Mondial tathe spindle repair.

[orjo]

Mondial lathe spindle repair.

I do not know if this is the right place to post this, so correct me if I'm wrong.

My Lathe


Mondial
6½” x 40”
Serial no: 9767


According to the website of lathes.co.uk it could be an MK 2 or an MK 1.
it had bronze bearings and a three speed pulley.


The Bearings on my lathe where completely run out, even the axle was damage. So it was in need of some drastic repair.
I have converted the bearings to conical bearings from SKF in order to do this I made a large boring bar with to places to place a cutter (HSS) which a put into big bearings mounted on plates so I could center the shaft in the middle of the existing bearings and parallel to the bed of the lathe.
The whole assembly was connected to an electric motor with gearbox that was connected to an other gearbox which was laying around in my shop. The speed of the boring bar came this way to 100 rpm. This whole assembly was mounted on the apron so I was able to give manual feed to the bit.
I then bored out the bearing caps to approximately the outside diameter that the new bearings where. The oil ways where filled with epoxy metal from Loctite . The the bearing caps where cut to the diameter needed for the bearings. The bearings where then installed.


The spindle needed some repair to, the bearing faces where cut down on both ends. On the far end from the chuck it was repaired with epoxy metal from Loctite, the end closest to the chuck was repaired with a bushing which was pressed on and the turned down to the diameter of the bearing.
Bushings where made to be able to take of the side play.


The lathe now runs in center like it supposed to be.


I have some pictures of the bearing caps included I forgot to take some pictures of the repaired spindle.

 

[vapremac]

I really like what you did there ,the time, effort and thought process.

William

 

[orjo]

Reworking the electrics

The past few weeks I have been doing some adjustments on my Lathe.
First I changed the electrical system. The original arm above the bed to which the switch was connected was discarded with a system activated with a remote switch mounted on the side of the apron where the clutch is operated on modern lathes.
This switch Then operates the according relays witch powers the motor and let it turn right or lefts.
The circuits is now protected with a thermal circuit breaker.
Al is mounted above the headstock assembly in the gray box with th yellow frame.
I also put in some control lights to see if the power is on and if the coolant switch is on.


Al this works great.

- - - Updated - - -

When I bought my lathe a few years ago I noticed it was not equipped with the original engine.
The original motor should be mad of cast iron and should have weight more the twice then the engine it came with ( aluminum casing).
After a while working with the lathe I noticed that the belt would slip if I gave to much feed.
I tried with a new belt, that helped with not what I was expecting.
I put some extra weight on the engine which helped but not enough.
Then suddenly while working I noticed that when I started the engine the engine was shaking and jumping in its belt, and after a while the belt broke.


In a posting on this forum I found something what could be the answer for my problem.
A tensioner.
So I took some time with my mill and drill press and came up with this simple tensioner.
One U shaped block was mounted to the engine cradle, the other L-shaped block rests on the side of the doorway and in between I mounted a spindle with left and right treads.
Changing the belt in an other gear is easy. I left up the tensioner with one hand and with the other I lift up the cradle.


- - - Updated - - -

The Chuck my lathe came with was a 200mm ( 8”) version. It was old had lots of play at the jaws and the jaws had been reworked often.
At my work I got hold of a chuck in pretty good condition. I knew they had minor problems with getting it lined up on the lathe ( the jaws needed a facing with a grinder). This chuck was however a 250mm (10”) diameter. It is much heavier and bigger the the chuck that was mounted on the lathe.


I also have a four chaw chuck which is even larger in diameter.


So I decided to make the change.
The chuck from work came with a backing plate with which the chuck was mounted on a conical spindle.
I First measured up my backing plate and then start cutting a chamber in the bigger backing-plate to fit over my chuck.
I kept the size a little smaller of the chamber. Then off came my old chuck. I turned the original mounting plate to the diameters of the chamber I cut making sure it was a tide fit. I needed the touch of a few hammer strokes to slide it over. The holes where marked and drilled and tapped with M10 treads. Then the backing plates where mounted together.
The the larger backing plate was turn on the lathe to make sure that my chuck would fit and it would be in the center of the lathe.


Everything is OK, I now only need to face the jaws like described on this forum

 

[mattthemuppet2]

really impressive work on the spindle repair, especially the jig you made to bore the bearing seats. I'm considering something similar, but my lathe is small enough that I can do everything on a mill.

 

[orjo]

The Lathe was working fine for a while.
But then when cutting off a piece of metal. It started vibrating.
I looked at everything, looking for play everywhere, but noting found. I tieded the bearings on the spindel and that helped for a while.

But now it is worse. When ever I try to take of more then 1 mm with a pass i get vibration and a very rough surface.
Oil is starting to come out of the rear spindle bearing and that got me started thinking.
I took a dial indicater and looked if there was any virtical play at the end of the spindel.
Well there is, about 0.25 mm.

That could only mean that the saxle bearing surface that i did repaire with epoxy metal is starting to break down. Loctite did advice for a thiknes of more the 1 mm, mine is a mere 0.5 mm thick.
The oil that is coming out has a rough feeling.

This means that i will have to repair the spindle again. But with something els perhaps even make a new axle?

 

[orjo]

Before the spindle got bad I have repaired my The tailstock.
I noticed during some time that there was play between the prisma guide and the tailstock. it was so bad that when setting the center it could always walk of center in no time.

I dismantled it took some measurements and started the mill.

Here are some pictures they clariffy the work i did.

 

[Marco Bernardini]

This means that i will have to repair the spindle again. But with something els perhaps even make a new axle?

I'd replace the bearing repaired with Loctite, along with its support:

View attachment 71602

Probably the new chuck is too heavy for it.
But it's better to listen to some lathe experts, before: an operation of this type is like open heart surgery, for a lathe… and metal don't cicatrize very well.

 

[orjo]

I'd replace the bearing repaired with Loctite, along with its support:

View attachment 71602

Probably the new chuck is too heavy for it.
But it's better to listen to some lathe experts, before: an operation of this type is like open heart surgery, for a lathe… and metal don't cicatrize very well.

The bearing support is strong enough, the loctite you see on this picture is only to make it possible to mount some bolts to hold the end plate together. It's the loctite on the spindle that is loosening.
I post some pictures as soon I have opened it up for repair.
That however could take some time.

 

[orjo]

Some time ago I checked the lathe again. And this is the conclusion, The bearings were not tight enough and the big chuck is to heavy, I replaced it with the original one.
And now for some bad news. I'm going to sell the lathe. Its taking up to much space and I bought some other machines that I need the place for.