I have an old Jacobs keyed drill chuck in my box-o-spares, and I need a drill chuck for my hobby lathe. I have a suitable tailstock arbour, but the drill chuck has something already installed, and I can't remove it.
The label reads:
JACOBS (r) MULTICRAFT (r) USA
and further around reads
3/8 (10mm) CAP 3/8 24 THD KG
Here's the shot up through the wide-open jaws. Inside is a large-flanged bolt with a shallow 1/8" hex socket. A 3mm tool spins in the hole, and a 3.5mm tool does not fit. Being a metric country, old imperial/SAE/standard/american sizes are less common. I have exactly one allen key that fits. As per photos, I've managed to pretzel the shaft by using a vice and pliers to apply torque in either direction.
- Is the little bolt going to be conventional right-hand thread or backwards left-hand thread? It doesn't move in either direction so far.
- Will applying heat damage the chuck? If there's thread-lock, heat may loosen it.
- Which two areas should I be applying torque between? The old arbour, the outer ring, or the hex tool in the small bolt?
- Is the old arbour threadded or some kind of taper? The Jacobs chuck references like http://www.michiganpneumatic.com/customer/mipnto/extrahtm/jacobsref.htm and http://www.jacobschuck.com/drill-chuck-removal-guide do not show how this model chuck is mounted.
- LAST RESORT - should I drill out the little bolt ? No idea what kind of steel its made from, but it didn't distort when I put a 90 degree twist into the allen key, so its likely to be hardened.
I do not need to save the old arbor. There's plenty of apprentice marks on it now from my vice.
I hope to mount it on this morse-taper0:threadded arbour from my Sherline lathe. The largest flange is 16.48mm in diameter on the old arbour and the MT0 from the lathe has 15.90mm
The chuck moves smoothly so I'm happy it will be good. I have not bothered cleaning it yet - unless I can remove the old arbour it will be pointless.
Certainly the usual solution would be to order parts, but given the C19 lockdown, I can't even leave my home, so everything needs to be in-stock already.