Denham Lathe Rescue

[DecK]

Ahhh, so that's what that does When I engaged it and tried to turn the chuck I thought it was locked solid. Never tried to run it like this cause I thought I'd burst something

 

[Maker]

When I engaged it and tried to turn the chuck I thought it was locked solid.

That's normal. Put a spanner on a chuck jaw and wou should be able to shift it. You can't cut threads without it.

 

[DecK]

LOL. I'll be shocked if I can cut threads even with it

 

[Pete.]

DecK - too many people mistake the back gear for a spindle lock. Some even use it to hold the spindle locked in order to remove the chuck. Quite often this results in a bull/back gear with busted teeth.

Look at the face of the large gear (the bull wheel) on the spindle, from the direction of that oiling cup. You should see a couple of nuts or bolts that can be loosened to slide and unlock the bull wheel to turn on the shaft.

 

[DecK]

This is probably a completely stupid question but if I unlock the stepped pulley from the spindle to engage the back gear, what drives the spindle? I mean, I would think unlocking the pulley from the spindle means the pulley won't turn the chuck and it's also the pulley that provides power to all the rest of the lathe. This is going to be the dumbest question ever asked on here isn't it There is a grub screw in the pulley on the centre step

 

[Pete.]

Don't undo that screw The pulley isn't locked to the spindle, it turns on it on a sleeve bearing. The bull gear is locked to the spindle. The pulley assembly and bull gear can be connected and disconnected. Here's an example of how:

http://r.ebay.com/ORnsCC

So if you lock the bull gear to the pulley you're in direct couple. If you unlock it the pulley spins on the spindle but the bull gear does not. If you then engage the back gear the pulley gear drives the back gear and the back gear drives the bull gear in a double-reduction so the bull gear and spindle turn very slowly but with huge torque.

 

[Pete.]

You can see the bull gear lock pin actually right here:

 

[DecK]

You can see the bull gear lock pin actually right here:

View attachment 76747

You my man, have the eyes of a hawk. Have a load of pictures that I've taken over the last 2 days and was going through them to try and see something

I'd be stripping that spindle right back (then getting distracted for a year or so and leaving it in bits... That's why I take pictures as I strip things )

Same as me so then

On another thing that's bugging me, the graduations on the cross slide collar is in segments up to 125. I thought this was thousands of an inch and each turn of the wheel would be 1/8" but when I move it through 1 full turn it moves the cross slide about 1/4". Am I missing something again or could the collar have been changed at some stage.

 

[DecK]

Pencil line is where the cross slide face sat before turning it through one turn. From the line to the face is ~6mm

 

[Pete.]

Probably had a new screw or a different dial. It doesn't make sense to ever have the dial read half the slide movement - you might find it the other way round where the slide moves half the dial reading, that's called a direct-reading cross-slide dial so what you read is what you are taking off the diameter. My Monarch is like that.

Do you have a dial gauge? You should use one of those to determine the cross slide screw pitch. From what you're saying it seems to be 4tpi which is very coarse for a cross-slide.

 

[penfold]

Theres a good possibility you can buy and fit a backplate to the chuck, 4 Jaw independant??

Stan

That's a certainty with the one with two studs; it just needs a backplate fitted.

 

[DecK]

By dial gauge do you mean DTI? That's used for checking run out? I have one ordered but will be next week before it comes. I can measure the pitch tomorrow anyway but it seems to be a fairly coarse thread. Picture might not be the clearest

That's a certainty with the one with two studs; it just needs a backplate fitted.

One of the jaws on that chuck isn't in good condition, might be able to get a replacement hopefully.

 

[Pete.]

A hundred year old metric lathe made in the U.K.? Highly unlikely. One way to find out would be to check the pitch of the lead screw and cross slide screw. I think it's a 4TPI screw and a 8TPI dial

 

[Pete.]

Deck you gotta stop winding the handles on this thing until you've at least cleaned the worst of the rust off the ways. The iron oxide dust is very abrasive and will grind the ways away fast.

 

[DecK]

Yea I know I shouldnt do that much moving of carriage but Id like to have an understanding of what does what before I start breaking it down. When I cleaned the collar on the cross slide wheel I saw the graduations and gave the handle 1 turn to see how accurate it was. Then measured it out as 6mm and got completely confused so decided to leave well enough alone.
The lead screw and screw for the cross slide are both 4 tpi so guessing if the cross slide screw was 8 tpi it would correspond with the graduations on the collar. I also found the pin that locks the bull gear to the pulley



Its just to remove the cover of the bull gear and it can be pulled out by hand. Have a wedding to go to today so this is probably as much as I'll get done

 

[DecK]

I got a bit more done on this today. Stripped back the head stock and cleaned out about 50 years of accumulated crud.



Found the source of the rattle and it was the thrust bearing. It would have been too easy of course if this was the only problem but it turns out the ball race from the bearing has worn a rather substantial divot in the spindle shaft. It must have been running like this for years to cause this sort of wear. The weird thing is that the housing washers seem to be flat faced. No track for the race to rotate in. Half thinking this is some kind of a botch job of a bearing replacement.



The divot is about 1/16" deep. Probably going to have to send this out to get it built up and machined back down to size. If I had a working lathe of my own I could do it myself I suppose

Stripped of the cross slide as well. Cross slide screw is 4 TPI. Since I'll be sending the spindle out for repair I'll probably carry the screw and nut and ask my repair fella what he would charge to knock up a new screw and nut. Thinking I best be sitting down for that price





Next up is to remove the saddle and clean up all the surfaces. So far there is surface rust but nothing too serious along the lines of pitting. Removing that saddle is going to be fun. I'm guessing ~200kg

 

[brightspark]

[QUOTE="DecK, post: 750380, member-
Next up is to remove the saddle and clean up all the surfaces. So far there is surface rust but nothing too serious along the lines of pitting. Removing that saddle is going to be fun. I'm guessing ~200kg [/QUOTE]that must be some size-lathe a saddle nearly-400 weight

 

[DecK]

That's my best guess really. Have I got the wrong name for it again. Is it the carriage and apron it's called? Talking about the whole lot combined. Took off the cross slide today and I felt that weight lifting it and I'd be used to 40-50kg on a daily basis

 

[penfold]

Have you got a picture of the whole of the spindle? Depending on the arrangement turning down and sleeving may be easier/quicker than welding or brazing; it may be possible to build up the groove with epoxy. It might even be possible to ignore it as any off-the-shelf replacement thrust race is likely to come with its own races.

how are the yellow metal sleeves fixed in place? They look removable.

 

[DecK]

Yea, they're removable. Say it's only to knock them out of their housing. Their the bearings for the spindle oiled by an oil cup that's wick fed down to a sponge in the top half of the bearing. There were a few shims between the housing on the front one when I removed it.