I've broken my lathe

[500e]

Not same model but gives you an idea.
If it is a Colchester there may be a breakaway clutch on main feed screw spring and balls beware

 

[fizzy]

@minimutly is the expert on fixing bent screws and wrecked things!

 

[Seadog]

nor did I kill the sacrificial pin.

It sounds like it's been replaced with an indestructible pin in that case

 

[skotl]

It sounds like it's been replaced with an indestructible pin in that case

Oooohhhhh... you think so? It certainly made some horrible noises from the back gears but they look ok visually, and the two big screws still turn.

That might be job #2 once I figure out the cross slide

To be honest I'd have much preferred the pin to break than what I'm dealing with just now

 

[Munkul]

sounds like you need to drop the apron to disengage the power feed, then you can at least eliminate the power feed mech and you'll know the jamming is in the screw or nut.

 

[prepman]

Darn, buttocks and poo are three words I did not use when this happened

I was using the power cross slide and wasn't paying attention when it crashed into its farthest extension. At that point, the manual cross slide lever would only allow it to move half a turn in either direction.
The good news is that the lead screw and feed rod are still working so it doesn't look like I wrecked any of the back gears, nor did I kill the sacrificial pin.

But... the cross slide was well and truly stuck. After a painful half an hour I've managed to get the cross slide off to reveal this:

View attachment 330910

That ?brass? lug is stuck tight on the screw so I suspect that I've churned its threads up. Is it brass because it is also supposed to be sacrifical?

I've tried heating it and turning the screw but it's stuck tight. Any suggestions? I'm thinking drastic (careful!) surgery with an angle grinder or dremel to get it off, then hopefully I'll be back on here with dimensions to see if anyone with a working lathe is able to make me a replacement.


Here's some other pics if that helps...


View attachment 330911

View attachment 330912

What is the full name of the lathe? Doesn't look like my Colchester.

 

[skotl]

What is the full name of the lathe? Doesn't look like my Colchester.

If I recall correctly, it's a 1930s Colchester Master

 

[prepman]

If I recall correctly, it's a 1930s Colchester Master

I made a new nut and feedscrew because the feedscrew was worn unevenly i.e. in the middle. So taking out the play with the nut wouldn't have worked. Reason I mention this is that it's not difficult remove normally. Your jamming ...is there a pin securing the leadscrew that will allow you to push it backwards to get the nut out of the casting pinch point? Or is the power feed still engaged. Easy to check if the feed shaft will or won't turn?

 

[Rannsachair]

If I recall correctly, it's a 1930s Colchester Master

Not sure if it helps, found the original photo's I took of it:

 

[prepman]

Not sure if it helps, found the original photo's I took of it:
View attachment 331581
View attachment 331582
View attachment 331583

From a purely rough approach have you tried tapping the handwheel with a soft mallet. I'm not recommending it but have you?
Had a browse over the net for a service or parts manual. But zilch. There's an expensive option on lathes.co.uk, But even that doesn't promise much.

 

[skotl]

Yep - done a fair bit of tapping. I suspect something is jammed in the apron.

 

[Pete.]

Have you tried loosening those apron screws yet mate? If you loosen them and the movement in the handle increases then you know it's not the nut and screw, it must be the gearing or apron feed. Lets hope it's not the worm gear coz those are a devil to make.

 

[skotl]

Not had a chance to get back out and try

 

[prepman]

Not had a chance to get back out and try

You didn't mention if the leadscrew can be turned, which should confirm if the feed is jammed?
Yours is nothing like mine. Mine has splined 2 part shaft designed to take a taper attachment, which sadly I didn't get with lathe.

 

[skotl]

You didn't mention if the leadscrew can be turned, which should confirm if the feed is jammed?
Yours is nothing like mine. Mine has splined 2 part shaft designed to take a taper attachment, which sadly I didn't get with lathe.

Yeah - lead and feed screw can both be turned with the levers disconnected

 

[prepman]

Yeah - lead and feed screw can both be turned with the levers disconnected

As Pete suggests, it's worth dropping the apron first. You've no gearbox to faff with, so it should be pretty straight forward to slip shafts out? To me it sounds like you are in a locknut situation. Heating the nut might work as it should heat up a lot faster than the surrounding metal work? Small blowlamp or large soldering iron?

 

[Martin-Sy]

I'm with @Pete. for dropping the apron. If it's not been off for a while it would probably benefit from a clean up inside anyway.
Hopefully no broken gears although I have a hunch that someone here has a nice little hobber

 

[skotl]

So.... mixed news...

On the upside I reckon we have a diagnosis, which is that the transfer gear from the feedscrew to the cross slide screw has stripped (at least) a couple of teeth.
Continuing the (relatively) good news, the screw is straight and the brass nut seems undamaged.

Have a look at this (short! 50 seconds...) video to see the problem. The transfer gear is in permanent contact with the cross slide screw so it jars when winding in and out.

I reckon the only sensible short term fix is to remove the transfer gear entirely so that the cross slide rotates freely, at least until I can find a replacement (if possible for a 1930s lathe)

The not so good news is that the apron appears to be a single cast unit, not like the diagram that @500e helpfully posted above - https://www.mig-welding.co.uk/forum/threads/ive-broken-my-lathe.119144/post-2004747

You can hopefully see that in the video, too.

So I'm not sure how I'm going to dismantle it to get that gear off, at least not without picking the whole lathe up and rotating it, then trying to slide the apron off the end (as I'm short of space the right hand side of the lathe is up against shelves / a wall).

Thanks for the help so far - any more suggestions appreciated!

 

[Fastdruid]

Can you support the apron and take the saddle off the top of it? I know I can do that on my Harrison (not it has to be said, easily but it is doable).

 

[skotl]

Can you support the apron and take the saddle off the top of it? I know I can do that on my Harrison (not it has to be said, easily but it is doable).

Sorry - I may be getting terminology wrong, but the whole lump (apron and saddle?) appears to be a single cast unit