Hi everyone, my first post here and looking to tap into the wisdom of the internet.
I'm a retired electrical engineer with an interest in oldish wood and metalworking machinery.
I'm in the process of renovating a Fobco 7-Eight pillar drill which was bought as a non runner, partially dismantled and I've reached the point where I need advice about angular contact spindle bearings. Context below, question at the end.
I checked runout of the spindle early on using a new but unproven test bar and 1-2MT adapter. It clocked approx 0.1mm 4 inches out from the end of the spindle so I've decided to replace the spindle bearings and have removed the spindle..
Spindle nose bearings are a pair of open angular contact bearings. Type unknown but measuring 72mm OD / 30mm ID / 16mm thick. They do appear to be metric although the machine is otherwise imperial.
There is a single SKF deep groove bearing at the top end of the quill to keep the spindle striaght.
I believe that the drill has had a fairly easy life but I don't know if the bearings are original. What is interesting is that the two races at the spindle nose are installed in tandem not F-F or B-B which I believe to be more common for machine spindles. Excellent for handling the load of heavy drilling but maybe the reason for the poor runout I measured as I did not think to place the spindle under axial load while measuring the runout.
Some simple estimates make me think that the 7-Eight should be designed to cope with axial drilling loads of maybe 400Kg force.
Does anyone know how the bearings are SUPPOSED to be mounted in the 7 and 10 Eights, and whether a new pair of bearings installed face to face for better precision would tolerate axial loads of this magnitude ?
Thanks in advance