On my WM250V, there'd be just less than 1/2" clearance between the lowest point of the 5" chuck and the top of the crossslide – if you could get it that close to the headstock, which just can't quite do because the telescopic leadscrew cover bottoms out.

So I think that if the 6" chuck is deeper than the as-issued 5" – which it likely is – you might want to rig up some kind of additional stop to avoid collision risk. The compound slide would probably still give you enough reach for close-in chuck work like parting and boring, but that's a bit of a guess.

My self, I'd wanna be really sure both that I needed the extra capacity, and that I could get the new chuck as true as the issued one – I think mine is the best I've ever used.

Edited By Mick B1 on 28/07/2019 18:18:18

I have a 160mm chuck on a Warco 250. The leadscrew cover stops the cross slide hitting the chuck body but if you're holding large diameters it is definitely worth checking the jaws and cross slide have clearance.

With the jaws the way around in the pics the chuck can hold 90mm dia stock and just clear the cross slides bed, it wont crash due to the leadscrew cover. Chances are with a tool mounted you'd hit the jaws with the tool tip first anyway. I haven't checked with the jaws reversed but when I took the skin off a 130mm dia piece of cast iron there was loads of clearance.