Dremel 4486 MultiPro Keyless Chuck

Q: I can't open this dremel Chuck. Used liquid wrench and try to open carefully. any suggestions?

I’m late to the party (1/20/21) but had the same issue. However my new 4300 Dremel chuck was stuck when it came out of the box. I never got a chance to take the chuck off. Jill O’s. advice from 2014 was helpful but I couldn’t find a small enough drill bit. I used the opposite end of the small wrench that came with the Dremel. I stuck the end of the wrench between the chuck and the plastic EZ Twist lock. I tapped the wrench with a piece of wood and did this continuing around the base. The chuck unlocked and the teeth opened.

Q: Does this work with the Milwawkee 12v rotary tool? Amazon advertises them together

It seems to work with any kind of rotary tool. I have both a dremel and a black&decker and it seems it is a standard size that fits all.

Q: Will this work with a Wen rotary tool, specifically the 101 piece kit here on Amazon?

Can't believe the hours I spent trying to get the shaft size information for my 2 rotary tools. (Wen and Katonah) (or is it called "a shank"? I'm new to this world of rotary tools.) Even called Wen and the guy didn't know the size. Even Dremell doesn't give the size of the Multi Chuck hole. It only gives the Dremell models it works with. Anyhow, the collet nuts are interchangeable on both my tools so I figured it was a standard size. I bought a knock off Multi chuck at Ebay and, at least the guy put the measurements of the hole in the picture. It was .7cm. Unfortunately, that is also the size of both my rotary tool shafts/shanks so, the multi chuck was too small to screw on to the rotary tools I have. But, I am glad I came across this answer since, I almost bought a Dremell Multi Chuck. It too is too small. Saved me about 10 bucks and another disappointment. Thanks.