but occasionally, I need to use 3.8mm to 5mm endmills...to save me having to swap the collet out, I was wondering if anyone has seen endmills that have a cutting diameter wider than the shank (therefore for example 4mm cutter on a 3.175mm shank).

yes, I know there probably wouldn't be much demand (on account such a cutter would be weaker than normal), but I only make light cuts on acrylic acrylic, FR4 & the time savings for me would be a massive win.

I'm not even *that* fussed about precision (I typically use the larger cutters to skim a bit of depth of some material), so had even thought about getting a 4mm standard endmill turned down so the shaft is 3.175mm etc.