A smaller chuck my be expected to hold a smaller drill more accurately. Some bozos seeing a 1/4 in chuck will assume they must use 1/4 in drills like, my particular peeve, the people who get a mini-lathe with a 4way toolpost that insist on using 20mm toolbits because they can squeeze them into said toolpost.

There is no doubt that the #0 is a delightful little thing:

MichaelG.

On 27 July 2024 at 05:53 DC31k Said:

Arc do a very nice 4mm capacity chuk on a JT0.

https://www.arceurotrade.co.uk/Catalogue/Chucks/Drill-Chucks/Key-Type-Drill-Chucks

Difficult decision: some people have a notion that brand and country-of-origin matter; others opt for engineering performance and good value.

But its minimum size is 0.4mm whereas the Jacobs goes down to 0. Depends how small a drill bit you want to use in it. If you are not drilling carburettor jets or similar tiny sizes, the 0.4mm minimum would work.

0 to 4 mm chuck is the one you want, the 1/4″ is huge in comparison and totally out of character on the UPT IMHO

Over the years I have had several different chucks on my UPT and have settled on a 0.2 to 4mm keyless from Rotagrip, the body is a bit larger than the previous chuck but the convenience out weighs that. The chucks that have seen service on my UPT are below and go from L to R Arc euro 0.3 to 4mm/ 0 to 5/32/ 1/64 to 1/4/ 0 to 5/16(for tapping)/0 to 1/8 keyless(too restrictive in capacity)/the current keyless/and lastly the tapping chuck made from drawings on Mikes Workshop site, fiddly but works well.