Denham Lathe Rescue

[DecK]

Finally got around to getting the carriage off this lathe. To make things interesting the housing on the end of the lead screw and feed shaft was kept in place with two bolts and also dowel pins which meant I couldn't get the clearance with the dowels to take off the end housing. Thought they could be hammered inwards but they weren't going in and couldn't get a grip to pull them out. Had to lift the carriage off first while keeping the apron supported and then get off the housing once I had some play in the lead screw and feed shaft and take off the apron


There is some scratching to the ways. Not sure if it's going to affect the operation of the lathe being honest.


The half nut lever wasn't engaging so had a look at that. Half nuts full of crud and there was a bolt in the feed shaft engagement mechanism that was blocking the movement of the half nut mechanism as well. Not sure what the bolt is for



Running theme with this has been finding numbers on everything with 6-xxx. Thinking maybe it's a model 6 lathe or something along those lines. Have had a look on the web and can't find anything relating to a Denham Model 6 or Type 6 or anything along those lines

 

[Shox Dr]

The 'divet' you describe in the main shaft doesnt look to be caused by wear. More like a grove for a circlip?

 

[DecK]

Well, there's wear there...

As to whether it's excessive or even noticeable in use is hard to tell from pictures.

It looks worse than it is really. Well to my untrained eye anyway. You can see them but when you run a finger over them they are only barely noticeable. Only way I could really describe them is that they're like the lines on your fingers. You can see them and faintly feel them.

The 'divet' you describe in the main shaft doesnt look to be caused by wear. More like a grove for a circlip?

Nope... I mightn't have the best knowledge of lathes but it's not the first machine I've ripped. The thrust bearing that was there was...I don't know, it seems like it was a home made job. There was no track in the washers for the race to be kept in place so it slid down between them and sat on the spindle shaft for years probably. The rotation of the shaft eventually led to it wearing that divot in the shaft. Also, if it was a groove for a circlip it would be right in the middle of where the thrust bearing should be to keep the spindle forward.

On another note, anyone recommend an oil type for the ways? Seems to be a wide variety talked about online.

 

[Maker]

On another note, anyone recommend an oil type for the ways? Seems to be a wide variety talked about online.

I think pretty much any oil will do but you can get proper slideway oil. I would guess there's different grades but the slideway oil I've got is really thick, almost like treacle. A thinner oil might be better as swarf really sticks to this stuff.

 

[DecK]

I think pretty much any oil will do but you can get proper slideway oil. I would guess there's different grades but the slideway oil I've got is really thick, almost like treacle. A thinner oil might be better as swarf really sticks to this stuff.

Yea, I read that was a problem with the heavy oils with swarf sticking in them. Maybe airtool oil? Might have a look again for slideway oil.

 

[Maker]

This is the stuff I've got. Very good on vertical surfaces but not so much on lathe beds. I tend to use car engine oil, simply because I have plenty of it and it's thinner

 

[Shox Dr]

just zoomed in on the forth picture in my post #48. I can now see the grove, right next to the machined grove i was refering to

 

[DecK]

This is the stuff I've got. Very good on vertical surfaces but not so much on lathe beds. I tend to use car engine oil, simply because I have plenty of it and it's thinner

Ahh... was just looking at this stuff on the bay.

http://www.ebay.co.uk/itm/5-Litre-S...002717?hash=item567048bd5d:g:46IAAOSw2s1U0i92

Have a Texaco place local that I use for all the fuel and oil for the farm so will give them a call tomorrow and see if they can get 5L of it in. I don't need 20L of the stuff knocking about...do I? Sure it couldn't take more than a half pint to do the whole bed.

just zoomed in on the forth picture in my post #48. I can now see the grove, right next to the machined grove i was refering to

It's only about 1/16" deep. The spindle shaft has a 1/2" wall at least. Thinking now that I'll just leave it. I can't see it causing any major problems to it operating.

 

[Pete.]

I was just scrolling down the posts and was going to suggest that actually. I'd fill it with devcon and smooth it off level with the spindle. Then if you have the space I would shim out the inboard thrust face to cover the groove and move it all up a bit.
Check the balls of the thrust bearing for flat spots. To wear a groove like that it must have been skidding I think.

 

[DecK]

Have a new bearing ordered. Will be in middle of next week. It is imperial type, 2 1/2" ID by 3/4" thick and my local place didn't have it in stock. Should hopefully mean I wont have to shim it out.

 

[penfold]

The half nut lever wasn't engaging so had a look at that. Half nuts full of crud and there was a bolt in the feed shaft engagement mechanism that was blocking the movement of the half nut mechanism as well. Not sure what the bolt is for

That's an interlock to prevent the leadscrew and the powerfeed being engaged at the same time and wrecking things.

 

[DecK]

I was just scrolling down the posts and was going to suggest that actually. I'd fill it with devcon and smooth it off level with the spindle. Then if you have the space I would shim out the inboard thrust face to cover the groove and move it all up a bit.
Check the balls of the thrust bearing for flat spots. To wear a groove like that it must have been skidding I think.

Sorry, made a dogs dinner out of replying to this last night as my eyes were closing. Called in to the local bearing place today to check that they had the right measurements and the closest I can get to that size is 11/16" thick with a 2 1/2" ID. I will have to shim it but probably only 1/16" if my measurements are right. Not enough to cover that divot with one of the bearing washers. 11/16" will definitely fit the space I have. Don't think I have much scope for movement either as the bullgear is rubbing the front bearing of the spindle and the casting of the headstock only allows for the pulley arrangement to move back about 1/4"

That's an interlock to prevent the leadscrew and the powerfeed being engaged at the same time and wrecking things.

Yea, your right. Read this earlier today and then it dawned on me that I'd read the two couldn't operate at the same time so this was to stop them engaging at the same time. Took apart the carriage tonight and it turns out that the disk that operates the two pegs to pull the half nuts together has a chip at the end of the way that operates the bottom half nut.

This allows the half nut to drop a little too far preventing the disk moving it back up again. Hoping I can get the disk off and turn it around so the top way, which appears to be in better condition, will operate the bottom half nut and not allow it to drop out. That's tomorrow nights job though at this stage