Feedshaft worm lubrication

[Roger HeadParticipant @rogerhead16992]

I own a generic Chinese 13×40 lathe, it works fine, but I'm chasing a couple of anomalies that might be associated with the carriage motion. The power feed shaft drives a worm that sits in what can best be described as being like a horses water trough, cantilevered behind and partially below the apron body. The worm and gear appear totally devoid of any oil, although there is evidence of long-dried lubricant film on the gear. Removing the apron to get a closer look at things would seem to be a significant job, so can anyone tell me how those gears are intended to be lubricated? The trough (with it's completely open top) and the worm are totally below the oil-level sight-glass for the apron, so there can't be any overt passage to the gears. Maybe a very fine drip-feed path somehow?

Part two of the question relates to the top of the trough and the worm being completely open to the world – and swarf. Granted, it's a fairly protected area, but… Putting a once-a-year dollop of grease in there would be almost guaranteeing contamination. So how are other lathes set up in that area?

Roger

[Roger HeadParticipant @rogerhead16992]

… or not, as the case may be

[egaParticipant @ega]

I think it would be normal to provide dedicated lubrication to this area. My photo shows the inside of the apron on my Willson slantbed: the small hole at one o'clock above the large bronze worm gear houses an oil pipe fed via nipple from the front and which drips onto the worm assembly. I believe that in its day, apart from the slantbed, this machine was conventional.

When I dismantled this I didn't find any swarf here although a misguided former owner had larded it with grease.

[Martin ConnellyParticipant @martinconnelly55370]

Power feed shafts do not spin at high rpm so will not sling the oil out of the trough so not a lot of topping up required, no grease sounds sensible.

Martin

[Roger HeadParticipant @rogerhead16992]

Thanks for the replies. I scoured the web for manuals for machines similar to mine. A few mention giving a squirt of oil to the apron worm gear, more (including mine) don't say anything about it at all. I spent the day R&R the rack, cleaning off ten years of crud (mostly paint) from the rack and the pinion, and blasting out the worm trough. Half-a-dozen pumps of the oil-can fill the trough to overflowing, but I think the level will quickly settle down to the bottom of the feedshaft., it's a pretty sloppy fit in the ends of the trough. I'll have a think about rigging up a simple swarf deflector.

Roger

[LathejackParticipant @lathejack]

 

Hello Roger.

This is the back of the apron of my Chinese 13×30 lathe, which is probably very similar, if not identical, to yours. The worm gear has to be lubricated manually, the only lubrication on it when delivered was the filth that the factory carelessly slapped on.

Every now and then I simply squirt some oil onto the worm, which last quite a while and works well. But there is the problem of swarf dropping onto the worm and wheel.

My lathe came fitted with telescopic leadscrew covers, but these had to be removed so that the carraige could travel further along the bed to make the lathe usable. But without these covers swarf falls onto the leadscrew and then off onto the worm drive.

There is just enough room between the leadscrew and the worm wheel gear to fit a simple thin metal plate cover to the apron to shield the gears from contamination. This is a job I have been planning for quite a while, and when I am at it I planned to also fit a pipe leading to the worm gear at one end, with the other end accessible from the side of the apron. This will make lubricating the gears a lot easier than trying to peer down the back of the apron while trying to squirt the oil in the correct place. I think oil is preferable to grease on these gears.

 

Edited By Lathejack on 01/01/2016 16:17:42

[Roger HeadParticipant @rogerhead16992]

Thanks for the pic, LJ. Yes, from what I can see with mirrors, lamps, etc, it's very much like mine, and in spite of the drawing in my manual (I think they are only suggestions as to how the machine might be built), I now understand a little more than I did before – am I correct in guessing that the lever from the upper half-nut is the safety lockout to prevent simultaneous engagement of the horizontal feed when the half-nuts are engaged? Does the other end of the lever engage in a slot on the shaft to prevent fore-aft movement, or … ??? How robust do you think the interlock is? My hand has knocked the half-nut lever a few times over the years when I've been doing a rapid disengagement of the carriage feed, and while there have been no catastrophes (yet), I have wondered just how secure the lockout is .

Roger

Edited By Roger Head on 02/01/2016 07:57:37

[LathejackParticipant @lathejack]

Hi Roger.

The design of the carraige interlocks is very simple and quite clever, and can work perfectly well. The only problem with it I have encounted on these machines is that the factory responsible for the assembly of these lathes sometimes use whatever piece of grotty off cut they find to make the flat bar lever at the back of the apron that locks the feeds.

On my lathe that interlocking lever was made from a piece of very battered, bent and corroded scrap. The corner that engages in the sliding shaft groove was badly formed with a hand file. So it worked, but only just, the lever in the photo is a new replacement I made.

It's a good solid system. There is a sliding shaft that sticks out the front of the apron and meshes with the feed control lever, the control lever slides the shaft in and out. This shaft passes right through the apron and internal gears and sticks out the back. When the power feed control lever is in neutral the deep groove machined into this sliding shaft is inline with the interlock flat bar lever at the back of the apron, the other end of the flat bar is attached to one of the leadscrew half nuts. This allows the half nuts to be closed because one end of the flat bar swings into the shafts groove, this then prevents the power feeds from being simultaneously engaged because the shaft is now prevented from sliding in or out.

When power feeds are engaged this slides the shaft in or out so that the groove in the shaft is no longer inline with the interlock lever, so this now prevents the half nuts from being engaged because the lever can't move far enough, it just buts against the shafts outer diameter.

 

Edited By Lathejack on 02/01/2016 13:29:58

Edited By Lathejack on 02/01/2016 13:33:16

[Roger HeadParticipant @rogerhead16992]

Thanks LJ. Noted.

Another question: Is there an obvious function for the lump of CI next to the half-nuts? Does it form a close-fit bearing/guide for the leadscrew, or …?

Roger

[LathejackParticipant @lathejack]

Yes, as you thought the cast lug is bored to form a guide to keep the leadscrew straight and central to the half nuts. The Wilson lathe apron shown in the post above by Ega appears to have one either side of its single half nut.

[egaParticipant @ega]

"The Wilson lathe apron shown in the post above by Ega appears to have one either side of its single half nut"

Lathejack: Yes, quite right. The place of the "missing" half nut is taken by the TDI pinion when this is engaged (just visible in my photo).

Roger Head: see PM

Edited By ega on 03/01/2016 10:10:46

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