Thrust bearings for the Boxford
The current state of the cross slide and compound slide:
The gap/play in the cross slide. This closes if you pull it back but of course the play is there.
The first two pictures show the lead screw of the cross slide removed, and notice the gap. The whole section slides back and forth and as you can see, when you slide it the other way the gap appears on the other side – pics 1 and 2.
The graduated dial has a huge screw and locks directly onto the leadscrew, there is no collar that fits under the graduate dial – so this isn`t a friction type. The little collar you can see locks and holds everything (i.e whats in picture 1 and 2) in place. It is the position of this collar which is giving me this play as it this collar which is allowing the section shown in the 2 pictures above to move left and right (left towards the lead screw and then right, it gets stopped by the collar)
But you can`t push the collar up any further against the back of the graduated dial (left in the picture) to remove the slack. Infact, looking at the picture, you can see the shoulder on the back of the grad dial and the grub screw sticking up, you can`t get in there to tighten the grub screw with the collar upto that section. It must be right how it is as a wider collar wouldn`t allow the grad dial front and back to close on itself
After posting on the Boxford Yahoo groups I found that my lathe is likely to be an original first version Model A which never had provisions for thrust bearings. If I`m going to go to the trouble of getting rid of this play, I may as well fit the bearings.
So the two thrust surfaces will be here between the grad dials:
And here, between the fixed column and the lead screw :
I was talking to Rob who had made his own thrust bearings and while trawling the internet, I came across these on ebay:
10mm bore, 18mm OD and 5mm Width, £5 for 4 – they seemed perfect!
I put one directly onto the lead screw where it butts up with the column but needed to take the 5mm off the column for the lead screw to still align with the cross power feed gearings.
I then slid one between the column and the moving face of the graduated dial. I got rid of the retaining ring/collar and machined the grad dial so there was a tiny gap between the two faces of the grad dial when the thrust bearings were between. I then machined a little off the end of the leadscrew and also added a washer so that the handle now locks everything tight on the leadscrew. The front grad dial can still move because of the slick motion of the thrust bearings so the collar is not needed.
Works a treat, super slick and very little play/movement, just the play in the nut (almost nothing) and I`m now 100% happy with the setup. I have two spare Thurst bearings but the compound slide feels just fine without and little play so I`m inclined to leave that axis for now unless I get time or feel inclined to do it in the future – it was only the cross slide that was annoying me and now fixed!.