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Spinning lathe bearing replacing doubt

a3ntin

Plastic
Joined
Jan 19, 2022
Location
Italy, Treviso
English is not my first language, so i will do my best.
This is my first post on this forum, i can't found information anywhere in the web. Sometimes i read discussions in this forum and they are a big help for me, i hope this time can be the same.

So, some weeks ago i've bought an old, rusty and mistreated spinning lathe from a scrapyard, and i would restore it to working condition.

The lathe seems to be some frankenstein machine, maybe assembled by someone using various part from other machines. The headstock and the tailstock seems to be original, only the pulley on spindle shaft appears to be modified to accommodate new (badly made) motor support. For the bed i'm not sure, but it pairs well with tailstock, and the headstock is just bolted on it. The legs are very different one to the other, i don't know which one of these is original or none of them.
Summing up: it's a mess, but seems it can be easy fixed. But this mess cause me some doubts.

The spindle shaft, as i said, already suffered some repairs e modification from non expert person, and i try to find whats wrong o right in this modification.

The main problems is about bearings. Actually the machine mount one double-row angular contact ball bearings near the spindle (the bigger one) and one self-aligning ball bearings on the rear of the shaft (the smaller one). The actual baring are burnt and broken in some point, they were clearly abused.
From my small knowledge of machine tool, and seeing the actual state of bearing i start to thinking that someone put the wrong bearings on this machine.

Considering the forces involved (spinning diameter up to 700mm) it wouldn't be correct put in it some tapered roller bearing?
The shaft configuration already have bearing lock nuts for preload, and i can find roller bearing with same measure of ball bearing.
Is there anybody in this forum that have or have seen a spinning lathe and know what type of bearing normally mount?

I send some photo of the machine and the shaft.
lathe.jpg rear.jpg spindle.jpg

Sorry for my English and thanks,
Andrea Trentin.
 

TGTool

Titanium
Joined
Sep 22, 2006
Location
Stillwater, Oklahoma
a3ntin,

No need to apologize for your Engish, it's perfectly good and you've expressed your concerns well.

I have no experience or expertise with that sort of lathe so I'm guessing from general bearing knowledge. A pair of angular contact bearings at the front and a simple bearing at the rear of the headstock is a reasonable design. The part that seems an anomaly is your comment about the locknut for preload at the rear. Ordinarily paired angular contact bearings should have their preload set for themselves (shims, threaded retainer) and the rear bearing would be allowed to float to allow for thermal expansion.

Tapered roller bearings at the front would have plenty of load capacity and could take the thrust. They're more limited in rpm that roller bearings, but I'm guessing that a spinning lathe for large pieces would not run at a high rpm so that might be a good design choice.
 

Bill D

Diamond
Joined
Apr 1, 2004
Location
Modesto, CA USA
Knowing nothing about spinning lathes I agree a tapered roller bearing would be fine. For that use a regular bearing for a car or truck should be accurate enough. I do not think you need a expensive high precision bearing. I could be wrong hopefully others will jump in with more knowledge.
What RPM will this spin when being used. What metal will be spun? Aluminum, copper or steel?
Bill D
 

Lanso

Cast Iron
Joined
Mar 16, 2013
Location
Cerritos, CA
It’s unlikely that you would ever create much force by the spin forming with that lathe, it’s the tail stock quill with the live center and a “follow block” clamping the material (circle) to your mandrel. Spinners like to clamp the circle TIGHT against the mandrel and that’s usually how the high axial force is created on a small spinning lathe.
 

a3ntin

Plastic
Joined
Jan 19, 2022
Location
Italy, Treviso
Thanks you all.
On last weekend i finish to disassembly all parts and start brushing and cleaning rust and old paint. I take some more accurate photos of the spindle assembly.

4_Rear_shaft_bearing_locking_nuts.jpg3_Spindle_shaft_bearing_locking_nuts.jpg2_Spindle_assembly_rear_view.jpg1_Spindle_assembly_front_view.jpg

Speaking of the tail stock quill and live center you better take that as seriously as the headstock
Don't worry, the tail stock quill is the best conserved part of all lathe, and in never be modified.

Thanks again,
Andrea Trentin.
 








 
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