CHJ
Established Member
Having just been fortunate enough to gain a new boy toy in the form of a 125mm diameter chuck I've been 'needing' for some time it occurred to me that one of the advantages of such an animal if your lathe will accommodate them might be missed by some members.
I use Cole Jaws quite a lot, both commercial and home made and one of the things that niggles when using them on a standard 100mm chuck is that between the hole PCD spacing (usually about 12.7mmR) and the limited chuck jaw movement the size you actually want is invariably in no mans land and causes frustration.
The increased Jaw travel that a 125mm or bigger chuck supplies removes this frustration completely.
The 125mm Chuck gives 40mm diameter difference on jaw travel with jaws still fully enmeshed which accommodates at least two button positions, and for light cuts there is a further 10mm diameter available with jaws still within safe holding limits.
An older 150mm Chuck I have is normally fitted with the lightweight Spigot jaws which have very limited diameter range when fitted to a 100mm chuck (see simulated middle picture) but can be very useful if used with care and light cuts on the bigger chuck.
I use Cole Jaws quite a lot, both commercial and home made and one of the things that niggles when using them on a standard 100mm chuck is that between the hole PCD spacing (usually about 12.7mmR) and the limited chuck jaw movement the size you actually want is invariably in no mans land and causes frustration.
The increased Jaw travel that a 125mm or bigger chuck supplies removes this frustration completely.
The 125mm Chuck gives 40mm diameter difference on jaw travel with jaws still fully enmeshed which accommodates at least two button positions, and for light cuts there is a further 10mm diameter available with jaws still within safe holding limits.
An older 150mm Chuck I have is normally fitted with the lightweight Spigot jaws which have very limited diameter range when fitted to a 100mm chuck (see simulated middle picture) but can be very useful if used with care and light cuts on the bigger chuck.